JP2019118154A - Speaker and headphones - Google Patents

Abstract

To provide a speaker in which the reproduction volume of the low frequency range is increased.SOLUTION: A speaker includes a back-release speaker unit (5), a plurality of sound emitting portions (5a) formed in a predetermined area on the back side and emitting sound, a housing portion (1) disposed so as to cover the back side of the speaker unit and forming a back cavity (Va) with the speaker unit (5), and a fin unit (12) having at least one annular or arc-shaped fin (12c) expanding in diameter with a distance from the speaker unit (5) and disposed in the back cavity (Va).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a speaker and a headphone, and more particularly to a speaker and a headphone using a back surface open type speaker unit.

In a speaker configured to include a speaker unit and an enclosure, a back surface release type may be used for the speaker unit.
In addition, a speaker unit used for a so-called overhead type headphone equipped with a headband is generally a back open type. The back surface open type speaker unit has an opening at the back surface of the case of the speaker unit and emits sound also from the back surface.
Patent Document 1 describes an overhead type headphone provided with the back surface release type speaker unit.

JP 2012-080219 A

In general, a speaker (speaker system) having a rear open type speaker unit and an enclosure to which the speaker unit is attached is empirically found that the deeper the enclosure (the longer the depth), the higher the reproduction volume of the bass region. It is known to.
In the overhead type headphone, the back cover of the housing unit that accommodates the speaker unit and is applied to the ear corresponds to this enclosure, and the housing unit corresponds to the speaker.
Therefore, it is considered to lengthen the depth of the housing part to increase the reproduction volume of the low frequency range, but the housing part in the headphone has a long depth shape from the viewpoint of the improvement of the fit to the ear and the design. It is difficult to
Therefore, for short-deep speakers and headphones, it is desirable to devise a technique for increasing the reproduction volume of the low-pitched range without lengthening the depth of the enclosure or back cover.

  Therefore, the problem to be solved by the present invention is to provide a speaker and a headphone in which the reproduction volume of the bass region is increased without increasing the depth.

In order to solve the above-mentioned subject, the present invention has the following composition.
1) A rear surface open type speaker unit, a plurality of sound emitting parts that are formed in a predetermined area on the rear surface of the speaker unit and emit sound, and are arranged to cover the rear surface side of the speaker unit And a fin unit having at least one annular or arc-shaped fin disposed in the back cavity and expanding in diameter away from the speaker unit. Speaker. 2) A headphone comprising the pair of speakers described in 1) and a headband connecting the pair of speakers.

  According to the present invention, there is an effect that the reproduction volume of the bass region is increased without lengthening the depth.

FIG. 1 is a perspective view for explaining an entire configuration of a headphone 51 which is an example of a headphone according to the embodiment of the present invention. FIG. 2 is a perspective sectional view for explaining the housing portion 1 in the headphone 51. As shown in FIG. FIG. 3 is a perspective assembly view for explaining the housing unit 1. FIG. 4 is a rear view of the speaker unit 5 housed in the housing unit 1. FIG. 5 is a perspective view for explaining the fin unit 12 provided in the housing unit 1 and is an enlarged view of the fin unit 12 shown in FIG. FIG. 6 is a perspective view of the fin unit 12 as viewed from the back side. FIG. 7 is a front view of the fin unit 12. FIG. 8 is a schematic cross-sectional view of the housing portion 1. FIG. 9 is a cross-sectional view for explaining a housing portion 101 not provided with the fin unit 12 as a comparative example. FIG. 10 is a graph showing sound pressure frequency characteristics of the housing 1 and the housing 101. As shown in FIG. FIG. 11 is a schematic view for explaining the cross-sectional area of the sound emitted from the back surface of the speaker unit 5 in the propagation path in the housing unit 1.

  A headphone according to an embodiment of the present invention will be described using a headphone 51 as a preferred embodiment with reference to FIGS.

FIG. 1 is an external perspective view for explaining the headphone 51. As shown in FIG.
The headphone 51 is an overhead type, and connects the housing 1 to be addressed corresponding to the left ear when used and the housing 2 to be addressed corresponding to the right ear, and the housing 1 and the housing 2 to be connected And a curved headband 3.
The housing parts 1 and 2 are formed in a substantially flat cylindrical shape, and the flexible ear pad 4 is detachably attached to each.
Speaker units 5 are accommodated in the housings 1 and 2 respectively.

  FIG. 2 is a perspective sectional view of the housing portion 1 of FIG. 1 at the S2-S2 position. FIG. 3 is a perspective assembly view of the housing part 1. The ear pad 4 is not shown in FIGS. 2 and 3. In the following description, the front direction and the back direction are defined as shown in FIG. In the use state of the headphones 51, the ear is positioned on the front direction side, and the back direction is a direction away from the head.

As shown in FIGS. 2 and 3, the housing portion 1 has a baffle plate 11 on the side facing in the front direction. The baffle plate 11 is formed in a disk shape, and the small diameter portion is a sound emitting portion 11 a capable of air circulation in the form of a radiation grid.
The speaker unit 5 is disposed on the back surface side (rear surface side) of the sound emitting portion 11 a of the baffle plate 11 in a posture in which the baffle plate 11 side is the front. In FIG. 3, the speaker unit 5 is schematically described in a disk shape.

  The housing unit 1 is disposed on the rear side of the speaker unit 5 and is fixed to the fin unit 12 by sandwiching the speaker unit 5 with the baffle plate 11 so as to cover the speaker unit 5 and the fin unit 12. And 11, a flat pot-like back cover 13 fixed by screws.

A space serving as a substantially sealed back cavity Va (see FIG. 2) is formed on the back surface side of the speaker unit 5 surrounded by the baffle plate 11 and the back cover 13. Hereinafter, the space Va is also referred to.
As shown in FIG. 2, the speaker unit 5 includes a case 5 c and a diaphragm 5 s supported by the case 5 c in the front direction.

  The speaker unit 5, the fin unit 12, and the back cover 13 have a substantially circular outer shape in plan view, and are assembled with their central axes as a common central axis CL1.

Next, the speaker unit 5 will be described with reference to FIG.
FIG. 4 is a rear view of the speaker unit 5. The speaker unit 5 is a back surface open type exhibiting a flat disk shape.
Therefore, at the time of voice output, the sound generated by the vibration of the diaphragm 5s is emitted not only from the front but also from the back surface sound emitting portion 5a on the back surface.
That is, the case 5c of the speaker unit 5 has a sound emission hole (not shown) on the front side, and also has a rear sound emission portion 5a as an opening on the rear side.

Specifically, the speaker unit 5 is provided as a back surface sound emitting portion 5a between the center sound emitting portion 5a1 provided as a circular range of the radius r1 centering on the position of the center axis line CL1, the radius r2 and the radius r3. And an annular sound emitting portion 5a2 provided as an annular range. The inner edge and the outer edge of the annular sound emitting portion 5a2 have similar shapes in this example.
An acoustic filter 5b1 and an acoustic filter 5b2 formed of a foamed resin sheet or the like are attached to the central sound emitting portion 5a1 and the annular sound emitting portion 5a2, respectively.

Next, the fin unit 12 will be described mainly with reference to FIGS.
FIG. 5 is an enlarged view of the fin unit 12 shown in a perspective view in FIG. FIG. 6 is a perspective view of the fin unit 12 as viewed from the rear side. FIG. 7 is a front view of the fin unit 12.

The fin unit 12 has three annular fins 12a, 12b and 12c which are concentric and different in diameter, and three radial support beams 12d for connecting the fins 12a to 12c, with the central axis CL1 as a center. It is made of resin.
As shown in FIGS. 2 and 5, each support beam 12d is formed with a rib 12d1 extending in the circumferential direction and protruding in the front direction.

  The three fins 12a to 12c are formed in an annular shape or an arc shape having diameter increasing portions 12a2 to 12c2 which have a minimum diameter at the side end portions 12a1 to 12c1 in the front direction and which increase in diameter as they progress in the back direction. Here, a trumpet-shaped member which is formed in an annular shape and goes in the back direction will be described. The fins 12a to 12c are formed in an arc when the terminals or the like are provided inside the housing portion 1 and can not be formed annularly, or when the wiring portion overlaps the annular portion.

The shapes of the fins 12a to 12c will be specifically described with reference mainly to FIGS.
The inner radius of the front end 12a1 is R4S, and the fin 12a gradually expands in diameter as advancing from the front end 12a1 to the back direction, and the annular enlarged diameter section 12a2 reaches the back end 12a3 of the radius R4E. Have.
The fin 12b has a radius R5S such that the inner radius of the front end 12b1 is larger than the radius R4E, and the diameter gradually increases toward the rear direction, and the annular enlarged diameter portion 12b2 reaches the rear end 12b3 of the radius R5E. have.
The fin 12c has a radius R6S where the inner radius of the front end 12c1 is larger than the radius R5E, and the ring 12c2 gradually expands in diameter toward the rear direction and reaches the rear end 12c3 of the radius R6E. have.

The fins 12c are further connected to the rear end 12c3 and extend in an annular shape with a radius R6E of substantially the same radius in the front direction to increase the propagation distance of the sound emitted from the rear sound release portion 5a. It has a part 12c4.
The fin 12c has three bosses 12c5 extending in the front direction and separated in the circumferential direction at positions corresponding to the support beams 12d on the side of the enlarged diameter portion 12c2 in the front direction. A pilot hole is formed in the boss 12c5, and is fixed to the baffle plate 11 with a tapping screw (not shown) from the side in the front direction.

In this fixed condition, the ribs 12d1 provided on each of the three support beams 12d are in contact with the non-opening 5c1 of the radius r1 to the radius r2 (see FIG. 4) in the case 5c of the speaker unit 5.
Thus, the speaker unit 5 is held between the baffle plate 11 and the fin unit 12 without a gap in the normal back direction.

Next, the back cover 13 will be described.
As shown in FIG. 3, the back cover 13 is formed of a resin and has a disc-shaped bottom wall 13a and a side wall 13b which is annularly erected from the periphery of the bottom wall 13a.
In the vicinity of the side wall 13b of the bottom wall 13a, four bosses 13a2 are provided so as to be spaced apart in the circumferential direction.
A pilot hole is formed in the boss 13a2, and the baffle plate 11 is fixed to the boss 13a2 with a tapping screw (not shown) from the side in the front direction.

By this clamping and fixing, a space Va surrounded by the baffle plate 11, the speaker unit 5, and the back cover 13 is formed in a substantially sealed state as a back cavity.
The bottom wall 13a is provided with a cone-shaped protrusion 13c having a top 13c1 on the central axis CL1. The inclined circumferential surface 13c2 of the protrusion 13c is concave in the radial direction cross section.

FIG. 8 is a schematic cross-sectional view for explaining the positional relationship between the back surface sound emitting portion 5a of the speaker unit 5 and the fins 12a to 12c of the fin unit 12 in the housing portion 1 in the radial direction and the normal back direction. is there. FIG. 8 is a schematic plan view showing the perspective cross-sectional shape of FIG.
In FIG. 8, the central sound emitting portion 5a1 and the annular sound emitting portion 5a2 are both at the same position in the normal / back direction, and the distance between that position and the inner surface 13a1 of the bottom wall 13a is the distance L1. .

As shown in FIG. 8, the front end 12 a 1 of the annular fin 12 a is at a position substantially corresponding to the outer peripheral edge of the center sound emitting portion 5 a 1 of the speaker unit 5.
That is, the radius r1 and the radius R4S correspond with relatively close values. For example, the radius R4S may be in the range of ± 5% of the radius r1.

The front side end 12 b 1 of the annular fin 12 b is at a position substantially corresponding to the small diameter peripheral edge of the annular sound emitting portion 5 a 2 of the speaker unit 5.
That is, the radius r2 and the radius R5S have relatively close values. For example, the radius R5S may be in the range of ± 10% of the radius r2.

The front side end 12 c 1 of the annular fin 12 c is at a position substantially corresponding to the large diameter peripheral edge of the annular sound emitting portion 5 a 2 of the speaker unit 5.
That is, the radius r3 and the radius R6S are relatively close values. For example, the radius R6S may be within ± 15% of the radius r3.
Since the fins 12a are smaller in diameter and inside the fins 12b and the fins 12c, they become inner fins for the fins 12b and the fins 12c. Similarly, the fins 12b serve as inner fins for the fins 12c.

The fins 12 a to 12 c are provided separately in the back direction so as to form a gap without contacting the case 5 c of the speaker unit 5.
Thereby, at the time of the output of the speaker unit 5, the contact noise between the case 5c and the fins 12a to 12c does not occur.

  The top 13c1 of the projection 13c of the back cover 13 is located between the front end 12a1 and the rear end 12a3 of the fin 12a in the normal back direction.

In the case where the housing unit 1 does not have the fin unit 12 and the protrusion 13 c due to the above-described configuration having the fin unit 12 and the protrusion 13 c, the sound emitted from the back surface sound release unit 5 a into the space Va (conventional housing unit Compared to), it is designed to propagate a long distance.
In addition, the fin unit 12 is disposed as a partition wall between the back surface sound emitting portion 5 a and the inner surface 13 a 1 of the back cover 13. Therefore, by having the fin unit 12, so-called return sound, which is emitted from the back surface sound emitting portion 5a and reflected by the inner surface 13a1 and returned to the back surface sound emitting portion 5a, is reduced.

FIG. 9 is a cross-sectional view showing a housing portion 101 as a comparative example in which the fin unit 12 and the projecting portion 13 c are removed from the housing portion 1. In detail, it is a figure explaining the example of a propagation aspect of sound when making an speaker unit 5 input an impulse signal.
In the housing portion 101, when the center sound D101 and the ring sound D102 emitted in the back direction from the center sound emitting portion 5a1 and the ring sound emitting portion 5a2 propagate the distance L1 in the back direction, the bottom wall 13a serving as a barrier The inner surface 13a1 is reached.
The central emitted sound D101 and the annular emitted sound D102 are reflected by the inner surface 13a1, and return to the central sound emitting portion 5a1 and the annular sound emitting portion 5a2 as the reflected sounds DH101 and DH102.
As described above, in the housing portion 101, the propagation distance of the center emission sound D101 and the ring emission sound D102 becomes the distance L1.

On the other hand, in the housing portion 1 shown in FIG. 8, the central emission sound D1 emitted in the back direction from the central sound emitting portion 5a1 is formed between the enlarged diameter portion 12a2 of the fin 12a and the inclined circumferential surface 13c2 of the projecting portion 13c. It is guided by them and travels in the back direction and propagates in the radial outward direction. By disposing the projecting portion 13 c, propagation in the radial direction is promoted. Even if the protrusion 13c is not disposed, the center emission sound D1 emitted in the back direction from the center sound emitting portion 5a1 propagates outward in the radial direction.
Then, the center emission sound D1 propagates radially outward along the inner surface 13a1 of the bottom wall 13a (arrow path D1a).
Next, the center emission sound D1 propagates to the front side between the side wall 13b and the return fin portion 12c4 (arrow path D1b).
Then, after the center emission sound D1 propagates toward the central axis line CL1 between the front end 12c6 of the return fin portion 12c4 and the back surface 11b of the baffle plate 11 (path arrow D1c), the enlarged diameter portion 12c2 of the fin 12c The surface 12c7 on the front direction side is reached (path arrow D1d).

That is, the propagation path of the central emission sound D1 is a path indicated by the path arrow D1a to the path arrow D1d, and the propagation distance is generally a distance obtained by adding 2.5 times the distance L1 and the distance L2.
The distance L2 is a distance from the central axis line CL1 to a midpoint between the side wall 13b and the return fin portion 12c4.

On the other hand, the annular sound D2 emitted in the rear direction from the annular sound emitting portion 5a2 passes between the enlarged diameter portion 12b2 of the fin 12b and the enlarged diameter portion 12c2 of the fin 12c and is guided by them and proceeds in the rear direction And propagate radially outward.
Then, it reaches the surface 12c7 on the front direction side of the enlarged diameter portion 12c2 of the fin 12c in the same propagation path as the central emission sound D1, that is, the paths indicated by the path arrows D1b to D1d.

That is, the propagation path of the annular emission sound D2 is a path indicated by the path arrow D2a and the path arrow D1b to the path arrow D1d, and the propagation distance is approximately a distance obtained by adding 2.5 times the distance L1 and the distance L3. Become.
The distance L3 is a distance between the radial center position of the annular sound emitting portion 5a2 and the maximum diameter position of the distance L2.

  As described above, the housing unit 1 includes the fin unit 12 so that the propagation path lengths (propagation distances) of the central emission sound D1 and the annular emission sound D2 are equal to each other even if the housing unit 101 and the depth have the same length. It has become significantly longer. By combining the propagation path of the central emission sound D1 and the propagation path of the annular emission sound D2 in this manner, the sounds emitted from the sound emission portions 5a1 and 5a2 are transmitted from the sound emission portions 5a1 and 5a2 of the propagation path. It becomes easy to reach the farthest route end.

FIG. 10 is a graph showing sound pressure frequency characteristics for comparing the difference between the reproduction sound by the housing unit 1 and the reproduction sound by the housing unit 101.
The solid line indicates the characteristic of the reproduced sound by the housing unit 1, and the dashed-dotted line indicates the characteristic of the reproduced sound by the housing unit 101.

FIG. 10 shows two characteristics different from the presence or absence of the fin unit 12 and the protrusion 13c, but the reproduction sound of the housing unit 1 having the fin unit 12 and the protrusion 13c has a lower sound pressure Is high and the volume is increasing.

As described above in detail, the housing portion 1 has the same distance L1 in the positive / back direction of the space Va as compared with the housing portion 101 not provided with the fin unit 12 and the projecting portion 13c with respect to the housing portion 1. , The propagation distance of the sound emitted from the back surface emission part 5a is long.
And it is confirmed by the actual value that the sound pressure of the low-pitched region is high.
That is, in the headphone 51 provided with the housing unit 1, the reproduction volume of the bass region is increased without lengthening the depth of the housing unit 1.

Further, the reflected sound DH101 generated in the housing portion 101 and returning to the central sound emitting portion 5a1 does not occur in the housing portion 1 because the projecting portion 13c is provided.
Therefore, the reflected sound returning to the center sound emitting portion 5a1 does not affect the vibration of the diaphragm 5s, and the reproduced sound by the housing portion 1 is less distorted.

Further, in the housing portion 1, the reflected sound which is emitted in the back direction from the annular sound emitting portion 5a2 and reaches the inner surface 13a1 of the bottom wall 13a and is reflected is mostly blocked by the fins 12b, so again the annular sound emitting portion 5a2 The reflected sound back to is slight.
Therefore, the degree to which the reflected sound of the annular emitted sound D2 emitted from the annular sound emitting portion 5a2 affects the vibration of the diaphragm 5s is only a slight degree, and the reproduced sound by the housing portion 1 is also less distorted at this point.

In the housing portion 1, the protrusions 13c of the fins 12a to 12c and the bottom wall 13a are set so that the cross sectional area (the cross sectional area in the direction orthogonal to the propagation direction) of the propagation path of the sound emitted from the annular sound emitting portion 5a2 becomes constant. The shape of is determined.
For example, in FIG. 8, the central emission sound D1 emitted from the central sound emitting portion 5a1 is guided by the enlarged diameter portion 12a2 of the fin 12a and the inclined circumferential surface 13c2 of the projecting portion 13c, and propagates in the back direction. Propagating outwards.

Since the fins 12a are formed in an annular shape as shown in FIG. 6 and the like, the center emission sound D1 propagates so as to expand in diameter over the entire circumference of 360 °.
Therefore, if the cross-sectional area of the unit angle range of the propagation path is constant, the total cross-section of the propagation path expands with the propagation.

It is empirically known that, when propagating in the space Va which is the back cavity, if the cross-sectional area in the direction orthogonal to the propagation direction, which is the cross-sectional area of the propagation path, changes significantly, the sound quality tends to deteriorate. There is.
Therefore, in the housing portion 1, each shape is set such that the cross-sectional area of the propagation path of the center emission sound D1 and the ring emission sound D2 propagating in an annular shape is substantially constant regardless of the diameter.

FIG. 11 is a perspective view schematically showing a method of making the cross-sectional area constant.
In FIG. 11, the path width at a position where the radius is Ra is assumed to be ha, and the path width at a position Rb where the radius is larger than Ra is assumed to be hb. Do.
The cross-sectional area Sa of the route T at the Ra position is Sa = 2πRa × ha, and the cross-sectional area Sb of the route T at the Rb position is Sb = 2πRb × hb.
In order to set Sa = Sb which is a preferred embodiment,
hb = (Ra / Rb) × ha (Equation 1)
And it is sufficient.

When this concept is applied to the housing portion 1, it becomes as shown in FIG.
That is, the width in the positive / back direction between the bottom wall 13a and the rear end 12a3 to 12c3 of the fins 12a to 12c is taken as the width h12a to h12c. Further, the radius of each of the rear side end portions 12a3 to 12c3 is R4E, R5E, and R6E (see also FIG. 7).
At this time, the route cross-sectional area S12a, S12b, at the rear end 12a3 to 12c3 position.
S12c is shown as follows.
S12a = 2πR4E × h12a (Equation 2)
S12b = 2πR5E × h12b (Equation 3)
S12c = 2πR6E × h12c (Equation 4)
Therefore, in order to set S12a = S12b = S12c in the preferred embodiment,
h12b = (R4E / R5E) × h12a (Equation 5)
h12c = (R4E / R6E) × h12a (Equation 6)
And it is sufficient.

The embodiment of the present invention is not limited to the above-described configuration, and may be modified within the scope of the present invention.
The headphones 51 are not limited to the so-called overhead type having a headband. Other types of headphones may be used, such as an ear-hook type headphone equipped with an ear-hanging hanger and attached to the pinna.
The annular sound emitting portion 5a2 may not be a continuous complete annular region. It may be C-shaped having discontinuous portions, that is, an arc-shaped region.
In addition, the center sound emitting portion 5a1 and the annular sound emitting portion 5a2 may be configured by a plurality of holes. In this case, the annular sound emitting portion 5a2 is arranged to form an annular or arc shape.
Also, the fins may not be continuous and completely annular. That is, it may be formed in an arc.
When any of the above fins 12a to 12c is combined with the annular sound emitting portion 5a2, when the fin is arc-shaped and the annular sound emitting portion 5a2 is annular, the effect of the present invention can be obtained in the arc circumferential range of the fins. Play. On the other hand, when the fins are annular and the annular sound emitting portion 5a2 is arc-shaped, the effect of the present invention is exerted in the circumferential direction of the fin corresponding to the arc of the annular sound emitting portion 5a2.

When the back cover 13 of the housing unit 1 is viewed as an enclosure, a speaker SP called a so-called speaker system is configured including the speaker unit 5 and the back cover 13. This speaker SP is also included in the present invention.
For example, in the case where the depth of the speaker SP can not be increased due to the restriction of the design, the same effect as the headphone 51 can be obtained by adopting the configuration of the embodiment including the fin unit 12 described above.

1, 2 housing part 3 head band 4 ear pad 5 speaker unit 5a back surface emission part, 5a1 center emission part, 5a2 annular output part 5b1, 5b2 acoustic filter, 5c case, 5c1 non-opening part 5s diaphragm 11 baffle Board, 11a Sound release part, 11b Back 12 fin unit 12a-12c Fin, 12a1-12c1 Front end 12a2-12c2 Expanded part, 12a3-12c3 Back end 12c4 Return fin part, 12c5 Boss, 12c6 Front end Section 12c7 (on the front direction side), 12d support beam, 12d1 rib 13 back cover 13a bottom wall, 13a1 inner surface, 13a2 boss, 13b side wall 13c projecting portion, 13c1 top portion, 13c2 inclined circumferential surface 51 headphone CL1 central axis D1 central axis D1 Emission sound, D2 ring emission sound DH1, H2, DH101, DH102 reflected sound ha, hb path width, L1 to L3 distance r1~r3, R4S, R4E, R5S, R5E, R6S, R6E, Ra, Rb radius,
Sa, Sb (of propagation path), T path Va space (back cavity)
SP speaker

Claims (4)

Rear open type speaker unit,
A plurality of sound emitting units formed in a predetermined area on the back surface of the speaker unit and emitting sound;
A housing portion disposed to cover the back side of the speaker unit and forming a back cavity between the speaker unit and the housing portion;
A fin unit having at least one annular or arc-shaped fin disposed in the back cavity and expanding in diameter with distance from the speaker unit;
A speaker characterized by having.  The bottom wall of the back cover constituting the side wall and the bottom wall of the back cavity is provided with a cone-shaped projection having a top on the central axis of the speaker unit and projecting in the front direction of the fin unit The speaker according to claim 1, characterized in that:   The fin unit includes a return fin portion connected to the largest diameter portion of the fin and extending in the front direction of the fin unit with a distance from the side wall of the back cavity. The speaker as described in 2. A headphone comprising: a pair of speakers according to any one of claims 1 to 3; and a headband connecting the pair of speakers.

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