Abstract:
A loudspeaker damper including: an outer damper; and an inner damper; wherein the outer damper and the inner damper configured to damp a vibrating portion relative to a fixed portion of a loudspeaker, wherein the outer damper supports the outer periphery of a voice coil of the vibrating portion, and supports the outer periphery of the voice coil relative to the fixed portion, wherein the inner damper supports the inner periphery of the voice coil, and supports the inner periphery of the voice coil relative to the fixed portion.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     The present invention contains subject matter related to Japanese Patent Application JP 2005-219330 filed in the Japanese Patent Office on Jul. 28, 2005, the entire contents of which being incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a loudspeaker damper, used for a loudspeaker or the like, and a method of mounting the loudspeaker damper.  
         [0004]     2. Description of the Related Art  
         [0005]     A damper playing the role of damping a voice coil of a vibrating portion so as to properly holding the voice coil in a magnetic pole space between a pole and a plate has been used for a loudspeaker in related art.  FIGS. 15A  to  15 C are diagrams showing the shapes of dampers according to the related art, in which  FIG. 15A  shows a track-shaped damper,  FIG. 15B  shows an inner damper, and  FIG. 15C  shows a butterfly damper.  
         [0006]     In the case of reducing the width of a diaphragm of a loudspeaker, a method may be used in which, as shown in  FIG. 15A , a track-shaped damper  151  is used in the state of surrounding the outer periphery of a track-shaped voice coil  152  having a minor diameter and a major diameter. According to the method in which the track-shaped damper  151  is used, the width of the diaphragm can be reduced to a width roughly equivalent to the minor diameter of the track-shaped damper  151 .  
         [0007]     Besides, as shown in  FIG. 15B , there may be adopted a method in which a damper  153  is used on the inside of a track-shaped voice coil  154  having a minor diameter and a major diameter, or a method in which a damper  155  is used on the inside of a circular voice coil  156 . According to the method in which the damper  153  is used on the inside of the track-shaped voice coil  154 , the width of the diaphragm can be reduced to a width roughly equivalent to the minor diameter of the track-shaped voice coil  154  or the diameter of the circular voice coil  156 .  
         [0008]     Further, as shown in  FIG. 15C , a method has been proposed in which use is made of a butterfly damper  157  having a frame portion  158  for supporting the outer periphery of a voice coil  161 , and a pair of support portions  159  and  160  for supporting the frame portion  158  from both sides in the major diameter direction. According to the method in which the butterfly damper  157  is used, there is no support in the minor diameter direction, so that the minimum resonance frequency F 0  of the diaphragm of the loudspeaker is not raised, and the width of the diaphragm can be reduced. Furthermore, there have been proposed a method in which the damper is eliminated and a method in which the damper is simplified. According to these methods, also, a sufficiently low minimum resonance frequency F 0  can be obtained, like in the case of using the butterfly damper.  
         [0009]     In addition, in order to realize a sound wave radiation such that the frequency response is flat and the harmonic distortion is little over the range from a low frequency region to a high frequency region, an electroacoustic transducer has been proposed in which a hook type suspension having one end fixed in the longitudinal direction of a voice coil and the other end fixed to a frame supporting a magnetic circuit is provided at each of both ends of the voice coil (Japanese Patent Laid-open No. 2003-47089).  
         [0010]     Besides, a loudspeaker damper has been proposed in which a voice coil has a major axis direction and a minor axis direction, a plurality of movable arms are formed along the major axis direction, a reinforcement member bridgingly provided between two movable arms of the plurality of movable arms is disposed substantially in parallel to the minor axis direction, in the vicinity of the voice coil support portion side (Japanese Patent No. 3506855).  
       SUMMARY OF THE INVENTION  
       [0011]     However, in the case of the method in which the track-shaped damper  151  shown in  FIG. 15A  is used, the length of the damper  151  in the minor diameter direction is small, so that the stiffness indicating the hardness of the diaphragm material of a cone edge, the damper or the like would be high. As a result, the minimum resonance frequency F 0  which is the lower limit of the reproduction band would be raised. Therefore, in order to design a loudspeaker having a sufficiently low minimum resonance frequency F 0 , it is necessary to enlarge the width of the damper in the minor diameter direction, with the result that the width of the loudspeaker would be large.  
         [0012]     Besides, according to the method in which the damper  153  is used on the inside of the voice coil  154  as shown in  FIG. 15B , the width of the damper  153  is no more than one half of the inside diameter of the voice coil  154 , so that the minimum resonance frequency F 0  would be raised.  
         [0013]     Furthermore, according to the method in which the butterfly damper  157  shown in  FIG. 15C  is used, the support exists only in the major diameter direction, and support in the minor diameter direction is absent. As a result, the voice coil  161  undergoes rolling in the minor diameter direction at the time of vibration in response to the input of a signal at a high level.  
         [0014]     In addition, the damper plays the role of mechanically supporting the vibrating portion such as the diaphragm and the voice coil. According to the method in which the damper is eliminated or simplified, therefore, the lacking of the damper leads to a lowering in input resistance indicative of the response of vibration to an input signal, and, accordingly, the voice coil would undergo rolling upon input of a high-level signal.  
         [0015]     Besides, in the technology described in Japanese Patent Laid-open No. 2003-47089, the voice coil is supported only in the longitudinal direction by the hook type suspensions, and there is no support in the transverse direction. Therefore, the voice coil would undergo rolling in the transverse direction.  
         [0016]     In addition, in the technology described in Japanese Patent No. 3506855, the damper is supported by the plurality of movable arms in the major axis, but, in the minor axis direction, there is only the reinforcement member bridgingly disposed between two movable arms in parallel to the minor axis direction. Therefore, it is only possible to reinforce the two movable arms by the reinforcement member, and there is no support in the minor axis direction, so that the voice coil would undergo rolling in the minor axis direction.  
         [0017]     It is desirable to provide a loudspeaker damper and a method of mounting the loudspeaker damper which make it possible to design a loudspeaker having a sufficiently low minimum resonance frequency F 0 , to disperse the support in a major axis direction and the support in a minor axis direction, and to prevent a voice coil from rolling in the minor axis direction at the time of vibration in response to a high input.  
         [0018]     According to an embodiment of the present invention, there is provided a loudspeaker damper including: an outer damper for supporting the outer periphery of a voice coil of a vibrating portion and supporting the outer periphery of the voice coil relative to a fixed portion; and an inner damper for supporting the inner periphery of the voice coil and supporting the inner periphery of the voice coil relative to the fixed portion.  
         [0019]     With this loudspeaker damper, the voice coil is supported in the major diameter direction by the outer damper on the outside thereof and in the minor diameter direction by the inner damper on the inside thereof, so that a vibrating portion can be supported firmly, and rolling of the voice coil or the like can be prevented from occurring even upon input of a high-level signal. Therefore, it is possible to provide a loudspeaker which is high in input resistance and also can reproduce a sound with little distortion even upon input of a high-level signal. In addition, according to an embodiment of the present invention, the minimum resonance frequency F 0 as the lower limit of the reproduction frequency of the loudspeaker would not be raised, so that sounds in sufficiently low frequency regions can also be reproduced with the small-width loudspeaker. This makes it possible to provide a loudspeaker which is high in input resistance, has a wide reproduction band, and is small in size in the width direction.  
         [0020]     According to another embodiment of the present invention, there is provided a method of mounting a loudspeaker damper, including the steps of: mounting an outer damper, by adhering the outer periphery of a voice coil and a frame portion for supporting the outer periphery of the voice coil, and by adhering a frame of a fixed portion and a pair of support portions for supporting the major diameter of the frame portion from both sides, through a mounting portion; and mounting an inner damper, by adhering the inner periphery of the voice coil and a frame portion for supporting the inner periphery of the voice coil, and by adhering a pole of the fixed portion and a pair of support portions for supporting the minor diameter of the frame portion from both sides, through a mounting portion; at a position where the outer damper and the inner damper are fixed by use of a jig which is fitted in the inner periphery of the voice coil having a track-like shape having a minor diameter and a major diameter of the vibrating portion and which is fitted over the outer periphery of the pole of the fixed portion.  
         [0021]     According to this mounting method, the adhesion of the support portion in the major diameter direction of the outer damper on the outside of the voice coil and the adhesion of the support portion in the minor diameter direction of the inner damper on the inside of the voice coil are performed at the position fixed by use of the jig, whereby the vibrating portion can be supported firmly, and the voice coil can be prevented from undergoing rolling or the like even upon input of a high-level signal. Therefore, it is possible to provide a loudspeaker which is high in input resistance and also can reproduce sounds with little distortions even upon input of a high-level signal. In addition, when the damper according to the present invention is used, the minimum resonance frequency F 0  as the lower limit of the reproduction frequency of the loudspeaker would not be raised, so that sounds in sufficiently low frequency regions can also be reproduced with a small-width loudspeaker. Accordingly, it is possible to produce a loudspeaker which is high in input resistance, has a wide reproduction band, and is small in size in the width direction.  
         [0022]     According to yet another embodiment of the present invention, the voice coil is supported in the major diameter direction by the outer damper on the outside thereof and in the minor diameter direction by the inner damper on the inside thereof, whereby the vibrating portion can be supported firmly, and rolling and the like can be prevented from occurring even upon input of a high-level signal. Therefore, a high input resistance is ensured, and sounds with little distortion can be reproduced even upon input of a high-level signal. Besides, according to the damper of the present invention, the minimum resonance frequency F 0  as the lower limit of the reproduction frequency of the loudspeaker would not be raised, so that sounds in sufficiently low frequency regions can be reproduced with a small-width loudspeaker.  
         [0023]     The above and other features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is an illustration of a vibrating portion of a loudspeaker;  
         [0025]      FIGS. 2A, 2B  and  2 C are perspective views of an outer damper, an inner damper and a voice coil, respectively;  
         [0026]      FIG. 3  is a perspective view showing the condition where the outer damper and the inner damper are mounted onto the voice coil;  
         [0027]      FIGS. 4A  to  4 C show an example of a fabric damper, in which  FIG. 4A  is a front view,  FIG. 4B  is an X-X sectional view, and  FIG. 4C  is a Y-Y sectional view;  
         [0028]      FIGS. 5A  to  5 C show an example of a butterfly damper, in which  FIG. 5A  is a front view,  FIG. 5B  is an X-X sectional view, and  FIG. 5C  is a Y-Y sectional view;  
         [0029]      FIG. 6  shows an example in which an inner damper is provided with at least one pair of support portions and at least one pair of mounting portions;  
         [0030]      FIG. 7  shows an example in which an outer damper and an inner damper are integral with each other;  
         [0031]      FIG. 8  shows a joined condition of an outer damper and an inner damper;  
         [0032]      FIG. 9  shows a method of mounting an outer damper in the case where the outer damper and an inner damper are separate members;  
         [0033]      FIG. 10  shows a method of mounting an inner damper;  
         [0034]      FIG. 11  shows a method of positioning an inner damper;  
         [0035]      FIGS. 12A and 12B  show insertion holes of a pole, in which  FIG. 12A  is a bottom view, and  FIG. 12B  is a partly sectional view;  
         [0036]      FIG. 13  sows the shape of a voice coil gage;  
         [0037]      FIG. 14  shows a method of mounting an outer damper in the case where the outer damper and an inner damper are integral with each other; and  
         [0038]      FIGS. 15A  to  15 C show the shapes of dampers in related art, in which  FIG. 15A  shows a track-shaped damper,  FIG. 15B  shows an inner damper, and  FIG. 15C  shows a butterfly damper. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]     Now, some embodiments of the present invention will be described in detail below, referring to the drawings.  
         [0040]      FIG. 1  is an illustration of a loudspeaker vibrating portion. A loudspeaker unit is configured to include the loudspeaker vibrating portion as shown in  FIG. 1 .  
         [0041]     A center cap  2  is provided for preventing a cone  1  from being deformed in the radial direction, and for preventing iron powder and dust from entering into a gap.  
         [0042]     An outer damper  7  supports the outer periphery of a voice coil  5  in the major diameter direction by one end of a support portion, and the other end of the support portion is attached to a fixed portion such as a frame  10 . In addition, an inner damper  11  supports the inner periphery of the voice coil  5  by a support portion in a minor diameter direction, and the support portion is attached to a fixed portion such as a pole  6 , whereby the voice coil  5  is held properly around the pole  6 . A gasket  8  is for fixing the edge  9  of the cone  1  to the frame  10 .  
         [0043]      FIGS. 2A, 2B  and  2 C are perspective views of the outer damper, the inner damper and the voice coil, respectively.  
         [0044]     In  FIG. 2A , the outer damper  7  includes a frame portion  12  for supporting the outer periphery of the voice coil  5 , a pair of support portions  13  and  14  for supporting the major diameter of the frame portion  12  from both sides, and mounting portions  15  and  16  for mounting both the support portions  13  and  14  onto the frame  10  of the fixed portion.  
         [0045]     In  FIG. 2B , the inner damper  11  includes a frame portion  21  for supporting the inner periphery of the voice coil  5 , a pair of support portions  22  and  23  for supporting the minor diameter of the frame portion  21  from both sides, and mounting portions  24  and  25  for mounting both the support portions  22  and  23  onto the pole  6  of the fixed portion.  
         [0046]     In  FIG. 2C , the voice coil  5  is configured to have a track-like shape having a minor diameter and a major diameter, and includes a bobbin portion  26  as a coil bobbin, a coil portion  27  wound around the bobbin portion  26 , and lead wires  28  led out from the coil portion  27 .  
         [0047]      FIG. 3  is a perspective view showing the condition where the outer damper and the inner damper are mounted onto the voice coil.  
         [0048]     In  FIG. 3 , the outer damper  7  supports the outer periphery of the track-shaped voice coil  5  having the minor diameter and the major diameter in the condition where the outer periphery of the voice coil  5  of the vibrating portion is fitted in the frame portion  12  of the outer damper  7 . In addition, the major diameter of the frame portion  12  is supported from both sides by the pairs of support portions  13  and  14 . Further, the mounting portions  15  and  16  provided at both ends of the support portions  13  and  14  mount fixingly both the support portions  13  and  14  onto the frame  10  of the fixed portion.  
         [0049]     The inner damper  11  supports the inner periphery of the track-shaped voice coil  5  having the minor diameter and the major diameter in the condition where the inner periphery of the voice coil  5  is fitted over the frame portion  21  of the inner damper  11 . In addition, the minor diameter of the frame portion  21  is supported alternately from both sides by the pairs of support portions  22  and  23 . Further, the mounting portions  24  and  25  provided in L shape at both ends of the support portions  22  and  23  mount alternately fixingly both the support portions  22  and  23  onto the upper surface of the pole  6  of the fixed portion disposed on the inside of the voice coil  5 .  
         [0050]     The voice coil  5  configured in the track-like shape having the minor diameter and the major diameter is respectively sharedly supported in the major diameter direction indicated by a-a by the outer damper  7  on the outside thereof and in the minor diameter direction indicated by b-b by the inner damper  11  on the inside thereof. As a result, the vibrating portion is damped so as to be properly held in a magnetic pole space between the pole  6  and a plate (not shown), whereby the vibrating portion is supported securely, and the voice coil  5  can be prevented from undergoing rolling or the like in the minor diameter direction indicated by b-b even upon input of a high-level signal.  
         [0051]      FIGS. 4A  to  4 C show an example of a fabric damper, in which  FIG. 4A  is a front view,  FIG. 4B  is an X-X sectional view, and  FIG. 4C  is a Y-Y sectional view.  
         [0052]     In  FIGS. 4A and 4B , an outer damper  31  supports the outer periphery of a track-shaped voice coil  5  having a minor diameter and a major diameter in the condition where the outer periphery of the voice coil  5  of the vibrating portion is fitted in a frame portion  33  of the outer damper  31 . In addition, the major diameter of the frame portion  33  is supported from both sides by a pair of support portions  32  and  34  each composed of a fabric folded in a corrugated form. Further, mounting portions, not shown in the figure, provided at both ends of the pair of support portions  32  and  34  each composed of a fabric folded in a corrugated form mount fixingly both the support portions  32  and  34  onto a frame  10  of a fixed portion.  
         [0053]     In  FIGS. 4B and 4C , an inner damper  41  supports the inner periphery of the track-shaped voice coil  5  having the minor diameter and the major diameter in the condition where the inner periphery of the voice coil  5  is fitted over a frame portion  42  of the inner damper  41 . Besides, the minor diameter of the frame portion  42  is supported alternately from both sides by a pair of support portions  43  and  44  each composed of a fabric folded in a corrugated form. Further, plate-like mounting portions  45  and  46  provided in L shape at both ends of the pair of support portions  43  and  44  each composed of a fabric folded in a corrugated form mount alternately fixingly both the support portions  43  and  44  onto the upper surface of a pole  6  of a fixed portion disposed on the inside of the voice coil  5 .  
         [0054]     The voice coil  5  configured to have the track-like shape having the minor diameter and the major diameter is supported respectively sharedly in the major diameter direction indicated by X-X by the fabric-made outer damper  31  folded in the corrugated form and provided on the outside of the voice coil  5 , and in the minor diameter direction indicated by Y-Y by the fabric-made inner damper  41  folded in the corrugated form and provided on the inside of the voice coil  5 . As a result, the vibrating portion is damped so as to be held properly in a magnetic pole space between the pole  6  and a plate, not shown in the figure, whereby the vibrating portion can be supported securely, and the voice coil  5  can be prevented from undergoing rolling or the like in the minor diameter direction indicated by Y-Y even upon input of a high-level signal.  
         [0055]      FIGS. 5A  to  5 C show an example of a butterfly damper, in which  FIG. 5A  is a front view,  FIG. 5B  is an X-X sectional view, and  FIG. 5C  is a Y-Y sectional view.  
         [0056]     In  FIGS. 5A and 5B , an outer damper  51  supports the outer periphery of a track-shaped voice coil  5  having a minor diameter and a major diameter in the condition where the outer periphery of the voice coil  5  of a vibrating portion is fitted in a frame portion  52  of the outer damper  51 . In addition, the major diameter of the frame portion  52  is supported from both sides by a pair of support portions  53  and  54  each configured in a butterfly-like shape by combining plastic-made S-shaped members. Further, mounting portions, not shown in the figure, provided at both ends of the pair of support portions  53  and  54  each configured in the butterfly-like shape by combining the plastic-made S-shaped members mount fixingly both the support portions  53  and  54  onto a frame  10  of a fixed portion.  
         [0057]     In  FIGS. 5B and 5C , an inner damper  61  supports the inner periphery of a track-shaped voice coil  5  having a minor diameter and a major diameter in the condition where the inner periphery of the voice coil  5  is fitted over a frame portion  62  of the inner damper  61 . In addition, the minor diameter of the frame portion  62  is supported alternately from both sides by a pair of support portions  63  and  64  each configured by combining plastic-made S-shaped members. Further, plate-like mounting portions  65  and  66  connected to each other in S shape and provided in L shape at both ends of the pair of support portions  63  and  64  each configured by combining the plastic-made S-shaped members mount alternately fixingly both the support portions  63  and  64  onto the upper surface of a pole  6  of a fixed portion disposed on the inside of the voice coil  5 .  
         [0058]     The voice coil  5  configured in the track-like shape having the minor diameter and the major diameter is supported respectively sharedly in the major diameter direction indicated by X-X by the butterfly-shaped outer damper  51  configured by combining the plastic-made S-shaped members and provided on the outside of the voice coil  5 , and in the minor diameter direction indicated by Y-Y by the inner damper  61  configured by combining the plastic-made S-shaped members and provided on the inside of the voice coil  5 . As a result, the vibrating portion is damped so as to be held properly in a magnetic pole space between the pole  6  and a plate, not shown in the figure, whereby the vibrating portion can be supported securely, and the voice coil  5  can be prevented from undergoing rolling or the like in the minor diameter direction indicated by Y-Y even upon input of a high-level signal.  
         [0059]      FIG. 6  shows an example in which an inner damper is provided with at least one pair of support portions and at least one pair of mounting portions. While  FIG. 6  shows an example in which three pairs of support portions and three pairs of mounting portions are provided, it shows that a plurality of pairs of support portions and a plurality of pairs of mounting portions can be provided according to the elongate shape of the loudspeaker.  
         [0060]     In  FIG. 6 , an outer damper  51  supports the outer periphery of an elongate track-shaped voice coil  5  having a minor diameter and a major diameter in the condition where the outer periphery of the voice coil  5  of a vibrating portion is fitted in an elongate frame portion  52  of the outer damper  51 . In addition, the major diameter of the frame portion  52  is supported from both sides by a pair of support portions  53  and  54  each configured in a butterfly-like shape by combining plastic-made S-shaped members. Further, mounting portions, not shown in the figure, provided at both ends of the pair of butterfly-shaped support portions  53  and  54  each configured by combining the plastic-made S-shaped members mount fixingly both the support portions  53  and  54  to a frame  10  of a fixed portion.  
         [0061]     An inner damper  61  supports the inner periphery of the elongate track-shaped voice coil  5  having the minor diameter and the outer diameter in the condition where the inner periphery of the voice coil  5  is fitted over an elongate frame portion  62  of the inner damper  61 . Besides, at a short portion on one side of the frame portion  62 , the minor diameter of the frame portion  62  is supported alternately from both sides by a pair of plastic-made S-shaped support portions  67 - 1  and  67 - 2 . Further, plate-like mounting portions  68 - 1  and  68 - 2  provided in L shape at both ends of the pair of plastic-made S-shaped support portions  67 - 1  and  67 - 2  mount alternately both the support portions  67 - 1  and  67 - 2  onto the upper surface of a pole  6  of a fixed portion disposed on the inside of the voice coil  5 .  
         [0062]     In addition, in the vicinity of the center of the frame portion  62 , the minor diameter of the frame portion  62  is supported alternately from both sides by a pair of plastic-made S-shaped support portions  67 - 3  and  67 - 4 . Further, plate-like mounting portions  68 - 3  and  68 - 4  provided in L shape at both ends of the pair of the plastic-made S-shaped support portions  67 - 3  and  67 - 4  mount alternately fixingly both the support portions  67 - 3  and  67 - 4  onto the upper surface of the pole  6  of the fixed portion disposed on the inside of the voice coil  5 . Here, the pair of support portions  67 - 3 ,  67 - 4  and the pair of mounting portions  68 - 3 ,  68 - 4  provided in the vicinity of the center of the frame portion  62  may be provided in pluralities of pairs.  
         [0063]     Besides, at a short portion on the other side of the frame portion  62 , the minor diameter of the frame portion  62  is supported alternately from both sides by a pair of plastic-made S-shaped support portions  67 - 5  and  67 - 6 . Further, plate-like mounting portions  68 - 5  and  68 - 6  provided in L shape at both ends of the pair of the plastic-made S-shaped support portions  67 - 5  and  67 - 6  mount alternately fixingly both the support portions  67 - 5  and  67 - 6  onto the upper surface of the pole  6  of the fixed portion disposed on the inside of the voice coil  5 .  
         [0064]     The voice coil  5  configured in the elongate track-like shape having the minor diameter and the major diameter is supported in the major diameter direction indicated by X-X (see  FIG. 5A ) by the elongate butterfly-shaped outer damper  51  configured by combining the plastic-made S-shaped members and provided on the outside of the voice coil  5 , and in the minor diameter direction indicated by Y-Y (see  FIG. 5A ) by the elongate inner damper  61  configured by combining the plastic-made S-shaped members. Thus, the voice coil  5  is supported respectively shared by the outer damper  51  and the inner damper  61 . As a result, the vibrating portion is damped so as to be held properly in a magnetic pole space between the pole  6  and a plate, not shown in the figure, and the vibrating portion is supported securely, so that the elongate voice coil  5  can be prevented from undergoing rolling or the like in the minor diameter direction indicated by Y-Y even upon input of a high-level signal.  
         [0065]     While an example wherein the outer damper and the inner damper are configured as separate bodies has been described in the embodiments above, this configuration is not limitative, and a configuration may be adopted in which the outer damper and the inner damper are integral with each other.  
         [0066]      FIG. 7  shows an example in which an outer damper and an inner damper are integral with each other.  FIG. 7  is different from the vibrating portion shown in  FIG. 1 , in that an outer damper  71  and an inner damper  75  are integrated with each other through a joint portion  79 .  
         [0067]     In this case, of a cone  1  constituting a diaphragm, that portion which may not be adhered directly to a voice coil  5  is adhered to the joint portion  79 . The joint portion  79  is joining a frame portion  72  of the outer damper  71  and a frame portion  76  of the inner damper  75  to each other in an angular U shape. As a result, the joint portion  79  is so formed as to pinch an upper end portion of the voice coil  5 , and a mounting portion  78  for mounting the inner damper  75  onto a pole  6  is fixedly mounted on the upper surface of the pole  6  disposed on the inside of the voice coil  5 .  
         [0068]      FIG. 8  shows a joined condition of an outer damper and an inner damper.  FIG. 8  shows the condition where the inner damper shown in  FIG. 6  is provided with one pair of support portions and one pair of mounting portions, and the outer damper and the inner damper are joined to each other through joint portions.  
         [0069]     In  FIG. 8 , the outer damper  81  supports the outer periphery of a track-shaped voice coil  5  having a minor diameter and a major diameter in the condition where the outer periphery of the voice coil  5  of a vibrating portion is fitted in a frame portion  82  of the outer damper  81 . Besides, the major diameter of the frame portion  82  is supported from both sides by a pair of butterfly-shaped support portions  83  and  84  each configured by combining plastic-made S-shaped members. Further, mounting portions, not shown in the figure, provided at both ends of the pair of butterfly-shaped support portions  83  and  84  each configured by combining the plastic-made S-shaped members mount fixingly both the support portions  83  and  84  onto a frame  10  of a fixed portion.  
         [0070]     Here, the frame portion  82  of the outer damper  81  and a frame portion  90  of the inner damper  85  are joined to each other, at their minor diameters through joint portions  91  and  92 , and at their major diameters through joint portions  93  and  94 . In this case, the joint portions  91  and  92  joining the minor diameters support the minor diameter of the track-shaped voice coil  5  by nipping upper end portions of the minor diameter of the voice coil  5 , whereas the joint portions  93  and  94  joining the major diameters support the major diameter of the track-shaped voice coil  5  by nipping upper end portions of the major diameter of the voice coil  5 .  
         [0071]     The inner damper  85  supports the inner periphery of the track-shaped voice coil  5  having the minor diameter and the major diameter in the condition where the inner periphery of the voice coil  5  is fitted over the frame portion  90  of the inner damper  85 . Besides, the minor diameter of the frame portion  90  is supported alternately from both sides by a pair of plastic-made S-shaped support portions  86  and  87 . Further, plate-like mounting portions  88  and  89  provided in L shape at both ends of the pair of plastic-made S-shaped support portions  86  and  87  mount fixingly both the support portions  86  and  87  onto the upper surface of a pole  6  of a fixed portion disposed on the inside of the voice coil  5 .  
         [0072]     The voice coil  5  configured in the track-like shape having the minor diameter and the major diameter is supported sharedly, in the major diameter direction indicated by X-X by the plastic-made S-shaped butterfly type outer damper  51  provided on the outside of the voice coil  5 , and in the minor diameter direction indicated by Y-Y by the plastic-made S-shaped inner damper  61  provided on the inside of the voice coil  5 . Besides, in this case, the support in the minor diameter direction is shared by the joint portions  91  and  92  joining the minor diameters, and the support in the major diameter direction is shared by the joint portions  93  and  94  joining the major diameters.  
         [0073]     As a result, the vibrating portion is damped so as to be held properly in a magnetic pole space between the pole  6  and a plate, not shown in the figure, and the vibrating portion is supported securely, so that the voice coil  5  can be prevented from undergoing rolling or the like in the minor diameter direction indicated by Y-Y even upon input of a high-level signal.  
         [0074]     Now, a method of mounting the outer damper and the inner damper configured as above will be describe below, based on FIGS.  9  to  14 .  
         [0075]      FIG. 9  shows a method of mounting an outer damper in the case where the outer damper and an inner damper are separate bodies.  
         [0076]     In  FIGS. 9, 10  and  11 , a method of mounting the outer damper  7  and the inner damper  11  for damping a voice coil  5  which is a vibrating portion, onto a plate  101 , a magnet  102  and a frame  10  which constitute a fixed portion of a loudspeaker.  
         [0077]     First, a voice coil gage  103  is fitted into the inner periphery of the track-shaped voice coil  5  having a minor diameter and a major diameter, of the vibrating portion, and is fitted over a pole  6  of the fixed portion.  
         [0078]     Next, at a position where the voice coil  5  is fixed by the voice coil gage  103 , as indicated by  104 , a frame portion  12  of the outer damper  7  supporting the outer periphery of the voice coil  5  and the outer periphery of the voice coil  5  are adhered to each other, and a frame  10  of the fixed portion and a pair of support portions  13  and  14  for supporting the major diameter of the frame portion  12  from both sides are adhered to each other through mounting portions  15  and  16 , whereby the outer damper  7  is mounted (see  FIG. 2A ).  
         [0079]      FIG. 10  shows a method of mounting the inner damper  11 .  
         [0080]     After the outer damper  7  is mounted at a position shown in  FIG. 9 , the voice coil gage  103  is detached from the inner periphery of the voice coil  5  and the outer periphery of the pole  6 . Since the positioning of the voice coil  5  has been achieved by the outer damper  7  mounted, the inner damper  11  is inserted into the inner periphery of the voice coil  5  in the positioned condition.  
         [0081]     Subsequently, as indicated by  111 , a frame portion  21  of the inner damper  11  supporting the inner periphery of the voice coil  5  and the inner periphery of the voice coil  5  are adhered to each other, and the pole  6  of the fixed portion and a pair of support portions supporting the minor diameter of the frame portion  21  are adhered to each other through mounting portions  24  and  25 , whereby the inner damper  11  is mounted.  
         [0082]      FIG. 11  shows a method of positioning the inner damper  11 .  
         [0083]     In mounting the inner damper  11  in  FIG. 10 , for achieving a more accurate positioning, the voice coil gate  103  is fitted into the inner periphery of the track-shaped voice coil  5  having the minor diameter and the major diameter, of the vibrating portion, from a lower portion of the plate  101 , and is fitted over the outer periphery of the pole  6  of the fixed portion.  
         [0084]      FIGS. 12A and 12B  show insertion holes  121 ,  122 ,  123 ,  124  provided in a lower portion of the plate  101  so as to penetrate to the outer periphery of the pole  6 , in which  FIG. 12A  is a bottom view, and  FIG. 12B  is a partly sectional view.  FIG. 13  shows the shape of the voice coil gage  103 . As shown in  FIG. 13 , the voice coil gate  103  is provided with notches  131 ,  132 ,  133 ,  134  in the periphery thereof, to form insertable portions  135 ,  136 ,  137 ,  138 .  
         [0085]     The insertable portions  135 ,  136 ,  137 ,  138  shown in  FIG. 13  are provided at positions corresponding to, and so as to be insertable into, the insertion holes  121 ,  122 ,  123 ,  124  shown in  FIG. 12A .  
         [0086]     Therefore, the insertable portions  135 ,  136 ,  137 ,  138  of the voice coil gate  103  shown in  FIG. 13  can be inserted through the insertion portions  121 ,  122 ,  123 ,  124  provided in the lower portion of the plate  101  shown in  FIG. 12A . The voice coil gage  103  is so inserted that the notches  131 ,  132 ,  133 ,  134  of the voice coil gate  103  are projected at the upper end of the pole  6 .  
         [0087]     In this case, since the notches  131  and  133  are provided in the major diameter direction whereas the notches  132  and  134  are provided in the minor diameter direction, the adhering positions between the frame portion  21  of the inner damper  11  and the voice coil  5  can be aligned to the positions of the notches  131  and  133  provided in the major diameter direction and the positions of the notches  132  and  134  provided in the minor diameter direction. At this aligned position, positioning for adhesion between the mounting portions  24 ,  25  of the inner damper  11  and the upper end of the pole  6  can be performed.  
         [0088]      FIG. 14  shows a method of mounting an outer damper  71  and an inner damper  75  in the case where the outer damper  71  and the inner damper  75  are integral with each other as shown in  FIG. 7 .  
         [0089]     First, a voice coil gage  103  is inserted into the inner periphery of a track-shaped voice coil  5  having a minor diameter and a major diameter, of a vibrating portion, and is fitted over the outer periphery of a pole  6  of a fixed portion, through the outer damper  71  and the inner damper  75  which are integral with each other.  
         [0090]     In this case, the joint portions  91 ,  92  relevant to the minor diameter and the joint portion  93 ,  94  relevant to the major diameter, which are shown in  FIG. 8 , can be aligned to the positions of the notches  132  and  134  formed in the voice coil gage  103  in the minor diameter direction and the positions of the notches  131  and  133  formed in the voice coil gage  103  in the major diameter direction as shown in  FIG. 13 .  
         [0091]     According to this embodiment as above, for reducing the width of the diaphragm of a loudspeaker, the shape of the voice coil is set to be a irregular shape having a longer diameter in one direction, whereby the outer periphery of the voice coil is enlarged as compared with a circular voice coil having the same width, so that the vibration characteristic at the time of reproducing a high-output signal can be made advantageous.  
         [0092]     In this case, for reducing the width, the outer damper in the support system located on the outside of the voice coil is supported relative to the frame of the fixed portion only in the major diameter direction, and is not supported in the minor diameter direction. This makes it possible to produce a loudspeaker with a smaller width.  
         [0093]     Besides, in this case, the inner damper is additionally provided in the inside of the voice coil. The inner damper inside the voice coil is configured to have support portions in at least one pair of symmetrical directions.  
         [0094]     Therefore, the pair of support portions in the minor diameter direction support different positions of the pole. This ensures that, while an ordinary inner damper copes with an amplitude equivalent to one half of the minor diameter of the voice coil, it is made possible to configure an inner damper which can cope with an amplitude of nearly double the amplitude of an ordinary inner damper by the pair of support portions. Accordingly, it is possible to produce a loudspeaker having a low minimum resonance frequency F 0  and a wide reproduction frequency band.  
         [0095]     In addition, since the supporting in the major diameter direction is made by the outer damper on the outside of the voice coil and the supporting in the minor diameter direction is made by the inner damper on the inside of the voice coil, the vibrating portion can be supported securely, and the voice coil can be prevented from undergoing rolling or the like due to vibration, even upon input of a high-level signal to the loudspeaker.  
         [0096]     Besides, by use of the outer damper on the outside of the voice coil and the inner damper on the inside of the voice coil, it is possible to fix the voice coil at two positions. As a result, the voice coil can be prevented from being deformed at the time of vibration, and frictional contact between the voice coil and a magnetic circuit can be prevented from occurring.  
         [0097]     Furthermore, examples of the material for the dampers include plastics, phenol resin-impregnated cotton fabric, phenol resin-impregnated polyesters, phenol-impregnated amide fibers, metals, and bakelite. In addition, the outer damper on the outside of the voice coil and the inner damper on the inside of the voice coil may be formed of different materials.  
         [0098]     The present invention naturally is not limited to the above-described embodiments, and modifications can be appropriately made within the scope of the claims of the invention.