Abstract:
A loudspeaker includes: a bottom plate; a center pole provided upwardly from the bottom plate; a yoke surrounding the center pole and having a plurality of slits; a magnet for providing a magnetic flux for the center pole and the yoke; a coil provided between the center pole and the yoke; a first annular member for supporting the coil; a plurality of support members for supporting the first annular member, the plurality of support members being inserted into the plurality of slits; and a diaphragm supported by the plurality of support members, wherein upper faces of the plurality of support members gradually decrease in height in a direction away from the first annular member, and wherein a lower face of the coil is located below a position at which the diaphragm is supported by the plurality of support members.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a thin loudspeaker having a relatively low profile.  
           [0003]    2. Description of the Related Art  
           [0004]    A loudspeaker structure is disclosed in Japanese Laid-Open Patent Publication No. 55-64500, which includes a yoke having slits formed therein, and support members inserted in the slits, such that a voice coil and a diaphragm are coupled via the support members.  
           [0005]    [0005]FIG. 39 is a cross-sectional view illustrating a conventional loudspeaker  7000  disclosed in Japanese Laid-Open Patent Publication No. 55-64500. FIG. 40 is a plan view illustrating a magnetic circuit and associated elements, as viewed from above a diaphragm  8  of the loudspeaker  7000 .  
           [0006]    The loudspeaker  7000  includes: a bottom plate  23 ; a magnet  1  provided on the bottom plate  23 ; a center pole  2  provided on the magnetic  1 ; a yoke  3  which is provided so as to surround the center pole  2  and which has a plurality of slits  11  in a radial arrangement; a coupling member  37 ; a voice coil  39  affixed to the inner periphery of the coupling member  37 ; a diaphragm  8  and dampers  10  affixed to the outer periphery of the coupling member  37 ; frames  12 A and  12 B; and a cover  34 . The coupling member  37  has support members  35  to be inserted in the plurality of slits  11 , and inner and outer rings  36  and  46 .  
           [0007]    The magnet  1 , the center pole  2 , the yoke  3 , and the bottom plate  23  together compose a magnetic circuit. A magnetic flux is generated within a magnetic gap  4  by the magnetic circuit.  
           [0008]    As an electric input is supplied to the voice coil  39  in the above structure, a driving force along a vertical direction is generated in the voice coil  39  according to Fleming&#39;s left-hand rule, due to the magnetic flux generated within the magnetic gap  4 . Since the diaphragm  8  is coupled to the voice coil  39  by means of the coupling member  37  (i.e., via the support members  35 ), the driving force generated in the voice coil  39  is transmitted to the diaphragm  8 , which vibrates and emits sound. Since this structure prevents the diaphragm  8  from contacting an upper face  3 A of the yoke  3 , there is no need to allow for an amplitude margin when designing the total height of the loudspeaker  7000 . As a result, the total height h can be reduced.  
           [0009]    [0009]FIG. 41 is a plan view showing a cylindrical coupling member  47  disclosed in Japanese Laid-Open Patent Publication No. 55-64500, supra. The cylindrical coupling member  47  is composed of an elongated metal foil which is folded at periodic lengths, so that the folded portions are linked together to form protruding support members  45  of the cylindrical coupling member  47 . A voice coil  39  is affixed to the inner periphery of the coupling member  47 .  
           [0010]    However, in accordance with the loudspeaker  7000  shown in FIGS. 39 and 40, it is necessary to attach the coupling member  37  to the outer periphery of the voice coil  39 . As the wire diameter for the voice coil  39  is changed in order to obtain various levels of driving force, the outer diameter of the voice coil  39  also varies. This necessitates a change in the inner diameter of the inner periphery of the coupling member  37  to which the voice coil  39  is attached. In other words, for each voice coil  39 , a coupling member  37  having corresponding geometry must be designed. This presents a problem, when mass producing various models, in that costs associated with the production of component parts and the production facility itself are increased, and that the storage and management of varying component parts becomes cumbersome.  
           [0011]    On the other hand, in the case where the coupling member  47  with support members  45  as shown in FIG. 41 is formed by folding a thin metal foil (especially due to mass productivity-related concerns), the support members  45  can only be adhered to the diaphragm  8  and the dampers  10  in an extremely small adhesion area, resulting in a poor adhesion strength. Consequently, peeling associated with the diaphragm  8  moving with a large amplitude or failure of the driving force generated in the voice coil  39  to be transmitted to the diaphragm  8  may occur, thereby unfavorably affecting the sound pressure characteristics of the loudspeaker  7000 .  
         SUMMARY OF THE INVENTION  
         [0012]    According to the present invention, there is provided a loudspeaker including: a bottom plate; a center pole provided upwardly from the bottom plate; a yoke surrounding the center pole and having a plurality of slits; a magnet for providing a magnetic flux for the center pole and the yoke; a coil provided between the center pole and the yoke; a first annular member for supporting the coil; a plurality of support members for supporting the first annular member, the plurality of support members being inserted into the plurality of slits; and a diaphragm supported by the plurality of support members, wherein upper faces of the plurality of support members gradually decrease in height in a direction away from the first annular member, and wherein a lower face of the coil is located below a position at which the diaphragm is supported by the plurality of support members.  
           [0013]    In one embodiment of the invention, the lower face of the coil is located below lower faces of the plurality of support members.  
           [0014]    In another embodiment of the invention, the coil is provided at an outer periphery of the first annular member.  
           [0015]    In still another embodiment of the invention, the loudspeaker further includes a plurality of dampers for supporting the plurality of support members.  
           [0016]    In still another embodiment of the invention, the plurality of support members each have a plate-like shape.  
           [0017]    In still another embodiment of the invention, the loudspeaker further includes a second annular member provided between the plurality of support members and the first annular member, wherein the plurality of support members support the first annular member via the second annular member.  
           [0018]    In still another embodiment of the invention, the plurality of support members and the first annular member are formed as an integral piece.  
           [0019]    In still another embodiment of the invention, the plurality of support members and the second annular member are formed as an integral piece.  
           [0020]    In still another embodiment of the invention, the loudspeaker further includes a third annular member provided between the plurality of support members and the diaphragm, wherein the plurality of support members support the diaphragm via the third annular member.  
           [0021]    In still another embodiment of the invention, the loudspeaker further includes a third annular member provided between the plurality of support members and the plurality of dampers, wherein the plurality of dampers support the plurality of support members via the third annular member.  
           [0022]    In still another embodiment of the invention, the plurality of support members and the third annular member are formed as an integral piece.  
           [0023]    In still another embodiment of the invention, the loudspeaker further includes a second annular member provided between the plurality of support members and the first annular member, wherein the plurality of support members support the first annular member via the second annular member.  
           [0024]    In still another embodiment of the invention, the magnet is provided between the bottom plate and the center pole.  
           [0025]    In still another embodiment of the invention, the bottom plate and the yoke are formed as an integral piece.  
           [0026]    In still another embodiment of the invention, the magnet surrounds the center pole.  
           [0027]    In still another embodiment of the invention, the magnet has a plurality of slits; and the plurality of slits of the magnet are disposed so as to be aligned with the plurality of slits of the yoke.  
           [0028]    In still another embodiment of the invention, the bottom plate and the center pole are formed as an integral piece.  
           [0029]    In still another embodiment of the invention, the first annular member is supported at a first end of each of the plurality of support members, and the diaphragm is supported at a second end of each of the plurality of support members; and a lower face of each of the plurality of support members has a stepped configuration such that the lower face is lower at the second end than at the first end.  
           [0030]    In still another embodiment of the invention, the loudspeaker further includes a cover provided so as to cover an upper face of the center pole.  
           [0031]    In still another embodiment of the invention, the cover and the first annular member are formed as an integral piece.  
           [0032]    Alternatively, a loudspeaker according to the present invention includes: a bottom plate; a center pole provided upwardly from the bottom plate; a yoke surrounding the center pole and having a plurality of slits; a magnet for providing a magnetic flux for the center pole and the yoke; a coil provided between the center pole and the yoke; a first annular member for supporting the coil; a coupling member composed essentially of a plate material folded into an annular shape having a plurality of protruding portions, the coupling member supporting the first annular member, wherein one of the plurality of protruding portions is inserted into two of the plurality of slits; and a diaphragm supported by the coupling member.  
           [0033]    In one embodiment of the invention, the loudspeaker further includes a plurality of dampers for supporting the coupling member.  
           [0034]    In another embodiment of the invention, the loudspeaker further includes a cover provided so as to cover an upper face of the center pole.  
           [0035]    In still another embodiment of the invention, the cover and the first annular member are formed as an integral piece.  
           [0036]    Alternatively, a loudspeaker according to the present invention includes: a bottom plate; a center pole provided upwardly from the bottom plate; a yoke surrounding the center pole and having a plurality of slits; a magnet for providing a magnetic flux for the center pole and the yoke; a coil provided between the center pole and the yoke; a coupling member composed essentially of a plate material folded into an annular shape having a plurality of protruding portions, the coupling member supporting the coil, wherein one of the plurality of protruding portions is inserted into two of the plurality of slits; and a diaphragm supported by the coupling member.  
           [0037]    In still another embodiment of the invention, the loudspeaker further includes a plurality of dampers for supporting the coupling member.  
           [0038]    Alternatively, a loudspeaker according to the present invention includes: a bottom plate; a center pole provided upwardly from the bottom plate; a yoke surrounding the center pole and having a plurality of slits; a magnet for providing a magnetic flux for the center pole and the yoke; a coil provided between the center pole and the yoke; a first annular member for supporting the coil; a plurality of support members, each having a first end and a second end, for supporting the first annular member at the first ends, the plurality of support members being inserted into the plurality of slits; and a diaphragm supported by the plurality of support members at the second ends, wherein a lower face of each of the plurality of support members has a stepped configuration such that the lower face is lower at the second end than at the first end, and the diaphragm supported by the plurality of support members at the second ends is supported at a position below the lower face, at the first end, of each of the plurality of support members.  
           [0039]    In one embodiment of the invention, the coil is provided at an outer periphery of the first annular member.  
           [0040]    In another embodiment of the invention, the loudspeaker further includes a plurality of dampers for supporting the plurality of support members.  
           [0041]    In still another embodiment of the invention, the loudspeaker further includes a second annular member provided between the plurality of support members and the first annular member, wherein the plurality of support members support the first annular member via the second annular member.  
           [0042]    In still another embodiment of the invention, the plurality of support members and the first annular member are formed as an integral piece.  
           [0043]    In still another embodiment of the invention, the plurality of support members and the second annular member are formed as an integral piece.  
           [0044]    In still another embodiment of the invention, the loudspeaker further includes a third annular member provided between the plurality of support members and the diaphragm, wherein the plurality of support members support the diaphragm via the third annular member.  
           [0045]    In still another embodiment of the invention, the loudspeaker further includes a third annular member provided between the plurality of support members and the plurality of dampers, wherein the plurality of dampers support the plurality of support members via the third annular member.  
           [0046]    In still another embodiment of the invention, the plurality of support members and the third annular member are formed as an integral piece.  
           [0047]    In still another embodiment of the invention, the loudspeaker further includes a second annular member provided between the plurality of support members and the first annular member, wherein the plurality of support members are interposed between the second annular member and the third annular member.  
           [0048]    In still another embodiment of the invention, the magnet is provided between the bottom plate and the center pole.  
           [0049]    In still another embodiment of the invention, the bottom plate and the yoke are formed as an integral piece.  
           [0050]    In still another embodiment of the invention, the magnet surrounds the center pole.  
           [0051]    In still another embodiment of the invention, the magnet has a plurality of slits; and the plurality of slits of the magnet are disposed so as to be aligned with the plurality of slits of the yoke.  
           [0052]    In still another embodiment of the invention, the bottom plate and the center pole are formed as an integral piece.  
           [0053]    In still another embodiment of the invention, the loudspeaker further includes a thin plate for interconnecting upper faces of at least two of the plurality of support members.  
           [0054]    In still another embodiment of the invention, the second end of each of the plurality of support members has a height-wise dimension greater than a height-wise dimension of the first end of the support member.  
           [0055]    In still another embodiment of the invention, the loudspeaker further includes a cover provided so as to cover an upper face of the center pole.  
           [0056]    In still another embodiment of the invention, the cover and the first annular member are formed as an integral piece.  
           [0057]    Alternatively, a loudspeaker according to the present invention includes: a bottom plate; a center pole provided upwardly from the bottom plate; a yoke surrounding the center pole and having a plurality of slits; a magnet for providing a magnetic flux for the center pole and the yoke; a coil provided between the center pole and the yoke; a first annular member for supporting the coil; a plurality of support members for supporting the first annular member, the plurality of support members being inserted into the plurality of slits; a diaphragm supported by the plurality of support members; and a second annular member provided between the plurality of support members and the diaphragm, wherein the plurality of support members support the diaphragm via the second annular member, and wherein a plurality of thin plates for reinforcing the second annular member are provided at at least one of an inner periphery and an outer periphery of the second annular member.  
           [0058]    In one embodiment of the invention, each of the plurality of support members has a constant dimension in a direction of vibration of the diaphragm.  
           [0059]    In another embodiment of the invention, the second annular member and the plurality of thin plates are formed as an integral piece.  
           [0060]    In still another embodiment of the invention, the loudspeaker further includes a third annular member provided between the plurality of support members and the first annular member, wherein the plurality of support members are interposed between the second annular member and the third annular member.  
           [0061]    In still another embodiment of the invention, the loudspeaker further includes a thin plate for interconnecting upper faces of at least two of the plurality of support members.  
           [0062]    In still another embodiment of the invention, the first annular member is supported at a first end of each of the plurality of support members, and the diaphragm is supported at a second end of each of the plurality of support members; and a lower face of each of the plurality of support members has a stepped configuration such that the lower face is lower at the second end than at the first end.  
           [0063]    In still another embodiment of the invention, the second end of each of the plurality of support members has a height-wise dimension greater than a height-wise dimension of the first end of the support member.  
           [0064]    In still another embodiment of the invention, the plurality of thin plates are provided at an outer periphery of the second annular member; the number of thin plates is equal to the number of support members; and the plurality of thin plates are positioned on extensions of the plurality of support members along a radial direction of the first annular member.  
           [0065]    In still another embodiment of the invention, the plurality of thin plates are provided at an inner periphery of the second annular member; and at least one of the plurality of thin plates is provided in closer proximity to one of the plurality of support members than to others of the plurality of thin plates.  
           [0066]    In still another embodiment of the invention, a lower face of the coil is located below lower faces of the plurality of support members.  
           [0067]    In still another embodiment of the invention, the coil is provided at an outer periphery of the first annular member.  
           [0068]    In still another embodiment of the invention, the loudspeaker further includes a cover provided so as to cover an upper face of the center pole.  
           [0069]    In still another embodiment of the invention, the cover and the first annular member are formed as an integral piece.  
           [0070]    Thus, the invention described herein makes possible the advantage of providing a loudspeaker incorporating a coupling member having a small mass and high mechanical strength, which can reduce the production cost associated with the mass production of various models and which can provide a sufficient vibration amplitude.  
           [0071]    This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0072]    [0072]FIG. 1 is a plan view illustrating a loudspeaker according to Example 1 of the present invention.  
         [0073]    [0073]FIG. 2 is a cross-sectional view illustrating a loudspeaker according to Example 1 of the present invention.  
         [0074]    [0074]FIG. 3 is a perspective view illustrating a variant of support members and a coupling member according to Example 1 of the present invention.  
         [0075]    [0075]FIG. 4 is a perspective view illustrating a variant of support members and a coupling member according to Example 1 of the present invention.  
         [0076]    [0076]FIG. 5 is a perspective view illustrating a variant according to Example 1 of the present invention including support members directly coupled to a voice coil, in which annular members are omitted.  
         [0077]    [0077]FIG. 6 is a cross-sectional view illustrating an alternative method for affixing a voice coil to a coupling member according to Example 1 of the present invention.  
         [0078]    [0078]FIG. 7 is a cross-sectional view illustrating a loudspeaker according to Example 1 of the present invention incorporating an external type magnetic circuit.  
         [0079]    [0079]FIG. 8 is a plan view illustrating another configuration of the magnetic circuit according to the Example 1 of the present invention.  
         [0080]    [0080]FIG. 9 is a plan view illustrating a loudspeaker according to Example 2 of the present invention.  
         [0081]    [0081]FIG. 10 is a cross-sectional view illustrating a loudspeaker according to Example 2 of the present invention.  
         [0082]    [0082]FIG. 11 is a cross-sectional view illustrating a loudspeaker according to Example 2 of the present invention incorporating an external type magnetic circuit.  
         [0083]    [0083]FIG. 12 is a plan view illustrating a loudspeaker according to Example 3 of the present invention.  
         [0084]    [0084]FIG. 13 is a cross-sectional view illustrating a loudspeaker according to Example 3 of the present invention.  
         [0085]    [0085]FIG. 14 is a cross-sectional view illustrating a loudspeaker according to Example 3 of the present invention incorporating an external type magnetic circuit.  
         [0086]    [0086]FIG. 15 is a cross-sectional view illustrating a loudspeaker according to Example 4 of the present invention.  
         [0087]    [0087]FIG. 16 is a bottom view illustrating a coupling member according to Example 4 of the present invention.  
         [0088]    [0088]FIG. 17 is a partial cross-sectional view illustrating a modification of the loudspeaker according to Example 4 of the present invention in the neighborhood of a coupling member having an alternative configuration.  
         [0089]    [0089]FIG. 18 is a partial cross-sectional view illustrating a modification of the loudspeaker according to Example 4 of the present invention in the neighborhood of a coupling member having an alternative configuration.  
         [0090]    [0090]FIG. 19 is a plan view illustrating a variant of the coupling member according to Example 4 of the present invention.  
         [0091]    [0091]FIG. 20 is a partial cross-sectional view illustrating a modification of the loudspeaker according to Example 4 of the present invention in the neighborhood of a coupling member having an alternative configuration.  
         [0092]    [0092]FIG. 21 is a partial cross-sectional view illustrating a modification of the loudspeaker according to Example 4 of the present invention in the neighborhood of a coupling member having an alternative configuration.  
         [0093]    [0093]FIG. 22 is a partial cross-sectional view illustrating a modification of the loudspeaker according to Example 4 of the present invention in the neighborhood of a coupling member having an alternative configuration.  
         [0094]    [0094]FIG. 23 is a cross-sectional view illustrating a loudspeaker according to Example 4 of the present invention incorporating an external type magnetic circuit.  
         [0095]    [0095]FIG. 24 is a cross-sectional view illustrating a loudspeaker according to Example 5 of the present invention.  
         [0096]    [0096]FIG. 25 is a plan view illustrating a coupling member and thin plates according to Example 5 of the present invention.  
         [0097]    [0097]FIG. 26 is a partial cross-sectional view illustrating a modification of the loudspeaker according to Example 5 of the present invention in the neighborhood of a coupling member having an alternative configuration.  
         [0098]    [0098]FIG. 27 is a plan view illustrating a variant of a coupling member and thin plates according to Example 5 of the present invention.  
         [0099]    [0099]FIG. 28 is a partial cross-sectional view illustrating a modification of the loudspeaker according to Example 5 of the present invention in the neighborhood of a coupling member having an alternative configuration.  
         [0100]    [0100]FIG. 29 is a cross-sectional view illustrating a loudspeaker according to Example 5 of the present invention incorporating an external type magnetic circuit.  
         [0101]    [0101]FIG. 30 is a bottom view illustrating a variant of a coupling member and thin plates according to Example 5 of the present invention.  
         [0102]    [0102]FIG. 31 is a partial cross-sectional view illustrating a modification of the loudspeaker according to Example 5 of the present invention in the neighborhood of a coupling member having an alternative configuration.  
         [0103]    [0103]FIG. 32 is a bottom view illustrating a variant of a coupling member and thin plates according to Example 5 of the present invention.  
         [0104]    [0104]FIG. 33 is a bottom view illustrating a variant of a coupling member and thin plates according to Example 5 of the present invention.  
         [0105]    [0105]FIG. 34 is a cross-sectional view illustrating a loudspeaker according to Example 6 of the present invention.  
         [0106]    [0106]FIG. 35 is a plan view illustrating the loudspeaker according to Example 6 of the present invention in the neighborhood of a coupling member.  
         [0107]    [0107]FIG. 36 is a perspective view showing a thin plate from which the coupling member according to Example 6 of the present invention may be formed.  
         [0108]    [0108]FIG. 37 is a cross-sectional view illustrating a modification of the loudspeaker according to Example 6 of the present invention.  
         [0109]    [0109]FIG. 38 is a plan view illustrating a modification of the loudspeaker according to Example 6 of the present invention in the neighborhood of a magnetic circuit having an alternative configuration.  
         [0110]    [0110]FIG. 39 is a cross-sectional view illustrating a conventional loudspeaker.  
         [0111]    [0111]FIG. 40 is a plan view illustrating a conventional loudspeaker in the neighborhood of a magnetic circuit.  
         [0112]    [0112]FIG. 41 is a plan view illustrating conventional support members formed by folding a thin metal plate (plate material). 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0113]    Hereinafter, the present invention will be described by way of examples, with reference to FIGS.  1  to  38 . Like numerals denote like components throughout the description of such examples.  
       EXAMPLE 1  
       [0114]    [0114]FIG. 1 is a plan view illustrating a loudspeaker  1000  according to Example 1 of the present invention.  
         [0115]    [0115]FIG. 2 is a cross-sectional view illustrating the loudspeaker  1000 , taken at line A-O-A in FIG. 1.  
         [0116]    Referring to FIGS. 1 and 2, the loudspeaker  1000  includes: a bottom plate  23 ; a magnet  1  provided on the bottom plate  23 ; a center pole  2  provided on the magnetic  1 ; a yoke  3  which is provided so as to surround the center pole  2  and which has a plurality of slits  11  in a radial arrangement; a coupling member  7 A; an annular voice coil bobbin  13  affixed to the inner periphery of the coupling member  7 A; a voice coil  9  wound around a lower portion of the voice coil bobbin  13 ; a diaphragm  8  and dampers  10  affixed to the outer periphery of the coupling member  7 A; frames  12 A and  12 B; and a cover  24 .  
         [0117]    The coupling member  7 A has support members  5 A to be inserted in the plurality of slits  11 , and inner and outer annular members  6 A and  6 B. The support members  5 A are interposed between the inner and outer annular members  6 A and  6 B. The voice coil bobbin  13  is affixed to the inner annular member  6 A, whereas the diaphragm  8  and the dampers  10  are affixed to the outer annular member  6 B. Each support member  5 A has a cross section which obliquely descends from a central portion of the loudspeaker  1000  toward the outer periphery. A bottom face  9 A of the voice coil  9  is located below the lower most face of the coupling member  7 A (e.g., a bottom face  26  of the outer annular member  6 B). The bottom face  9 A of the voice coil  9  is located below a junction portion (on the outer annular member  6 B) between each support member  5 A and the diaphragm  8 .  
         [0118]    In any of the plan views employed for the illustration of specific examples of the present invention, one or more component elements (e.g., the cover  24 ) may conveniently be omitted for clarity.  
         [0119]    Now, the operation of the above-described structure will be described.  
         [0120]    The magnet  1 , the yoke  3  having the radial arrangement of slits  11 , the center pole  2 , and the bottom plate  23  together compose a magnetic circuit. A magnetic flux is generated within a magnetic gap  4  by the magnetic circuit.  
         [0121]    As an electric input is supplied to the voice coil  9  in the above structure, a driving force is generated in the voice coil  9  which is inserted within the magnetic gap  4  according to Fleming&#39;s left-hand rule, causing the voice coil  9  to vibrate along a vertical direction. Since the voice coil  9  is coupled to the diaphragm  8  by means of the voice coil bobbin  13  and the coupling member  7 A (i.e., via the support members  5 A), the driving force generated in the voice coil  9  is transmitted to the diaphragm  8 . Thus, the diaphragm  8  is vibrated along the vertical direction with an amplitude in proportion to the electrical input to the voice coil  9 , thereby emitting sound.  
         [0122]    Since this structure prevents the diaphragm  8  from contacting an upper face  3 A of the yoke  3 , there is no need to allow for an amplitude margin when designing the total height of the loudspeaker  1000 . As a result, the total height of the loudspeaker  1000  can be reduced.  
         [0123]    In the case where the cover  24  is affixed to the voice coil bobbin  13 , the cover  24  vibrates along the vertical direction as the voice coil  9  vibrates along the vertical direction. Alternatively, the cover  24  and the voice coil bobbin  13  may be detached from each other.  
         [0124]    The voice coil  9  is wound around the outer periphery of the voice coil bobbin  13 . Therefore, even if the wire diameter for the voice coil  9  is changed, thereby also changing the outer diameter of the voice coil  9 , the voice coil bobbin  13  always has a constant outer diameter. Therefore, there is no need to change the inner diameter of the inner annular member  6 A, which is affixed to the outer periphery of the voice coil bobbin  13 . Thus, a single type of coupling member  7 A can always be used for various types of voice coils  9  having different wire diameters for obtaining different levels of driving force. When mass producing various models, this presents the advantages of lower cost and ease of storage and management of component parts. It is also possible to employ a single type of voice coil bobbin  13  for various types of voice coils  9 .  
         [0125]    Although FIG. 2 illustrates an example in which the yoke  3  and the bottom plate  23  are composed of discrete elements, the yoke  3  and the bottom plate  23  may be formed as an integral piece.  
         [0126]    The cover  24  for dust prevention purposes and the voice coil bobbin  13  may also be formed as an integral piece.  
         [0127]    As mentioned above, the bottom face  9 A of the voice coil  9  is located below the bottom face  26  of the outer annular member  6 B. Therefore, as far as the vibration along the vertical direction is concerned, an amplitude margin Y′ between the bottom face  26  of the outer annular member  6 B and the frame  12 A is equal to or greater than an amplitude margin X between the bottom face  9 A of the voice coil  9  and the bottom plate  23 . Therefore, only the amplitude margin X between the bottom face  9 A of the voice coil  9  and the bottom plate  23  needs to be considered when designing an amplitude margin for the loudspeaker  1000 . Thus, the design process can be facilitated, and defects associated with the collision between the bottom face  26  of the outer annular member  6 B and the frame  12 A can be minimized even when the loudspeaker  1000  is mass produced.  
         [0128]    Moreover, the bottom face  9 A of the voice coil  9  is located below a junction portion (on the outer annular member  6 B) between each support member  5 A and the diaphragm  8 , where the diaphragm  8  is supported by the support members  5 A. This allows the overall height of the coupling member  7 A to be reduced, which in turn leads to a reduced mass of the coupling member  7 A, whereby the vibration performance of the loudspeaker  1000  is enhanced. Especially, the overall height of the coupling member  7 A can be effectively reduced if the bottom face  26  of the outer annular member  6 B is located above the bottom face  9 A of the voice coil  9 , as opposed to if the bottom face  26  of the outer annular member  6 B is located below the bottom face  9 A of the voice coil  9 . Again, this will lead to a reduced mass of the coupling member  7 A, whereby the vibration performance of the loudspeaker  1000  can be enhanced.  
         [0129]    The loudspeaker  1000  shown in FIG. 2 is an internal type magnetic circuit, i.e., the magnet  1  is positioned inside the yoke  3 . Alternatively, as in a loudspeaker  1001  shown in FIG. 7, a magnet  1 ′ may be provided around the outer periphery of a center pole  2 ′, and a plurality of slits  11 ′ may be provided in both a magnet  1 ′ and a yoke  3 ′ to compose an external type magnetic circuit. The center pole  2 ′ and the bottom plate  23 ′ may be formed as an integral piece. Reference numeral  3 A′ denotes an upper face of the yoke  3 ′.  
         [0130]    [0130]FIGS. 3, 4, and  5  are perspective views showing variants ( 7 B,  7 C, and  7 D) of the coupling member  7 A having support members  5 A according to Example 1 of the present invention.  
         [0131]    The coupling member  7 B shown in FIG. 3 includes a plurality of support members  5 B affixed to the outer periphery of one annular member  6 C. The bottom face  9 A of the voice coil  9  is located below bottom faces  26 B of the support members  5 B.  
         [0132]    The coupling member  7 C shown in FIG. 4 includes a plurality of support members  5 C affixed to the inner periphery of one annular member  6 D. The bottom face  9 A of the voice coil  9  is located below bottom faces  26 C of the annular member  6 D.  
         [0133]    The coupling member  7 D shown in FIG. 5 includes a plurality of support members  5 D, while omitting annular member  6 A or  6 B. The support members  5 D directly support the voice coil bobbin  13 . The bottom face  9 A of the voice coil  9  is located below bottom faces  26 D of the support members  5 D.  
         [0134]    The coupling members  7 B,  7 C, or  7 D may replace the coupling member  7 A in the present example of the present invention.  
         [0135]    The coupling members  7 B,  7 C, and  7 D contribute to a reduced vibrating system mass as compared to that realized with the coupling member  7 A having two annular members  6 A and  6 B shown in FIG. 1, whereby the vibration performance of the loudspeaker  1000  can be enhanced. In addition, when the coupling member  7 A having two annular members  6 A and  6 B shown in FIG. 1 is produced by using a mold, it may be difficult to pour a metal or resin material into the mold, or there may be some pressing problems, making the molding process difficult. In comparison, the coupling members  7 B,  7 C, and  7 D would be relatively easy to mold, and therefore may be more advantageous for mass production.  
         [0136]    [0136]FIG. 6 is a cross-sectional view illustrating a method for affixing the voice coil  9  to a coupling member  7 E according to Example 1 of the present invention. The coupling member  7 E, which may replace the aforementioned coupling member  7 A, includes support members  5 E and inner and outer annular members  6 E and  6 F. Whereas the voice coil  9  is provided at the inner periphery of the inner annular member  6 A via the voice coil bobbin  13  in the structure shown in FIG. 2, the voice coil bobbin  13  is omitted in the structure shown in FIG. 6, so that the voice coil  9  is affixed to a lower portion of the inner annular member  6 E. Thus, the mass of the vibrating system is reduced, and the magnetic gap  4  can be made narrow, whereby the vibration performance of the loudspeaker  1000  can be enhanced.  
         [0137]    As shown in a plan view of FIG. 8, the loudspeaker  1000  may have a magnetic circuit which is configured in a polygonal shape. In this case, the center pole  2  of the loudspeaker  1000  is replaced by a center pole  102 ; the voice coil bobbin  13  is replaced by a voice coil bobbin  113 ; the inner and outer annular members  6 A and  6 B and support members  5 A composing the coupling member  7 A are replaced by inner and outer annular members  106 A and  106 B and support members  105 A composing a coupling member  107 A; and the yoke  3  is replaced by a yoke  103 . The yoke  103  has slits  111  formed therein. Thus, a polygonal magnetic gap  104  is formed in the structure shown in FIG. 8. Reference numeral  103 A denotes an upper face of the yoke  103 . The loudspeaker  1000  may be formed in any configuration that allows for easy production. As used herein, the term “annular” is broadly defined to encompass such polygonal shapes.  
       EXAMPLE 2  
       [0138]    [0138]FIG. 9 is a plan view illustrating a loudspeaker  2000  according to Example 2 of the present invention. FIG. 10 is a cross-sectional view illustrating the loudspeaker  2000 , taken at line B-O-B in FIG. 9.  
         [0139]    The loudspeaker  2000  includes support members  16  having a double-stepped shape. The support members  16  are inserted into slits  11  provided in a yoke  3 . A voice coil bobbin  13 , a diaphragm  8 , and dampers  10  are directly affixed to the support members  16 . The loudspeaker  2000  lacks inner and outer annular members  6 A and  6 B in the loudspeaker  1000  shown in FIGS. 1 and 2; otherwise, the loudspeaker  2000  has the same structure as that of the loudspeaker  1000 .  
         [0140]    In accordance with the loudspeaker  2000 , a bottom face  9 A of the voice coil  9  is located below a bottom face  20  of each support member  16 .  
         [0141]    Now, the operation of the above-described structure will be described.  
         [0142]    The magnet  1 , the yoke  3 , a center pole  2 , and a bottom plate  23  together compose a magnetic circuit. A magnetic flux is generated within a magnetic gap  4  by the magnetic circuit. As an electric input is supplied to the voice coil  9 , a driving force is generated in the voice coil  9  according to Fleming&#39;s left-hand rule, causing the voice coil  9  to vibrate along a vertical direction. The driving force generated in the voice coil  9  is transmitted to the voice coil bobbin  13 , the support members  16 , and to the diaphragm  8 . The diaphragm  8  is vibrated along the vertical direction with an amplitude in proportion to the electrical input to the voice coil  9 , thereby emitting sound.  
         [0143]    The effects provided by this structure will be described.  
         [0144]    The voice coil  9  is wound around the outer periphery of the voice coil bobbin  13 , as is the case with Example 1. Therefore, even if the wire diameter for the voice coil  9  is changed for loudspeaker characteristics adjustment, thereby also changing the outer diameter of the voice coil  9 , the voice coil bobbin  13  always has a constant outer diameter. Therefore, there is no need to change the size of the support members  16 , which are affixed to the outer periphery of the voice coil bobbin  13 . Thus, a single type of support member  16  can always be used for various types of voice coils  9  having different wire diameters for changing the loudspeaker characteristics during production. When mass producing various models, this presents the advantages of lower cost and ease of storage and management of component parts. It is also possible to employ a single type of voice coil bobbin  13  for voice coils  9  of various wire diameters.  
         [0145]    In contrast, in accordance with the conventional loudspeaker  7000  shown in FIGS. 39 and 40, the coupling member  37  are affixed to the outer periphery of the voice coil  39 . Therefore, as the outer diameter of the voice coil  39  changes, it is necessary to change the inner diameter of the coupling member  37  (i.e., the inner diameter of the ring  36 ) to which the voice coil  39  is attached. In other words, each coupling member  37  can only be adapted to a voice coil  39  of a given wire diameter.  
         [0146]    Since the support members  16  have a double-stepped shape, a junction portion between each support member  16  and the diaphragm  8  can be located close to the plane on which the voice coil  9  is located. Thus, the overall height of the loudspeaker  2000  can be reduced.  
         [0147]    As shown in FIG. 10, the bottom face  9 A of the voice coil  9  is located below the bottom faces  20  of the support members  16 . Therefore, as far as the vibration along the vertical direction is concerned, an amplitude margin Y between the bottom faces  20  of the support members  16  and the frame  12 A is equal to or greater than an amplitude margin X between the bottom face  9 A of the voice coil  9  and the bottom plate  23 . Therefore, only the amplitude margin X between the bottom face  9 A of the voice coil  9  and the bottom plate  23  needs to be considered when designing an amplitude margin for the loudspeaker  2000 . Thus, the design process can be facilitated, and defects associated with the collision between the bottom faces  20  of the support members  16  and the frame  12 A can be minimized even when the loudspeaker  2000  is mass produced.  
         [0148]    Especially, the overall height of the support members  16  can be effectively reduced if the bottom faces  20  of the support members  16  are located above the bottom face  9 A of the voice coil  9  (as shown in FIG. 10), as opposed to if the bottom faces  20  of the support members  16  are located below the bottom face  9 A of the voice coil  9 . Again, this will lead to a reduced mass of the support members  16 , whereby the vibration performance of the loudspeaker  2000  can be enhanced.  
         [0149]    The loudspeaker  2000  shown in FIG. 10 is an internal type magnetic circuit, i.e., the magnet  1  is affixed to a lower portion of the center pole  2 . Alternatively, as in a loudspeaker  2001  shown in FIG. 11, a magnet  1 ′ may be provided around the outer periphery of a center pole  2 ′, and a plurality of slits  11 ′ may be provided in both a magnet  1 ′ and a yoke  3 ′ to compose an external type magnetic circuit. The center pole  2 ′ and the bottom plate  23 ′ may be formed as an integral piece.  
         [0150]    Although the illustrated support members  16  have a double-stepped shape, they may alternatively have three or more steps.  
       EXAMPLE 3  
       [0151]    [0151]FIG. 12 is a plan view illustrating a loudspeaker  3000  according to Example 3 of the present invention. FIG. 13 is a cross-sectional view illustrating the loudspeaker  3000 , taken at line C-O-C in FIG. 12.  
         [0152]    The loudspeaker  3000  includes a coupling member  17 . The coupling member  17  has support members  16 A, which are inserted into slits  11  provided in a yoke  3 , and inner and outer annular members  14  and  15 . The support members  16 A are interposed between the inner and outer annular members  14  and  15 . A voice coil bobbin  13  is affixed to the inner annular member  14 , whereas a diaphragm  8  and dampers  10  are affixed to the outer annular member  15 . As is the case with the support members  16  in Example 2, the support members  16 A have a double-stepped shape. A bottom face  9 A of the voice coil  9  is located below a bottom face  21  of the outer annular member  15 . Otherwise, the loudspeaker  3000  has the same structure as that of the loudspeaker  2000 .  
         [0153]    Now, the operation of the above-described structure will be described.  
         [0154]    The magnet  1 , the yoke  3 , a center pole  2 , and a bottom plate  23  together compose a magnetic circuit. A magnetic flux is generated within a magnetic gap  4  by the magnetic circuit. As an electric input is supplied to the voice coil  9 , a driving force is generated in the voice coil  9  according to Fleming&#39;s left-hand rule, causing the voice coil  9  to vibrate along a vertical direction. The driving force generated in the voice coil  9  is transmitted to the voice coil bobbin  13 , the coupling members  17  and to the diaphragm  8 . The diaphragm  8  is vibrated along the vertical direction with an amplitude in proportion to the electrical input to the voice coil  9 , thereby emitting sound.  
         [0155]    The effects provided by this structure will be described.  
         [0156]    The voice coil  9  is wound around the outer periphery of the voice coil bobbin  13 , and the inner annular member  14  is affixed to the outer periphery of the voice coil bobbin  13 . Therefore, even if the wire diameter for the voice coil  9  is changed for loudspeaker characteristics adjustment, thereby also changing the outer diameter of the voice coil  9 , the voice coil bobbin  13  always has a constant outer diameter. Therefore, there is no need to change the size of the inner diameter of the inner annular member  14 . Thus, a single type of coupling member  17  can always be used for various types of voice coils  9  having different wire diameters for changing the loudspeaker characteristics during production. When mass producing various models, this presents the advantages of lower cost and ease of storage and management of component parts.  
         [0157]    Since the support members  16 A have a double-stepped shape, a junction portion between each support member  16 A and the diaphragm  8  can be located close to the plane on which the voice coil  9  is located. Thus, the overall height of the loudspeaker  3000  can be reduced.  
         [0158]    As shown in FIG. 13, the bottom face  9 A of the voice coil  9  is located below the bottom face  21  of the outer annular member  15 . Therefore, as far as the vibration along the vertical direction is concerned, an amplitude margin Z between the bottom face  21  of the outer annular member  15  and the frame  12 A is equal to or greater than an amplitude margin X between the bottom face  9 A of the voice coil  9  and the bottom plate  23 . Therefore, only the amplitude margin X between the bottom face  9 A of the voice coil  9  and the bottom plate  23  needs to be considered when designing an amplitude margin for the loudspeaker  3000 . Thus, the design process can be facilitated, and defects associated with the collision between the bottom face  21  of the outer annular member  15  and the frame  12 A can be minimized even when the loudspeaker  3000  is mass produced.  
         [0159]    Especially, the overall height of the outer annular member  15  can be effectively reduced if the bottom face  21  of the outer annular member  15  is located above the bottom face  9 A of the voice coil  9  (as shown in FIG. 13), as opposed to if the bottom face  21  of the outer annular member  15  is located below the bottom face  9 A of the voice coil  9 . Again, this will lead to a reduced mass of the coupling member  17 , whereby the vibration performance of the loudspeaker  3000  can be enhanced.  
         [0160]    Since the support members  16 A of the loudspeaker  3000  are formed in a double-stepped shape as shown in FIG. 13, it is possible to reinforce the outer annular member  15  in its radial direction. As a result, the outer annular member  15  is prevented from having unwanted resonation, so that the driving force generated in the voice coil  9  can be transmitted to the diaphragm  8  without substantial loss. Thus, the coupling member  17  can be prevented from undergoing mechanical destruction without undermining the sound pressure characteristics and the sound quality of the loudspeaker  3000 .  
         [0161]    The coupling member  17  composed of the support members  16 A and the inner and outer annular members  14  and  15  may be formed of a resin or metal material as an integral piece. The outer annular member  15  and the diaphragm  8  may be formed as an integral piece. The coupling member  17  and the diaphragm  8  may be formed as an integral piece. When such elements are formed as integral pieces, whereby the number of component parts can be reduced, the production process is facilitated and the product cost reduced.  
         [0162]    The loudspeaker  3000  shown in FIG. 13 is an internal type magnetic circuit, i.e., the magnet  1  is affixed to a lower portion of the center pole  2 . Alternatively, as in a loudspeaker  3001  shown in FIG. 14, a magnet  1 ′ may be provided around the outer periphery of a center pole  2 ′, and a plurality of slits  11 ′ may be provided in both a magnet  1 ′ and a yoke  3 ′ to compose an external type magnetic circuit. The center pole  2 ′ and the bottom plate  23 ′ may be formed as an integral piece.  
       EXAMPLE 4  
       [0163]    [0163]FIG. 15 is a cross-sectional view illustrating a loudspeaker  4000  according to Example 4 of the present invention. FIG. 16 is a plan view showing a coupling member  17 A and a thin plate  18  of the loudspeaker  4000 , as seen from the bottom side of the magnetic circuit of the loudspeaker  4000 . The cross-sectional view of Figure  15  is taken at line D-O-D in FIG. 16.  
         [0164]    The loudspeaker  4000  includes the coupling member  17 A. The coupling member  17 A has support members  16 B, which are inserted into slits  11  provided in a yoke  3 , and inner and outer annular members  14 A and  15 A. The support members  16 B are interposed between the inner and outer annular members  14 A and  15 A. A voice coil bobbin  13  is affixed to the inner annular member  14 A, whereas a diaphragm  8  and dampers  10  are affixed to the outer annular member  15 A. As is the case with the support members  16 A in Example 3, the support members  16 B have a double-stepped shape. The support members  16 B are connected at their upper ends by means of the thin plate  18 . A bottom face  9 A of the voice coil  9  is located below a bottom face  21 A of the outer annular member  15 A. Otherwise, the loudspeaker  4000  has the same structure as that of the loudspeaker  3000 .  
         [0165]    The coupling member  17 A has the same function as that of the coupling member  17  in the loudspeaker  3000  according to Example 3. The operation and effects provided by the loudspeaker  4000  are similar to those of the loudspeaker  3000 .  
         [0166]    In addition, the thin plate  18 , which covers the upper face of the slits  11  and the upper face of the yoke  3 A, prevents dust from gathering at the slits  11  and the magnetic gap  4 . By designing the thin plate  18  so as to resonate or vibrate in a high-frequency region in the neighborhood of, e.g., 10 kHz, it becomes possible to provide compensation for the high-frequency characteristics of the loudspeaker  4000 . The thin plate  18  further provides reinforcement effects for the coupling member  17 A.  
         [0167]    [0167]FIGS. 17 and 18 are partial cross-sectional views illustrating modifications of the loudspeaker  4000  having variants  17 B and  17 C, respectively, of the coupling member  17 A according to Example 4 of the present invention.  
         [0168]    The coupling member  17 B shown in FIG. 17 includes support members  16 C and an annular member  15 A. The coupling member  17 B differs from the coupling member  17 A in that the inner annular member  14 A is omitted, and the voice coil bobbin  13  is affixed to the support members  16 C. Since the mass of the coupling member  17 B is reduced by the mass of the inner annular member  14 A, the vibration performance of the loudspeaker  4000  can be enhanced.  
         [0169]    The coupling member  17 C shown in FIG. 18 includes support members  16 D and an annular member  14 A. The coupling member  17 C differs from the coupling member  17 A in that the annular member  15 A is omitted. Since the mass of the coupling member  17 C is reduced by the mass of the annular member  15 A, the vibration performance of the loudspeaker  4000  can be enhanced.  
         [0170]    [0170]FIG. 19 is a plan view illustrating a variant of the thin plate  18  provided on the upper face of the coupling member  17 A according to Example 4 of the present invention. As shown in FIG. 19, thin plates  18 C provide partial coupling between the upper faces of the support members  16 B. By adjusting the number of such thin plates  18 C, it is possible to adjust the total mass of the coupling member  17 A and the thin plates  18 C.  
         [0171]    [0171]FIGS. 20 and 21 are partial cross-sectional views illustrating modifications of the loudspeaker  4000  having variants  18 D and  18 E, respectively, of the thin plate  18  according to Example 4 of the present invention.  
         [0172]    The thin plate  18 D shown in FIG. 20 covers the entire coupling member  17 A. A voice coil bobbin  13 D and a cover  24 D may have, as shown, their size adapted to the thin plate  18 D. Since the thin plate  18 D covers the entire coupling member  17 A, the magnetic circuit of the loudspeaker  4000  is protected from dust, and the high-frequency characteristics of the loudspeaker  4000  can be adjusted. In this case, the cover  24 D may be omitted.  
         [0173]    The cross section of the thin plate  18 E shown in FIG. 21 presents an arc shape. Through such modification of the cross-sectional shape of the thin plate  18 E, it becomes possible to adjust the high-frequency characteristics of the loudspeaker  4000 . A coupling member  17 F, as one variant of the coupling member  17 A, includes support members  16 G and inner and outer annular members  14 E and  15 E which are adapted to the arc shape of the thin plate  18 E.  
         [0174]    A coupling member  17 N shown in FIG. 22, which is one variant of the coupling member  17 A, is such that an annular member  15 M located at the outer periphery of the coupling member  17 N presents an L-shaped cross section. Such an annular member  15 M has a more enhanced mechanical strength than that of the annular member  15 A. FIG. 22 is a partial cross-sectional view illustrating a modification of the loudspeaker  4000 . Since the diaphragm  8  or the dampers  10  can be adhered to the convex underpart of the L-shaped annular member  15 M, the production process can be facilitated, and the adhesion strength of the diaphragm  8  and the dampers  10  to the coupling member  17 N can be enhanced. As a result, the loudspeaker  4000  is made more mechanically durable.  
         [0175]    Any of the coupling members  17 A,  17 B,  17 C,  17 F, and  17 N may be formed as a single integral piece. Any of the coupling members  17 A,  17 B,  17 C,  17 F, and  17 N, and a corresponding one of the thin plates  18 ,  18 C and  18 E, may be formed as an integral piece using a resin or metal material, etc., or as an assembly of elements composed of different materials.  
         [0176]    Any of the annular members  15 A,  15 E and  15 M and the diaphragm  8  may be formed as an integral piece. Any of the coupling members  17 A,  17 B,  17 C,  17 F and  17 N and the diaphragm  8  may be formed as an integral piece.  
         [0177]    Any one of the various structures described above may be selected as appropriate at the time of production, while paying attention to factors such as ease of production, mass, reinforcement effects, and the high-frequency characteristics adjustments of the loudspeaker  4000 .  
         [0178]    The loudspeaker  4000  shown in FIG. 16 is an internal type magnetic circuit, i.e., the magnet  1  is affixed to a lower portion of the center pole  2 . Alternatively, as in a loudspeaker  4001  shown in FIG. 23, a magnet  1 ′ may be provided around the outer periphery of a center pole  2 ′, and a plurality of slits  11 ′ may be provided in both a magnet  1 ′ and a yoke  3 ′ to compose an external type magnetic circuit.  
       EXAMPLE 5  
       [0179]    [0179]FIG. 24 is a cross-sectional view illustrating a loudspeaker  5000  according to Example 5 of the present invention. FIG. 25 is a plan view showing a coupling member  17 G and thin plates  18  and  19  of-the loudspeaker  5000 . The cross-sectional view of FIG. 24 is taken at line E-O-E in FIG. 25.  
         [0180]    The loudspeaker  5000  includes the coupling member  17 G. The coupling member  17 G has support members  16 H, which are inserted into slits  11  provided in a yoke  3 , and inner and outer annular members  14 A and  15 A. The support members  16 H are interposed between the inner and outer annular members  14 A and  15 A. A voice coil bobbin  13  is affixed to the inner annular member  14 A, whereas a diaphragm  8 A and dampers  10  are affixed to the outer annular member  15 A. The support members  16 H have a rectangular cross section for ease of molding. The support members  16 H are connected at their upper ends by means of the thin plate  18 . In addition, the thin plates  19  are attached to the outer periphery of the outer annular member  15 A, thereby reinforcing the outer annular member  15 A. The illustrated diaphragm  8 A has a shape which would be left after omitting any portion overlapping between the thin plates  19  and the diaphragm  8 A. Alternatively, the diaphragm  8  may be employed instead of the diaphragm  8 A, on the proviso that the diaphragm  8  and the thin plates  19  are not provided in an overlapping relationship with each other. Otherwise, the loudspeaker  5000  has the same structure as that of the loudspeaker  4000 . A bottom face  9 A of the voice coil  9  is located below a bottom face  21 A-of the outer annular member  15 A.  
         [0181]    The coupling member  17 G has the same function as that of the coupling member  17 A in the loudspeaker  4000  according to Example 4. The support members  16 H may have a stepped shape, as is the case with the support members  16 B shown in FIG. 28.  
         [0182]    The operation and effects provided by the loudspeaker  5000  are similar to those of the loudspeaker  4000  according to Example 4.  
         [0183]    In addition, the thin plates  19  affixed to the outer periphery of the outer annular member  15 A serve to enhance the reinforcement effects for the outer annular member  15 A, or the coupling member  17 G.  
         [0184]    Although the height of the thin plates  19  along the direction of vibration is shown to extend up to the plane on which the bottom faces of the support members  16 H are located in FIG. 24, the thin plates  19  may be further elongated as shown in FIG. 26 for enhanced reinforcement effects. FIG. 26 is a partial cross-sectional view illustrating a modification of the loudspeaker  5000 .  
         [0185]    Furthermore, as shown in FIG. 27, the support members  16 H and the thin plates  19  do not need to be aligned on the same lines along radial directions. The number of thin plates  19  and the number of support members  16 H do not need to be equal.  
         [0186]    The aforementioned modification may be selected as appropriate at the time of production, while paying attention to factors such as reinforcement effects, mass, and ease of production of the loudspeaker  5000 .  
         [0187]    The loudspeaker  5000  shown in FIG. 24 is an internal type magnetic circuit, i.e., the magnet  1  is affixed to a lower portion of the center pole  2 . Alternatively, as in a loudspeaker  5001  shown in FIG. 29, a magnet  1 ′ may be provided around the outer periphery of a center pole  2 ′, and a plurality of slits  11 ′ may be provided in both a magnet  1 ′ and a yoke  3 ′ to compose an external type magnetic circuit.  
         [0188]    Alternatively, the thin plates  19  may be provided at the inner periphery of the outer annular member  15 A. Such modifications are illustrated in FIGS. 30 and 31. FIG. 30 is a bottom view of the coupling member  17 G. FIG. 31 is a partial cross-sectional view of a modified loudspeaker  5000 . As shown in FIG. 30, at the inner periphery of the outer annular member  15 A, thin plates  22  are provided as reinforcement elements, which serve to enhance the reinforcement effects for the outer annular member  15 A or the coupling member  17 G. By placing the reinforcement elements  22  in the neighborhood of the support members  16 H on the inner periphery of the outer annular member  15 A as shown in FIG. 30, particularly strong reinforcement effects are provided for portions of the coupling member  17 G present between the respective support members  16 H. Thus, such reinforcement elements  22  may be effectively employed in the case where the support members  16 H alone cannot provide adequate reinforcement. The support members  16 H may have a stepped shape, as is the case with the support members  16 B shown in FIG. 28. FIG. 28 is a partial cross-sectional illustrating a modified loudspeaker  5000 .  
         [0189]    In the case where the thin plates  19  are provided at the outer periphery of the outer annular member  15 A (as shown in FIG. 25), it is necessary to ensure that the diaphragm  8  and the dampers  10  are adapted so as not to interfere with such thin plates  19 . On the other hand, the thin plates  22  provided at the inner periphery of the outer annular member  15 A (as shown in FIG. 30), which replace the thin plates  19 , facilitate the attachment of the diaphragm  8  and/or the dampers  10  to the outer annular member  15 A, thereby facilitating the production process, without undermining the reinforcement effects.  
         [0190]    Alternatively, the thin plates  22  may be provided on only one side of each support members  16 H as shown in FIG. 32, or in a random deployment as shown in FIG. 33. Such arrangements will help to disperse a resonance frequency distribution of the coupling member  17 G, so as to minimize any unfavorable effects on the loudspeaker characteristics that are associated with a single resonance frequency.  
         [0191]    It will be appreciated that, the support members  16 H in FIGS. 24, 26,  29 , and  31 , which are not illustrated as being inserted in the slits  11  or  11 ′, are to be inserted in the slits  11  or  11 ′ when driving the voice coil  9 .  
       EXAMPLE 6  
       [0192]    [0192]FIG. 34 is a cross-sectional view illustrating a loudspeaker  6000  according to Example 6 of the present invention. FIG. 35 is a plan view showing a coupling member  7 G inserted into slits  11  of a yoke  3  of the loudspeaker  6000 . FIG. 34 is a cross-sectional view of FIG. 35 taken at line F-O-F in FIG. 35.  
         [0193]    [0193]FIG. 36 is a perspective view showing a shaped thin plate  7 G′, from which the coupling member  7 G is to be formed. The coupling member  7 G, which can be obtained by folding the thin plate  7 G′ into a corrugated and annular shape, couples a diaphragm  8  to a voice coil bobbin  13 . Regions  5 G which extend in parallel to the radial direction of the coupling member  7 G are inserted into the slits  11  formed in the yoke  3 .  
         [0194]    The coupling member  7 G can be obtained by winding a thin plate, e.g., the thin plate  7 G′, around the outer periphery the voice coil bobbin  13  or a voice coil  9 . A diaphragm  8  and dampers  10  are affixed to the outer periphery of the coupling member  7 G.  
         [0195]    The coupling member  7 G, which can be formed by folding a single plate-like piece of metal or resin, is easy to process and admits of high productivity. Since a relatively large adhesion area exists between the diaphragm  8  and the dampers  10 , a good adhesion strength results. Consequently, problems such as failure of the driving force from the voice coil  9  to be transmitted to the diaphragm  8  or peeling of the diaphragm  8  from the coupling member  7 G associated with the diaphragm  8  moving with a large amplitude are prevented.  
         [0196]    Since the width of the slits  11  can be reduced in accordance with the thickness of the coupling member  7 G, the yoke  3  can have an increased volume, so that the magnetic flux density in the magnetic gap  4  can be increased, whereby the driving force can be enhanced.  
         [0197]    [0197]FIG. 35 illustrates the coupling member  7 G being coupled to the diaphragm  8  and the dampers  10  at four positions around its outer periphery, any number of such positions may be provided for ease of production and/or adjustment of the adhesion area.  
         [0198]    The yoke  3  and the bottom plate  23  may be formed as an integral piece.  
         [0199]    The illustrated loudspeaker  6000  is an internal type magnetic circuit, i.e., the magnet  1  is located inside the yoke  3 . Alternatively, as described with respect to Examples 1 to 5, a magnet  1 ′ may be provided around the outer periphery of a center pole  2 ′, and a plurality of slits  11 ′ may be provided in both a magnet  1 ′ and a yoke  3 ′ to compose an external type magnetic circuit.  
         [0200]    As in the plan view of FIG. 38, the magnetic circuit of the loudspeaker  6000  may be formed in a polygonal configuration. In this case, the center pole  2  of the loudspeaker  6000  is replaced by a center pole  202 ; the voice coil bobbin  13  is replaced by a voice coil bobbin  213 ; the coupling member  7 G is replaced by a coupling member  7 H; and the yoke  3  is replaced by a yoke  203 . The yoke  203  has slits  211  formed therein. Thus, a polygonal magnetic gap  204  is formed in the structure shown in FIG. 38. Reference numeral  203 A denotes an upper face of the yoke  203 . The coupling member  7 H may be molded into a shape which is in accordance with the polygonal magnetic circuit. The loudspeaker  6000  may be formed in any configuration that allows for easy production.  
         [0201]    [0201]FIG. 37 is a cross-sectional view illustrating a loudspeaker  6100  including a voice coil  9  provided at the inner periphery of a coupling member  7 G. This structure, which allows a voice coil bobbin to omitted, makes for a reduced vibrating system mass, and enhanced performance of the loudspeaker  6100 . Moreover, since a thin plate of the coupling member  7 G is directly coupled to the voice coil  9 , the voice coil  9  can be cooled more effectively. As a result, a withstand input level of the loudspeaker  6100  can be improved.  
         [0202]    Thus, according to the present invention, a single type of coupling member can always be used for various types of voice coils having different wire diameters, which result in different voice coil outer diameters. This presents the advantages of lower production cost and ease of storage and management of component parts. Since a coupling member having a small mass and adequate strength is provided while allowing for a sufficient vibration amplitude, a loudspeaker which has a reduced profile, and in which the coupling member is prevented from undergoing mechanical destruction, can be provided.  
         [0203]    Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.