JP2007110236A - Speaker system and speaker enclosure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the low band and output the increased low sound component, even if a speaker enclosure is small. <P>SOLUTION: When a speaker 10 is driven, the vibrations of cone paper of the speaker 10 are propagated to the air in the speaker enclosure 90, and a vibration region 91a of a diaphragm 91 is vibrated by the vibrations of the air. At this time, since medium/high sounds radiated inside the speaker enclosure 90 from the speaker are suppressed (or interrupted) by a partition 92, the medium/high sounds can be prevented from directly reaching an opening 90b and being radiated to the outside through the diaphragm 91 or an edge 40. Thus, deterioration in frequency characteristics or degradation in localization can be prevented and clear sound quality having no distortion feeling can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a speaker system and a speaker enclosure technology.

Various types of speaker systems have been developed, for example, those using bass reflex or drone cones.
The bass reflex enhances the bass by using Helmholtz resonance, and the drone cone attaches a speaker unit without a drive circuit, and enhances the bass by using resonance with air in the volume of the enclosure.

  In bass reflex, when the volume of the enclosure is small, in order to lower the resonance frequency, the resonance tube must be made small and slender, the air resistance increases and the bass enhancement function is significantly reduced. There is a problem that wind noise such as a whistle is generated because the speed of the passing air becomes very high.

  In the case of a drone cone, in order to lower the resonance frequency, its mass must be increased. In order to reduce the resonance frequency, the compliance of the edge that supports the diaphragm must be large, but in order to support a diaphragm with a large mass, the spring property and strength of the edge must be large. It will be in conflict with. In addition, it is difficult for a heavy diaphragm to vibrate completely in parallel, and is likely to be accompanied by abnormal vibrations called rolling and rocking. This abnormal vibration increases distortion and consumes wasted energy, reducing efficiency.

In order to compensate for the above-described drawbacks of the drone cone, for example, Japanese Patent Laid-Open No. 2002-531036 has been proposed. According to this method, rolling and rocking can be prevented, but because the structure supports the weight of the diaphragm (flap) with the edge provided around it, the edge needs strength, and its braking effect Therefore, there is a problem that the Q of vibration becomes small.
Japanese translation of PCT publication No. 2002-531036

  In order to solve the above problems, the present invention can output a sufficient bass component even in a small size, prevent rolling and rocking, and increase the vibration Q of the diaphragm, and a speaker. The object is to provide an enclosure.

  The speaker system according to the present invention includes a speaker enclosure sealed inside, a speaker attached to the speaker enclosure, a diaphragm that can vibrate elastically with one end fixed on one surface of the speaker enclosure, and the vibration One surface provided with a plate is provided at a position corresponding to a vibration part of the diaphragm, and is attached between the diaphragm and the opening structure, the opening structure exposing the internal space of the speaker enclosure, The space exposed by the opening structure is closed in a state in which the vibration of the diaphragm is enabled, and a sealing member that maintains the airtightness of the speaker enclosure is provided along a predetermined interval with respect to the diaphragm. High impedance to sound waves of a predetermined frequency range emitted from the speaker Characterized by comprising a partition wall serving as a Nsu.

In a preferred aspect, the partition wall is provided in an internal space of the speaker enclosure.
In another preferred embodiment, the partition wall is provided so as to cover the exposure of the diaphragm from the outside.
In a more preferred aspect, the one surface on which the diaphragm and the opening are provided is another surface different from the surface on which the speaker is attached.
As a more preferred aspect, a plurality of the speakers are provided on the same surface of the speaker enclosure.

  The speaker enclosure according to the present invention is a sealed speaker enclosure having a speaker mounting hole in which a speaker is mounted, and a vibration plate capable of elastically vibrating with one end fixed to one surface of the speaker enclosure; and the vibration One surface provided with a plate is provided at a position corresponding to a vibration part of the diaphragm, and is attached between the diaphragm and the opening structure, the opening structure exposing the internal space of the speaker enclosure, The space exposed by the opening structure is closed in a state in which the vibration of the diaphragm is enabled, and a sealing member that maintains the airtightness of the speaker enclosure is provided along a predetermined interval with respect to the diaphragm. High impedance for sound waves of a predetermined frequency range emitted from the speaker Characterized by comprising a scan become bulkhead.

Embodiments of the present invention will be described below with reference to the drawings.
1 and 2 are diagrams showing a configuration of a speaker system according to an embodiment of the present invention, in which (a) in FIG. 1 is a front view, (b) is a rear view, and (c) is shown in (a). AA line sectional view, (d) is a BB line sectional view shown in (a). FIG. 2 is an exploded view as seen from the oblique back direction. In the figure, reference numerals 10 and 10 denote speakers equipped with voice coils, magnets, and the like, which are attached to the front surface of the speaker enclosure 90. The speaker enclosure 90 is a sealed enclosure and is formed of a plate-like member (for example, wood, synthetic resin, metal, or a synthetic material obtained by bonding them).

  Reference numerals 90a and 90a denote baffle plates joined at a predetermined angle in the horizontal direction on the front surface of the speaker enclosure 90. Speaker mounting holes are provided so as to be bilaterally symmetric through the baffle plates 90a and 90a, and the above-described speakers 10 and 10 are inserted into these speaker mounting holes. In this case, the front frame of the speaker 10 is fixed to the baffle plates 90a and 90a by screws.

As shown in FIG. 1D, an opening 90b through which the internal space of the speaker enclosure 90 is exposed is formed on the back surface of the speaker enclosure 90. A thin plate-like diaphragm 91 is attached to the back surface of the speaker enclosure 90. The diaphragm 91 is formed to have substantially the same size as the back surface of the speaker enclosure 90 and covers the entire back surface of the speaker enclosure 90 so as to cover the opening 90b. More specifically, the diaphragm 91 is formed of a member having both acoustically sufficient strength and elasticity. Here, “acoustically sufficient strength” means that the air does not pass through, has a density sufficiently higher than air, and has strength and elasticity to generate sound waves when vibrated. In addition, the diaphragm 91 has a property capable of blocking sound waves to some extent by itself.
Further, the degree of “elasticity” is such that when one side of the diaphragm 91 is fixed and placed horizontally, it can support its own weight and be kept almost horizontal. In order to satisfy such characteristics, the diaphragm 91 is made of, for example, a thin wooden board, a thin synthetic resin, a metal board, or a synthetic material obtained by bonding them together.

  Next, 40 is an edge that is provided between the outer peripheral edge of the vibration part 91a of the diaphragm 91 and the frame member 95 provided at the edge of the opening 90b, and maintains the airtightness of the speaker enclosure 90. The outer peripheral edge of the edge 40 is bonded to the outer peripheral edge of the vibration portion 91a of the diaphragm 91 and the frame member 95, whereby the airtightness of the speaker enclosure 90 is maintained. Further, when the edge 40 is bent freely, the vibration of the vibration portion 91a is not hindered and becomes free vibration. The frame member 95 can be omitted if the edge 40 is easily fixed around the opening 90b of the speaker enclosure 90.

Reference numeral 92 denotes a partition wall that is close to the rear surface side in the speaker enclosure 90 and is provided at a predetermined distance from the diaphragm 91. The speaker enclosure 90 is separated into a space on the front surface side and the rear surface side. Yes. The partition wall 92 is provided with a rectangular hole 93 at a lower portion thereof. As shown in FIGS. 1B and 2, the hole 93 is formed in the lower part of the partition wall 92 in the width direction of the speaker enclosure 90, and the width is slightly shorter than the width of the speaker enclosure 90 (in the example shown in the figure). 84 mm), and the height is set to about 1/3 of the height of the partition wall 92 (30 mm in the example shown).
Since the hole 93 communicates with the opening 90b, a space in the speaker enclosure 90 is exposed from the opening 90b through the hole 93. Further, a beam member 94 extending in the horizontal direction is provided on the upper portion of the partition wall 92, and the above-described diaphragm 91 is fixed to the beam member 94. By setting the height of the beam member 94 to about 10% of the height of the diaphragm 91 and firmly fixing the diaphragm 91, the diaphragm 91a can be flexibly vibrated. In this embodiment, the positional relationship is such that the lower end of the beam member 94 and the upper end of the frame member 95 are in contact with each other.
The partition wall 92 is provided for the purpose of attenuating (or blocking) middle and high sound waves generated from the speaker 10. For this reason, the partition wall 92 is made of a material that does not easily vibrate due to the sound pressure from the speaker 10. It is desirable that it has high strength and can block sound waves. Alternatively, the material may be a material that has an appropriate internal loss and that converts or consumes sound wave energy into heat internally.

  Further, the hole 93 is provided at a position where the attenuation effect of the middle and high sounds by the partition wall 92 is not lost. In the case of this embodiment, the sound wave (low sound component) of the speaker 10 is provided below the partition wall 92 and is transmitted to the diaphragm 91 by passing through the hole 93.

  In the configuration described above, when the speaker 10 is driven, the vibration of the cone paper of the speaker 10 is propagated to the air in the speaker enclosure 90, and the vibration portion 91a of the diaphragm 91 vibrates due to the vibration of the air. At this time, the diaphragm 91 that vibrates while being kept airtight at the edge 40 compresses or expands the air volume in the speaker enclosure 90 when vibrated. Therefore, a new resonance frequency is obtained between the compliance (mechanical flexibility) in which the air spring of the speaker enclosure 90 is added in addition to the elasticity of the diaphragm 91 and the equivalent mass of the diaphragm 91. As a result, a sound reproduced around the resonance frequency of the diaphragm 91 is generated. Specifically, in the case shown in FIG. 1, two speakers having an effective diameter of 3 cm and a minimum resonance frequency of 190 Hz are accommodated in a 400 cc speaker enclosure, and the resonance frequency of the diaphragm is adjusted to 120 Hz, thereby increasing the frequency from 100 Hz (−10 dB). Is possible.

  Here, the elasticity (spring property) of the air spring and the diaphragm 91 functions equivalently so that two springs are connected in parallel, but the compliance of the air spring is smaller than that of the diaphragm 91. Therefore, the resonance frequency of the diaphragm 91 as the speaker system is substantially determined by air compliance and the equivalent mass of the diaphragm 91.

  The resonance frequency determined as described above can be easily set to a desired value in the low frequency range. Thus, in the present embodiment, by using the bending vibration of the diaphragm 91, an action as a passive radiator such as a drone cone can be obtained.

  In addition, the vibration portion 91a performs low-pitched sound reproduction in a primary vibration mode that vibrates while being bent as a whole like a “round fan”. This is because the vibration plate 91 has secondary, tertiary or higher vibration modes, but the entire vibration plate 91 is driven by air, so the primary vibration mode is generated most strongly, and other vibrations are generated. This is because the mode generation level becomes small. Further, when it is desired to further suppress the higher-order mode, adjustment can be made by the material and thickness of the diaphragm 91 or by bonding a plurality of materials.

  In the present embodiment, since the diaphragm 91 has sufficient elasticity to support its own weight, the diaphragm 91 can be kept horizontal even when the diaphragm 91 is placed horizontally. Further, the elasticity of the diaphragm 91 itself becomes a compliance of free resonance. However, since the internal loss of the elastic diaphragm 91 is much smaller than the internal loss of the edge 40 having the same elasticity, the loss during vibration is sufficient. small.

Further, the edge 40 in the present embodiment can be made of a softer material than the edge used in a conventional drone cone or the like, and does not require mechanical strength. In a conventional passive radiator such as a drone cone, a structure in which a rigid diaphragm is supported by an edge is required. Therefore, the edge has two functions of supporting the diaphragm and ensuring airtightness. However, in the present embodiment, the support function of the diaphragm 91 is given to the diaphragm 91 itself, and thus the edge 40 does not need a support function. Therefore, since it is sufficient for the edge 40 to be able to maintain the airtightness in the speaker enclosure 90, it is possible to use an unprecedented soft material, to create a situation that does not hinder the vibration of the diaphragm 91, and to set the vibration Q. Can be bigger.
Further, the resonance frequency of the diaphragm 91 can be lowered by increasing the mass of the diaphragm 91. In other words, the adjustment can be made according to the size and material of the diaphragm 91, and the adjustment can also be easily performed by attaching some member to the diaphragm 91.

Here, the difference between the present invention and the prior art will be described using an equivalent circuit. FIG. 3 is an electrical equivalent circuit of the speaker. A low-frequency resonance circuit (resonance frequency = F0) composed of Cmes, Res, and Lces is voltage-driven through a voice coil impedance.
here,
Re = voice coil DC resistance Le, L2, R2 = high-frequency impedance increasing element Cmes = equivalent mass capacity of speaker vibration system Lces = equivalent compliance inductance of speaker vibration system Res = mechanical braking resistance of speaker vibration system.

FIG. 4 is an equivalent circuit of the speaker enclosure, where Lve = equivalent volume inductance.
FIG. 5 is an equivalent circuit of a passive radiator such as a conventional drone cone or hinge fixing flap. As shown in the figure, the circuit configuration is such that the factor of the voice coil is eliminated from the speaker. The mass Cmep is supported by the compliance Lcep and braking resistance Rep of the edge.
here,
Cmep = Equivalent Mass Capacity of Passive Radiator Lcep = Equivalent Compliance Inductance of Passive Radiator Rep = Mechanical Braking Resistance of Passive Radiator FIG. 6 is an equivalent circuit of a conventional passive radiator system. The signal voltage drives the speaker and the sound output of the speaker drives the passive radiator through the speaker enclosure volume.

  The low-frequency resonance frequency as a system is approximately the resonance frequency of Cmep and Lve. In order to reduce the resonance frequency with a small volume, it is necessary to increase Cmep, which means that the passive radiator becomes heavy. To support a heavy passive radiator, a strong and strong edge is required. On the other hand, since the edge is required to be flexible, soft materials such as rubber and urethane are used, but it is necessary to increase the thickness in order to increase the strength. However, increasing the edge means decreasing the equivalent compliance Lcep and simultaneously increasing the braking force (when expressed in an electrical equivalent circuit, the resistance value Rep decreases). For this reason, the loss of the passive radiator is increased, and the reproduction capability of bass is lowered.

FIG. 7 is an equivalent circuit of the diaphragm according to the present invention. Since one side of the diaphragm is completely fixed, the diaphragm itself has a compliance Lceb and supports its own weight. Since the diaphragm is made of an elastic material, resistance components such as edge materials can be ignored. Since the edge does not need to support the dead weight of the diaphragm, it may be made of a thin material, and the compliance Lcex can be made very large, thereby inevitably reducing the loss (in terms of an electric equivalent circuit, the braking resistance Rex Becomes larger).
In FIG.
Cmeb = equivalent mass capacity of diaphragm Lceb = equivalent compliance inductance of diaphragm Lcex = equivalent compliance inductance of diaphragm edge Rex = mechanical braking resistance of diaphragm edge FIG. 8 is an equivalent circuit of the speaker system according to the present invention. When compared with FIG. 6, if the speaker and speaker enclosure volume are the same,
Cmep = Cmeb
If so, the low-band resonance frequency is the same. The same compliance is required to support this weight, but since Lcep in FIG. 6 and Lcex >> Lceb in FIG. 8, it is almost Lceb, and if appropriate design is achieved, almost Lcep = Lceb
It becomes. There is no significant difference in the factors so far. However, as is clear from the above description,
Rex >> Rep
This is an important feature of the present invention, and it can be seen that the loss is greatly reduced as compared with the conventional method, and bass reproduction is advantageous.

By the way, in a loudspeaker system in which bass is increased by a diaphragm, mid-high sounds radiated from the loudspeaker into the loudspeaker enclosure are directly reflected in the opening without being attenuated by reflection inside the loudspeaker enclosure. May leak out to the outside. In particular, in a small speaker system, it is difficult to ensure the distance between the speaker and the opening. Therefore, when a diaphragm is provided in the immediate vicinity of the back of the speaker, sound leakage becomes noticeable and frequency characteristics deteriorate or are localized. May cause deterioration.
In addition, when a diaphragm is provided in the speaker system, since the speaker enclosure has a large opening, the mechanical strength of the speaker enclosure is insufficient, and reinforcement around the opening is often required.

  On the other hand, in this embodiment, as shown in FIG. 1, by providing a partition wall 92 between the speaker 10 and the opening 90 b, the partition wall 92 suppresses leakage of middle and high sounds through the diaphragm 91. The middle and high sounds radiated from the back surface of the speaker 10 into the speaker enclosure 90 directly reach the opening 90b and can be prevented from being radiated to the outside through the diaphragm 91 and the edge 40. Outputs only the bass component. Therefore, it is possible to prevent deterioration of frequency characteristics and sound image localization, and to obtain clear sound quality with little distortion.

  Further, by providing a hole 93 in a part of the partition wall 92 at a position where mid-high sounds are not directly emitted in the viewer direction, mid-high sounds leak through the diaphragm 91 while the diaphragm 91 is driven by the back pressure of the speaker 10. Can be suppressed.

  In addition, since the strength of the speaker enclosure 90 around the opening 90b is improved by the partition wall 92, a decrease in internal pressure due to deformation of the speaker enclosure 90 can be suppressed, so that the diaphragm 91 is driven by the back pressure of the speaker 10 with little loss. It also has an effect.

<Modification>
As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can implement with another various form. An example is shown below.
(1) In the above-described embodiment, an example is shown in which one speaker is attached to each of the two baffle plates 90a and 90a joined at an angle, and the diaphragm 91 is formed on the back surface of the speaker enclosure. Instead, for example, a configuration as shown in FIG. 9 may be used. The example shown in FIG. 9 is an example in which speakers are attached to the left and right side surfaces of the speaker enclosure 100 and a diaphragm 91 is formed on the front surface thereof. 9A is a side view, FIG. 9B is a front view, and FIG. 9C is a sectional view taken along line AA shown in FIG. 9B. In this case, an opening 102 is formed in the front, and a diaphragm 91 is provided so as to cover the opening 102, and the diaphragm 91 is fixed to the upper surface of the speaker enclosure 100.
The partition wall 101 is provided in the speaker enclosure 100 so as to extend downward from the inner wall of the upper surface at a predetermined distance with respect to the diaphragm 91, and the upper end and the side end thereof are respectively formed on the inner wall of the speaker enclosure 100. It is fixed. The length of the partition wall 101 is configured to be shorter than the height of the speaker enclosure 100, so that a hole 103 is formed between the lower end of the partition wall 101 and the lower surface of the speaker enclosure 100. The hole 103 performs the same function as the hole 93 in the embodiment shown in FIG.
Here, in the case shown in the figure, bass reproduction from 100 Hz (−10 dB) can be achieved by placing two speakers having an effective diameter of 3 cm and a minimum resonance frequency of 190 Hz in a 300 cc speaker enclosure and adjusting the resonance frequency of the diaphragm to 120 Hz. Is possible.

(2) In the embodiment described above, the partition wall is provided inside the speaker enclosure. However, the installation position of the partition wall is not limited to this. Any position is possible. For example, as shown in FIG. 10, a partition wall 92 may be provided so as to cover the diaphragm 91 from the outside. In the example shown in FIG. 10, the front surface, top surface, and side surface of the speaker enclosure 110 protrude forward by a predetermined width, and the front end, top end, and rear end of the partition wall 92 are the right side surface, top surface, and left side surface of the speaker enclosure 110, respectively. It is joined to. The position of the lower end of the partition wall 92 is a predetermined distance from the floor surface, and an opening structure is formed between the floor surface and the floor surface.
Even with the above-described configuration, it is possible to suppress leakage of middle and high sounds, as in the above-described embodiment, and the bass generated by the vibration of the diaphragm 91 can be reduced with the floor surface of the partition wall 92. Released from the opening structure in between.

(3) Further, the shape of the diaphragm is not limited to that described above, and may be, for example, a shape as shown in FIG. FIG. 11A is a perspective view showing the appearance of a speaker system according to this modification, and FIG. 11B is a perspective view of the modification viewed from the back. FIG. 11C is a side sectional view. In this example, as shown in the figure, an opening 60 that is elongated in a U shape from the center to the bottom is provided on the surface facing the baffle plate 50a, that is, the back surface of the speaker enclosure 50. In this case, the U-shaped inner portion functions as the diaphragm 51. That is, since the upper part of the diaphragm 51 is integral with the baffle plate 50a and the other parts are separated from the baffle plate 50a by the U-shaped opening 60, the upper end of the diaphragm 51 is fixed. Can vibrate freely. In addition, the opening 60 is covered from the inside of the speaker enclosure 50 by an edge 70 having an arched cross section, whereby the airtightness of the speaker enclosure 50 is maintained.

  In the example shown in FIG. 11, the partition wall 52 is provided in the speaker enclosure 50 so as to extend downward from the inner wall of the upper surface at a predetermined distance from the diaphragm 51, and its upper end and side end are respectively It is fixed to the inner wall of the speaker enclosure 50. The length of the partition wall 52 is configured to be shorter than the height of the speaker enclosure 50, whereby a hole 53 is formed between the lower end of the partition wall 101 and the lower surface of the speaker enclosure 50.

(4) The position of the hole or opening structure provided in the partition wall is preferably set to a position where the sound wave from the speaker unit does not directly reach the viewer's ear.

(5) A bass reflex type duct may be provided at the lower end or part of the partition wall. For example, as shown by a broken line in FIG. 9C, a duct 105 protruding inside a predetermined distance may be provided. By providing such a duct, it becomes possible to reflect and attenuate medium and high tones inside the duct.
Moreover, the opening structure provided in the partition and the shape of the hole can take various shapes such as a round shape and a square shape, and the number thereof is also arbitrary. About these, what has almost no air resistance in the zone | band which a diaphragm tries to reproduce | regenerate is preferable.
A plurality of partition walls may be provided, and the number of holes and opening structures in these partition walls is arbitrary.

(6) In the embodiment shown in FIG. 1, the back space (opening 90 b) of the diaphragm 91 is formed in the internal space of the speaker enclosure 90, and the same back space (opening 102) is formed in the embodiment shown in FIG. 9. Is formed. These back spaces may be configured by providing a hole in the speaker enclosure, with the upper end fixed to the speaker enclosure, and a diaphragm surrounded by edges on the left and right sides and the lower part so as to cover the hole.

It is a figure which shows the structure of the speaker system which is embodiment of this invention. It is an exploded view of the same embodiment. It is an electric equivalent circuit of a speaker. It is an electrical equivalent circuit of a speaker enclosure. It is the equivalent circuit of the conventional passive radiator. It is an equivalent circuit of the conventional passive radiator system. It is an equivalent circuit of the diaphragm concerning this invention. It is an equivalent circuit of the speaker system concerning this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Speaker, 40 ... Edge, 90, 100, 110 ... Speaker enclosure, 90b, 102 ... Opening, 91 ... Diaphragm, 92 ... Partition, 53, 93, 103 ... Hole, 94 ... Beam member, 95 ... Frame member .

Claims (6)

A speaker enclosure that is sealed inside;
A speaker attached to the speaker enclosure;
A diaphragm that can vibrate elastically with one end fixed on one surface of the speaker enclosure;
An opening structure that is provided at a position corresponding to a vibration part of the diaphragm on the one surface on which the diaphragm is provided, and that exposes the internal space of the speaker enclosure;
A sealing member that is attached between the diaphragm and the opening structure, closes a space exposed by the opening structure in a state that enables the diaphragm to vibrate, and maintains the airtightness of the speaker enclosure;
A speaker system, comprising: a partition wall provided at a predetermined interval with respect to the diaphragm, and having a high impedance with respect to sound waves in a predetermined frequency region emitted from the speaker.   The speaker system according to claim 1, wherein the partition wall is provided in an internal space of the speaker enclosure.   The speaker system according to claim 1, wherein the partition wall is provided so as to cover the exposure of the diaphragm from the outside.   4. The speaker system according to claim 1, wherein one surface on which the diaphragm and the opening are provided is another surface different from a surface on which the speaker is attached.   The speaker system according to claim 1, wherein a plurality of the speakers are provided on the same surface of the speaker enclosure. In a sealed speaker enclosure having a speaker mounting hole to which a speaker is mounted,
A diaphragm that can vibrate elastically with one end fixed to one surface of the speaker enclosure;
An opening structure that is provided at a position corresponding to a vibration part of the diaphragm on the one surface on which the diaphragm is provided, and that exposes the internal space of the speaker enclosure;
A sealing member that is attached between the diaphragm and the opening structure, closes a space exposed by the opening structure in a state that enables the diaphragm to vibrate, and maintains the airtightness of the speaker enclosure;
A speaker enclosure, comprising: a partition wall provided at a predetermined interval with respect to the diaphragm, and having a high impedance to sound waves in a predetermined frequency region emitted from the speaker.

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