Loudspeaker

Abstract

Provided is a speaker capable of effectively releasing heat generated by a voice coil to an external space. The magnetic circuit part (10) forms a magnetic gap (G) between a rear inner yoke (12c) and a rear outer yoke (13) which are formed at the rear part of the center yoke (12), and the voice coil (25) is located in the magnetic gap (G) located at the rear of the magnetic circuit part (10). The magnetic gap (G) is open to an external space rearward of the magnetic circuit part (10), and the voice coil (25) is at least at a front-rear neutral position, and a part of the voice coil (25) protrudes to the external space. Therefore, the heat of the voice coil (25) can be released to the rear external space.

Description

Technical Field

[0001] The present invention relates to a loudspeaker capable of effectively dissipating heat emitted from a voice coil vibrating within a magnetic gap in the magnetic circuit section. Background Technology

[0002] The loudspeaker has a voice coil wound around a tube that vibrates together with the diaphragm, located in the magnetic gap of the magnetic circuit. The diaphragm is driven by an electromagnetic force generated by a driving current flowing through the voice coil and a magnetic field passing through it. However, the voice coil heats up due to Joule heating during vibration. The voice coil is constructed by winding wire in multiple turns around the tube, resulting in a relatively large mass, which increases the load on the vibrating part containing the diaphragm. Reducing the cross-sectional area of ​​the wire forming the voice coil can reduce the mass, but using thinner wires increases Joule heating, and the wires sometimes melt during loudspeaker operation. Therefore, the magnetic circuit needs a structure that allows the heat generated by the voice coil to dissipate to the outside.

[0003] Patent Document 1 describes a loudspeaker in which multiple through holes are radially formed in the magnet constituting the magnetic circuit, penetrating both the outer and inner circumferences, allowing external air to easily circulate within the semi-enclosed magnetic circuit. Patent Document 2 describes a loudspeaker in which a through hole is formed in the central pillar of the magnetic circuit, and a groove communicating with the through hole is formed on the bottom surface of a base plate integral with the central pillar. Even when the bottom surface of the magnetic circuit is pressed against the inner wall of the housing, air present in the space surrounded by the tube can be released to the outside through the through hole and the groove. Patent Document 3 describes a loudspeaker in which multiple slits are radially arranged on the outer periphery of the central pillar, communicating with the upper and lower surfaces, and a vent is formed on the bottom surface of the bowl-shaped magnetic yoke. The slits and vent improve ventilation and prevent excessive temperature rise.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 8-9494 Patent Document 2: Japanese Patent Application Publication No. 2002-262387 Patent Document 3: Japanese Utility Model Application Publication No. 5-9099 Summary of the Invention

[0005] The problem that the invention aims to solve The loudspeaker described in Patent Document 1 requires the use of a special magnet with multiple through holes machined into a radial pattern, which is impractical. Furthermore, opening holes inside the magnet results in reduced volume and decreased magnetic force. In the loudspeakers described in Patent Documents 2 and 3, the magnetic gap where the voice coil is located is at the front of the magnetic circuit. Therefore, heat generated from the voice coil tends to remain trapped inside the magnetic circuit, making it difficult to efficiently dissipate heat to the outside through vents at the bottom of the magnetic circuit.

[0006] The present invention was made to solve the above-mentioned prior art problems, and its purpose is to provide a loudspeaker that can efficiently release the heat from the voice coil inside the magnetic gap to the external space by opening the magnetic gap to the external space.

[0007] Methods for solving problems The loudspeaker of the present invention comprises: a support portion including a frame and a magnetic circuit portion fixed to the rear of the frame; a diaphragm plate flexibly supported on the frame; and a tube and a voice coil, wherein the tube vibrates together with the diaphragm plate, and the voice coil is disposed in the tube. The loudspeaker is characterized in that the magnetic circuit section has a driving magnet, and a magnetic gap is formed between a rear inner magnetic yoke and a rear outer magnetic yoke located behind the driving magnet, with the voice coil located inside the magnetic gap. The magnetic gap opens into the space behind the magnetic circuit section.

[0008] The loudspeaker of the present invention can be configured such that the magnetic circuit portion has a magnetic gap formed between a front inner magnetic yoke and a front outer magnetic yoke located in front of the driving magnet. The tube is provided with a voice coil inside the magnetic gap located between the front inner yoke and the front outer yoke, and a voice coil inside the magnetic gap located between the rear inner yoke and the rear outer yoke.

[0009] Preferably, in the loudspeaker of the present invention, at least when the tube is in a neutral position in the front-to-back vibration direction, a portion of the voice coil protrudes from the rear surface of the magnetic circuit portion toward the rear space.

[0010] In the speaker of the present invention, an actuating hole is formed in the support portion between the diaphragm and the magnetic circuit portion, extending in the front-to-back direction and communicating with the magnetic gap. A portion of the tube vibrates back and forth inside the actuating hole.

[0011] For example, the actuation hole is formed on the magnetic yoke constituting the magnetic circuit section.

[0012] The loudspeaker of the present invention can be configured such that a cut-out portion open at its front end is formed in the tube and a continuous portion located between adjacent cut-out portions. The multiple continuous parts vibrate back and forth inside the multiple actuating holes.

[0013] Preferably, the loudspeaker of the present invention has a reinforcing member that connects the plurality of continuous portions at a position further forward than the actuation hole.

[0014] Alternatively, the reinforcing component may be a cap fitted into the front end of the tube.

[0015] Invention Effects In the loudspeaker of the present invention, a magnetic gap is formed between the rear inner magnetic yoke and the rear outer magnetic yoke located behind the driving magnet in the magnetic circuit section. The magnetic gap opens into the rear space. Preferably, at least when the tube is in a neutral position in the front-to-back vibration direction, a portion of the voice coil protrudes from the rear surface of the magnetic circuit section toward the rear space. Therefore, the heat emitted from the voice coil can be effectively released to the rear space, and the temperature of the voice coil and its surroundings can be easily prevented from becoming too high. Attached Figure Description

[0016] Figure 1 This is a diagram showing a loudspeaker according to the first embodiment of the present invention, and is a perspective view including a longitudinal section. Figure 2 This indicates that it is set in Figure 1 The image shows a partial exploded perspective view of the loudspeaker's tube, voice coil, and magnetic circuit. Figure 3 Represented in a plane Figure 1 and Figure 2 The diagram of the magnetic circuit shown is cut along line III-III. Figure 1 The cross-sectional view of the loudspeaker shown is as follows. Figure 4 This is a partial perspective view showing a modified example of the present invention with a reinforcing member provided with a reinforcing tube. Figure 5 This is a longitudinal cross-sectional view showing the loudspeaker according to the second embodiment of the present invention. Figure 6 It means formed in Figure 5 The diagram shown is of the actuation hole on the magnetic circuit section of the loudspeaker, cut along line VI-VI. Figure 4 The image shows a partial cross-sectional view of the loudspeaker. Figure 7 The graph shows simulation results used to illustrate the effects of the present invention. (A) represents an embodiment model of the present invention, and (B) represents a comparative example model. Figure 8 It means Figure 7 Line graphs showing the variation of the average temperature around the voice coil in the illustrated embodiment model and comparative example model.

[0017] Symbol Explanation 1. 101 speakers 2 frames 3 Vibrating Plate 10Magnetic circuit part 11 Fixed magnets 12c rear inner magnetic yoke 13 Rear Outer Magnetic Yoke 14 actuation holes 20mm bobbin 21 Cylindrical section 22 Incision site 23 consecutive parts 25 voice coil 26 reinforced components 27 covers 110 Magnetic Circuit Department 112 rear outer magnetic yoke 113 Front outer magnetic yoke 114a rear inner magnetic yoke 114b Front outer magnetic yoke 120mm bobbin 121 Cylindrical section 122 Incision 123 Continuous Section 125 rear voice coil 126 Front Voice Coil G magnetic gap G1 rear magnetic gap G2 front magnetic gap O Central axis Detailed Implementation

[0018] In the embodiments of the present invention, the Y1-Y2 direction of the speaker 1 is a front-to-back direction, with Y1 being the front and Y2 being the rear. The sound-emitting direction of the speaker 1 varies depending on the usage; sometimes the Y1 direction is used as the sound-emitting direction, and sometimes the Y2 direction is used. Figure 1 The diagram shows the central axis O extending along the front-to-back direction (Y1-Y2 direction). The main part of the loudspeaker 1 has a roughly rotationally symmetrical structure centered on the central axis O.

[0019] Figure 1 The speaker 1 shown has a frame 2. The frame 2 is made of a non-magnetic or magnetic material and is a cone shape that gradually increases in diameter towards the front (Y1 direction). The frame 2 has a rear fixing part 2a at the rear (Y2 direction), and an opening 2b is formed in the rear fixing part 2a.

[0020] A magnetic circuit section 10 is fixed to the rear fixing part 2a of the frame 2. The magnetic circuit section 10 is a so-called external magnetic type, having a ring-shaped drive magnet 11 centered on the central axis O. A central magnetic yoke 12 is provided in the magnetic circuit section 10. The central magnetic yoke 12 integrally forms a central post 12a located inside the drive magnet 11 and a front magnetic yoke 12b extending around the front of the central post 12a. The portion of the central magnetic yoke 12 that is rearward of the central post 12a functions as a rear inner magnetic yoke 12c. The drive magnet 11 is fixed to the rear surface of the front magnetic yoke 12b, and a ring-shaped rear outer magnetic yoke 13 is fixed to the rear surface of the drive magnet 11. The central magnetic yoke 12 and the rear outer magnetic yoke 13 are formed of a magnetic material, i.e., a magnetic metal material. The rear outer magnetic yoke 13 is located behind the central magnetic yoke 12, i.e., the outer periphery of the rear inner magnetic yoke 12c. A magnetic gap G is formed along a circle centered on the central axis O between the outer peripheral surface of the rear inner magnetic yoke 12c and the inner peripheral surface of the rear outer magnetic yoke 13.

[0021] The magnetic circuit section 10 is disposed on the rear surface of the rear fixing section 2a of the frame 2, and the rear fixing section 2a and the front magnetic yoke 12b of the magnetic circuit section 10 are fixed by a plurality of fixing screws 9. The frame 2 and the magnetic circuit section 10 constitute a "support section".

[0022] like Figure 1 and Figure 2 As shown, on the central yoke 12, multiple actuation holes 14 are formed at the boundary between the central post 12a and the front yoke 12b. At least a portion of the actuation holes 14 are formed through the entire structure. Figure 3 As shown, when viewing the magnetic circuit section 10 from above, a portion of the central pillar 12a, a portion of the rear outer magnetic yoke 13, and a portion of the magnetic gap G are visible inside each actuation hole 14. Figure 1 As shown, the internal space of the actuation hole 14 is connected to the magnetic gap G through the gap 15 between the outer peripheral surface of the central column 12a and the inner peripheral surface of the driving magnet 11.

[0023] A cylindrical tube 20 is provided at the center of the loudspeaker 1. The cylindrical tube 20 is cylindrical in shape with the central axis O as its center. Figure 2 As shown, the bobbin 20 has: a cylindrical portion 21 located at the rear (Y2 direction); a plurality of slits 22 continuously formed from the front of the cylindrical portion 21 to the front end of the bobbin 20; and a plurality of continuous portions 23 remaining between adjacent slits 22. The plurality of slits 22 and the plurality of continuous portions 23 are arranged alternately in the circumferential direction of the cylinder. A voice coil 25 is provided at the rear end of the bobbin 20. The voice coil 25 is formed by repeatedly winding a wire around the outer circumference of the cylindrical portion 21 of the bobbin 20.

[0024] like Figure 2As shown, the tube 20 is assembled to the magnetic circuit section 10 from the rear (Y2 direction) towards the front (Y1 direction). During assembly, the continuous portion 23 of the tube 20 is inserted from the rear towards the interior of the magnetic gap G in the magnetic circuit section 10, and the continuous portion 23 is inserted into the actuation hole 14 through the gap 15 between the outer peripheral surface of the central post 12a and the inner peripheral surface of the drive magnet 11. Figure 1 As shown, when the tube 20 is assembled into the magnetic circuit section 10, the front parts of the multiple continuous sections 23 protrude forward from each actuation hole 14. The cylindrical section 21 of the tube 20 is located inside the gap 15 and inside the magnetic gap G, and the voice coil 25 is located inside the magnetic gap G. The magnetic circuit section 10 and the voice coil 25 constitute a "magnetic drive section".

[0025] like Figure 1 As shown, a vibrating plate 3 is provided on the inner side of the front portion of the frame 2. The vibrating plate 3 is a two-piece structure assembled with a rear plate portion 4 and a front plate portion 5 spaced apart, each being conical in shape. An elastically deformable edge member 5a is integrally formed on the outer periphery of the front plate portion 5 of the vibrating plate 3, and the edge member 5a is joined to the front periphery portion 2c of the frame 2. When the magnetic circuit portion 10 is fixed to the rear surface of the rear fixing portion 2a of the frame 2 using the fixing screw 9, the actuation hole 14 of the magnetic circuit portion 10 appears inside the opening 2b of the rear fixing portion 2a. The continuous portion 23 of the tube 20 passes through the actuation hole 14, and its front end 23a is bonded to the inner peripheral surface of the center hole 4a formed in the rear plate portion 4 of the vibrating plate 3. An inner peripheral fixing portion 2d is formed on the inner surface of the middle part of the frame 2, and the outer periphery of the damping member 6, which has a corrugated cross-section and is capable of elastic deformation, is fixed to the inner peripheral fixing portion 2d of the frame 2 by adhesive. The inner periphery 6a of the damping component 6 is bonded and fixed to the outer periphery of the continuous portion 23 of the tube 20.

[0026] The diaphragm 3, the tube 20, and the voice coil 25 are supported by the elastic deformation of the edge member 5a and the damping member 6, allowing them to vibrate freely in the front-rear direction (Y1-Y2 direction) relative to the frame 2 (relative to the support). The diaphragm 3, the tube 20, and the voice coil 25 constitute a "vibrating part" that vibrates in the front-rear direction (Y1-Y2 direction) relative to the "support" containing the frame 2.

[0027] Next, the sound-producing action of speaker 1 will be explained.

[0028] During the sound production process, a driving current is supplied to the voice coil 25 based on the audio signal output from the audio amplifier. In the magnetic circuit section 10, the driving magnetic flux F emitted from the driving magnet 11 passes through the rear inner magnetic yoke 12c, which is part of the central magnetic yoke 12, traverses the magnetic gap G, and reaches the rear outer magnetic yoke 13. Through the electromagnetic force excited by the driving magnetic flux F traversing the voice coil 25 in the magnetic gap G and the driving current flowing in the voice coil 25, the vibrating part including the tube 20, the voice coil 25, and the resonating plate 3 vibrates in the front-to-back direction (Y1-Y2 direction), generating a sound pressure corresponding to the frequency of the driving current, and emitting sound in the front or rear.

[0029] When the loudspeaker 1 operates, Joule heating is generated due to the amount of driving current flowing in the voice coil 25 and the resistance of the voice coil 25. The temperature of the voice coil 25 rises, and the temperature inside the narrow magnetic gap G also rises. However, the magnetic gap G is open to the external space behind the magnetic circuit section 10, and the internal space of the magnetic gap G is directly connected to the external space behind it. Therefore, heat inside the magnetic gap G can easily escape to the external space behind it. Furthermore, when the tube 20 is in a neutral position in at least the front-to-back vibration direction, the rear end 25a of the voice coil 25 protrudes from the bottom of the magnetic circuit section 10 to the external space behind it. Preferably, the rear end 25a protrudes from the bottom of the magnetic circuit section 10 to the external space behind it throughout the entire range of movement of the tube 20. Therefore, the heat of the voice coil 25 can be directly radiated to the external space, the temperature rise around the magnetic gap G can be suppressed, and phenomena such as the wires constituting the voice coil 25 melting due to high temperature can be prevented.

[0030] Figure 7 The models used in the simulation to verify the effects of the present invention are shown. (A) is an embodiment model of the present invention, in which the magnetic gap G directly opens the external space behind the magnetic circuit section 10, and the voice coil 25 protrudes behind the magnetic circuit section at least in the neutral position. (B) is a comparative example model, which is the same as the known technology described in Patent Document 2, with a vent 31 extending through the center column. In the settings of each model, the voice coil is made of copper, the tube is made of polypropylene (PP), and the yoke containing the center column is made of iron. In the simulation, the voice coil is moved ±10 mm from the neutral position in the forward and backward direction at a frequency of 60 Hz, and the power supplied to the voice coil, which is the heating element, is set to 150 W. Figure 8 The vertical axis represents the average temperature of the heating element, and the horizontal axis represents the driving time. Figure 8 In the figures, (i) represents the temperature change of the embodiment model, and (ii) represents the temperature change of the comparative example model. In this simulation, the saturation temperature of the heating element centered on the voice coil in the embodiment model was reduced by approximately 20% compared to the comparative example model.

[0031] The loudspeaker 1 of the present invention preferably has a damping member 6 formed of a material that substantially prevents air from passing through. The damping member 6 is generally formed of a fibrous structure, but by impregnating the fibrous structure with resin, it can be made into a structure that prevents air from passing through. Since the internal space of the tube 20 is covered by the upper front plate portion 5, if the damping member 6 is a structure that substantially prevents air from passing through, when the damping member 6 vibrates up and down together with the diaphragm 3, the air in the substantially enclosed space, i.e., between the damping member 6 and the magnetic circuit portion 10, flows into the magnetic gap G through the actuation hole 14 and the gap 15, easily causing the air in the magnetic gap G to be discharged into the space further rear of the magnetic circuit portion 10. Furthermore, "substantially prevents air from passing through" means that when the damping member 6 vibrates back and forth at the frequency and amplitude used by the loudspeaker 1, air does not pass through the damping member 6 to the extent that the air pressure changes caused by the vibration.

[0032] Figure 4 This illustrates a variation of the invention. In Figure 4 In the illustrated configuration, after the tube 20 is assembled to the magnetic circuit section 10 from rear to front, multiple continuous portions 23 protruding forward from the actuation hole 14 of the magnetic circuit section 10 are interconnected by reinforcing members 26, thereby reinforcing the tube 20. The reinforcing members 26 are formed in a ring shape from a lightweight resin sheet identical to that of the tube 20 and are bonded to the outer or inner circumferential surfaces of all the continuous portions 23. By providing the reinforcing members 26, the tube 20 with the slit portion 22 can be strengthened, and deformation of the tube 20 due to vibration can be suppressed.

[0033] like Figure 4 As shown, the cover 27 can be used as a reinforcing member. The cover 27 has a top plate 27a and a partially cylindrical peripheral portion 27b, which is fitted into the outer peripheral surface of all the continuous portions 23 and fixed with adhesive. When the cover 27 is used as a reinforcing member, the relative positions of adjacent continuous portions 23 along the cylindrical surface can improve the reinforcing effect of the tube 20.

[0034] Figure 5A loudspeaker 101 according to a second embodiment of the present invention is shown. The magnetic circuit portion 110 provided in the loudspeaker 101 is a so-called external magnet type, having an annular drive magnet 111 located outside the tube 120. An annular rear outer magnetic yoke 112 is fixed to the rear surface of the drive magnet 111, and an annular front outer magnetic yoke 113 is fixed to the front surface of the drive magnet 111. A central magnetic yoke 114 is provided inside the tube 120. The rear outer magnetic yoke 112, the front outer magnetic yoke 113, and the central magnetic yoke 114 are formed of magnetic material. The rear portion of the central magnetic yoke 114 functions as a rear inner magnetic yoke 114a, and a rear magnetic gap G1 is formed between the outer peripheral surface of the rear inner magnetic yoke 114a and the inner peripheral surface of the rear outer magnetic yoke 112. The front portion of the central magnetic yoke 114 functions as the front inner magnetic yoke 114b, and a front magnetic gap G2 is formed between the outer peripheral surface of the front inner magnetic yoke 114b and the inner peripheral surface of the front outer magnetic yoke 113.

[0035] The front outer magnetic yoke 113 and the central magnetic yoke 114 are fixed to the rear surface of the magnetic circuit bracket 117, which is fixed to the rear fixing part 2a of the frame 2 by fixing screws 9. The magnetic circuit bracket 117 is made of magnetic or non-magnetic material. Multiple through-holes 115 are formed at various locations on the magnetic circuit bracket 117, and these through-holes 115 communicate with the front magnetic gap G2 and the rear magnetic gap G1 via gaps 116 on the outer periphery of the central magnetic yoke 114.

[0036] The tube 120 has a cylindrical portion 121, a cut-out portion 122, and a continuous portion 123. A rear voice coil 125 and a front voice coil 126 are provided at a distance from each other in the front-rear direction (Y1-Y2 direction) on the outer peripheral surface of the cylindrical portion 121. The rear voice coil 125 and the front voice coil 126 are formed by winding a single wire in opposite directions. In the assembled state where the tube 120 is assembled from the rear to the magnetic circuit portion 110, the continuous portion 123 protrudes forward through the actuation hole 115, and the front end of the continuous portion 123 engages with the center hole 4a of the rear plate portion 4 of the resonator 3, the rear voice coil 125 is located within the rear magnetic gap G1, and the front voice coil 126 is located within the front magnetic gap G2.

[0037] exist Figure 5 In the magnetic circuit section 110 shown, the driving magnetic flux F1 emitted from the driving magnet 111 traverses the front magnetic gap G2 from the front outer magnetic yoke 113, traverses the rear magnetic gap G1 from the central magnetic yoke 114, and returns to the driving magnet 111 via the rear outer magnetic yoke 112. The front voice coil 126 in the front magnetic gap G2 and the rear voice coil 125 in the rear magnetic gap G1 exert symmetrical driving forces in the front-rear direction, thus enabling linear vibration to be maintained in the front-rear direction of the vibrating section. Figure 5In the loudspeaker 101, the rear magnetic gap G1 is also open to the external space further rear than the magnetic circuit section 110, and a portion of the rear voice coil 125 protrudes into the external space, thus facilitating the release of heat from the rear voice coil 125. Furthermore, the front magnetic gap G2 and the front voice coil 126 are also close to the external space, thus facilitating the release of heat from the front voice coil 126 to the rear as well.

[0038] Figure 5 The magnetic circuit section 110 shown, via the front outer yoke 113, the central yoke 114, and the rear outer yoke 112, roughly completes the surrounding path of the driving magnetic flux F1 emitted from the driving magnet 111. The actuating hole 115 formed in the magnetic circuit bracket 117 is not located on the surrounding path of the driving magnetic flux F1; therefore, the actuating hole 115 does not function as magnetic resistance relative to the driving magnetic flux F1. Thus, as... Figure 6 As shown, even if the actuating hole 115 formed in the magnetic circuit support 117 is opened in a longer circumferential direction, it will not affect the driving of the vibrating part. Therefore, as Figure 6 As shown, the spool 120 can reduce the circumferential width W1 of the cut portion 122 and increase the circumferential width W2 of the continuous portion 123. Therefore, the spool 120 can maintain high strength even with the cut portion 122.

[0039] In addition, Figure 5 In the second embodiment, the magnetic circuit bracket 117 may be omitted, and the front outer magnetic yoke 113 and the central magnetic yoke 114 may be directly fixed to the rear fixing part 2a of the frame 2 by fixing screws 9. In this case, an actuation hole for the continuous part 123 of the tube 120 to pass through is formed in the rear fixing part 2a of the frame 2.

[0040] Figure 1 The magnetic circuit section 10 shown and Figure 5 The magnetic circuit section 110 shown is an external magnetic type where the driving magnet is disposed on the outer periphery of the tube, but these magnetic circuit sections can also be configured as internal magnetic types. That is, in Figure 1 In the magnetic circuit section 10 shown, the circular plate-shaped drive magnet and the rear inner yoke can also be disposed inside the tube 20. Additionally, in Figure 5 In the magnetic circuit section 110 shown, the circular plate-shaped drive magnet, the rear inner yoke, and the front inner yoke can also be arranged inside the tube 120.

Claims

1. A speaker having: a support portion including a frame and a magnetic circuit portion fixed to a rear of the frame; a diaphragm vibrationally supported to the frame; and a bobbin that vibrates together with the diaphragm and a voice coil provided to the bobbin, The speaker is characterized in that: the magnetic circuit portion has a driving magnet, a rear inner side yoke and a rear outer side yoke between which a magnetic gap is formed at a rear of the driving magnet, and the voice coil is located inside the magnetic gap, the magnetic gap is open to a space at a rear of the magnetic circuit portion.

2. The speaker according to claim 1, the magnetic circuit portion has a magnetic gap formed between a front inner side yoke and a front outer side yoke at a front of the driving magnet, the bobbin is provided with a voice coil located inside the magnetic gap between the front inner side yoke and the front outer side yoke, and a voice coil located inside the magnetic gap between the rear inner side yoke and the rear outer side yoke.

3. The speaker according to claim 1 or 2, at least when the bobbin is at a neutral position in a front-rear vibration direction, a portion of the voice coil protrudes from a rear surface of the magnetic circuit portion toward the space at the rear.

4. The speaker according to claim 1 or 2, an operation hole that penetrates in a front-rear direction and communicates with the magnetic gap is formed in the support portion, midway between the diaphragm and the magnetic circuit portion, a portion of the bobbin vibrates in the front-rear direction inside the operation hole.

5. The speaker according to claim 4, the operation hole is formed in a yoke that constitutes the magnetic circuit portion.

6. The speaker according to claim 4, a cutout portion that is open at a front end portion thereof and a continuous portion located between adjacent cutout portions are formed in the bobbin, a plurality of the continuous portions vibrate in the front-rear direction inside a plurality of the operation holes.

7. The speaker according to claim 6, a reinforcing member that links a plurality of the continuous portions is provided at a position forward of the operation hole.

8. The speaker according to claim 7, the reinforcing member is a cover that is fitted to the front end portion of the bobbin. ​

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