Headphones

Abstract

The present invention comprises a baffle plate 4, an ear pad 2, a back case 7, a first speaker unit 10, a second speaker unit 20, and a speaker holding part 6. The speaker holding part 6 is provided with a bottom wall 61 that separates the first speaker unit and the second speaker unit, a first peripheral wall 62 that extends forward from the outer peripheral edge of the bottom wall 61 and surrounds the second speaker unit 20, and a second peripheral wall 66 that has a cylindrical shape passing through the outer peripheral side of the first peripheral wall 62 and extending rearward from the baffle plate 4, surrounds the first speaker unit 10, and partitions a slit B2. The baffle plate 4 has formed therein a communication hole 32 that allows a space A2 outside the second peripheral wall 66 among the space partitioned by the back case 7 and the baffle plate 4 to communicate with a pad space A1.

Description

Headphones

[0001] The present invention relates to headphones.

[0002] As a speaker device, a so-called coaxial type device in which two speaker units are arranged side by side in a predetermined direction is known (see, for example, Patent Document 1). In a coaxial speaker device, the sound source positions of the low-frequency sound radiated from one speaker unit and the high-frequency sound radiated from the other speaker can be made equivalent, so that sound image localization can be clarified and a balanced sound can be realized.

[0003] It is conceivable to apply a coaxial speaker device to headphones. However, in headphones, simply arranging the speaker units coaxially worsens the sound balance.

[0004] International Publication No. 2022 / 185866

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide headphones capable of realizing a balanced sound.

[0006] A headphone according to one aspect of the present invention comprises a plate-shaped baffle plate, ear pads protruding forward from the outer edge of the baffle plate to cover the user's ears, a rear case disposed behind the baffle plate and partitioning a space between itself and the rear surface of the baffle plate, a first speaker unit that radiates sound forward, a second speaker unit disposed in front of the first speaker unit and radiating higher frequency sounds forward than the first speaker unit, and a speaker holding portion disposed inside the rear case and holding the first speaker unit and the second speaker unit, wherein the speaker holding portion holds the first speaker unit in the front-rear direction The baffle plate has a bottom wall separating the baffle plate from the second speaker unit, a first peripheral wall extending forward from the outer peripheral edge of the bottom wall and surrounding the second speaker unit, and a second peripheral wall that is cylindrical on the outer peripheral side of the first peripheral wall and extends rearward from the baffle plate, surrounding the first speaker unit, and partitioning a slit between itself and the first peripheral wall that connects the space between the bottom wall and the front surface of the first speaker unit with the pad space, which is the space inside the ear pad, and the baffle plate has a communication hole formed therein that connects the space outside the second peripheral wall, which is the space partitioned by the baffle plate and the rear case, with the pad space.

[0007] This configuration allows for a well-balanced sound.

[0008] Figure 1 is a perspective view showing headphones according to an embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view taken along line II-II in Figure 1. Figure 3 is a schematic diagram showing an example of a headphone device to which the headphones of this embodiment are applied. Figure 4 is a perspective view showing the second housing and its surrounding portion. Figure 5 is a perspective view showing the second housing as seen from the front. Figure 6 is a perspective view showing the second housing as seen from the rear. Figure 7 is an enlarged view of a part of Figure 2. Figure 8 is a cross-sectional view taken along line VIII-VIII in Figure 7. Figure 9 is a simplified circuit diagram of the headphones. Figure 10 is a schematic graph showing the relationship between the frequency of sound radiated from a bass speaker and the sound pressure of that sound in the pad space. Figure 11 is a schematic graph showing the relationship between the frequency of sound radiated from a tweeter and the sound pressure of that sound in the pad space. Figure 12 is a schematic graph showing the relationship between the frequency of sound radiated from a bass speaker and the sound pressure of that sound in the pad space. Figure 13 is a perspective view taken from the front of a second housing according to another example. Figure 14 is a perspective cross-sectional view of headphones relating to a reference example.

[0009] (Knowledge forming the basis of this disclosure) In a coaxial speaker system, two speaker units are arranged side by side in a orientation that radiates sound in the same direction, allowing each speaker unit to radiate sound in different frequency ranges while bringing these sound sources closer to a point source. As a result, sound image localization can be clearly defined, and a balanced sound can be achieved by flattening the sound pressure in each frequency range.

[0010] In headphones, there is a desire for clear sound localization and a balanced sound. Therefore, coaxial speaker placement in headphones is a possible solution. However, simply applying coaxial speaker placement to headphones will disrupt the sound balance.

[0011] As a result of diligent research on the aforementioned points, the inventors of this application have discovered that in headphones, the small space behind the speaker unit increases the air resistance acting on the speaker unit when it vibrates, and as a result, low-frequency sounds are not properly generated, causing the sound balance to be disrupted.

[0012] This disclosure is based on the aforementioned findings.

[0013] (1) A headphone in one aspect of the present disclosure comprises a plate-shaped baffle plate, ear pads protruding forward from the outer edge of the baffle plate to cover the user's ears, a rear case disposed behind the baffle plate and partitioning a space between itself and the rear surface of the baffle plate, a first speaker unit that radiates sound forward, a second speaker unit disposed in front of the first speaker unit and radiating higher frequency sounds forward than the first speaker unit, and a speaker holding portion disposed inside the rear case and holding the first speaker unit and the second speaker unit, wherein the speaker holding portion is positioned in the front-rear direction of the first speaker The unit has a bottom wall separating the unit from the second speaker unit, a first peripheral wall extending forward from the outer peripheral edge of the bottom wall and surrounding the second speaker unit, and a second peripheral wall that is cylindrical on the outer peripheral side of the first peripheral wall and extends rearward from the baffle plate, surrounding the first speaker unit, and partitioning a slit between itself and the first peripheral wall that connects the space between the bottom wall and the front surface of the first speaker unit with the pad space, which is the space inside the ear pad. The baffle plate has a communication hole formed therein that connects the space outside the second peripheral wall, which is the space partitioned by the baffle plate and the rear case, with the pad space.

[0014] In this configuration, the first and second speaker units are arranged side-by-side in the front-to-back direction, both radiating sound forward. This allows for clear sound image localization by bringing the sound source from each speaker unit closer to a point source. Furthermore, the first and second speaker units are separated by the bottom wall and the first surrounding wall, while the sound from the first speaker unit is radiated into the pad space through a passage and slit along the bottom wall. This suppresses intermodulation distortion between the low-frequency sound radiated from the first speaker unit and the high-frequency sound radiated from the second speaker unit, and allows for the low-frequency sound radiated from the first speaker unit to be guided into the pad space while cutting off the high-frequency sound radiated from the first speaker unit without using coils.

[0015] Furthermore, in this configuration, a communication hole is formed in the baffle plate that connects the space outside the second peripheral wall surrounding the first speaker unit (which is partitioned by the rear case and the baffle plate) with the pad space. Through this communication hole, the rear space of the first speaker unit and the front space of the first speaker unit are in communication. Therefore, the air resistance acting on the first speaker unit during vibration can be kept low, thereby promoting the vibration of the first speaker unit. Consequently, low-frequency sounds can be appropriately generated from the first speaker unit, resulting in a well-balanced sound.

[0016] (2) In the headphones described in (1) above, the communication hole may be covered with a damping cloth that attenuates sound passing through the communication hole.

[0017] This configuration prevents interference between the sound radiated from the front of the first speaker unit and the sound radiated from the rear, thereby preventing the sound pressure from becoming excessively low due to such interference.

[0018] (3) In the headphones described in (1) or (2) above, the speaker holding portion may have a resonant portion that communicates with the space between the bottom wall and the front surface of the first speaker unit or with the slit to define a resonant space.

[0019] This configuration allows the sound radiated from the first speaker unit to be transmitted forward through the slit while suppressing excessive sound pressure at the resonance point, thereby achieving a flat sound.

[0020] (4) In the headphones described in any of (1) to (3) above, the speaker holding portion holds the second speaker unit in a state in which a space is partitioned between it and the bottom wall, and has a volume portion provided behind the baffle plate and on the outer circumference side of the second speaker unit that communicates with the space between the second speaker unit and the bottom wall, and the baffle plate may have a second communication hole formed therein that connects the inner space of the volume portion with the pad space.

[0021] With this configuration, the rear space and the front space of the second speaker unit are connected via the volume section and the second communication hole, thereby reducing the air resistance when the second speaker unit vibrates. Consequently, the vibration of the second speaker unit is promoted, allowing sound to be properly radiated from the second speaker unit.

[0022] (5) In the headphones described in (4) above, the second communication hole may be covered with a damping cloth that attenuates sound passing through the second communication hole.

[0023] This configuration prevents interference between the sound radiated from the front of the second speaker unit and the sound radiated from the rear, thereby preventing the sound pressure from becoming excessively low due to such interference.

[0024] (6) In the headphones described in (4) or (5) above, the speaker holding portion has a resonant portion that communicates with the space between the bottom wall and the front surface of the first speaker unit or with the slit to define a resonant space, and the resonant portion and the volume portion may be arranged side by side along the outer circumferential surface of the second speaker unit.

[0025] With this configuration, sound radiated from the first speaker unit is transmitted forward through the slit, while the resonance section prevents the sound pressure of the sound from becoming excessive at the resonance point. Furthermore, the resonance section and the volume section can be compactly arranged around the outer circumference of the second speaker unit, preventing the speaker holder and, consequently, the headphones from becoming too large in the front-to-back direction.

[0026] (7) In the headphones described in (6) above, the speaker holding portion has two resonant portions arranged opposite to each other with the second speaker unit in between, and two volume portions arranged opposite to each other with the second speaker unit in between, and the resonant portions and volume portions may be arranged alternately along the outer surface of the second speaker unit.

[0027] This configuration allows the sound radiated from the second speaker unit to resonate in a balanced manner in the resonance section, and also makes the air resistance acting on the second speaker unit more uniform, allowing the second speaker unit to vibrate more uniformly.

[0028] (8) In the headphones described in any one of (1) to (7) above, the first speaker unit has a diaphragm that constitutes its front surface and an edge that connects the outer peripheral edge of the diaphragm to the second peripheral wall in a manner that allows the diaphragm to vibrate, and the slit may be provided at a position spaced inward from the outer peripheral edge of the edge when viewed in the front-to-back direction.

[0029] This configuration allows for a steeper slope in the high-frequency attenuation characteristics of the first speaker unit, resulting in a clearer sound.

[0030] (9) In the headphones described in (1) above, the first speaker unit has a diaphragm that constitutes its front surface and an edge that connects the outer edge of the diaphragm to the second peripheral wall in a manner that allows the diaphragm to vibrate, and the speaker holding portion may have a void compartment portion provided at a position opposite to the edge and that compartmentalizes the space opening toward the edge.

[0031] This configuration also allows for a steeper slope in the high-frequency attenuation characteristics of the first speaker unit, resulting in a clearer sound.

[0032] Embodiments of the present invention will be described below with reference to the attached drawings. Note that the embodiments described below are all specific examples of this disclosure. The numerical values, shapes, and components shown in the following embodiments are examples only and are not intended to limit this disclosure. Furthermore, components in the following embodiments that are not described in the independent claim representing the highest-level concept will be described as optional components. Also, in all embodiments, the contents of each can be combined.

[0033] (Embodiment) Figure 1 is a perspective view of the headphones 1 of the present disclosure. Figure 2 is a schematic cross-sectional view taken along line II-II in Figure 1. The headphones 1 are a device that outputs sound when worn on the user's ears and have a speaker 5 that converts electrical signals into sound. The headphones 1 are applied to a headphone device 100 in which a pair of left and right headphones 1 are connected by a headband 101 extending from them, as shown in Figure 3. In this headphone device 100, each headphone 1 is worn on the left and right ears of the user by placing the headband 101 over the head. The devices to which the headphones 1 are applied are not limited to this, and the headphones 1 may also be applied to a headphone device that has only one headphone 1 and is configured so that the headphone 1 is directly placed over the ears.

[0034] The headphones 1 have ear pads 2 that are worn on and cover the user's ears, and a headphone body 3 arranged alongside the ear pads 2. When the ear pads 2 are worn on the ears, the headphone body 3 is positioned on the opposite side of the ears, with the ear pads 2 in between. In this specification, the direction in which the ear pads 2 and the headphone body 3 are aligned is referred to as the front-to-back direction, with the ear pad 2 side being the front and the opposite side being the back. Figure 1 and other figures show this defined direction.

[0035] The ear pad 2 has a cylindrical shape with a central axis O1 extending in the front-to-back direction. When the ear pad 2 is worn, the user's ear is housed inside the ear pad 2, that is, in the pad space A1, which is the space surrounded by the ear pad 2. In this embodiment, the size of the ear pad 2 is set to cover the user's entire ear. In this embodiment, several components, which will be described later, are arranged coaxially with the ear pad 2, and hereafter, the central axis O1 of the ear pad 2 will be referred to as the headphone central axis O1 as appropriate.

[0036] The headphone body 3 includes a baffle plate 4, a speaker 5, a speaker holder 6, and a rear case 7.

[0037] The baffle plate 4 is roughly disc-shaped with the headphone's central axis O1 at its center. The ear pads 2 are fixed to the baffle plate 4 so as to protrude forward from its outer edge, and the baffle plate 4 closes the opening at the rear end of the ear pads 2.

[0038] In this embodiment, the baffle plate 4 is composed of a first baffle plate 30 and a second baffle plate 40, each exhibiting a substantially annular shape centered on the headphone's central axis O1. The outer diameter of the second baffle plate 40 is smaller than the inner diameter of the first baffle plate 30, and the second baffle plate 40 is disposed on the inner side of the first baffle plate 30, with a gap defined around its entire circumference. The first baffle plate 30 and the second baffle plate 40 are positioned so that their respective front surfaces are substantially flush. The ear pads 2 are fixed to the outer edge of the first baffle plate 30.

[0039] The headphones 1 are closed-type headphones, and the rear case 7 is a component that houses the speaker 5 inside and restricts the leakage of sound radiated from the speaker 5 to the outside. The rear case 7 is positioned behind the baffle plate 4 and partitions the space between it and the rear surface 4A of the baffle plate 4. Specifically, the rear case 7 has a cylindrical case peripheral wall 71 extending rearward from the rear surface 4A of the baffle plate 4, and a case bottom wall 72 that closes the rear end of the case peripheral wall 71. In this embodiment, the case peripheral wall 71 has a substantially cylindrical shape with the headphone central axis O1 as its central axis, and the case bottom wall 72 has a substantially disc shape with the headphone central axis O1 as its central axis. The case bottom wall 72 covers almost the entire rear end of the case peripheral wall 71. The front edge of the case peripheral wall 71 abuts against the rear surface 4A of the baffle plate 4 over its entire circumference. With this configuration, a substantially sealed space is partitioned between the case perimeter wall 71, the case bottom wall 72, and the baffle plate 4. The speaker 5 and speaker holder 6 are housed in this substantially sealed space, i.e., inside the rear case 7, spaced apart from the case perimeter wall 71 and the case bottom wall 72.

[0040] (Speaker) Speaker 5 is coaxial and includes two speaker units (first speaker unit 10 and second speaker unit 20).

[0041] The first speaker unit 10 is a bass speaker unit that radiates lower frequencies than the second speaker unit 20. Hereinafter, the first speaker unit 10 will be referred to as the bass speaker 10. The bass speaker 10 has a diaphragm 11, a voice coil 14, a magnet 15, and a yoke 16. The diaphragm 11 is substantially disc-shaped. More specifically, the diaphragm 11 has a bowl shape with its center bulging away from the voice coil 14. The bass speaker 10 is held in the speaker holder 6 with the diaphragm 11 forming its front surface and radiating sound forward. The bass speaker 10 is also held in the speaker holder 6 with the central axes of the diaphragm 11 and the voice coil 14 coinciding with the headphone central axis O1. An edge 12 is provided on the outer circumference of the diaphragm 11. The edge 12 is substantially annular in shape and extends outward from the outer edge of the diaphragm 11. The edge 12 is curved such that its central portion bulges forward in the radial direction. The edge 12 connects the outer edge of the diaphragm 11 to the first housing 50, which will be described later, while the diaphragm 11 is in a state where it can vibrate.

[0042] The second speaker unit 20 is a high-frequency speaker unit that radiates higher frequencies than the bass speaker 10. The second speaker unit 20 is a so-called tweeter, and hereafter, the second speaker unit 20 will be referred to as the tweeter 20 as appropriate. Although not shown in the diagram, like the bass speaker 10, the tweeter 20 also has a roughly disc-shaped diaphragm, a voice coil, a magnet, and a yoke. The tweeter 20 is a smaller speaker unit than the bass speaker 10, and the outer diameter of the diaphragm of the tweeter 20 is smaller than the outer diameter of the diaphragm 11 of the bass speaker 10. Like the bass speaker 10, the tweeter 20 is also held in the speaker holder 6 with the diaphragm forming its front surface and radiating sound forward. The tweeter 20 is held in the speaker holder 6 in front of the bass speaker 10, such that the central axis of its diaphragm and voice coil coincides with the headphone central axis O1, and consequently with the central axis of the diaphragm 11 and voice coil 14 of the bass speaker 10.

[0043] In this embodiment, as shown in FIG. 1, a protector 80 for protecting the tweeter 20 is attached to the front surface of the tweeter 20. The protector 80 has a substantially disc shape. A plurality of holes penetrating the front and back surfaces are formed in the protector 80 so as not to impede the forward radiation of the sound output from the tweeter 20. In FIG. 2 and the like, the illustration of the protector 80 is omitted.

[0044] (Speaker holding portion) The speaker holding portion 6 holds the speaker 5. The speaker holding portion 6 mainly includes a first housing 50 that holds the woofer 10 and a second housing 60 that is disposed in front of the first housing 50 and mainly holds the tweeter 20. The second housing 60 is fixed to the first baffle plate 30. The first housing 50 is connected to the second housing 60 and is supported by the first baffle plate 30 via the second housing 60.

[0045] The first housing 50 has a cylindrical shape extending in the front-rear direction with the headphone central axis O1 as the central axis. In this embodiment, the first housing 50 has a substantially cylindrical shape. The woofer 10 is housed inside the first housing 50. Specifically, a stepped portion is formed on the inner peripheral surface of the first housing 50 such that the diameter is smaller on the rear side than on the front side. The woofer 10 is held by the first housing 50 in a state where the outer peripheral edge of its edge 12 is supported by this stepped portion.

[0046] The first housing 50 is a bottomless cylindrical body and is open at the front and rear. The rear surface of the woofer 10 is exposed to the space A2 outside the speaker holding portion 6 among the spaces defined by the case peripheral wall 71, the case bottom wall 72, and the baffle plate 4 through the opening at the rear end of the first housing 50. This space A2 constitutes the rear space of the woofer 10. Hereinafter, the space A2 outside the speaker holding portion 6 among the spaces defined by the case peripheral wall 71, the case bottom wall 72, and the baffle plate 4 will be appropriately referred to as the woofer rear space A2.

[0047] The first baffle plate 30 is formed with a through-hole 32 for a bass speaker that penetrates it from front to back. The through-hole 32 for a bass speaker is formed on the inner peripheral side of the case peripheral wall 71 and the outer peripheral side of the speaker holding portion 6 when viewed in the front-rear direction, and communicates the back space A2 of the bass speaker and the pad space A1. The through-hole 32 for a bass speaker corresponds to the "through-hole" of the present disclosure.

[0048] In the present embodiment, three through-holes 32 for bass speakers are formed in each of the regions facing each other with the tweeter 20 interposed therebetween. In each region, the three through-holes 32 for bass speakers are arranged along the circumferential direction of the first baffle plate 30. Each through-hole 32 for a bass speaker is covered with a damping cloth 33. The damping cloth 33 is a cloth for attenuating the sound passing through each through-hole 32 for a bass speaker, and is composed of a woven fabric or a non-woven fabric that allows air circulation while suppressing it. The damping cloth 33 is fixed one by one at positions corresponding to the above regions on the front surface of the first baffle plate 30, and the three adjacent through-holes 32 for bass speakers are commonly blocked by one damping cloth 33.

[0049] FIG. 4 is a perspective view showing the second housing 60 and its peripheral portion. FIG. 5 is a perspective view showing the second housing 60 viewed from the front side. FIG. 6 is a perspective view showing the second housing 60 viewed from the rear side. FIG. 7 is an enlarged view of a part of FIG. 2. FIG. 8 is a cross-sectional view taken along line VIII-VIII of FIG. 7.

[0050] The second housing 60 has a bottom wall 61 parallel to the baffle plate 4 and a cylindrical first peripheral wall 62 on the tweeter side that extends forward from the outer peripheral edge of the bottom wall 61. The bottom wall 61 closes the opening at the rear end of the first peripheral wall 62 on the tweeter side. The first peripheral wall 62 on the tweeter side has a substantially cylindrical shape centered on the headphone central axis O1, and the bottom wall 61 has a substantially disc shape centered on the headphone central axis O1. The first peripheral wall 62 on the tweeter side corresponds to the "first peripheral wall" of the present disclosure.

[0051] On the inner circumference of the tweeter-side first circumferential wall 62, a pair of tweeter-side second circumferential walls 63, 63 are provided, extending forward from the bottom wall 61. In a view in the front-to-back direction, the two tweeter-side second circumferential walls 63, 63 each exhibit an arc shape along a circle centered on the headphone's central axis O1. In this embodiment, the two tweeter-side second circumferential walls 63, 63 each extend over a range of approximately 90 degrees around the circle centered on the headphone's central axis O1. The two tweeter-side second circumferential walls 63, 63 face each other. Specifically, the two tweeter-side second circumferential walls 63, 63 are positioned at approximately 90 degrees apart around the headphone's central axis O1, along the circle centered on the central axis O1.

[0052] As shown by the dashed line in Figure 5 and as shown in Figure 7, the tweeter 20 is housed in a roughly cylindrical space in front of the bottom wall 61 and enclosed by a circle along which the second circumferential walls 63, 63 on the tweeter side are located. The tweeter 20 is surrounded by the second circumferential walls 63, 63 on the tweeter side and the first circumferential wall 62 on the tweeter side. The inner diameter of the second circumferential walls 63, 63 on the tweeter side (the diameter of the circle along which these inner surfaces are located) is set to be approximately the same as the outer diameter of the tweeter 20, and the outer surface of the tweeter 20 is in contact with the second circumferential walls 63, 63 on the tweeter side. The tweeter 20 is held in the second housing 60 by its outer surface being fixed to the second circumferential walls 63, 63 on the tweeter side. Hereinafter, the roughly cylindrical space enclosed by the bottom wall 61 and the second surrounding walls 63, 63 on the tweeter side, in which the tweeter 20 is housed, will be referred to as the tweeter housing space C1.

[0053] The tweeter 20 is held at a position spaced forward from the bottom wall 61, and when the tweeter 20 is housed in the tweeter housing space C1, a space is partitioned behind the tweeter 20. Hereinafter, the space that constitutes part of the tweeter housing space C1 and is partitioned behind the tweeter 20 will be referred to as the tweeter rear space C2.

[0054] The bottom wall 61 is located between the bass speaker 10 and the tweeter 20, separating them in the front-to-back direction. The outer diameter of the bottom wall 61 is set to be approximately the same as the diameter of the top 12A of the edge 12, which is the radially central part of the edge 12 and is located furthest forward. As a result, the first circumferential wall 62 on the tweeter side, which extends forward from the outer edge of the bottom wall 61, faces the vicinity of the top 12A of the edge 12.

[0055] The bottom wall 61 and the front surface of the bass speaker 10 (specifically, the front surfaces of the diaphragm 11 and edge 12) are spaced apart in the front-to-back direction, and a gap B1 is defined between them. In this embodiment, a recess 61B is formed on the rear surface of the bottom wall 61, which is recessed forward along the diaphragm 11, and this recess 61B ensures a gap between the diaphragm 11 and the bottom wall 61. Hereinafter, the gap B1, that is, the space between the bottom wall 61 and the front surface of the bass speaker 10, will be referred to as the sound path B1.

[0056] The second baffle plate 40 is fixed to the front surfaces of the tweeter-side first peripheral wall 62 and the tweeter-side second peripheral wall 63. The second baffle plate 40 closes off the portion of the front opening end of the tweeter-side first peripheral wall 62 that is on the outer periphery of the tweeter housing space C1, in the region between the circle along which the tweeter-side second peripheral wall 63 is located and the tweeter-side first peripheral wall 62.

[0057] The second enclosure 60 is provided with side walls 64 that extend forward from the bottom wall 61 and connect the circumferential ends of each tweeter-side second circumferential wall 63, 63 to the tweeter-side first circumferential wall 62. These side walls 64 and the tweeter-side second circumferential walls 63, 63 divide the space enclosed by the bottom wall 61 and the tweeter-side first circumferential wall 62, on the outer periphery of the tweeter housing space C1, into four spaces. The front of each of these four spaces is closed off by the second baffle plate 40.

[0058] Of the four spaces described above, two spaces C3, specifically those along the second peripheral wall 63 on the tweeter side, function as resonant spaces that resonate the sound radiated from the bass speaker 10 when they are blocked by the second baffle plate 40. Hereafter, these spaces C3 will be referred to as resonant spaces C3. Resonant spaces C3 do not communicate with the tweeter housing space C1 and the tweeter rear space C2. On the other hand, the remaining two spaces C4 communicate with the tweeter housing space C1 and the tweeter rear space C2. Hereafter, these spaces C4 will be referred to as communicating spaces C4.

[0059] The communication space C4 is partitioned between adjacent ends of one tweeter-side second circumferential wall 63 and the other second circumferential wall in the circumferential direction, and the resonance space C3 and the communication space C4 are arranged alternately along the circle along which the tweeter-side second circumferential walls 63, 63 follow, and consequently along the outer surface of the tweeter 20.

[0060] In this embodiment, the two tweeter-side second peripheral walls 63 face each other with the tweeter 20 in between. Accordingly, the two resonance spaces C3 and the two communication spaces C4 are formed in positions facing each other. More specifically, the two resonance spaces C3 and the two communication spaces C4 are partitioned at positions approximately 90 degrees apart along a circle centered on the headphone's central axis O1. Furthermore, the four spaces C3 and C4 each occupy a region extending approximately 90 degrees along a circle centered on the headphone's central axis O1.

[0061] The above configuration can be rephrased as follows: The second housing 60 is composed of a bottom wall 61, a first circumferential wall 62 on the tweeter side, a second circumferential wall 63 on the tweeter side, and a side wall 64, and has a resonant section 161 that, together with the second baffle plate 40, defines the resonant space C3. The second housing 60 also has a volume section 162 composed of the bottom wall 61, the first circumferential wall 62 on the tweeter side, and the side wall 64, which is located behind the second baffle plate 40 and on the outer circumference side of the tweeter 20, and has a volume section 162 that defines a communication space C4 that communicates with the tweeter rear space C2. In this embodiment, the second housing 60 has two resonant sections 161 and two volume sections 162. Furthermore, in this embodiment, the two resonant sections 161 face each other, and the two volume sections 162 face each other. The resonant sections 161 and volume sections 162 are arranged alternately along a circle centered on the headphone's central axis O1, and thus along the outer circumferential surface of the tweeter 20.

[0062] A through-hole 61C is formed in the portion of the bottom wall 61 that demarcates the resonant space C3 (the portion that constitutes the resonant section 161), penetrating both its front and back surfaces. One through-hole 61C is formed in the bottom wall 61 for each resonant space C3. The through-hole 61C is formed near the center of the region of the bottom wall 61 that demarcates the resonant space C3, and opens toward the region between the top 12A and its inner peripheral edge of the edge 12 of the bass speaker 10. Each resonant space C3 is in communication with the sound path B1 through this through-hole 61C.

[0063] A tweeter communication hole 42 is formed in the portion of the second baffle plate 40 that closes the front of the communication space C4, and it penetrates through both its front and back surfaces. As a result, the communication space C4 communicates with the pad space A1 via the tweeter communication hole 42. One tweeter communication hole 42 is formed in the second baffle plate 40 for each communication space C4. The tweeter communication hole 42 is formed near the center of the region of the second baffle plate 40 that demarcates the resonance space C3. The aforementioned tweeter communication hole 42 corresponds to the "second communication hole" in this disclosure.

[0064] The tweeter communication hole 42 is covered by a damping cloth 44. The damping cloth 44 is a cloth used to attenuate sound passing through the tweeter communication hole 42, and is made of a woven or non-woven fabric that allows airflow while suppressing it. The damping cloth 44 is fixed to the front surface of the second baffle plate 40 so as to completely cover the tweeter communication hole 42.

[0065] The second housing 60 has a cylindrical tweeter-side third circumferential wall 66 that extends in the front-rear direction on the outer circumference of the tweeter-side first circumferential wall 62. The tweeter-side third circumferential wall 66 has a substantially cylindrical shape with the headphone central axis O1 as its central axis and extends rearward from the first baffle plate 30. The tweeter-side third circumferential wall 66 extends forward from the front end of the first housing 50. The tweeter-side third circumferential wall 66 and the first housing 50 are coaxial, and the tweeter-side third circumferential wall 66 and the first housing 50 constitute a cylindrical wall that extends rearward from the first baffle plate 30 and surrounds the bass speaker 10. This cylindrical wall formed by the tweeter-side third circumferential wall 66 and the first housing 50 corresponds to the "second circumferential wall" in this disclosure.

[0066] The inner diameter of the third circumferential wall 66 on the tweeter side is larger than the outer diameter of the first circumferential wall 62 on the tweeter side, and a slit B2 is defined radially between them. The third circumferential wall 66 on the tweeter side is connected to the first circumferential wall 62 on the tweeter side by a connecting portion 69 that extends from the outer circumferential surface of the first circumferential wall 62 on the tweeter side to the inner circumferential surface of the third circumferential wall 66. In this embodiment, four connecting portions 69 are provided at equal intervals along the outer circumferential surface of the first circumferential wall 62 on the tweeter side, and a slit B2 is defined between each of the connecting portions 69. As shown in Figure 5, etc., in this embodiment, each connecting portion 69 is provided at approximately the same position as the lateral wall 64 in the circumferential direction of the third circumferential wall 66 on the tweeter side. In a view in the front-rear direction, the slit B2 is located opposite the vicinity of the top 12A of the edge 12, and is defined at a position on the inner side of the outer circumferential edge of the edge 12.

[0067] On the rear surface of the second circumferential wall 63 on the tweeter side, a recess 66A is formed in the portion facing the edge 12, which is recessed forward and opens toward the edge 12. As shown in Figure 6, the recess 66A is provided around the entire circumference of the second circumferential wall on the tweeter side. In this embodiment, the recess 66A is formed on the outer circumference side of the slit B2 and communicates with the slit B2. Here, in this embodiment, the recess 66A corresponds to the "empty compartment" in this disclosure.

[0068] (Speaker Impedance) The headphones 1 are equipped with an electrical circuit (not shown) housed inside the rear case 7. Figure 9 is a simplified circuit diagram of this electrical circuit. As shown in Figure 9, a capacitor 122 is provided between the tweeter 20 and the input terminal 121 that receives audio signals supplied from the outside. The capacitor 122 cuts out low-frequency signals, i.e., bass signals, from the audio signal. On the other hand, there is no capacitor or coil for cutting out high-frequency sounds between the bass speaker 10 and the input terminal 121, so signals of almost all frequencies are input to the bass speaker 10. In this embodiment, the impedance of the voice coil of the tweeter 20 is set to be lower than the impedance of the voice coil of the bass speaker 10. For example, the impedance of the bass speaker 10 is set to about 32Ω, while the impedance of the tweeter 20 is set to about 4Ω.

[0069] (Effects, etc.) With headphones 1 configured as described above, it is possible to clearly define the sound image and achieve a balanced sound.

[0070] Specifically, in the headphones 1 according to the above embodiment, a bass speaker 10 that radiates low-frequency sounds and a tweeter 20 that radiates high-frequency sounds are arranged such that their respective diaphragms and voice coils are coaxial. Therefore, these speaker units 10 and 20 can radiate sounds of different frequency ranges while bringing these sound sources closer to a point source.

[0071] Furthermore, the bass speaker 10 and the tweeter 20 are separated by the bottom wall 61 of the second housing 60 and the first peripheral wall 62 on the tweeter side, and the sound output from the bass speaker 10 is radiated into the pad space A1 through the sound path B1 and the slit B2. As a result, the sound radiated from the bass speaker 10 can be guided into the pad space A1, and the occurrence of intermodulation distortion between the sound radiated from the bass speaker 10 and the sound radiated from the tweeter 20 can be suppressed, resulting in good sound quality.

[0072] Here, the high-frequency components of the sound output from the bass speaker 10 are cut off by passing through the slit B2, which has a narrow passage area. Therefore, in the above embodiment, a coil for cutting off high-frequency sounds can be omitted, and the headphones 1 can be made smaller while improving sound quality by making the frequency ranges of the bass speaker 10 and the tweeter 20 different.

[0073] Furthermore, in the headphones 1 according to the above embodiment, the space A2 behind the bass speaker and the pad space A1 are in communication via the bass speaker communication hole 32. Therefore, when the bass speaker 10 vibrates, air can be compressed and expanded in a wider space, and the air resistance acting on the bass speaker 10 can be kept low. Consequently, the vibration of the bass speaker 10 can be promoted, allowing for the proper generation of low-frequency sounds and a good balance of sound.

[0074] However, if a communication hole 32 for the bass speaker is provided, the sound radiated forward from the bass speaker 10 and the sound radiated backward may interfere with each other, potentially causing some sounds to be reduced in volume. In contrast, in the headphones 1 according to the above embodiment, the communication hole 32 for the bass speaker is covered with damping fabric 33. Therefore, the aforementioned sound interference can be suppressed, and a well-balanced sound can be reliably achieved.

[0075] Furthermore, in the headphones 1 according to the above embodiment, the resonance space C3 is partitioned and communicates with the sound path B1 through a through hole 61C.

[0076] Therefore, while transmitting the sound radiated from the bass speaker 10 into the pad space A1 via the sound path B1 and slit B2, it is possible to suppress the sound pressure of the sound from becoming excessively high at the resonance point. Figure 10 is a schematic graph showing the relationship between the frequency of the sound radiated from the bass speaker 10 and the sound pressure of the sound in the pad space A1. If there is no resonance space C3, the sound pressure becomes excessively high at a predetermined frequency F1, as shown by the dashed line in Figure 10. In contrast, with the headphones 1 according to the above embodiment, the resonance space C3 and the sound path B1 are connected, so the increase in sound pressure can be suppressed, as shown by the solid line in Figure 10.

[0077] Furthermore, a communication space C4 is defined on the outer periphery side of the tweeter 20 of the second housing 60, which communicates with the tweeter rear space C2, and this communication space C4 and the pad space A1 are in communication with each other through a tweeter communication hole 42 formed in the second baffle plate 40.

[0078] Therefore, the air resistance acting on the tweeter 20 during its vibration can be reduced, allowing it to radiate sound appropriately.

[0079] Furthermore, since the tweeter communication hole 42 is covered with damping fabric 44, excessive interference between the sound from the front and rear of the tweeter 20 via the tweeter communication hole 42 can be suppressed, resulting in a good balance of sound from the tweeter 20.

[0080] Specifically, Figure 11 is a schematic graph showing the relationship between the frequency of sound radiated from the tweeter 20 and the sound pressure of that sound within the pad space A1. If the communication space C4 (volume section 162) and the tweeter communication hole 42 are not provided, as shown by the dashed line in Figure 11, the sound pressure of the low-frequency sound will decrease, and resonance will occur at a predetermined frequency F2, causing the sound pressure to become excessive. In contrast, according to the headphones 1 of the above embodiment, a communication space C4 is provided that communicates with the tweeter rear space C2, and the communication space C4 and the pad space A1 are connected, so as shown by the solid line in Figure 11, the sound pressure of the low-frequency sound can be increased and excessive sound pressure can be suppressed.

[0081] Furthermore, in the headphones 1 according to the above embodiment, the resonant space C3 and the communication space C4 are partitioned along the outer circumferential surface of the tweeter 20. That is, the resonant portion 161 that partitions the resonant space C3 and the volume portion 162 that partitions the communication space C4 are arranged side by side along the outer circumferential surface of the tweeter 20. As a result, these spaces C3 and C4, i.e., the resonant portion 161 and the volume portion 162, can be compactly arranged on the outer circumferential surface of the tweeter 20, and the dimensions of the second housing 60 and, consequently, the headphones 1 in the front-to-back direction can be prevented from increasing.

[0082] Furthermore, in the headphones 1 according to the above embodiment, two resonant spaces C3, i.e., two resonant sections 161, and two communicating spaces C4, i.e., two volume sections 162, are provided in positions facing each other with the tweeter 20 in between. In addition, these resonant spaces C3, i.e., resonant sections 161, and the communicating spaces C4, i.e., volume sections 162, are arranged alternately along the outer circumferential surface of the tweeter 20.

[0083] Therefore, the sound radiated from the tweeter 20 can be resonated in a balanced manner within the resonant space C3, and the air resistance acting on the tweeter 20 can be made more uniform, allowing the second speaker unit to vibrate more uniformly. In addition, by compactly arranging the resonant space C3 (resonant section 161) and the communication space C4 (volume section 162) around the outer circumference of the tweeter 20, it is possible to prevent the dimensions of the speaker holder 6 and, consequently, the headphones 1 in the front-to-back direction from becoming larger.

[0084] Furthermore, in the headphones 1 according to the above embodiment, the slit B2 is provided at a position facing the top 12A of the edge 12 of the bass speaker 10 when viewed in the front-to-back direction, and spaced inward from the outer edge of the edge 12.

[0085] Figure 12 is a schematic graph showing the relationship between the frequency of sound radiated from the bass speaker 10 and the sound pressure of that sound within the pad space A1. In Figure 12, the dashed line is the graph when the slit B2 is located near the outer edge of the edge 12, and the solid line is the graph when the slit B2 is located further inward from the outer edge of the edge 12. As is clear from comparing the dashed and solid lines in Figure 12, by placing the slit B2 further inward from the outer edge of the edge 12, the slope of the attenuation characteristics of high-frequency sound radiated from the bass speaker 10 can be made steeper. Thus, according to the headphones 1 of the above embodiment, by setting the position of the slit B2 as described above, the slope of the attenuation characteristics of high-frequency sound radiated from the bass speaker 10 can be made steeper, and a clearer sound can be achieved.

[0086] If the slit B2 is positioned further inward, the space for housing the tweeter 20, and consequently the space behind the tweeter 20, which is partitioned inside the slit B2, becomes smaller, and the air resistance acting on the tweeter 20 increases. In contrast, as described above, in the headphones 1 according to the embodiment, the air resistance can be reduced by the communication space C4, thus achieving a well-balanced and clearer sound.

[0087] Furthermore, it has been found that if a space is partitioned at a position opposite to the edge 12, opening toward the edge 12, the attenuation characteristics of high-frequency sound from the bass speaker 10 can be made steeper. In contrast, in the headphones 1 according to the above embodiment, a recess 66A is formed on the rear surface of the second peripheral wall 63 on the tweeter side, in the portion opposite to the edge 12, which is recessed forward and opens toward the edge 12. Therefore, according to the headphones 1 according to the above embodiment, the slope of the attenuation characteristics of high-frequency sound radiated from the bass speaker 10 can be made even steeper, resulting in an even clearer sound.

[0088] Furthermore, in the headphones 1 according to the above embodiment, the impedance of the voice coil of the tweeter 20 is set to be lower than the impedance of the voice coil of the bass speaker 10. Therefore, it is possible to make the sound pressure of the sound radiated from the tweeter 20 and the bass speaker 10 the same, making the sound pressure across the entire frequency range almost flat, or equal. Specifically, if the impedance of each voice coil were to be equal, the sound pressure of the sound radiated from the tweeter 20 would be lower than the sound pressure of the sound radiated from the bass speaker 10, due to the tweeter 20 being smaller than the bass speaker 10. In contrast, by increasing the impedance of the voice coil of the tweeter 20, it is possible to make the sound pressure of the sound radiated from the tweeter 20 and the bass speaker 10 the same. Furthermore, if the impedance of the bass speaker 10 is set to 32Ω and the impedance of the tweeter 20 is set to 4Ω, the current flowing through the tweeter 20 will be eight times that of the current flowing through the bass speaker 10, and the sound pressure level of the tweeter 20 can be increased by, for example, about 18dB.

[0089] (Modification) In the above embodiment, the case was described in which the central axes of the ear pads 2, baffle plates 30, 40, bass speaker 10 (diaphragm 11 and voice coil 14 of the bass speaker 10), tweeter 20 (diaphragm and voice coil of the tweeter 20), first housing 50 and second housing 60 (bottom wall 61 of the second housing 60, first peripheral wall 62 on the tweeter side, second peripheral wall 63 on the tweeter side, and third peripheral wall 66 on the tweeter side) all coincide. However, it is sufficient that the bass speaker 10 and the tweeter 20 are coaxial, and the central axes of the other components do not need to coincide.

[0090] In the above embodiment, the case in which the baffle plates 30 and 40 are substantially annular in shape was described, but their specific shapes are not limited to this. Also, the specific shape of the first housing 50 is not limited to a substantially cylindrical shape. Furthermore, the specific shape of the bottom wall 61 of the second housing 60 is not limited to a disc shape. Similarly, the specific shapes of the first circumferential wall 62 on the tweeter side, the second circumferential wall 63 on the tweeter side, and the third circumferential wall 66 on the tweeter side are not limited to a cylindrical shape.

[0091] In the above embodiment, the case in which the slit B2 is provided at a position opposite the top 12A of the edge 12 was described, but the position of the slit B2 is not limited to this. However, as described above, if the slit B2 is placed on the inner side of the outer edge of the edge 12, the slope of the attenuation characteristic of the high-frequency sound radiated from the bass speaker 10 can be made steeper.

[0092] In the above embodiment, the case in which the recess 66A communicates with the slit B2 was described, but the recess 66A does not have to communicate with the slit B2. Also, the recess 66A may be provided on the inner circumference side of the edge 12, relative to the slit B2.

[0093] In the above embodiment, the case in which the resonance space C3 (resonance portion 161) and the communication space C4 (volume portion 162) are provided along the outer circumferential surface of the tweeter 20 was described, but the positions of the resonance space C3 (resonance portion 161) and the communication space C4 (volume portion 162) are not limited to this. Furthermore, when the resonance space C3 (resonance portion 161) and the communication space C4 (volume portion 162) are provided along the outer circumferential surface of the tweeter 20, they do not have to be arranged alternately. Also, the resonance spaces C3 (resonance portions 161) and the communication spaces C4 (volume portions 162) may be provided at positions other than those facing each other.

[0094] In the above embodiment, a case was described in which two resonant spaces C3 (resonant section 161) and two communicating spaces C4 (volume section 162) are provided, but the number of resonant spaces C3 (resonant section 161) and two communicating spaces C4 (volume section 162) is not limited to two.

[0095] In the above embodiment, a case was described in which both a resonant space C3 (resonant portion 161) and a communication space C4 (volume portion 162) are provided in the second housing 60, but one or both of these may be omitted.

[0096] For example, when a resonant space C3 (resonant section 161) is provided in the second housing 60, as shown in Figure 13, the entire space on the outer periphery of the tweeter housing space C1 and thus the tweeter 20 may be made into the resonant space C3. Specifically, in the second housing 260 shown in Figure 13, the tweeter-side second circumferential wall 63 extends along the entire circumference of the tweeter-side first circumferential wall 62, and all four spaces partitioned between the tweeter-side second circumferential wall 63 and the tweeter-side first circumferential wall 62 are resonant spaces C3. That is, through holes 61C are formed in the bottom wall 61 in the parts corresponding to these four spaces, and each space communicates with the sound path B1. In Figure 13, elements similar to those in the above embodiment are denoted by the same reference numerals as in that embodiment. Also, in the example shown in Figure 13, only a part of the four spaces may function as the resonant space C3. In other words, through holes 61C may be formed in only a portion of the bottom wall 61 corresponding to the four spaces, thereby connecting only a portion of the space to the sound path B1.

[0097] Furthermore, although the above embodiment described a case in which a through hole 61C is formed in the bottom wall 61 to connect the resonance space C3 and the sound path B1, the through hole 61C may also be formed in the tweeter-side first peripheral wall 62 to connect the resonance space C3 to the slit B2. In this case as well, some of the sound radiated from the bass speaker 10 can be made to resonate when passing through the slit B2, preventing the sound pressure of that sound from becoming excessive.

[0098] (Reference Example) Next, a reference example of headphones 300 will be described using Figure 14. Figure 14 is a perspective cross-sectional view of a reference example of headphones 300 to which a part of the configuration of the above embodiment is applied. The same reference numerals are used for elements that are the same as in the above embodiment. Unlike the above embodiment, the reference example of headphones 300 is an open type. Specifically, the headphones 300 shown in Figure 14 do not have a rear case, the speaker holding part 6 arranged behind the baffle plate 4 is exposed to the outside, and the bass speaker 10 is open to the outside.

[0099] In the headphones 300 according to the reference example, similar to the embodiment described above, a plurality of communication holes 301 are formed in the portion of the baffle plate 4 that is on the outer periphery side of the speaker holding portion 6, penetrating both the front and back surfaces to connect the front space and the rear space of the baffle plate 4, and these communication holes 301 are covered with damping fabric 303.

[0100] In the reference example, since the speaker 5 is open to the rear, the air resistance on the diaphragm 11 is kept to a minimum. Therefore, as in the above embodiment, it is not necessary to form a communication hole in the baffle plate 4 for the purpose of promoting the vibration of the diaphragm 11. On the other hand, in the reference example, the promotion of the vibration of the diaphragm 11 may cause the sound pressure of the bass speaker 10 to become excessive. In detail, although the rear of the speaker 5 is open to the atmosphere, the pad space A1 in front of the speaker 5 is a narrow space surrounded by the user's ear and its surroundings and the ear pad 2. Therefore, if the vibration of the diaphragm 11 is excessively promoted, high vibration energy will be released into the narrow pad space A1, and the sound pressure of the bass speaker 10 heard by the user will become excessive.

[0101] In contrast, in the reference example, the presence of the communication hole 301 allows the sound radiated forward from the bass speaker 10 toward the pad space A1 and the sound radiated backward from the bass speaker 10 to interfere with each other through the communication hole 301. This reduces the sound pressure within the pad space A1, preventing the sound pressure of the low-frequency sounds heard by the user from becoming excessive. Furthermore, the fact that the communication hole 301 is covered by the damping fabric 303 suppresses excessive interference, allowing the user to be provided with sound at an appropriate sound pressure.

[0102] This invention is useful in the field of headphone devices that reproduce audio signals such as music.

Claims

1. The speaker comprises a plate-shaped baffle plate, ear pads protruding forward from the outer edge of the baffle plate to cover the user's ears, a rear case disposed behind the baffle plate and partitioning a space between itself and the rear surface of the baffle plate, a first speaker unit that radiates sound forward, a second speaker unit disposed in front of the first speaker unit and radiating higher frequency sounds forward than the first speaker unit, and a speaker holding part disposed inside the rear case and holding the first speaker unit and the second speaker unit, wherein the speaker holding part comprises a bottom wall separating the first speaker unit and the second speaker unit in the front-to-back direction, and a first peripheral wall extending forward from the outer edge of the bottom wall and surrounding the second speaker unit. The headphones are characterized in that the first peripheral wall has a cylindrical shape extending rearward from the baffle plate on its outer peripheral side, surrounding the first speaker unit, and has a second peripheral wall between it and the first peripheral wall that defines a slit connecting the space between the bottom wall and the front surface of the first speaker unit and the pad space, which is the space inside the ear pad, and the baffle plate has a communication hole formed therein that connects the space outside the second peripheral wall, which is the space separated by the baffle plate and the rear case, with the pad space.

2. The headphones according to claim 1, characterized in that the communication hole is covered with a damping cloth that attenuates sound passing through the communication hole.

3. The headphones according to claim 1, characterized in that the speaker holding portion has a resonant portion that communicates with the space between the bottom wall and the front surface of the first speaker unit or with the slit to define a resonant space.

4. The headphones according to claim 1, wherein the speaker holding portion holds the second speaker unit in a state in which a space is partitioned between it and the bottom wall, and has a volume portion provided behind the baffle plate and on the outer circumference side of the second speaker unit, which communicates with the space between the second speaker unit and the bottom wall, and the baffle plate has a second communication hole formed therein that connects the inner space of the volume portion and the pad space.

5. The headphones according to claim 4, characterized in that the second communication hole is covered with a damping cloth that attenuates sound passing through the second communication hole.

6. The headphones according to claim 4, wherein the speaker holding portion has a resonant portion that communicates with the space between the bottom wall and the front surface of the first speaker unit or with the slit to define a resonant space, and the resonant portion and the volume portion are arranged side by side along the outer circumferential surface of the second speaker unit.

7. The headphones according to claim 6, wherein the speaker holding portion has two resonant portions arranged opposite to each other with the second speaker unit in between, and two volume portions arranged opposite to each other with the second speaker unit in between, and the resonant portions and volume portions are arranged alternately along the outer circumferential surface of the second speaker unit.

8. The headphones according to claim 1, wherein the first speaker unit has a diaphragm that constitutes its front surface and an edge that connects the outer peripheral edge of the diaphragm and the second peripheral wall in a manner that allows the diaphragm to vibrate, and the slit is provided at a position spaced inward from the outer peripheral edge of the edge when viewed in the front-to-back direction.

9. The headphones according to claim 1, wherein the first speaker unit has a diaphragm that constitutes its front surface and an edge that connects the outer peripheral edge of the diaphragm to the second peripheral wall in a manner that allows the diaphragm to vibrate, and the speaker holding portion is provided at a position opposite to the edge and has a void compartment portion that divides a space that opens toward the edge.

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