Electroacoustic transducer and unit for electroacoustic transducer

Abstract

To obtain an electroacoustic transducer and a unit for the electroacoustic transducer capable of reproducing high-quality sound by improving the reduction in sound pressure in an intermediate frequency band between low and high frequencies while achieving miniaturization.SOLUTION: An electroacoustic transducer 10 is provided with a port 36 leading the frequency band component of at least a part of sound radiated from a first diaphragm 28 in the direction opposite to a direction in which the front face 38A of a second diaphragm 38 faces to an external space S1 on the front face 38A side of the second diaphragm 38. The electroacoustic transducer 10 is provided with the port 36 so as to be configured such that the sound pressure of a synthesized sound in the vicinity of a crossover frequency of the sound radiated from the first diaphragm 28 and the second diaphragm 38 when a drive unit 16 generates vibration is the sound pressure or more at the crossover frequency of sound radiated from only one of the first diaphragm 28 and the second diaphragm 38.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electroacoustic transducer and a unit for an electroacoustic transducer. [Background technology]

[0002] The following Patent Document 1 discloses an exciter. This exciter includes a vibrating body having a yoke and a magnet, a frame that houses the vibrating body and supports the vibrating body via a damper so that the vibrating body can vibrate, a voice coil bobbin that is installed inside the frame and has one end attached to the frame and the other end extended to the vicinity of the vibrating body, and a voice coil installed at the other end of the voice coil bobbin. In this exciter, the vibrating body is vibrated in response to an acoustic signal flowing through the voice coil, and the vibration of the vibrating body is transmitted to the frame via the damper, making it possible to output low-frequency sound via a transmission medium on which the frame is installed.

[0003] In addition, in this exciter, an opening is formed in the frame, and the outer peripheral surface of the one end side of the voice coil bobbin is attached to the periphery of the opening of the frame. A vibrating member is provided so as to cover the open portion of the one end side of the voice coil bobbin. This allows vibration of the voice coil to be transmitted to the vibrating member via the voice coil bobbin, making it possible to output high-frequency sounds from the vibrating member to the outside of the frame.

[0004] In this way, in the above prior art, a single driver can be used to realize both the vibration function for outputting low-frequency sounds and the function for outputting high-frequency sounds, making it possible to achieve a smaller size than a multi-way speaker system. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6325957 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with the above-mentioned prior art, in the frequency band between low and high frequencies, the phase of the sound produced by the transmission medium and the phase of the sound produced by the vibrating member are reversed, resulting in a band (dip) where the sound pressure drops significantly.

[0007] In consideration of the above, the present invention aims to provide an electro-acoustic transducer and an electro-acoustic transducer unit that are capable of reproducing high-quality sound by improving the reduction in sound pressure in the frequency band between low and high frequencies while achieving compactness. [Means for solving the problem]

[0008] The electroacoustic transducer of the present invention described in claim 1 has a drive unit that generates vibrations by generating an action force on a reaction unit by an action unit in response to an electric input signal and by causing the reaction unit to apply a reaction force to the action unit, a first diaphragm connected to the action unit or the reaction unit which has a smaller mass, and a second diaphragm that has an area larger than the first diaphragm, to which the first diaphragm is connected via at least a first suspension and to which the action unit or the reaction unit which has a larger mass is connected via at least a second suspension, and which can emit sound to an external space on the front side when the drive unit generates vibrations, and is configured to provide a port that guides at least a portion of the frequency band components of the sound radiated from the first diaphragm in the direction opposite to the direction in which the front of the second diaphragm faces to the external space on the front side of the second diaphragm, so that the sound pressure of the composite sound near the crossover frequency of the radiated sounds from the first diaphragm and the second diaphragm when the drive unit generates vibrations is greater than or equal to the sound pressure at the crossover frequency of the radiated sound from only one of the first diaphragm and the second diaphragm. The "crossover frequency" in claim 1 refers to the frequency at which the radiation sound from the first diaphragm and the radiation sound from the second diaphragm are radiated with the same sound pressure (the same applies to the "crossover frequency" in the following specification).

[0009] According to the above configuration, the driving unit generates vibrations by causing the action unit to generate an action force on the reaction unit in response to an electrical input signal, and the reaction unit causes a reaction force to act on the action unit. The first diaphragm is connected to the action unit or the reaction unit which has the smaller mass. Therefore, when the action unit or the reaction unit which has the smaller mass vibrates, the first diaphragm vibrates integrally. The first diaphragm has a smaller area than the second diaphragm, and high-frequency sounds can be reproduced from the first diaphragm.

[0010] Moreover, the second diaphragm to which the first diaphragm is connected at least via the first suspension is connected to the acting part and the reaction part, whichever has the larger mass, via at least the second suspension. The second diaphragm has a larger area than the first diaphragm, and is capable of emitting sound to the external space on the front side when the driving part generates vibration. Here, when the driving part generates vibration, the vibration of the first diaphragm, which vibrates integrally with the acting part and the reaction part, which has the smaller mass, is input to the second diaphragm at least via the first suspension, and the force acting from the acting part and the reaction part, which has the smaller mass, to the acting part and the reaction part, which has the larger mass, is input to the second diaphragm at least via the second suspension. As a result, when the driving part generates vibration, vibration in the low frequency range is input to the second diaphragm, so that the generation of resonant sound that is likely to occur in the high frequency range is suppressed, and low frequency sound can be reproduced on the front side of the second diaphragm.

[0011] In this way, the electroacoustic transducer of the present invention can vibrate two diaphragms, the first diaphragm and the second diaphragm, with one driving unit, so that it can be made compact. Furthermore, the electroacoustic transducer of the present invention is configured to provide a port that guides at least a part of the frequency band components of the sound radiated from the first diaphragm in the direction opposite to the direction in which the front of the second diaphragm faces to the external space on the front side of the second diaphragm, so that the sound pressure of the composite sound near the crossover frequency of the radiated sounds from the first diaphragm and the second diaphragm when the driving unit generates vibration is equal to or higher than the sound pressure at the crossover frequency of the radiated sounds from only one of the first diaphragm and the second diaphragm. This improves the decrease in sound pressure in the frequency band between the low and high frequencies, making it possible to reproduce high quality sound.

[0012] The electro-acoustic transducer of the present invention described in claim 2, in the configuration described in claim 1, is configured such that the front direction of the first diaphragm is aligned with the front direction of the second diaphragm so that sound can be emitted from the front of the first diaphragm to the external space on the front side of the second diaphragm, and the port is configured to guide components of a certain frequency band of sound radiated from the back side of the first diaphragm into the cavity on the back side of the first diaphragm to the external space on the front side of the second diaphragm.

[0013] According to the above configuration, the direction of the front of the first diaphragm is aligned with the direction of the front of the second diaphragm, so that sound can be emitted from the front of the first diaphragm to the external space on the front side of the second diaphragm. Meanwhile, the port guides a part of the frequency band components of the sound radiated from the rear side of the first diaphragm into the cavity on the rear side of the first diaphragm to the external space on the front side of the second diaphragm. As a result, the sound from the rear side of the first diaphragm is added to the frequency band of the dip in the sound pressure frequency characteristic when the sound from the front of the first diaphragm and the sound from the front of the second diaphragm are combined, and the sound pressure in the frequency band between the low and high frequencies is improved compared to the conventional technology (the above-mentioned prior art).

[0014] The electro-acoustic transducer of the present invention described in claim 3 is configured in the configuration described in claim 1, such that the front direction of the first diaphragm is set in the opposite direction to the front direction of the second diaphragm and sound from the back side of the first diaphragm is not emitted to the external space on the front side of the second diaphragm, and the port is configured to guide at least a portion of the frequency band components of the sound radiated from the front of the first diaphragm in the direction opposite to the direction in which the front of the second diaphragm faces, to the external space on the front side of the second diaphragm.

[0015] According to the above configuration, the front of the first diaphragm is set to face in the opposite direction to the front of the second diaphragm. Also, sound from the rear of the first diaphragm is not emitted to the external space on the front side of the second diaphragm. The port guides at least a part of the frequency band components of the sound radiated from the front of the first diaphragm in the direction opposite to the direction in which the front of the second diaphragm faces to the external space on the front side of the second diaphragm. As a result, the sound from the electro-acoustic converter is a composite sound of the sound from the front of the second diaphragm and at least a part of the sound from the front of the first diaphragm facing the opposite side to the front of the second diaphragm. Here, according to the above configuration, in a frequency band between low-frequency sounds and high-frequency sounds, the phase of the sound from the front of the second diaphragm and the phase of the sound from the front of the first diaphragm are not reversed, so that the sound pressure in the frequency band between low-frequency sounds and high-frequency sounds is improved compared to the conventional technology (the above-mentioned prior art).

[0016] The electro-acoustic transducer of the present invention described in claim 4 has the configuration described in claim 2, in which a communication portion is formed within the cavity on the rear side of the first diaphragm to connect two spaces separated by the second suspension.

[0017] According to the above configuration, of the two spaces separated by the second suspension within the cavity on the rear side of the first diaphragm, not only the air in one space adjacent to the rear side of the first diaphragm but also the air in the other space can be effectively utilized to adjust the resonant frequency of the sound from the rear side of the first diaphragm.

[0018] The electro-acoustic transducer of the present invention described in claim 5 has the configuration described in claim 2 or claim 4, in which a hole is formed through the second diaphragm, and when viewed from the front side of the second diaphragm, the first diaphragm and the outlet of the port are arranged inside the hole, and further, components including the drive unit, the first diaphragm, the first suspension, the second suspension and the port are unitized and arranged so as not to protrude toward the front side of the second diaphragm.

[0019] According to the above configuration, sound from the front of the first diaphragm and sound from the outlet of the port are output from the hole in the second diaphragm. Also, since the components including the drive unit, the first diaphragm, the first suspension, the second suspension, and the port are unitized, the electro-acoustic transducer can be easily manufactured by attaching the unitized components so that they are continuous with the hole in the second diaphragm. Furthermore, since the unitized components do not protrude from the front side of the second diaphragm, a neat form can be realized.

[0020] The electroacoustic transducer unit of the present invention described in claim 6 comprises a housing provided with an attachment portion, a drive portion accommodated in the housing and configured to generate an acting force on a reaction portion by an acting portion in response to an electric input signal and to cause the reaction portion to act on the acting portion with a reaction force, thereby generating vibrations, a first diaphragm provided inside the housing and connected to one of the acting portion and the reaction portion having a smaller mass, a first suspension provided inside the housing and connecting the first diaphragm and the housing, and a second suspension provided inside the housing and connecting the one of the acting portion and the reaction portion having a larger mass to the housing, and the unit can be operated from an attached state in which the attachment portion of the housing is attached to the second diaphragm having an area larger than that of the first diaphragm. The unit is an electro-acoustic transducer unit used in an electro-acoustic transducer in which the second diaphragm can emit sound into the external space on the front side thereof when the driving unit generates vibrations, and a port is provided that can guide at least a portion of the frequency band components of the sound radiated from the first diaphragm in a direction opposite to the direction in which the front of the second diaphragm faces to the external space on the front side of the second diaphragm when the driving unit generates vibrations in the attached state, and by providing the port, the sound pressure of the combined sound near the crossover frequency of the sounds radiated from the first diaphragm and the second diaphragm when the driving unit generates vibrations in the attached state is configured to be equal to or greater than the sound pressure at the crossover frequency of the sound radiated from only one of the first diaphragm and the second diaphragm.

[0021] According to the above configuration, the driving section accommodated in the housing generates an acting force on the reaction section by the acting section in response to an electric input signal, and the reaction section applies a reaction force to the acting section, thereby generating vibration. The first diaphragm provided inside the housing is connected to the acting section or the reaction section, whichever has the smaller mass. Therefore, when the acting section or the reaction section, which has the smaller mass, vibrates, the first diaphragm vibrates integrally. Inside the housing, the first suspension connects the first diaphragm to the housing, and the second suspension connects the acting section or the reaction section, whichever has the larger mass, to the housing. The electroacoustic transducer unit of the present invention is used in an electroacoustic transducer in which the mounting section of the housing is attached to the second diaphragm, which has an area larger than the first diaphragm, and in a mounting state in which the mounting section of the housing is attached to the second diaphragm, and when the driving section generates vibration, the second diaphragm can emit sound to an external space on the front side of the second diaphragm. In this way, the electroacoustic transducer unit of the present invention can vibrate two diaphragms, the first diaphragm and the second diaphragm.

[0022] In the electroacoustic transducer unit of the present invention, when the mounting portion of the housing is attached to the second diaphragm and the drive unit generates vibrations, at least a portion of the frequency band components of the sound radiated from the first diaphragm in the direction opposite to the direction in which the front of the second diaphragm faces can be guided to the external space on the front side of the second diaphragm by the port. The electroacoustic transducer unit is configured such that, by providing the port, the sound pressure of the composite sound near the crossover frequency of the sounds radiated from the first diaphragm and the second diaphragm when the drive unit generates vibrations in the attached state is equal to or greater than the sound pressure at the crossover frequency of the sounds radiated from only one of the first diaphragm and the second diaphragm. This improves the reduction in sound pressure in the frequency band between the low and high frequencies, making it possible to reproduce high quality sound. Effect of the Invention

[0023] As described above, the present invention has the excellent effect of enabling high-quality sound reproduction by improving the reduction in sound pressure in the frequency band between low and high frequencies while realizing compactness. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic cross-sectional view showing an electroacoustic transducer including an electroacoustic transducer unit according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a vibration model of the electroacoustic transducer of FIG. [Diagram 3] 2 is a graph showing sound pressure frequency characteristics in the electroacoustic transducer of FIG. 1 and a comparative example. [Figure 4] Fig. 4(A) is a graph showing the sound pressure frequency characteristics of treble and bass radiated sounds in a comparative example, and Fig. 4(B) is a graph showing the sound pressure frequency characteristics in a comparative example. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing an electroacoustic transducer including an electroacoustic transducer unit according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a schematic cross-sectional view showing an electroacoustic transducer including an electroacoustic transducer unit according to a third embodiment of the present invention. [Figure 7] 7 is a perspective view showing a leaf spring (butterfly damper) applied as a second suspension of the electroacoustic transducer unit of FIG. 6. FIG. [Figure 8] 7 is a graph showing sound pressure frequency characteristics in the electroacoustic transducer of FIG. 6 and a comparative example. [Figure 9] Fig. 9(A) is a graph showing the sound pressure frequency characteristics of the sound from each of the front of the first diaphragm, the front of the second diaphragm, and the port of the electroacoustic transducer of Fig. 6. Fig. 9(B) is a graph showing the sound pressure frequency characteristics of the total composite sound output from the electroacoustic transducer of Fig. 6, the radiation sound from the first diaphragm (composite sound of the sound from the front of the first diaphragm and the sound from the port), and the sound from the front of the second diaphragm. [Figure 10] FIG. 13 is a perspective view showing a spider (damper) applicable as a second suspension of the third embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view showing an electroacoustic transducer including an electroacoustic transducer unit according to a fourth embodiment of the present invention. [Figure 12]FIG. 11 is a schematic cross-sectional view showing an electroacoustic transducer including an electroacoustic transducer unit according to a fifth embodiment of the present invention. [Figure 13] FIG. 13 is a schematic cross-sectional view showing an electroacoustic transducer including an electroacoustic transducer unit according to a sixth embodiment of the present invention. [Figure 14] FIG. 13 is a schematic cross-sectional view showing an electroacoustic transducer including a unit for electroacoustic transducer according to a seventh embodiment of the present invention. [Figure 15] FIG. 13 is a schematic cross-sectional view showing an electroacoustic transducer including a unit for electroacoustic transducer according to an eighth embodiment of the present invention. [Figure 16] FIG. 13 is a perspective view showing, in a partially cutaway state, an electroacoustic transducer including an electroacoustic transducer unit according to a ninth embodiment of the present invention. [Figure 17] FIG. 23 is a perspective view showing an electro-acoustic transducer according to a tenth embodiment of the present invention in a partially cutaway state. [Figure 18] FIG. 23 is an exploded perspective view showing an electroacoustic transducer according to an eleventh embodiment of the present invention, divided into front and rear halves and partially cut away. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] [First embodiment] An electroacoustic transducer including an electroacoustic transducer unit according to a first embodiment of the present invention will be described with reference to Figs. 1 to 4. Fig. 1 shows a schematic cross-sectional view of an electroacoustic transducer 10 including an electroacoustic transducer unit (also called a "driver") 12 according to the first embodiment. An arrow FR shown in Fig. 1 indicates the front direction (listening position side) from which the electroacoustic transducer 10 emits sound. In the following, when the front-rear direction is used for the description, it means the front-rear direction when viewed from the electroacoustic transducer 10 as a reference, unless otherwise specified. In the following, when the front-rear direction is used for the electroacoustic transducer unit 12, it means the front-rear direction in a state where the electroacoustic transducer unit 12 is installed to form a part of the electroacoustic transducer 10.

[0026] As shown in Fig. 1, the electroacoustic transducer unit 12 includes a housing 14. The housing 14 includes a front wall portion 14F disposed on the front side, a rear wall portion 14R disposed on the rear side opposite the front wall portion 14F, and a cylindrical peripheral wall portion 14S connecting an outer peripheral end portion of the front wall portion 14F and an outer peripheral end portion of the rear wall portion 14R. The housing 14 is also provided with an attachment portion 14A for attachment to another member. As an example, the attachment portion 14A protrudes in a flange shape from a portion where the rear wall portion 14R and the peripheral wall portion 14S intersect so as to be perpendicular to the front-rear direction.

[0027] The housing 14 houses a driving unit 16. The attachment of the driving unit 16 to the housing 14 will be described later. The driving unit 16 includes a magnetic circuit unit 20 as an acting unit, and a voice coil unit 18 as a reacting unit. In this embodiment, the magnetic circuit unit 20 has a larger mass than the voice coil unit 18.

[0028] The voice coil section 18 includes a voice coil bobbin 18A formed by forming a film into a cylindrical shape, and a voice coil body 18B wound around the front part of the outer circumferential surface of the voice coil bobbin 18A. In the drawing, the cross section of the voice coil bobbin 18A is shown by a thick line for convenience, and the cross section of the voice coil body 18B is shown in a simplified manner. The material of the voice coil bobbin 18A can be, for example, a resin material such as polyimide (PI), a paper material such as craft paper, or a metal material such as an aluminum alloy. The voice coil body 18B is made of an enamel wire in which an electric wire (for example, a copper wire) that is a linear conductor is covered with an enamel coating, and is wound around the voice coil bobbin 18A in, for example, two layers.

[0029] The magnetic circuit section 20 is composed of a yoke 22, a magnet 24, and a plate 26. The magnetic circuit section 20 of this embodiment is an internal magnet type magnetic circuit section that can reduce the size of the driving section 16. The yoke 22 is made of a ferromagnetic material and is formed in a bottomed cylindrical shape, and includes a bottom 22A and a cylindrical section 22B. The yoke 22 is arranged so that its central axis direction is along the front-rear direction (the direction of the arrow FR and the opposite direction thereto) and the bottom 22A is on the front side. A base section 22A1 is formed on the rear side of the bottom 22A of the yoke 22, except for the outer periphery. The magnet 24 is formed in a disk shape and is fixed to the rear side of the base section 22A1 of the yoke 22. The magnet 24 is formed to have a smaller diameter than the base section 22A1 of the yoke 22. The plate 26 is made of a ferromagnetic material and is formed in a disk shape and is fixed to the rear side of the magnet 24. The plate 26 is formed to have a diameter larger than the base portion 22A1 of the yoke 22 and the magnet 24.

[0030] A magnetic gap 20A is formed between the rear part of the inner peripheral surface of the cylindrical portion 22B of the yoke 22 and the outer peripheral surface of the plate 26. The voice coil body 18B is inserted into this magnetic gap 20A together with the voice coil bobbin 18A. The magnetic circuit section 20 uses the Lorentz force based on an electric input signal to the voice coil body 18B to vibrate the voice coil section 18 in the front-rear direction. That is, the driving section 16 is configured so that the magnetic circuit section 20 generates an acting force on the voice coil section 18 in response to the electric input signal, and the voice coil section 18 applies a reaction force to the magnetic circuit section 20, thereby generating vibration. The dimension in the front-rear direction of the voice coil section 18 applied to the electro-acoustic transducer 10 of this embodiment is set to be longer in consideration of the fact that the magnetic circuit section 20 vibrates in the front-rear direction.

[0031] A first diaphragm 28 is connected to the rear end of the voice coil bobbin 18A of the voice coil section 18. The first diaphragm 28 is provided inside the housing 14, and a cavity S2 is formed on the rear surface 28B side of the first diaphragm 28. The side of the first diaphragm 28 opposite to the side adjacent to the voice coil bobbin 18A (in other words, the side facing the rear wall portion 14R of the housing 14) is set as the front surface 28A. The direction of the front surface 28A of the first diaphragm 28 is set in the opposite direction to the front side of the electroacoustic transducer 10 (see the direction of the arrow FR). For convenience, the first diaphragm 28 is shown in a simplified and schematic manner in the drawing. Also, in the drawing, the direction in which the sound propagates from the first diaphragm 28 is shown by a simplified white arrow a.

[0032] As an example, a paper cone (a cone made of a material containing pulp fiber, etc.) can be used for the first diaphragm 28. Note that, as the material for the first diaphragm 28, for example, a papermaking material such as pulp fiber, a resin material such as polypropylene (PP), polyimide (PI), polyetherimide (PEI), polycarbonate (PC), etc., or a metal material such as an aluminum alloy can also be used. Also, a film-like one (thin one) can be used for the first diaphragm 28.

[0033] The first diaphragm 28 and the housing 14 are connected by a first suspension 30. The first suspension 30 is provided inside the housing 14, is formed in a ring shape when viewed from the front, and is joined to the outer periphery of the first diaphragm 28 and also to a portion on the inner surface side of the housing 14. This first suspension 30 is an element that can be understood as a mechanical filter having a function of passing low-frequency vibrations and blocking high-frequency vibrations.

[0034] An example of a member corresponding to the first suspension 30 is a well-known edge. The material and shape of the edge are such that they can acoustically isolate the space in front of and behind the first diaphragm 28. For the edge, please refer to FIG. 16 of the ninth embodiment described later, which illustrates a part of a first suspension 120 formed with an edge. The electroacoustic transducer unit 12 is configured so that sound from the back surface 28B of the first diaphragm 28 is not emitted to the space outside the housing 14 (external space S1 on the front surface 38A side of the second diaphragm 38 described later in detail).

[0035] As shown in FIG. 1, a second suspension 32 is provided inside the housing 14, on the front side of the first suspension 30. The second suspension 32 is formed in an annular shape when viewed from the front, and connects the cylindrical portion 22B of the yoke 22, which is a part of the magnetic circuit portion 20, to a portion on the inner side of the housing 14. This second suspension 32 is an element that can be understood as a mechanical filter having a function of passing low-frequency vibration and blocking high-frequency vibration. Examples of members corresponding to the second suspension 32 include a known spider and a metal leaf spring (also called a "butterfly damper"). Note that for the leaf spring, a leaf spring (second suspension 33) is illustrated in FIG. 7 of the third embodiment described later, so please refer to that.

[0036] As shown in Fig. 1, the electroacoustic transducer 10 has a second diaphragm 38. The front surface 38A of the second diaphragm 38 faces the same direction as the front side of the electroacoustic transducer 10 (see the direction of the arrow FR). The housing 14 of the electroacoustic transducer unit 12 described above is disposed on the front surface 38A side of the second diaphragm 38, and the mounting portion 14A of the housing 14 is attached to the second diaphragm 38. By attaching the mounting portion 14A of the housing 14 to the second diaphragm 38 in this manner, the first diaphragm 28 is connected to the second diaphragm 38 via the first suspension 30 and the housing 14, and the magnetic circuit section 20 is connected to the second diaphragm 38 via the second suspension 32 and the housing 14.

[0037] The second diaphragm 38 has a larger area than the first diaphragm 28 and is capable of vibrating in the front-rear direction over a wider range than the first diaphragm 28. Examples of the second diaphragm 38 include a table, and the dashboard and A-pillar of a vehicle.

[0038] To summarize the above, the electroacoustic transducer unit 12 is used in the electroacoustic transducer 10 in which the second diaphragm 38 can emit sound into the external space S1 on its front surface 38A side when the mounting portion 14A of the housing 14 is attached to the second diaphragm 38 and the drive portion 16 generates vibrations. In the figure, the direction of sound propagation from the front surface 38A of the second diaphragm 38 is simply indicated by the outline arrow b.

[0039] On the other hand, the electroacoustic transducer unit 12 is provided with a port (also called a "sound path") 36 capable of guiding at least a part of the frequency band components of the sound radiated from the front surface 28A of the first diaphragm 28 in the direction opposite to the direction in which the front surface 38A of the second diaphragm 38 faces to the external space S1 on the front surface 38A side of the second diaphragm 38 when the drive unit 16 generates vibration in a mounting state in which the mounting portion 14A of the housing 14 is mounted on the second diaphragm 38. The electroacoustic transducer unit 12 is configured such that, by providing the port 36, the sound pressure of the composite sound near the crossover frequency of the radiated sounds from the first diaphragm 28 and the second diaphragm 38 when the drive unit 16 generates vibration in a mounting state in which the mounting portion 14A of the housing 14 is mounted on the second diaphragm 38 is equal to or greater than the sound pressure at the crossover frequency of the radiated sound from only one of the first diaphragm 28 and the second diaphragm 38.

[0040] In other words, the electro-acoustic transducer 10 is configured by providing a port 36 that directs at least a portion of the frequency band components of the sound radiated from the front surface 28A of the first diaphragm 28 in the direction opposite to the direction in which the front surface 38A of the second diaphragm 38 faces, to the external space S1 on the front surface 38A side of the second diaphragm 38, so that when the driving unit 16 generates vibration, the sound pressure of the combined sound near the crossover frequency of the sounds radiated from the first diaphragm 28 and the second diaphragm 38 is greater than or equal to the sound pressure at the crossover frequency of the sound radiated from only one of the first diaphragm 28 and the second diaphragm 38.

[0041] In the present embodiment, as an example, the port 36 is configured as a through hole formed in the rear end portion of the peripheral wall portion 14S and having the circumferential direction of the peripheral wall portion 14S as the longitudinal direction. A large number of the ports 36 are formed in a line in the circumferential direction of the peripheral wall portion 14S, and are set to guide as much of the sound radiated from the front surface 28A of the first diaphragm 28 as possible to the external space S1 on the front surface 38A side of the second diaphragm 38.

[0042] Here, a supplementary explanation will be given of the simulation of the sound pressure frequency characteristics of the electroacoustic transducer 10 with reference to Fig. 2. Fig. 2 shows a vibration model of the electroacoustic transducer 10 of Fig. 1. In other words, the electroacoustic transducer 10 shown in Fig. 1 is replaced with a vibration model consisting of mechanical elements shown in Fig. 2.

[0043] In FIG. 2, reference numeral 380 corresponds to the fixed portion of the second diaphragm 38. K3 corresponds to the hardness of the fixed portion of the second diaphragm 38, R2 corresponds to the damping resistance of the fixed portion of the second diaphragm 38, and M2 corresponds to the mass on the second diaphragm 38 side. K1 corresponds to the hardness of the first suspension 30, and K2 corresponds to the hardness of the second suspension 32. M3 corresponds to the mass of the magnetic circuit section 20 (the larger of the magnetic circuit section 20 and the voice coil section 18 in the driving section 16), F corresponds to the driving force by the driving section 16, and R1 corresponds to the damping resistance generated in the driving section 16. M1 corresponds to the mass on the first diaphragm 28 side.

[0044] The vibration velocity characteristics of the first diaphragm 28 and the second diaphragm 38 can be obtained from an electric circuit (equivalent circuit) created based on the vibration model shown in Fig. 2. Then, the sound pressure frequency characteristics of the electroacoustic transducer 10 at a predetermined listening position can be obtained based on the vibration velocities of the first diaphragm 28 and the second diaphragm 38.

[0045] Next, the operation and effects of the first embodiment will be described.

[0046] 1, the driving section 16 is configured to generate an acting force on the voice coil section 18 by the magnetic circuit section 20 in response to an electric input signal, and the voice coil section 18 generates a reaction force on the magnetic circuit section 20, thereby generating vibration. A first diaphragm 28 is connected to the voice coil section 18, which has the smaller mass of the magnetic circuit section 20 and the voice coil section 18. Therefore, when the voice coil section 18 vibrates in response to an electric input signal, the first diaphragm 28 vibrates integrally. The first diaphragm 28 has a smaller area than the second diaphragm 38, and high-frequency sounds are reproduced from the first diaphragm 28.

[0047] Further, the magnetic circuit section 20, which is the larger mass of the magnetic circuit section 20 and the voice coil section 18, is connected to the second diaphragm 38 to which the first diaphragm 28 is connected at least via the first suspension 30, at least via the second suspension 32. The second diaphragm 38 has a larger area than the first diaphragm 28, and is capable of emitting sound to the external space S1 on the front surface 38A side when the driving section 16 generates vibration. Here, when the driving section 16 generates vibration, the vibration of the first diaphragm 28, which vibrates integrally with the voice coil section 18, is input to the second diaphragm 38 via the first suspension 30, etc., and the reaction force acting on the magnetic circuit section 20 from the voice coil section 18 is input to the second diaphragm 38 via the second suspension 32, etc. As a result, when the driving section 16 generates vibration, vibration in the low frequency range is input to the second diaphragm 38, so that the generation of resonant sound that is likely to occur in the high frequency range is suppressed, and low frequency sound can be reproduced on the front surface 38A side of the second diaphragm 38.

[0048] In this way, in the electroacoustic transducer of this embodiment, two diaphragms, the first diaphragm 28 and the second diaphragm 38, can be vibrated by one driving section 16, so that it is possible to achieve miniaturization (space saving) and cost reduction. Also, since the electroacoustic transducer unit 12 is provided with the mounting section 14A for mounting to another member, it can be mounted to various members, and various members can be used as the second diaphragm.

[0049] Furthermore, the electroacoustic transducer 10 of this embodiment is configured to provide a port 36 that guides at least a portion of the frequency band components of the sound radiated from the first diaphragm 28 in the direction opposite to the direction in which the front face 38A of the second diaphragm 38 faces to the external space S1 on the front face 38A side of the second diaphragm 38, so that the sound pressure of the composite sound near the crossover frequency of the sounds radiated from the first diaphragm 28 and the second diaphragm 38 when the drive unit 16 generates vibration is equal to or greater than the sound pressure at the crossover frequency of the sounds radiated from only one of the first diaphragm 28 and the second diaphragm 38. This improves the reduction in sound pressure in the frequency band between the low and high frequencies, making it possible to reproduce high quality sound.

[0050] More specifically, in this embodiment, the direction of the front surface 28A of the first diaphragm 28 is set to be opposite to the direction of the front surface 38A of the second diaphragm 38. Also, sound from the back surface 28B of the first diaphragm 28 is not emitted to the external space S1 on the front surface 38A side of the second diaphragm 38. Then, the above-mentioned port 36 guides at least a part of the frequency band components of the sound radiated from the front surface 28A of the first diaphragm 28 in the direction opposite to the direction in which the front surface 38A of the second diaphragm 38 faces, to the external space S1 on the front surface 38A side of the second diaphragm 38.

[0051] As a result, the sound from the electroacoustic transducer 10 is a composite sound of the sound from the front face 38A of the second diaphragm 38 and at least a part of the sound from the front face 28A of the first diaphragm 28 facing the opposite side to the front face 38A of the second diaphragm 38. Here, in a frequency band between the low and high frequencies, the phase of the sound from the front face 38A of the second diaphragm 38 and the phase of the sound from the front face 28A of the first diaphragm 28 are not reversed, so that the sound pressure in the frequency band between the low and high frequencies is improved compared to the conventional technology (the above-mentioned prior art).

[0052] This point will be further explained with reference to Figs. 3 and 4. In Figs. 3 and 4, the horizontal axis indicates frequency in logarithm, and the vertical axis indicates sound pressure. Fig. 3 is a graph showing the sound pressure frequency characteristics of the electroacoustic transducer 10 of this embodiment and a comparative example. The solid line in the graph of Fig. 3 shows the sound pressure frequency characteristics of the electroacoustic transducer 10 of this embodiment, and the dashed line shows the sound pressure frequency characteristics of the comparative example. Fig. 4(A) is a graph showing the sound pressure frequency characteristics of the treble side radiated sound and the bass side radiated sound in the comparative example, and Fig. 4(B) is a graph showing the sound pressure frequency characteristics in the comparative example.

[0053] In the comparative example, an exciter with a diaphragm is installed on a flat plate, and the front and rear of the electroacoustic transducer unit 12 in the electroacoustic transducer 10 shown in Fig. 1 are arranged in reverse, and a sound emitting opening is formed through only the side of the housing 14 facing the first diaphragm 28. The dotted line (···) in the graph of Fig. 4(A) indicates the sound pressure due to the vibration of the diaphragm of the exciter (in other words, the sound pressure of the radiated sound on the high-pitched sound side), and the dashed line (---) indicates the sound pressure due to the vibration of the flat plate excited by the exciter (in other words, the sound pressure of the radiated sound on the low-pitched sound side).

[0054] In contrast, high-frequency sounds are reproduced by the vibration of the diaphragm of the exciter (see the dotted line in FIG. 4(A)), and low-frequency sounds are reproduced by the vibration of the flat plate excited by the exciter (see the dashed line in FIG. 4(A)). Here, in the case of sound from the front of the diaphragm of the exciter, as the frequency becomes smaller than the low-frequency limit frequency of the diaphragm, the sound pressure decreases and the phase of the sound pressure advances when the phase of the applied voltage is used as the reference. In contrast, in the case of sound from the front of the flat plate excited by the exciter, as the frequency becomes larger than the high-frequency limit frequency of the diaphragm, the sound pressure decreases and the phase of the sound pressure delays when the phase of the applied voltage is used as the reference. As a result, in the frequency band between the low-frequency sounds and the high-frequency sounds (in other words, near the crossover frequency), the phase of the sound from the front of the diaphragm of the exciter and the phase of the sound from the front of the flat plate excited by the exciter are reversed. This results in a band (dip) where the sound pressure drops significantly, as shown in Fig. 4(B) where the area where the sound pressure drops significantly is surrounded by a dashed line.

[0055] In contrast, in the electroacoustic transducer 10 of this embodiment, in a frequency band intermediate between the low and high frequencies, the sound from the front surface 38A of the second diaphragm 38 and at least a part of the sound from the front surface 28A of the first diaphragm 28 facing the opposite side to the front surface 38A of the second diaphragm 38 are synthesized and emitted so that the phase of the sound from the first diaphragm 28 and the phase of the sound from the second diaphragm 38 shown in Fig. 1 are not reversed. Therefore, in the electroacoustic transducer 10 of this embodiment, as shown by the solid line diagram in Fig. 3, the sound pressure in the frequency band intermediate between the low and high frequencies is improved compared to the comparative example.

[0056] As described above, according to this embodiment, it is possible to improve the reduction in sound pressure in the frequency band between low and high frequencies while realizing miniaturization, thereby enabling high-quality sound to be reproduced.

[0057] [Second embodiment] Next, an electroacoustic transducer including an electroacoustic transducer unit according to a second embodiment of the present invention will be described with reference to Fig. 5. Fig. 5 shows a schematic cross-sectional view of an electroacoustic transducer 40 including an electroacoustic transducer unit 42 according to the second embodiment. In the second embodiment, components substantially similar to those in the first embodiment are appropriately designated with the same reference numerals and description thereof will be omitted. For convenience, the cavity S2 on the rear surface 28B side of the first diaphragm 28 is designated with the same reference numerals as in the first embodiment (the same applies to the third to ninth embodiments).

[0058] The electroacoustic transducer unit 42 includes a housing 44 instead of the housing 14 (see FIG. 1 for both) of the electroacoustic transducer unit 12 of the first embodiment. The housing 44 includes a front wall 44F disposed on the front side, a rear wall 44R disposed on the rear side facing the front wall 44F, and a cylindrical peripheral wall 44S connecting an outer periphery end of the front wall 44F and an outer periphery end of the rear wall 44R. An outer periphery of the first suspension 30 and an outer periphery of the second suspension 32 are joined to the peripheral wall 44S, similar to the peripheral wall 14S of the first embodiment (see FIG. 1).

[0059] The housing 44 is provided with an attachment portion 44A for attachment to another member. As an example, the attachment portion 44A protrudes in a flange shape perpendicular to the front-rear direction from a portion where the front wall portion 44F and the peripheral wall portion 14S intersect. The housing 44 is disposed on the rear surface 41B side of the second diaphragm 41, and the attachment portion 44A of the housing 44 is attached to the second diaphragm 41. The second diaphragm 41 has a larger area than the first diaphragm 28. By attaching the attachment portion 44A of the housing 44 to the second diaphragm 41, the first diaphragm 28 is connected to the second diaphragm 41 via the first suspension 30 and the housing 44, and the magnetic circuit portion 20 is connected to the second diaphragm 41 via the second suspension 32 and the housing 44. The second diaphragm 41 is capable of emitting sound to the external space S1 on the front surface 41A side when the driving unit 16 generates vibration (see arrow b).

[0060] The mounting portion 44A of the housing 44 in the electroacoustic transducer unit 42 is attached to the second diaphragm 41 in the above-mentioned state to form the electroacoustic transducer 40. The electroacoustic transducer 40 is configured so that the front surface 28A of the first diaphragm 28 faces in the opposite direction to the front surface 41A of the second diaphragm 41, and so that sound from the back surface 28B of the first diaphragm 28 is not emitted to the external space S1 on the front surface 41A side of the second diaphragm 41.

[0061] On the other hand, a hole 46H is formed through the rear wall 44R of the housing 44 in the electroacoustic transducer unit 42, corresponding to the center of the front surface 28A of the first diaphragm 28. A short cylindrical horn mounting portion 44Z is formed on the rear surface side of the rear wall 44R, protruding rearward from the periphery of the hole 46H. One end of a horn 46D constituting a part of the electroacoustic transducer unit 42 is attached to the outer periphery of the horn mounting portion 44Z. The horn 46D is formed in a substantially J-shape. The front portion of the horn 46D is formed in a shape that gradually expands in diameter toward the end side on the second diaphragm 41 side. The front end of the horn 46D is connected to a hole 41H formed in the second diaphragm 41 by press-fitting, for example. An attachment portion to the second diaphragm 41 may be provided separately at the front end side of the horn 46D. In the second diaphragm 41, the hole 41H is formed through the second diaphragm 41 in the vicinity of the portion where the electroacoustic transducer unit 42 is installed.

[0062] The hole 46H and the horn 46D of the housing 44 constitute the port 46 of this embodiment. The port 46 is configured to guide at least a part (for example, all) of the frequency band components of the sound radiated from the front surface 28A of the first diaphragm 28 in the direction opposite to the direction in which the front surface 41A of the second diaphragm 41 faces, to the external space S1 on the front surface 41A side of the second diaphragm 41. The electroacoustic transducer 40 is configured such that, by providing the port 46, the sound pressure of the composite sound near the crossover frequency of the radiated sounds from the first diaphragm 28 and the second diaphragm 41 when the driving unit 16 generates vibration becomes equal to or greater than the sound pressure at the crossover frequency of the radiated sound from only one of the first diaphragm 28 and the second diaphragm 41.

[0063] The configuration of the second embodiment described above can provide substantially the same actions and effects as the first embodiment. In addition, this embodiment does not require a protruding portion on the front side of the second diaphragm 41, so a neat form can be achieved.

[0064] [Third embodiment] Next, an electroacoustic transducer including an electroacoustic transducer unit according to a third embodiment of the present invention will be described with reference to Fig. 6 to Fig. 9. Fig. 6 shows a schematic cross-sectional view of an electroacoustic transducer 50 including an electroacoustic transducer unit 52 according to the third embodiment. Note that components substantially similar to those in the first embodiment will be appropriately designated by the same reference numerals and description thereof will be omitted.

[0065] The electroacoustic transducer unit 52 includes a housing 54 instead of the housing 14 of the electroacoustic transducer unit 12 of the first embodiment (see FIG. 1 for both). The housing 54 includes a rear wall 54R disposed on the rear side, and a cylindrical peripheral wall 54S erected from the outer periphery of the rear wall 54R. The rear wall 54R of the housing 54 is substantially the same component as the rear wall 14R of the housing 14 of the first embodiment (see FIG. 1 for both).

[0066] The housing 54 is also provided with an attachment portion 54A for attachment to another member. As an example, the attachment portion 54A protrudes in a flange shape perpendicular to the front-rear direction from a portion where the rear wall portion 54R and the peripheral wall portion 54S intersect. The housing 54 is disposed on the front surface 38A side of the second diaphragm 38, and the attachment portion 54A of the housing 54 is attached to the second diaphragm 38. In this way, the electro-acoustic transducer unit 52 is attached to the second diaphragm 38, thereby forming the electro-acoustic transducer 50.

[0067] When viewed with the rear wall 54R as a reference, the components inside the housing 54 are arranged in the reverse order to the components inside the housing 14 (see FIG. 1) of the first embodiment, but are otherwise substantially similar to the components inside the housing 14 of the first embodiment, except that a second suspension 33 is provided instead of the second suspension 32 (see FIG. 1). Therefore, for convenience, the components inside the housing 54, except for the second suspension 33, are given the same reference numerals as the components inside the housing 14 (see FIG. 1) of the first embodiment, and descriptions thereof will be omitted as appropriate.

[0068] The electroacoustic transducer 50 is configured such that the orientation of the front surface 28A of the first diaphragm 28 is aligned with the orientation of the front surface 38A of the second diaphragm 38, so that sound can be emitted from the front surface 28A of the first diaphragm 28 to an external space S1 on the front surface 38A side of the second diaphragm 38. The first suspension 30 connects the outer periphery of the first diaphragm 28 to the housing 54. Thus, in the electroacoustic transducer 50, the first diaphragm 28 is connected to the second diaphragm 38 via the first suspension 30 and the housing 54. In addition, the driving unit 16 is disposed on the rear surface 28B side of the first diaphragm 28.

[0069] The second suspension 33 connects the outer periphery of the magnetic circuit section 20 to the housing 54. As a result, in the electro-acoustic transducer 50, the magnetic circuit section 20 is connected to the second diaphragm 38 via the second suspension 33 and the housing 54. The second diaphragm 38 is capable of emitting sound into the external space S1 on the front surface 38A side when the drive section 16 generates vibrations.

[0070] FIG. 7 shows a perspective view of a leaf spring (butterfly damper) used as the second suspension 33. For example, a metal material such as stainless steel or a synthetic resin material such as bakelite can be used as the material of the second suspension 33 shown in FIG. 7. As shown in FIG. 7, the second suspension 33 is formed in an annular shape when viewed from the front, and has a plurality of communication holes 33H formed therethrough as communication portions. As an example, the plurality of communication holes 33H extend along the circumferential direction of the second suspension 33. The communication holes 33H communicate two spaces S21 and S22 partitioned by the second suspension 33 in the cavity S2 on the rear surface 28B side of the first diaphragm 28 shown in FIG. 6.

[0071] A port 56 is provided continuously with a portion on the rear end side of the peripheral wall portion 54S of the housing 54. As an example, the port 56 is formed of a through hole 56H formed in the portion on the rear end side of the peripheral wall portion 54S of the housing 54, and a cylindrical duct 56D formed continuously with the through hole 56H and extending in a direction perpendicular to the front-rear direction.

[0072] The port 56 is configured to guide components of a certain frequency band of sound radiated from the rear surface 28B of the first diaphragm 28 into the cavity S2 on the rear surface 28B side of the first diaphragm 28 (in other words, sound radiated from the rear surface 28B of the first diaphragm 28 in the direction opposite to the direction in which the front surface 38A of the second diaphragm 38 faces) to the external space S1 on the front surface 38A side of the second diaphragm 38.

[0073] 9B shows a graph showing the sound pressure frequency characteristics of the total composite sound output from the electroacoustic transducer 50, the radiation sound from the first diaphragm 28 (a composite sound of the sound from the front surface 28A of the first diaphragm 28 and the sound from the port 56), and the sound from the front surface 38A of the second diaphragm 38. In FIG. 9B, the horizontal axis shows the frequency in logarithmic scale, and each vertical axis shows the sound pressure. The solid line in the graph of FIG. 9B shows the sound pressure of the total composite sound output from the electroacoustic transducer 50, the dashed line shows the sound pressure of the radiation sound from the first diaphragm 28 (a composite sound of the sound from the front surface 28A of the first diaphragm 28 and the sound from the port 56), and the dashed line shows the sound pressure of the sound from the front surface 38A of the second diaphragm 38. As can be seen from the graph shown in Figure 9(B), the electro-acoustic transducer 50 is configured so that, by providing a port 56, the sound pressure of the combined sound near the crossover frequency of the sounds radiated from the first diaphragm 28 and the second diaphragm 38 when the driving unit 16 generates vibration is greater than the sound pressure at the crossover frequency of the sounds radiated from only one of the first diaphragm 28 and the second diaphragm 38 (the sound pressure at the intersection of the dotted line and the dashed line in Figure 9(B)) (more specifically, so that it is greater than the sound pressure at the crossover frequency of the sounds radiated from only one of the first diaphragm 28 and the second diaphragm 38).

[0074] 6 is configured to output a sound in a frequency band between low and high frequencies by utilizing resonance between an air spring in cavity S2 on the rear surface 28B side of first diaphragm 28 and the mass of air inside port 56. Note that the principle and settings for outputting a sound in a predetermined frequency band are similar to those of a known bass reflex port, and therefore a detailed description will be omitted.

[0075] Next, the operation and effects of the third embodiment will be described.

[0076] In the electroacoustic transducer 50 shown in Fig. 6, when the driving section 16 generates vibrations in response to an electric input signal, the first diaphragm 28 vibrates integrally with the voice coil section 18. As a result, high-frequency sounds are reproduced forward from the front surface 28A of the first diaphragm 28. At this time, when the electroacoustic transducer unit 52 vibrates, the second diaphragm 38 vibrates in response. As a result, low-frequency sounds are reproduced forward from the front surface 38A of the second diaphragm 38.

[0077] Furthermore, a port 56 provided continuously with the housing 54 guides components of a portion of the frequency band of the sound radiated from the rear surface 28B of the first diaphragm 28 into the cavity S2 on the rear surface 28B side of the first diaphragm 28 to the external space S1 on the front surface 38A side of the second diaphragm 38. As a result, the sound from the rear surface 28B of the first diaphragm 28 is added to the frequency band of the dip in the sound pressure frequency characteristic when the sound from the front surface 28A of the first diaphragm 28 and the sound from the front surface 38A of the second diaphragm 38 are combined, and the sound pressure in the intermediate frequency band between the low and high frequencies is improved compared to the conventional technology (the above-mentioned prior art).

[0078] This point will be further explained with reference to Fig. 8 and Fig. 9(A). In Fig. 8 and Fig. 9(A), the horizontal axis indicates the frequency in logarithm, and the vertical axis indicates the sound pressure. Fig. 8 is a graph showing the sound pressure frequency characteristics of the electroacoustic transducer 50 of this embodiment and the comparative example. In Fig. 8, the solid line indicates the sound pressure frequency characteristics of the electroacoustic transducer 50 of this embodiment, and the dashed line indicates the sound pressure frequency characteristics of the comparative example. The comparative example is the same as the comparative example described in the explanation of Fig. 3. Fig. 9(A) is a graph showing the sound pressure frequency characteristics of the sound from each of the front surface 28A of the first diaphragm 28, the front surface 38A of the second diaphragm 38, and the port 56 of the electroacoustic transducer 50. The dotted line in the graph of Fig. 9(A) indicates the sound pressure of the sound from the front surface 28A of the first diaphragm 28, the fine dashed line indicates the sound pressure of the sound from the front surface 38A of the second diaphragm 38, and the coarse dashed line indicates the sound pressure of the sound from the port 56.

[0079] As shown in Fig. 9(A), sound from the port 56 is added to the intermediate frequency band between the low and high frequencies. The phase of the sound from the port 56 is not reversed to the phase of the sound from the front surface 38A of the second diaphragm 38. As a result, when the sounds from the front surface 28A of the first diaphragm 28 of the electro-acoustic transducer 50, the front surface 38A of the second diaphragm 38, and the port 56 are synthesized, the sound pressure in the intermediate frequency band between the low and high frequencies is improved compared to the comparative example, as shown in Fig. 8.

[0080] 6, a communication hole 33H (see FIG. 7) is formed to communicate two spaces S21, S22 partitioned by the second suspension 33. For this reason, of the two spaces S21, S22 partitioned by the second suspension 33 in the cavity S2 on the rear surface 28B side of the first diaphragm 28, not only the air in one space S21 that contacts the rear surface 28B of the first diaphragm 28 but also the air in the other space S22 can be effectively used to adjust the resonance frequency of the sound from the rear surface 28B of the first diaphragm 28.

[0081] As described above, the third embodiment also makes it possible to improve the reduction in sound pressure in the intermediate frequency band between low and high frequencies while realizing miniaturization, thereby enabling reproduction of high quality sound.

[0082] Instead of the second suspension 33 (see FIG. 7) of the third embodiment, a spider (also called a "damper") 34 shown in FIG. 10 may be applied as the second suspension. As shown in FIG. 10, the spider 34 is formed in a ring shape when viewed from the front and in a ripple shape (concentric wave shape). The spider 34 is made by hot pressing a material in which a woven fabric such as cotton or chemical fiber is impregnated with a thermosetting resin. The spider 34 has gaps between the threads of the woven fabric and is breathable. The gaps in the spider 34 are not shown in FIG. 10.

[0083] [Fourth embodiment] Next, an electroacoustic transducer including an electroacoustic transducer unit according to a fourth embodiment of the present invention will be described with reference to Fig. 11. Fig. 11 shows a schematic cross-sectional view of an electroacoustic transducer 60 including an electroacoustic transducer unit 62 according to the fourth embodiment. Note that components substantially similar to those in the third embodiment will be appropriately designated by the same reference numerals and description thereof will be omitted.

[0084] The electroacoustic transducer unit 62 includes a housing 64 instead of the housing 54 (see FIG. 6 for both) of the electroacoustic transducer unit 52 of the third embodiment. The housing 64 includes a rear wall portion 64R disposed on the rear side, and a cylindrical wall portion 64B standing on the outer periphery of the rear wall portion 64R. The housing 64 is also provided with an attachment portion 64A for attachment to another member. As an example, the attachment portion 64A protrudes in a flange shape from a front side portion of the outer periphery of the housing 64 so as to be perpendicular to the front-rear direction.

[0085] On the other hand, the second diaphragm 61 to which the electroacoustic transducer unit 62 is attached has a larger area than the first diaphragm 28. A hole 61H is formed through the second diaphragm 61. The mounting portion 64A of the housing 64 is disposed on the rear surface 61B side of the second diaphragm 61 and around the hole 61H, and is attached to the second diaphragm 61. The electroacoustic transducer 60 is configured by attaching the electroacoustic transducer unit 62 to the second diaphragm 61. The second diaphragm 61 is capable of emitting sound to the external space S1 on the front surface 61A side when the drive unit 16 generates vibration.

[0086] The components inside the housing 64 are substantially the same as the components inside the housing 54 (see FIG. 6) of the third embodiment. As in the third embodiment, the electroacoustic transducer 60 is configured such that the direction of the front surface 28A of the first diaphragm 28 is aligned with the direction of the front surface 61A of the second diaphragm 61, so that sound can be emitted from the front surface 28A of the first diaphragm 28 to the external space S1 on the front surface 61A side of the second diaphragm 61. The first suspension 30 connects the outer periphery of the first diaphragm 28 to the cylindrical wall portion 64B of the housing 64. As a result, in the electroacoustic transducer 60, the first diaphragm 28 is connected to the second diaphragm 61 via the first suspension 30 and the housing 64. Also, as in the third embodiment, the driving unit 16 is disposed on the rear surface 28B side of the first diaphragm 28.

[0087] The second suspension 33 connects the outer periphery of the magnetic circuit portion 20 and the cylindrical wall portion 64B of the housing 64. As a result, in the electro-acoustic transducer 60, the magnetic circuit portion 20 is connected to the second diaphragm 61 via the second suspension 33 and the housing 64.

[0088] A port 66 is provided continuously with a part of the cylindrical wall portion 64B of the housing 64. As an example, the port 66 is formed by a through hole 66H formed in a rear end side portion of the cylindrical wall portion 64B of the housing 64, and a duct portion 66D formed continuously with the through hole 66H. The duct portion 66D is formed so that its internal space extends along the front-rear direction. The rear end of the duct portion 66D is a closed portion 66D1, and the front end of the duct portion 66D is an outlet 66E of the port 66. Also, as an example, a part of the duct portion 66D is formed by a part of the cylindrical wall portion 64B.

[0089] The port 66 is configured to guide a part of the frequency band components (more specifically, sounds in a frequency band between low and high frequencies) of the sound radiated from the back surface 28B of the first diaphragm 28 into the cavity S2 on the back surface 28B side of the first diaphragm 28 (in other words, sounds radiated from the back surface 28B of the first diaphragm 28 in the direction opposite to the direction in which the front surface 61A of the second diaphragm 61 faces) to the external space S1 on the front surface 61A side of the second diaphragm 61. The electroacoustic transducer 60 is configured such that the sound pressure of the composite sound near the crossover frequency of the sounds radiated from the first diaphragm 28 and the second diaphragm 61 when the driving unit 16 generates vibration by providing the port 66 becomes equal to or greater than the sound pressure at the crossover frequency of the sounds radiated from only one of the first diaphragm 28 and the second diaphragm 61.

[0090] Moreover, the first diaphragm 28 and the outlet 66E of the port 66 are disposed inside the hole 61H when viewed from the front surface 61A side of the second diaphragm 61. Furthermore, the electroacoustic transducer unit 62, in which components including the drive section 16, the first diaphragm 28, the first suspension 30, the second suspension 33 and the port 66 are unitized, is disposed relative to the second diaphragm 61 so as not to protrude toward the front surface 61A side.

[0091] Next, the operation and effects of the fourth embodiment will be described.

[0092] 11, sound is emitted from the front surface 61A of the second diaphragm 61, and sound from the front surface 28A of the first diaphragm 28 and sound from the outlet 66E of the port 66 are output from the hole 61H of the second diaphragm 61. This provides substantially the same effects and advantages as the third embodiment.

[0093] In addition, in the fourth embodiment, the electroacoustic transducer 60 can be easily manufactured by attaching the electroacoustic transducer unit 62 so that it is continuous with the hole portion 61H of the second diaphragm 61, and since the electroacoustic transducer unit 62 does not protrude toward the front surface 61A of the second diaphragm 61, a neat shape can be realized.

[0094] [Fifth embodiment] Next, an electroacoustic transducer including an electroacoustic transducer unit according to a fifth embodiment of the present invention will be described with reference to Fig. 12. Fig. 12 shows a schematic cross-sectional view of an electroacoustic transducer 70 including an electroacoustic transducer unit 72 according to the fifth embodiment. As shown in Fig. 12, the electroacoustic transducer 70 differs from the electroacoustic transducer 50 according to the third embodiment in that it includes a port 76 instead of the port 56 (see Fig. 6) in the third embodiment. The other configurations are substantially similar to those of the third embodiment. Therefore, the same reference numerals are appropriately used for components substantially similar to those of the third embodiment, and description thereof will be omitted.

[0095] The electroacoustic transducer unit 72 includes a housing 74 instead of the housing 54 (see FIG. 6 for both) of the electroacoustic transducer unit 52 of the third embodiment. The housing 74 includes a rear wall portion 74R disposed on the rear side and a cylindrical peripheral wall portion 74S erected from the outer periphery of the rear wall portion 74R. The housing 74 includes an attachment portion 74A to be attached to the second diaphragm 38. The attachment portion 74A is a component similar to the attachment portion 54A (see FIG. 6) of the third embodiment. The housing 74 has substantially the same configuration as the housing 54 (see FIG. 6) of the third embodiment, except for the points described below. In addition, in FIG. 12, a double-pointed arrow B is a schematic representation of the air permeability of the second suspension 33.

[0096] A port 76 is provided continuously in a portion of the peripheral wall 74S of the housing 74 rearward of the portion where the first suspension 30 is attached and forward of the portion where the second suspension 33 is attached. As one example, the port 76 is formed by a through hole 76H formed in the peripheral wall 74S of the housing 74 and a cylindrical duct 76D formed continuously with the through hole 76H and extending along a direction perpendicular to the front-rear direction.

[0097] The port 76 is configured to guide a part of the frequency band components (more specifically, sounds in a frequency band between low and high frequencies) of the sound radiated from the back surface 28B of the first diaphragm 28 into the cavity S2 on the back surface 28B side of the first diaphragm 28 (in other words, sounds radiated from the back surface 28B of the first diaphragm 28 in the direction opposite to the direction in which the front surface 38A of the second diaphragm 38 faces) to the external space S1 on the front surface 38A side of the second diaphragm 38. The electroacoustic transducer 70 is configured such that the sound pressure of the composite sound near the crossover frequency of the sounds radiated from the first diaphragm 28 and the second diaphragm 38 when the driving unit 16 generates vibration by providing the port 76 becomes equal to or greater than the sound pressure at the crossover frequency of the sounds radiated from only one of the first diaphragm 28 and the second diaphragm 38.

[0098] The configuration of the fifth embodiment described above can also provide substantially the same actions and effects as the third embodiment described above.

[0099] [Sixth embodiment] Next, an electroacoustic transducer including an electroacoustic transducer unit according to a sixth embodiment of the present invention will be described with reference to Fig. 13. Fig. 13 shows a schematic cross-sectional view of an electroacoustic transducer 80 including an electroacoustic transducer unit 82 according to the sixth embodiment. As shown in Fig. 13, the electroacoustic transducer 80 differs from the electroacoustic transducer 60 according to the fourth embodiment in that it includes a port 86 instead of the port 66 (see Fig. 11) in the fourth embodiment. The other configurations are substantially similar to those of the fourth embodiment. Components substantially similar to those of the fourth embodiment, etc., are appropriately designated by the same reference numerals and will not be described.

[0100] The second vibration plate 81 of this embodiment shown in Figure 13 has substantially the same components as the second vibration plate 61 of the fourth embodiment (see Figure 11), but the hole portion 81H formed through the second vibration plate 81 has a slightly different shape from the hole portion 61H formed through the second vibration plate 61 of the fourth embodiment (both see Figure 11), and therefore is given a different symbol.

[0101] The electroacoustic transducer unit 82 of this embodiment includes a housing 84 instead of the housing 64 (see FIG. 11) of the electroacoustic transducer unit 62 of the fourth embodiment. The housing 84 includes a rear wall portion 84R disposed on the rear side and a cylindrical peripheral wall portion 84S erected from the outer periphery of the rear wall portion 84R. The peripheral wall portion 84S is substantially the same as the cylindrical wall portion 64B (see FIG. 11) of the fourth embodiment. The housing 84 is provided with an attachment portion 84A that is attached to the rear surface 81B side of the second diaphragm 81 and to the periphery of the hole portion 81H. The housing 84 has substantially the same configuration as the housing 64 (see FIG. 11) of the fourth embodiment except for the points described below.

[0102] A port 86 is provided in a portion of the peripheral wall 84S of the housing 84 that is rearward of the portion where the first suspension 30 is attached and forward of the portion where the second suspension 33 is attached. As an example, the port 86 is formed by a through hole 86H formed in the peripheral wall 84S of the housing 84 and a cylindrical duct 86D formed in continuity with the through hole 86H. The duct 86D extends from the through hole 86H in a direction perpendicular to the front-rear direction, with a tip end in the extending direction being closed and a front portion on the tip side in the extending direction being an outlet 86E of the port 86.

[0103] The port 86 is configured to guide a part of the frequency band components (more specifically, sounds in a frequency band between low and high frequencies) of the sound radiated from the back surface 28B of the first diaphragm 28 into the cavity S2 on the back surface 28B side of the first diaphragm 28 (in other words, sounds radiated from the back surface 28B of the first diaphragm 28 in the direction opposite to the direction in which the front surface 81A of the second diaphragm 81 faces) to the external space S1 on the front surface 81A side of the second diaphragm 81. The electroacoustic transducer 80 is configured such that the sound pressure of the composite sound near the crossover frequency of the sounds radiated from the first diaphragm 28 and the second diaphragm 81 when the driving unit 16 generates vibration by providing the port 86 becomes equal to or greater than the sound pressure at the crossover frequency of the sounds radiated from only one of the first diaphragm 28 and the second diaphragm 81.

[0104] Moreover, when viewed from the front surface 81A side of the second diaphragm 81, the first diaphragm 28 and the outlet 86E of the port 86 are disposed inside the hole 81H of the second diaphragm 81. Furthermore, the electroacoustic transducer unit 82, in which components including the drive section 16, the first diaphragm 28, the first suspension 30, the second suspension 33 and the port 86 are unitized, is disposed relative to the second diaphragm 81 so as not to protrude on the front surface 81A side thereof.

[0105] The configuration of the sixth embodiment described above can also provide substantially the same actions and effects as the fourth embodiment described above.

[0106] [Seventh embodiment] Next, an electroacoustic transducer including an electroacoustic transducer unit according to a seventh embodiment of the present invention will be described with reference to FIG. 14. FIG. 14 shows a schematic cross-sectional view of an electroacoustic transducer 90 including an electroacoustic transducer unit 92 according to the seventh embodiment. As shown in FIG. 14, the electroacoustic transducer 90 differs from the electroacoustic transducer 70 according to the fifth embodiment in that it includes a second suspension 98 instead of the second suspension 33 (see FIG. 12) of the fifth embodiment, and in that it includes a port 96 instead of the port 76 (see FIG. 12) of the fifth embodiment. The other configurations are substantially similar to those of the fifth embodiment. Components substantially similar to those of the fifth embodiment, etc., are appropriately designated by the same reference numerals and will not be described.

[0107] The second suspension 98 of the electroacoustic transducer unit 92 is substantially similar to the second suspension 33 of the fifth embodiment (see FIG. 12) except that it does not have air permeability. The second suspension 98 is provided with a sealing coating, for example, to block air permeability in the front-rear direction. The housing 94 of the electroacoustic transducer unit 92 has a similar configuration to the housing 74 of the fifth embodiment except that a port 96 is provided instead of the port 76 of the housing 74 of the fifth embodiment (see FIG. 12). Therefore, for the components of the housing 94 that are similar to those of the housing 74 of the fifth embodiment (see FIG. 12), the reference numerals are indicated in the drawing with "1" added to the beginning of the reference numerals of the corresponding components of the housing 74 (specifically, the rear wall portion 74R, the peripheral wall portion 74S, the mounting portion 74A, and the through hole 76H), and the description thereof will be omitted.

[0108] The port 96 is formed by a through hole 176H formed in the peripheral wall portion 174S of the housing 94 and a cylindrical duct 96D formed continuously with the through hole 176H and extending in a direction perpendicular to the front-rear direction. The length of the port 96 is set so as to obtain substantially the same effect as in the fifth embodiment, and is configured similarly to the port 76 in the fifth embodiment, except that the length is set longer than the port 76 in the fifth embodiment. The electroacoustic transducer 90 is configured so that the sound pressure of the composite sound near the crossover frequency of the radiated sounds from the first diaphragm 28 and the second diaphragm 38 when the driving unit 16 generates vibration by providing the port 96 is equal to or greater than the sound pressure at the crossover frequency of the radiated sound from only one of the first diaphragm 28 and the second diaphragm 38.

[0109] Here, a supplementary explanation will be given regarding the configuration of this embodiment. When the second suspension 98 has no air permeability as in this embodiment, the port 96 needs to be provided so as to communicate with the internal space between the first suspension 30 and the second suspension 98. In such a configuration, the volume of the cavity in contact with the port is smaller than when the second suspension 33 (see FIG. 12) has air permeability as in the fifth embodiment. On the other hand, if the cavity volume in contact with the port is V, the port cross-sectional diameter (in the case of a circular shape) is Dp, and the port length is lp, then the air spring stiffness K ∝ Dp 4 / V, port mass M ∝ Dp 2 × lp, and the resonant frequency f0 of the sound from the port is calculated using the following formula 1.

[0110]

number

[0111] For this reason, in a configuration in which the second suspension has no ventilation, the air spring of the cavity in contact with the port becomes harder than in a configuration in which the second suspension has ventilation, and the resonance frequency of the sound from the port is likely to be high. Therefore, in order to set the resonance frequency to a desired frequency, it is necessary to reduce the passage cross-sectional area of ​​the port, or to increase the length of the port, or to reduce the passage cross-sectional area of ​​the port and increase the length of the port, compared to a case in which the second suspension has ventilation. From this viewpoint, in the seventh embodiment, as described above, the port 96 is set to be longer than the port 76 (see FIG. 12) of the fifth embodiment.

[0112] The seventh embodiment described above can achieve substantially the same effects and advantages as the fifth embodiment.

[0113] As a modified example of the seventh embodiment, a port having a smaller passage cross-sectional area than port 76 (see FIG. 12) of the fifth embodiment may be provided, or a port having a smaller passage cross-sectional area and a longer length than port 76 (see FIG. 12) of the fifth embodiment may be provided.

[0114] [Eighth embodiment] Next, an electroacoustic transducer including a unit for electroacoustic transducer according to an eighth embodiment of the present invention will be described with reference to FIG. 15. FIG. 15 shows a schematic cross-sectional view of an electroacoustic transducer 100 including a unit for electroacoustic transducer 102 according to the eighth embodiment. As shown in FIG. 15, the electroacoustic transducer 100 is different from the electroacoustic transducer 80 according to the sixth embodiment in that the electroacoustic transducer 100 includes the second suspension 98 of the seventh embodiment instead of the second suspension 33 (see FIG. 13) of the sixth embodiment, and includes a port 106 instead of the port 86 (see FIG. 13) of the sixth embodiment. The other configurations are substantially similar to those of the sixth embodiment. Components substantially similar to those of the sixth embodiment and the like are appropriately designated by the same reference numerals and will not be described.

[0115] 15 has substantially the same components as the second diaphragm 81 of the sixth embodiment (see FIG. 13), but the hole 101H penetrating the second diaphragm 101 is slightly different in shape from the hole 81H penetrating the second diaphragm 81 of the sixth embodiment (see FIG. 13), and is therefore denoted by a different reference numeral. Reference numeral 101A denotes the front surface of the second diaphragm 101, and reference numeral 101B denotes the back surface of the second diaphragm 101.

[0116] The housing 104 of the electroacoustic transducer unit 102 has the same configuration as the housing 84 of the sixth embodiment, except that a port 106 is provided instead of the port 86 of the housing 84 of the sixth embodiment (see FIG. 13 for both). Therefore, for components of the housing 104 that are the same as those of the housing 84 of the sixth embodiment (see FIG. 13), the reference numerals of the corresponding components of the housing 84 (specifically, the rear wall portion 84R, the peripheral wall portion 84S, the mounting portion 84A, and the through hole 86H) are indicated in the drawing with "1" added to the beginning, and their description will be omitted.

[0117] The port 106 is formed by a through hole 186H formed in the peripheral wall portion 184S of the housing 104 and a duct 106D formed continuously with the through hole 186H. The duct 106D extends from the through hole 186H in a direction perpendicular to the front-rear direction, and the tip end portion in the extending direction is closed, and the front portion on the tip end side in the extending direction is an outlet 106E of the port 106. The length of the port 106 is set so as to obtain substantially the same effect as in the sixth embodiment, and is configured similarly to the port 86 in the sixth embodiment except that the length is set longer than the port 86 in the sixth embodiment (see FIG. 13). The electroacoustic transducer 100 is configured so that the sound pressure of the composite sound near the crossover frequency of the radiated sounds from the first diaphragm 28 and the second diaphragm 101 when the driving unit 16 generates vibration by providing the port 106 is equal to or greater than the sound pressure at the crossover frequency of the radiated sounds from only one of the first diaphragm 28 and the second diaphragm 101.

[0118] The configuration of the eighth embodiment described above can also provide substantially the same actions and effects as the sixth embodiment described above.

[0119] As a modified example of the eighth embodiment, a port having a smaller passage cross-sectional area than port 86 (see FIG. 13) of the sixth embodiment may be provided, or a port having a smaller passage cross-sectional area and a longer length than port 86 (see FIG. 13) of the sixth embodiment may be provided.

[0120] [Ninth embodiment] Next, an electroacoustic transducer including an electroacoustic transducer unit according to a ninth embodiment of the present invention will be described with reference to FIG. 16. FIG. 16 shows a perspective view of an electroacoustic transducer 110 including an electroacoustic transducer unit 112 according to the ninth embodiment, with a part cut away. As shown in FIG. 16, the electroacoustic transducer 110 of the ninth embodiment is different from the electroacoustic transducer 50 of the third embodiment (see FIG. 6) in that the first suspensions 120, 122 and the second suspensions 124, 126 are provided in two (multiple in a broad sense) instead of one each. The other configurations are substantially similar to those of the third embodiment. Components substantially similar to those of the third embodiment are appropriately designated by the same reference numerals and will not be described.

[0121] The first diaphragm 28 is formed in an annular shape when viewed from the front, and has a cone shape with the front surface gradually recessed toward the center. A dome-shaped center cap 27 is joined to the center of the front surface of the first diaphragm 28. A first first suspension 120 made of an elastic material such as rubber is joined to the outer periphery 28D of the first diaphragm 28 around the entire circumference. The first first suspension 120 is called an edge, and is formed in an annular shape when viewed from the front, and is joined to an annular mounting portion 54B on the front end side of the housing 54 around the entire circumference.

[0122] As an example, the housing 54 includes a frame 54X that forms the front and front-rear middle of the housing 54, and a case 54Y that is attached to the rear end of the frame 54X and forms the rear of the housing 54. A shelf-like portion 54Z that extends radially inward of the frame 54X is formed at the rear end of the frame 54X. The outer circumferential surface of a cylindrical inner tube member 55 is fixed to the inner circumferential surface of the front-rear middle of the housing 54 in contact with the entire periphery. Furthermore, the front surface of the shelf-like portion 54Z and the rear end surface of the inner tube member 55 are slightly spaced apart in the front-rear direction.

[0123] On the other hand, a short cylindrical inner peripheral end 28C bent backward is provided at the center of the first diaphragm 28. This inner peripheral end 28C is joined to the outer peripheral portion of the front end side of the voice coil bobbin 18A. Also, an inner peripheral portion of a second first suspension 122 is joined to the inner peripheral end 28C of the first diaphragm 28. The second first suspension 122 is a member that is substantially the same as the spider 34 shown in FIG. 10, although the shape of the second first suspension 122 is slightly different. As shown in FIG. 16, a short cylindrical peripheral wall portion 122A bent backward is formed on the outer peripheral portion side of the second first suspension 122, and a flange portion 122B that protrudes from the rear end of the peripheral wall portion 122A in a brim-like shape is formed. The flange portion 122B of the second first suspension 122 is connected to a portion on the inner peripheral side of the housing 54 via other members (specifically, the first second suspension 124 described later and the inner cylindrical member 55 described above).

[0124] As a result, the first first suspension 120 and the second first suspension 122 are disposed at an interval in the front-rear direction (the vibration direction of the first diaphragm 28 and the voice coil section 18). The first diaphragm 28 is connected to the second diaphragm 38 via the first first suspension 120 and the housing 54, and is also connected to the second diaphragm 38 via multiple members including the second first suspension 122 and the housing 54.

[0125] Also, the inner peripheral portion of the first second suspension 124 is joined over the entire circumference to the front end surface portion of the tube portion 22B of the yoke 22. The first second suspension 124 is formed in an annular shape in a front view, has a communication hole 124H formed therethrough as a communication portion, and is substantially the same member as the second suspension 33 shown in FIG. 7. As shown in FIG. 16, the rear surface of the outer peripheral portion of the first second suspension 124 is joined to the front surface of the inner tube member 55. That is, the outer peripheral portion of the first second suspension 124 is connected to the inner peripheral side portion of the housing 54 via the inner tube member 55. Note that the flange portion 122B of the second first suspension 122 described above is overlapped and joined to the front surface of the outer peripheral portion of the first second suspension 124.

[0126] Further, the inner peripheral portion of the second second suspension 126 is joined over the entire circumference to the outer peripheral portion of the rear surface of the yoke 22. The second second suspension 126 is formed in an annular shape when viewed from the front, has a communication hole 126H formed therethrough as a communication portion, and is made of a material substantially similar to that of the first second suspension 124. The outer peripheral portion of the second second suspension 126 is disposed between the rear surface of the inner cylinder member 55 and the front surface of the shelf-like portion 54Z of the housing 54 and is joined to the housing 54.

[0127] As a result, the first second suspension 124 and the second second suspension 126 are disposed at an interval in the front-rear direction (the vibration direction of the magnetic circuit section 20). The magnetic circuit section 20 is connected to the second diaphragm 38 via the first second suspension 124, the inner cylinder member 55, and the housing 54, and is also connected to the second diaphragm 38 via the second second suspension 126 and the housing 54.

[0128] The configuration of the ninth embodiment described above also makes it possible to achieve compact size while improving the reduction in sound pressure in the frequency band between low and high frequencies through an action substantially similar to that of the third embodiment described above, thereby enabling the reproduction of high quality sound.

[0129] In the ninth embodiment, the first first suspension 120 and the second first suspension 122 are provided at an interval in the vibration direction of the first diaphragm 28 and the voice coil section 18, so that the first diaphragm 28 and the voice coil section 18 can vibrate in the front-rear direction basically without rolling. The first second suspension 124 and the second second suspension 126 are provided at an interval in the vibration direction of the magnetic circuit section 20, so that the magnetic circuit section 20 can vibrate in the front-rear direction basically without rolling. In this way, the rolling of the first diaphragm 28, the voice coil section 18, and the magnetic circuit section 20 is suppressed, so that the part of the voice coil section 18 arranged in the magnetic gap 20A of the magnetic circuit section 20 can be prevented or effectively suppressed from coming into contact with the magnetic circuit section 20.

[0130] Incidentally, there may be cases where it is not possible to provide a plurality of first suspensions and a plurality of second suspensions due to space restrictions, such as when the length of the electroacoustic transducer unit in the front-rear direction must be shortened. In such cases, it is sufficient to assume rolling of the voice coil section (18) and the magnetic circuit section (20) and set the width of the magnetic gap (20A) of the magnetic circuit section (20) large so that the portion of the voice coil section (18) located in the magnetic gap (20A) of the magnetic circuit section (20) does not come into contact with the magnetic circuit section (20) even when the assumed rolling occurs. However, this is disadvantageous in terms of driving force.

[0131] [Tenth embodiment] Next, an electroacoustic transducer according to a tenth embodiment of the present invention will be described with reference to Fig. 17. Fig. 17 shows a perspective view of an electroacoustic transducer 130 according to the tenth embodiment in a partially cutaway state. The electroacoustic transducer 130 according to the tenth embodiment has components substantially similar to the driving section 16 and the first diaphragm 28 (both see Fig. 6) in the electroacoustic transducer 50 of the third embodiment. In the tenth embodiment, components substantially similar to those of the electroacoustic transducer 50 of the third embodiment (see Fig. 6) are denoted by the same reference numerals and will not be described.

[0132] As shown in FIG. 17, a first suspension 132 is disposed on the rear surface 28B side of the first diaphragm 28. The first suspension 132 is formed in a cylindrical and bellows-like shape, and is disposed so that the cylinder axis direction is the front-rear direction. One open end of the first suspension 132 in the cylinder axis direction is joined to the outer periphery of the rear surface 28B of the first diaphragm 28. The other open end of the first suspension 132 in the cylinder axis direction is joined to the front surface 138A of the second diaphragm 138. That is, the first diaphragm 28 is connected to the second diaphragm 138 via the first suspension 132.

[0133] The driving unit 16 is disposed inside the first suspension 132. The second suspension 134 is disposed behind the driving unit 16. The second suspension 134 is formed in a cylindrical and bellows-like shape, and is set to have a smaller diameter and a shorter length in the axial direction than the first suspension 132. The second suspension 134 is disposed so that the axial direction of the second suspension 134 is the front-rear direction, and the central axis (not shown) of the second suspension 134 is aligned with that of the first suspension 132. An open end on one side in the axial direction of the second suspension 134 is joined to the outer periphery of the rear surface 22R of the yoke 22. An open end on the other side in the axial direction of the second suspension 134 is joined to the front surface 138A of the second diaphragm 138. That is, the magnetic circuit unit 20 is connected to the second diaphragm 138 via the second suspension 134.

[0134] A communication hole 134H for communicating an inner space with an outer space is formed through the second suspension 134. The communication hole 134H communicates two spaces S31, S32 partitioned by the second suspension 134 in the cavity S3 on the rear surface 28B side of the first diaphragm 28. A plurality of communication holes 134H are formed so as to be aligned in the circumferential direction of the second suspension 134.

[0135] The second diaphragm 138 has a larger area than the first diaphragm 28, and is capable of emitting sound to an external space S1 on the front surface 138A side when the driving unit 16 generates vibration. The second diaphragm 138 has a first hole 138C formed therethrough at a portion inside the second suspension 134 in a front view, and a second hole 138D formed therethrough at a portion outside the first suspension 132 in a front view. One end of a port 136 is connected to the first hole 138C, and the other end of the port 136 is connected to the second hole 138D. The port 136 is bent into an approximately C-shape.

[0136] The port 136 is configured to guide a part of the frequency band components (more specifically, sounds in a frequency band between low and high frequencies) of the sound radiated from the back surface 28B of the first diaphragm 28 into the cavity S3 on the back surface 28B side of the first diaphragm 28 (in other words, sounds radiated from the back surface 28B of the first diaphragm 28 in the direction opposite to the direction in which the front surface 138A of the second diaphragm 138 faces) to the external space S1 on the front surface 138A side of the second diaphragm 138. The electroacoustic transducer 130 is configured so that the sound pressure of the composite sound near the crossover frequency of the sounds radiated from the first diaphragm 28 and the second diaphragm 138 when the driving unit 16 generates vibration by providing the port 136 becomes equal to or greater than the sound pressure at the crossover frequency of the sounds radiated from only one of the first diaphragm 28 and the second diaphragm 138.

[0137] The configuration of the tenth embodiment described above also makes it possible to achieve compact size while improving the reduction in sound pressure in the frequency band between low and high frequencies through an action generally similar to that of the third embodiment described above, thereby enabling the reproduction of high-quality sound.

[0138] As a modification of the tenth embodiment, instead of the first hole (138C) in the second diaphragm (138), a first hole is formed penetrating the second diaphragm (138) at a portion outside the second suspension (134) and inside the first suspension (132) in a front view, and the first hole and the second hole (138D) are connected by a port. As a further modification of such a modification, the second suspension (134) may not be provided with a communication hole (134H). In these modifications, the dimensions of the port are set so as to obtain substantially the same effects as those in the tenth embodiment.

[0139] [Eleventh embodiment] Next, an electroacoustic transducer according to an eleventh embodiment of the present invention will be described with reference to FIG. 18. FIG. 18 shows an exploded perspective view of an electroacoustic transducer 140 according to the eleventh embodiment, which is divided into front and rear halves and partially cut away. As shown in FIG. 18, the electroacoustic transducer 140 of the eleventh embodiment is different from the electroacoustic transducer 110 of the ninth embodiment (see FIG. 16) in that a driver unit 142 not including a port 156 is attached to a case 154Y in a state in which the case 154Y provided with a port 156 is attached to the second diaphragm 38 in advance. The other configurations are substantially similar to those of the ninth embodiment, except for two points: the port 156 is provided instead of the port 56 (see FIG. 16) of the ninth embodiment, and the rear wall portion 154R is attached to the second diaphragm 38 without the attachment portion 54A (see FIG. 16) of the ninth embodiment. Components substantially similar to those of the ninth embodiment are appropriately designated by the same reference numerals and will not be described.

[0140] The driver unit 142 has a substantially similar configuration to that of the electroacoustic transducer unit 112 of the ninth embodiment shown in FIG. 16 with the case 54Y removed. The frame 154X of the driver unit 142 shown in FIG. 18 has a substantially similar configuration to the frame 54X of the ninth embodiment (see FIG. 16), but is given a different reference number from the frame 54X of the ninth embodiment for convenience. The annular mounting portion 154B in the frame 154X is a similar component to the annular mounting portion 54B of the ninth embodiment (see FIG. 16), and the shelf-like portion 154Z ​​in the frame 154X is a similar component to the shelf-like portion 54Z of the ninth embodiment (see FIG. 16). The cylindrical peripheral wall portion 154C in the frame 154X is a similar component to the portion of the peripheral wall portion 54S of the housing 54 of the ninth embodiment shown in FIG. 16 that is constituted by the frame 54X. As shown in FIG. 18, a rear end surface 154M of the peripheral wall portion 154C is attached to a front end surface 154F of the case 154Y.

[0141] The case 154Y includes a rear wall 154R disposed on the rear side and a cylindrical peripheral wall 154D erected from the outer periphery of the rear wall 154R. The peripheral wall 154D is substantially the same as the portion of the peripheral wall 54S of the housing 54 of the ninth embodiment shown in FIG. 16 that is constituted by the case 54Y. In other words, the peripheral wall 154D of the case 154Y shown in FIG. 18 constitutes the peripheral wall 154S extending in the front-rear direction together with the peripheral wall 154C of the frame 154X. Then, a cavity S2 is formed on the rear surface 28B side of the first diaphragm 28 by the container 154 constituted by the frame 154X and the case 154Y. Note that, for convenience, in FIG. 18, the frame 154X side is given the reference symbol 154 indicating the container, and the inner side of the peripheral wall 154D of the case 154Y is given the reference symbol S2 indicating the cavity.

[0142] A port 156 is provided continuously with the peripheral wall portion 154D of the case 154Y. As an example, the port 156 is formed by a cylindrical duct 156D extending from the peripheral wall portion 154D to the inside of the peripheral wall portion 154D in a direction perpendicular to the front-rear direction, and a through hole (not shown) formed in the peripheral wall portion 154D so as to be continuous with the inner space of the duct 156D.

[0143] The port 156 is configured to guide a part of the frequency band components of the sound radiated from the back surface 28B of the first diaphragm 28 into the cavity S2 on the back surface 28B side of the first diaphragm 28 (in other words, the sound radiated from the back surface 28B of the first diaphragm 28 in the direction opposite to the direction in which the front surface 38A of the second diaphragm 38 faces) to the external space S1 on the front surface 38A side of the second diaphragm 38. The electroacoustic transducer 140 is configured such that, by providing the port 156, the sound pressure of the composite sound near the crossover frequency of the radiated sounds from the first diaphragm 28 and the second diaphragm 38 when the driving unit 16 generates vibration becomes equal to or greater than the sound pressure at the crossover frequency of the radiated sound from only one of the first diaphragm 28 and the second diaphragm 38.

[0144] The eleventh embodiment described above can also provide substantially the same functions and effects as the ninth embodiment.

[0145] [Supplementary explanation of the embodiment] In the first to eleventh embodiments shown in Figures 1 to 18, the magnetic circuit section 20 is an internal magnet type magnetic circuit section, and such a configuration is preferable from the viewpoint of miniaturizing the drive section 16, but a configuration in which the magnetic circuit section is an external magnet type magnetic circuit section may also be adopted.

[0146] As a modified example of the first to eleventh embodiments, a configuration may be adopted in which the magnetic circuit portion (20) as the acting portion has a smaller mass than the voice coil portion (18) as the reacting portion, the first diaphragm (28) is connected to the magnetic circuit portion (20), and the voice coil portion (18) is connected to the second diaphragm (38, 41, 61, 81, 101, 138) via at least the second suspension (32, 33, 98, 124, 126, 134).

[0147] In the above first to eleventh embodiments, the driving unit 16 has a magnetic circuit unit 20 as an acting unit and a voice coil unit 18 as a reacting unit, and the driving unit 16 utilizes the Lorentz force. However, as a modification of the above embodiments, the driving unit may have a configuration other than the Lorentz force, such as a known linear actuator that is capable of generating vibration by having two mass bodies, an acting unit and a reacting unit. Note that a linear actuator having two mass bodies, an acting unit and a reacting unit, is known, for example, in JP-A-2003-235232, and therefore detailed description thereof will be omitted.

[0148] Incidentally, with regard to the driving unit other than that disclosed in the above-mentioned JP-A-2003-235232, a speaker having a driving unit capable of generating vibration by having two mass bodies, an action part and a reaction part, without using the Lorentz force is publicly known, for example, in JP-A-3749662, and the driving unit disclosed in the same publication can also be applied to the driving unit of the present invention. In addition, although it is a configuration using the Lorentz force, a driving unit having a configuration different from the driving unit 16 of the above-mentioned first to tenth embodiments is publicly known, for example, in JP-A-2936009 (an example of a moving magnet type), JP-A-61-45745 (an example in which a magnetic circuit part is divided into an action part and a reaction part), and JP-A-10-285689 (an example in which a secondary current is induced in a secondary coil when a current is supplied to a driving coil, generating a driving force), and the driving units disclosed in these publications can also be applied to the driving unit of the present invention.

[0149] As a modification of the first, third, fifth, seventh and ninth embodiments, for example, a configuration may be adopted in which the housing of the electroacoustic transducer unit does not have any of the components corresponding to the rear wall portions 14R, 54R, 74R, 174R and the flange-shaped mounting portions 14A, 54A, 74A, 174A shown in Figures 1, 6, 12, 14 and 16, and the portions corresponding to the rear ends of the peripheral walls 14S, 54S, 74S, 174S serve as the mounting portions for the second diaphragm 38. In such a modification, further miniaturization can be achieved.

[0150] In addition, it is essential that the joint between the housing and the second diaphragm of the electroacoustic transducer unit has a joint strength sufficient to prevent the housing from coming off and a joint area sufficient to transmit vibration from the housing to the second diaphragm. The joint area sufficient to transmit vibration from the housing to the second diaphragm varies depending on the rigidity of the second diaphragm. In addition, in an electroacoustic transducer including an electroacoustic transducer unit, a cavity and a port communicating with the cavity are formed in a joint state between the housing and the second diaphragm, and the shape of the housing is based on this premise, but the shape of the part of the housing that is overlapped and joined to the second diaphragm can take various shapes. To provide a supplementary explanation with an example, the part of the housing that is overlapped and joined to the second diaphragm may be, for example, an arc-shaped part that is intermittently arranged along the outer periphery of the cavity when viewed in the thickness direction of the second diaphragm.

[0151] As a modification of the first to eleventh embodiments, the first diaphragm and the first suspension (an edge as an example) may be integrally connected.

[0152] The first to eleventh embodiments and the multiple modifications described above can be implemented in appropriate combinations.

[0153] While one example of the present invention has been described above, the present invention is not limited to the above, and it goes without saying that the present invention can be implemented in various modified forms without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0154] 10,40,50,60,70,80,90,100,110,130,140 Electroacoustic transducer 12,42,52,62,72,82,92,102,112 Electroacoustic transducer units 14,44,54,64,74,84,94,104 Case 14A, 44A, 54A, 64A, 74A, 84A, 174A, 184A mounting part 16 Drive unit 18 Voice coil section (reaction section) 20 Magnetic circuit section (action section) 28 First diaphragm 28A Front of the first diaphragm 28B Back of first diaphragm 30,120,122,132 First Suspension 32, 33, 98, 124, 126, 134 Second Suspension 33H, 124H, 126H, 134H Communication hole (communication part) 36,46,56,66,76,86,96,106,136,156 ports 38,41,61,81,101,138 Second diaphragm 38A, 41A, 61A, 81A, 101A, 138A Front of the second diaphragm 61H,81H,101H Hole S1 External space S2, S3 cavity

Claims

1. a drive unit configured to generate vibration by causing an action unit to generate an action force on a reaction unit in response to an electrical input signal and for the reaction unit to apply a reaction force to the action unit; a first diaphragm connected to one of the action portion and the reaction portion, the one having a smaller mass; a second diaphragm having an area larger than that of the first diaphragm, to which the first diaphragm is connected via at least a first suspension and to which one of the action part and the reaction part, which has a larger mass, is connected via at least a second suspension, and which is capable of emitting sound to an external space on the front side when the drive part generates vibration; having An electro-acoustic transducer is configured such that, by providing a port that directs at least some of the frequency band components of the sound radiated from the first diaphragm in a direction opposite to the direction in which the front of the second diaphragm faces, to the external space on the front side of the second diaphragm, the sound pressure of the combined sound near the crossover frequency of the sounds radiated from the first diaphragm and the second diaphragm when the driving unit generates vibration is greater than or equal to the sound pressure at the crossover frequency of the sound radiated from only one of the first diaphragm and the second diaphragm.

2. The front direction of the first diaphragm is aligned with the front direction of the second diaphragm so that sound can be emitted from the front of the first diaphragm to an external space on the front side of the second diaphragm, 2. The electroacoustic transducer of claim 1, wherein the port is configured to guide components of a certain frequency band of sound radiated from the rear surface of the first diaphragm into the cavity on the rear surface side of the first diaphragm to the external space on the front surface side of the second diaphragm.

3. The front direction of the first diaphragm is set in a direction opposite to the front direction of the second diaphragm, and sound from the back surface of the first diaphragm is not emitted to an external space on the front side of the second diaphragm, 2. The electro-acoustic transducer of claim 1, wherein the port is configured to guide at least a portion of the frequency band components of sound radiated from the front surface of the first diaphragm in a direction opposite to the direction in which the front surface of the second diaphragm faces, to an external space on the front side of the second diaphragm.

4. 3. The electroacoustic transducer according to claim 2, further comprising a communication portion formed in the cavity on the rear side of the first diaphragm to communicate with two spaces partitioned by the second suspension.

5. A hole is formed through the second diaphragm, 5. The electroacoustic transducer of claim 2, wherein when viewed from the front side of the second diaphragm, the first diaphragm and the outlet of the port are positioned inside the hole portion, and further wherein a component including the drive unit, the first diaphragm, the first suspension, the second suspension and the port is unitized and positioned so as not to protrude toward the front side of the second diaphragm.

6. A housing provided with a mounting portion; a drive unit that is accommodated in the housing and is configured to generate an acting force on a reaction unit by an acting unit in response to an electrical input signal and to cause the reaction unit to act on the acting unit with a reaction force, thereby generating vibration; a first diaphragm provided inside the housing and connected to one of the action portion and the reaction portion, which has a smaller mass; a first suspension provided inside the housing and connecting the first diaphragm and the housing; a second suspension provided inside the housing and connecting one of the action part and the reaction part, which has a larger mass, to the housing; having An electroacoustic transducer unit used in an electroacoustic transducer in which, when the mounting portion of the housing is attached to a second diaphragm having an area larger than that of the first diaphragm and the drive portion generates vibrations, the second diaphragm can emit sound into an external space on a front side thereof, A unit for an electro-acoustic transducer is provided with a port capable of directing at least a portion of the frequency band components of the sound radiated from the first diaphragm in a direction opposite to the direction in which the front of the second diaphragm faces when the driving unit generates vibrations in the attached state, to the external space on the front side of the second diaphragm, and the provision of the port is configured so that the sound pressure of the combined sound near the crossover frequency of the sounds radiated from the first diaphragm and the second diaphragm when the driving unit generates vibrations in the attached state is greater than or equal to the sound pressure at the crossover frequency of the sound radiated from only one of the first diaphragm and the second diaphragm.

Images