Patent Publication Number: US-2007098206-A1

Title: Speaker grille and speaker device

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a speaker grille and a speaker device.  
      The present application claims priority from Japanese Application No. 2005-314514, the disclosure of which is incorporated herein by reference.  
      A vehicle speaker or the like is usually provided with a speaker grille on its front side for protecting its diaphragm or the like. Generally, a vehicle speaker is provided such that a listener seldom listens in a right ahead direction of the speaker, but usually in an inclined direction forming an inclined angle with the right ahead direction. For this reason, there have been known various types of speaker grilles providing a directivity satisfying such an inclined direction. For example, Japanese Unexamined Patent Application Publication No. 2002-305784 has disclosed a speaker grille in which a plurality of ring-shaped members of different diameters are concentrically arranged and supported by ribs, with the members on one side arranged at a pitch narrower than on the other side. In such a speaker grille, a sound pressure distribution on one side having the narrower pitch will rise, thereby providing a directivity to a sound wave (compression wave).  
      However, since the above-mentioned speaker has a complex structure in which a plurality of ring-shaped members of different diameters are concentrically arranged, such a speaker has only a low strength and requires a long time in its manufacturing. For this reason, it has been demanded that a speaker grille be made simpler in its structure.  
      On the other hand, a compression wave emitted in an inclined direction from a diaphragm is a synthesized wave containing different phase components corresponding to different paths from different portions of vibration surface of the diaphragm. As a result, a compression wave emitted in a specifically inclined direction will suffer from an interference caused by some inverted phase components, resulting in a deteriorated sound quality in a specified frequency range.  
     SUMMARY OF THE INVENTION  
      The present invention is to solve the above-mentioned problem and makes this as one of its tasks. Namely, it is an object of the present invention to provide an improved speaker grille and thus an improved speaker device capable of preventing a deterioration of the quality of a sound propagated in an inclined direction, using only a simplified structure.  
      In order to achieve the foregoing object, the present invention has at least the following configurations included in the following aspects.  
      According to one aspect of the present invention, there is provided a speaker grille provided on a front side of a speaker having a diaphragm. The grille comprises: an open area formed in front of the diaphragm and allowing an entire diameter of the diaphragm to be open in a right ahead direction of the diaphragm; and shield are as formed outside the open area and shielding part of the diaphragm viewed in an inclined direction of the diaphragm.  
      According to another aspect of the present invention, there is provided a speaker device having a diaphragm and a speaker grille provided in front of the diaphragm. The speaker grille comprises: an open area formed in front of the diaphragm and allowing an entire diameter of the diaphragm to be open in a right ahead direction of the diaphragm; shield areas formed outside the open area and shielding part of the diaphragm viewed in an inclined direction of the diaphragm.  
      The speaker device according to one embodiment of the present invention has a diaphragm and a grille provided in front of the diaphragm. The grille is formed in a position in front of the diaphragm, and has an open area in which an entire diameter of the diaphragm is opened in a right ahead direction of the diaphragm, also has shield areas formed on both sides of the open area for shielding part of the diaphragm viewed in an inclined direction.  
      With regard to the speaker device having the above-described configuration, shield areas formed in the speaker grille are located on both sides of the open area, thereby shielding part of the diaphragm viewed in an inclined direction thereof. Therefore, among compression waves emitted from an inclined surface of the diaphragm, part of the compression waves along inclined direction having a predetermined angle is shielded by the shield areas. In this way, it is possible to inhibit a sound quality deterioration in a specific frequency range which will otherwise be caused due to interference of phase component corresponding to path difference from various portions of the diaphragm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and other objects and advantages of the present invention will become clear from the following description with reference to the accompanying drawings, wherein:  
       FIG. 1  is a front elevation showing a speaker device according to one embodiment of the present invention;  
       FIG. 2  is a cross sectional view taken along A-A line of the speaker device shown in  FIG. 1 ;  
       FIG. 3  is a cross sectional view taken along B-B line of the speaker device shown in  FIG. 1 ;  
       FIG. 4  is a perspective view showing a grille of  FIG. 1  when viewed from the front side of the speaker device;  
       FIG. 5  is a perspective view showing a grille of  FIG. 1  when viewed from the back side of the speaker device;  
       FIG. 6  is a front view of the grille shown in  FIG. 1 ;  
       FIG. 7  is an explanatory view showing a path difference of a sound wave (compression wave) emitted in an inclined direction inclining a predetermined angle from the speaker center axis O towards y-axis direction;  
       FIG. 8  is an explanatory view showing a path difference of a sound wave (compression wave) emitted in an inclined direction inclining a predetermined angle from the speaker center axis O towards x-axis direction;  
       FIG. 9  is a graph showing a frequency response in the right ahead direction (0°) of the speaker device  1  equipped with the grille  4  formed according to an embodiment of the present invention, and that of a conventional speaker device equipped with a conventional grille; and  
       FIG. 10  is a graph showing a frequency response in an inclined direction (30°) of the speaker device  1  equipped with the grille  4  formed according to an embodiment of the present invention, and that of a conventional speaker device equipped with a conventional grille. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      In the following, description will be given to explain a speaker device according to one embodiment of the present invention, with reference to the accompanying drawings.  
       FIG. 1  is a front view showing the speaker device  1  according to one embodiment of the present invention.  FIG. 2  is a cross sectional view taken along A-A line of the speaker device shown in  FIG. 1 .  FIG. 3  is a cross sectional view taken along B-B line of the speaker device  1  shown in  FIG. 1 .  
      As shown in FIGS.  1  to  3 , the speaker device  1  according to the present embodiment includes two concentrically arranged speakers. In detail, the speaker device  1  includes a low-pitched sound playback speaker  2 , a high-pitched sound playback speaker  3 , and a grille  4 . The grille  4  corresponds to an embodiment of a speaker grille according to the present invention. The low-pitched sound playback speaker  2  and the high-pitched sound playback speaker  3  are connected by virtue of a support member  5 .  
      Here, the speaker device  1  is a coaxial type two-way speaker, with the low-pitched sound playback speaker  2  disposed close to the front side of the speaker device and the high-pitched sound playback speaker  3  close to the rear side thereof in a mutually coaxial relation. However, the speaker device  1  should not be limited to the above-mentioned configuration and it is possible for the speaker device to be composed of single one speaker. In fact, the low-pitched sound playback speaker  2  may be a speaker device capable of low-pitched sound playback or medium-pictured sound playback, while the high-pitched sound playback speaker  3  may be a speaker device capable of medium-pitched sound playback or high-pitched sound playback.  
      [Low-Pitched Sound Playback Speaker  2 ] 
      The low-pitched sound playback speaker  2 , as shown in FIGS.  1  to  3 , includes a magnetic circuit  21  and a vibration system  22 . The magnetic circuit  21  can be an external type magnetic circuit or an internal type magnetic circuit. The magnetic circuit  21  of the present embodiment is an external type magnetic circuit, including a magnet  211 , a pole piece  212 , and a plate  213 . The magnet  211  is ring-shaped and formed of a permanent magnet such as a neodymium magnet, a samarium cobalt magnet, an Alnico magnet, and a ferrite magnet. The pole piece  212  is formed so that it has an inverted generally T-shaped section, as shown in  FIG. 2 . Further, as shown in  FIG. 2 , the pole piece  212  includes a yoke  212   a , a center pole  212   b , and openings  212   c  and  212   d . The yoke  212   a  is formed into a flange member and positioned under the ring-shaped magnet  211 . The center pole  212   b  has a cylindrical shape and a conical concave portion on the lower side thereof close to its center axis. Further, the center pole  212   b  is formed with an opening  212   c  on the lower side thereof and another opening  212   d  on the upper side thereof. The opening  212   c  and the opening  212   d  are communicated with each other along the center axis. In more detail, the opening  212   d  extends from a position near a generally central portion of the center pole  212   b  to the upper side thereof, while the opening  212   c  extends from the position near a generally central portion of the center pole  212   b  to the lower side thereof. The diameter of the opening  212   d  is larger than that of the opening  212   c , while the support member  5  is inserted through the openings  212   c  and  212   d.    
      The ring-shaped plate  213  is positioned over the ring-shaped magnet  211 . A magnetic gap  210  is formed between the inner circumferential surface of the plate  213  and the outer periphery surface of the pole piece  212 , thereby allowing the magnetic flux produced by the magnet  211  to be collected in the magnetic gap  210 .  
      As shown in FIGS.  1  to  3 , the vibration system  22  includes a voice coil bobbin  221 , a voice coil  222 , a diaphragm  223 , a speaker frame (frame)  224 , and a damper  225 . The voice-coil bobbin  221  has a cylindrical shape, with its lower end being wound around by the voice coil  22 . The voice coil  222  wound around the lower end of the voice-coil bobbin  221  is positioned in the magnetic gap  210  formed between the plate  213  and the pole piece  212 . An electrically conductive wire LN 1  is electrically connected with the voice coil  222 , while the other end of the electrically conductive wire LN 1  is electrically connected to a terminal section  224   a  provided on the speaker frame  224 . Here, the diaphragm  223  can be formed into various configurations including a conical shape. In practice, the diaphragm  223  may be formed of various materials such as a paper, a high molecule material, and a metal. The edge of the diaphragm  223  is fixed to the frame  224  through an edge portion  223   a . The edge portion  223   a  is formed to be flexibly movable with respect to the movement of the diaphragm  223 . Specifically, the edge portion  223   a  can function as a terminal for an acoustical vibration of the diaphragm  223 , also as means for supporting the perimeter of the diaphragm  223  and holding the same in a predetermined position, as means for preventing a lateral vibration of the diaphragm  223 , and as a shield for preventing a sound wave on the back side of the diaphragm  223  from interfering into the sound wave on the front side thereof.  
      The frame  224  has a function of supporting various essential components of the speaker device  1 . In detail, the frame  224  is formed into an upwardly open structure, with its bottom portion  224   b  disposed on the plate  213  and its upper portion  224   c  fixed with the edge portion  223   a . Moreover, a flange portion  224   d  for supporting the damper  225  is formed near the generally central portion of the frame  224 .  
      Here, the damper  225  is provided to freely movably support the voice bobbin  221 . In more detail, the damper  225  is formed so that it has a corrugated cross section, with its outer perimeter portion fixed and its inner circumferential portion fixed with the diaphragm  223 .  
      [Support Member  5 ] 
      The support member  5  is provided between the low-pitched sound playback speaker  2  and the high-pitched sound playback speaker  3  so as to support the high-pitched sound playback speaker  3  on the low-pitched sound playback speaker  2 . For example, an engaging portion  5   a  for engaging into the openings  212   c  and  212   d  of the pole piece  212  is formed on the lower end of the support member  5 . An opening  5   b  is formed on the upper end of the support member  5 , while a frame portion  33  of the high-pitched sound playback speaker  3  is engaged into the opening  5   b.    
      [High-Pitched Sound Playback Speaker  3 ] 
      The high-pitched sound playback speaker  3 , as shown in FIGS.  1  to  3 , includes a magnetic circuit  31  and a vibration system  32 . The magnetic circuit  31  can be an external type magnetic circuit or an internal type magnetic circuit. The magnetic circuit  31  of the present embodiment is an internal type magnetic circuit, including a magnet  311 , a yoke  312 , and a plate  313 .  
      The magnet  311  has a solid cylindrical shape and is formed of a permanent magnet such as a neodymium magnet, a samarium cobalt magnet, an Alnico magnet, and a ferrite magnet. The yoke  312  is formed so that it has a U-shaped section, while the magnet  311  is mounted on the bottom surface thereof. The plate  313  is a ring-shaped member and mounted on the magnet  311 . A magnetic gap  310  is formed between the outer periphery of the plate  313  and the inner circumferential surface of the plate  312 , thereby allowing magnetic flux produced by the magnet  311  to be collected in the magnetic gap  310 .  
      The vibration system  32  includes a diaphragm  321  and a voice coil  322 . The diaphragm  321  is formed in a manner such that its central portion has a dome-like shape and its outer periphery surface has a cone-like shape, thereby forming a U-shaped cross section in which the voice coil is disposed in an intermediate position. The perimeter portion of the diaphragm  321  is supported by the frame  33  and the voice coil  322  is supported by the diaphragm  321  in the vicinity of the magnetic gap  31 . Further, the electrically conductive wire LN 1  extending from the terminal section  224   a  is electrically connected to the voice coil  323  through a shield cover  34 . The frame  33  is formed on its lower portion with an engagement portion  33   a  for engaging into the opening of the support member  5 , with a magnetic circuit  31  being arranged inside. The shield cover  34  is disposed on the front side of the frame  33 .  
      As shown in  FIG. 2  and  FIG. 3 , the shield cover  34  is formed along the perimeter of the frame  33 , while the outer diameter of the shield cover  34  is equal to about ⅔ of the outer diameter of the diaphragm  223 . The shield cover  34  has a function of shielding or reflecting part of the compression wave emitted from the central portion of the diaphragm  223 . Further, the shield cover  34  is formed to cover the central portion of the diaphragm  223  in front of the diaphragm, while its inclined portion is formed to cover part of the vibration surface of the diaphragm  223 .  
      [Grille  4 ] 
       FIG. 4  is a perspective view of the speaker grille shown in  FIG. 1  when viewed from the front side.  FIG. 5  is a perspective view of the speaker grille shown in  FIG. 1  when viewed from the backside.  FIG. 6  is a front view illustrating the speaker grille shown in  FIG. 1 . As shown in FIGS.  1  to  6 , the grille  4  has an open area  41 , shield areas  42 , and a protection cover (punched net)  43 .  
      The open area  41  is formed on the front position of the diaphragm  223 , while the diaphragm  223  covering its entire diameter is formed to be in an open state when viewed from its front side.  
      The shield areas  42  are formed on both sides of the open area  41 , while part of the diaphragm  223  is shielded when viewed in an inclined direction. Further, as shown in  FIGS. 2 and 3 , the shield areas  42  include two areas arranged on the left and right sides of the open area  41  in the x-axis direction, thereby shielding part of the vibration surface of the diaphragm  233  on the left or right side.  
      In more detail, as shown in  FIGS. 2 and 3 , the shield areas  42  include a first shield area  421  and a second shield area  422  located on the left and right sides of the open area  41  in the x-axis direction. In the present embodiment, the first shield area  421  and the second shield area  422  are formed symmetrically on the left and right sides. The first shield area  421  is formed to shield part of the left or right vibration surface of the diaphragm  223  in an inclined direction, while the second shield area  422  is formed into a shape not shielding the vibration surface of the diaphragm  322  in an inclined direction. Moreover, the shield areas  42  serve to shield an area in the vicinity of an edge portion  223   a  of the diaphragm  223  on the front side thereof. In fact, the shield areas  42  can also be formed into a shape capable of shielding, in front of the diaphragm  223 , an area near part of an edge portion  223   a  of the diaphragm  223  and part of the vibration surface of the diaphragm  223   a . Here, the shield areas  42  can be made of various materials including a metal material such as iron or the like, a resin material such as ABS (ACRYLONITRILE-BUTADIENE-STYRENE) resin or the like.  
      The protection cover (punched net)  43  is formed with a plurality of apertures and provided to cover the open area  41 . Such a protection cover  43  may be formed of a metal material such as iron or the like, a resin material such as ABS resin or the like. The compression wave radiated from the diaphragm will be transmitted through the protection cover by way of the apertures formed in the protection cover  43 , with an acoustic load being low at least in the right ahead direction.  
      Next, description will be given to explain an example of the grille  4 . As shown in FIGS.  1  to  6 , the grille  4  is formed with arm-shaped shield areas  42  located on both the left and right sides thereof for adjusting a directivity. In fact, the shield areas  42  are formed to cover only the edge portion  223   a  of the diaphragm  223  when viewed from the front side, or to cover both the edge portion  223   a  and the vibration surface of the diaphragm  223 . Preferably, as shown in  FIG. 6 , the shield areas are formed within an angle range A of 55-80° predetermined in the maximum circumferential direction of the diaphragm  223 . Preferably, the second shield area  422  is formed such that its numerical aperture (a minimum size C between the first and second shield areas  421  and  422 /a maximum diameter  D of the diaphragm) in the horizontal direction (x-axis direction) is about 65%-80%. Further, it is preferable not to form an acoustic load in the vertical direction (y-axis direction) of the grille, but to open an arc B in the circumferential direction to an angle of 90°. Moreover, as shown in  FIGS. 2 and 4 , the shield areas  42  are formed in a manner such that when it is viewed in an inclined direction forming a predetermined angle such as 30° with the front axis (center axis O of the speaker), its shield area  422  will cover part of the diaphragm  223 , with no acoustic load based on the grille  4  occurring in other directions. Various sizes and shapes such as the foregoing angle range A, numerical aperture, angle B and the like can be properly set according to an external environment of the speaker device  1 , as well as acoustic performances of the low-pitched sound playback speaker  2  and the high-pitched sound playback speaker  3 .  
      A brief description will now be given to explain an operation of the speaker device  1  having the above-described structure. Namely, an electrical signal is applied from the terminal  224   a  to the voice coils  222 , 322  through the electric conductive wire LN 1 . In this way, driving forces will occur in the voice coils  222  and  322 , thereby causing the diaphragms  223 , 321  to vibrate in the axial direction O (z-axis direction) of the speaker device  1 . As a result, the speaker device  1  emits a sound wave (compression wave) in the right-ahead direction.  
      [Right-Ahead Direction (Center Axis Direction)] 
      At this time, the compression wave emitted from the diaphragm  223  in the right-ahead direction (z-axis direction) of the speaker device  1  is transmitted through the open area  41  of the grille  4 . In more detail, the compression wave is emitted to the front side through the protection cover  43  covering the open area  41 . At this moment, an acoustic load on the protection cover  43  is almost zero.  
      [Inclined Direction (Inclined with Respect to Y-Axis Direction)] 
       FIG. 7  is an explanatory sectional view showing a path difference of a sound wave (compression wave) emitted in an inclined direction inclining a predetermined angle from the center axis O of the speaker towards the y-axis direction. For example, as shown in  FIG. 7 , when a listening is performed in an inclined direction (30°) with respect to the center axis O of the speaker device, a sound wave (compression wave) from various portions of the vibration surface of the diaphragm  223  of the speaker device  1  will have a maximum path difference LD 1 . For example, with regard to a speaker provided with a diaphragm having a diameter of 10 cm, if a listening is performed in an inclined direction 30°, a maximum path difference LD 1  will be about 0.036 m, as shown in the following equation (1). Such a path difference 0.036 m is equal to a half wavelength of the sound wave having a frequency of about 4.7 kHz. In this way, once there is an interference from a sound wave (compression wave) having a phase deviation which is the half wave-length, i.e., a sound wave having a phase deviation of 180°, a sound pressure level will decrease.  
                   Wavelength   =     sound   ⁢           ⁢     speed   /   frequency                   =     340   ⁢           ⁢       (     m   ⁢     /     ⁢   s     )     /   4700     ⁢           ⁢     (   Hz   )                   =     0.072   ⁢           ⁢     (   m   )                   =     0.036   ⁢           ⁢     (   m   )     ×   2                 =     half   ⁢           ⁢   wavelength   ×   2                   (   1   )               
      [Inclined Direction (Inclined with Respect to X-Axis Direction)] 
       FIG. 8  is an explanatory sectional view showing a sound wave (compression wave) emitted in an inclined direction inclining a predetermined angle from the center axis O of the speaker towards the x-axis direction. For example, as shown in FIGS.  1  to  6  and  FIG. 8 , since the shield areas  42  are formed into a shape capable of shielding part of the diaphragm viewed in an inclined direction of the diaphragm  223 , part of the compression wave transmitting along an inclined direction (30°) inclining from the center axis O toward the x-axis direction will be shielded by the shield areas  42 , with part of the compression wave being reflected.  
      In more detail, as shown in  FIG. 8 , a compression wave emitted from part of the left or right portion of the vibration surface of the diaphragm  223 , for example, the whole or part of the compression wave emitted from an area  223   p  near the upper end of the diaphragm  322  close to the second shield area  422  can be shielded, so that it is possible to remarkably reduce an interference with a compression wave emitted from an opposed vibration surface of the diaphragm  223 , thereby making it possible to prevent a decrease of sound pressure level, thus preventing a sound quality deterioration.  
      [Comparison] 
      In order to confirm the performance of the speaker device formed according to one embodiment of the present invention, the inventors of the present application have conducted a comparison between the grille  4  formed with the shield areas  42  according to one embodiment of the present invention and a conventional grille, by measuring and comparing frequency responses in the right ahead direction (0°), an inclined direction (30°) of both grilles.  
       FIG. 9  is a graph showing a frequency response in the right a head direction (0°) of the speaker device  1  equipped with the grille  4  formed according to an embodiment of the present invention and that of a speaker device equipped with a conventional grille.  FIG. 10  is another graph showing a frequency response in an inclined direction (30°) of the speaker device  1  equipped with the grille  4  formed according to an embodiment of the present invention and that of a speaker device equipped with a conventional grille. These frequency responses correspond to the results of the measurements performed in a manner such that the sound pressure levels at 1 m point correspond to frequencies so as to form continuous curves. In  FIGS. 9 and 10 , solid lines represent the measurement results of the speaker device  1  equipped with the grille  4  formed according to an embodiment of the present invention, while the broken lines represent the measurement results of a conventional speaker device equipped with a conventional grille.  
      [A Conventional Speaker Device] 
      As shown in  FIGS. 9 and 10 , regarding an inclined direction (30°) rather than a right ahead direction, a conventional speaker device has a remarkable decrease in sound pressure level within a frequency range of about 5 to 8 kHz. Such a decrease in sound pressure level is caused mainly due to the path difference LD 1  along the inclined direction, as shown in  FIG. 7 . As shown in  FIG. 9 , when there is an interference from a compression wave having a wavelength equal to a half wavelength of the compression wave, there will be a decrease in the sound pressure level within a frequency range (about 5-9 kHz) having a wavelength equal to the half wavelength.  
      [Speaker Device  1  According to an Embodiment of the Present Invention] 
      Regarding to the speaker device  1  formed according to an embodiment of the present invention, as shown in  FIGS. 8 and 9 , although a frequency response in an inclined direction (30°) rather than a right ahead direction causes a result that a sound pressure level within a frequency range of about 5 to 9 kHz will decrease, such a decrease is smaller than a conventional speaker device  1 , so that a resulting sound pressure level is greatly improved as compared with the conventional speaker device.  
      Moreover, since the grille  4  has the open area  41  in which the entire outer diameter of the diaphragm  223  is in an open state in the right ahead direction of the diaphragm  223 , the compression wave emitted from the diaphragm  223  in the right ahead direction will transmit through the grille  4  with a low acoustic load, thereby preventing a decrease in the sound pressure level. On the other hand, if simply a reflection plate is formed for providing a directivity to the front side of the diaphragm, a sound quality in the right ahead direction will become deteriorated. To solve this problem, the grille  4  of the present invention is formed with the open area  41  in the right ahead direction, so that a sound quality in the right ahead direction will not become deteriorated.  
      As described above, the speaker device  1  of the present embodiment is comprised of the diaphragm  223  and the grille  4  provided in front of the diaphragm  223 . The grille  4  has the open area  41  which is located in front of the diaphragm  223  and allows the entire diameter of the diaphragm  223  to be open in the right ahead direction of the diaphragm  223 . The grille  4  also has the shield areas  42  capable of shielding part of the diaphragm  223  in an inclined direction of the diaphragm  223 . In this way, it is possible to prevent a sound quality deterioration in the inclined direction using a simple structure. Moreover, since the above-described grille  4  is formed with the open area  41  in the right ahead direction, there would be no sound quality deterioration in the right ahead direction.  
      Moreover, since the shield areas  42  of the present embodiment are formed on left and right sides of the open area  41  so as to shield part of the vibration surface of the diaphragm  223  in an inclined direction on left or right side, it is possible to prevent a sound quality deterioration in an inclined direction on both the left and right sides.  
      In more detail, the shield areas  42  include first and second shield areas  421  and  422  on left and right sides of the open area  41 , with the first shield area  421  shielding part of left or right side vibration surface of the diaphragm  22  in an inclined direction on the left or right side, but the second shield area  422  formed into a shape not covering the vibration surface of the diaphragm  223  in an inclined direction. In this way, it is possible to prevent a sound quality deterioration in an inclined direction on the left or right side. Namely, in an inclined direction on left or right side, either the first shield area  421  or the second shield area  422  is formed into a shape capable of shielding the vibration surface of the diaphragm  223 , thereby making it possible to prevent a sound quality deterioration in an inclined direction, without applying any additional acoustic load.  
      Besides, since the shield areas  42  can shield an area near the edge of the diaphragm  223  in the right ahead direction of the diaphragm  223 , even if in an inclined direction where the shield areas  42  are formed, it is still possible to prevent a sound quality deterioration using the shield areas  42  to shield part of the diaphragm  223 .  
      Moreover, the speaker device  1  of the present embodiment is so formed that the low-pitched sound playback speaker  2  and the high-pitched sound playback speaker  3  are positioned concentrically on an identical axis. Further, since the high-pitched sound playback speaker  3  is formed with the shield cover  34 , and since part of the diaphragm  223  can be shielded by the shield cover  34  and the shield areas  42  in an inclined direction, it is exactly possible to prevent a sound quality deterioration.  
      However, the present invention is by no means to be limited to the above-described embodiment.  
      For example, although the speaker device  1  according to the above-described embodiment is provided with two speakers including the low-pitched sound playback speaker  2  and the high-pitched sound playback speaker  3 , the present invention should not be limited to such a specific embodiment. In fact, it is also possible for the speaker device of the present invention to include only one speaker, or more than two speakers.  
      Further, although the speaker device  1  according to the above-described embodiment has been explained based on a speaker device having a cone-shaped diaphragm, the present invention should not be limited to such a specific embodiment. Actually, the speaker device of the present invention may also use a diaphragm which may be dome-shaped, flat, circular, or elliptical.  
      Moreover, although the speaker device  1  according to the above-described embodiment has been explained based on a speaker device which is a conductive drive type, the present invention should not be limited to such a specific embodiment. In fact, it is also possible to adopt various other driving types such as electromagnetic type, electrostatic type, and piezoelectric type. Further, as a magnetic circuit, it is possible to use either an internal type magnetic circuit or an external type magnetic circuit.  
      In addition, although the speaker device  1  according to the above-described embodiment has the grille  4  including the shield areas  42  made of resin and the open area  41  equipped with the protection member (punched net)  43 , the present invention should not be limited to such a specific embodiment. For example, the grille  4  may be a protection member (punched net) in which a plurality of apertures are formed in the open area  41  but no aperture is formed in the shield areas  42  or the apertures of the shield areas  42  are clogged, thereby obtaining the advantages of the present invention using a simple configuration.  
      Moreover, although the above-described embodiment has been described based on a circular speaker, this should not form any limitation to the present invention. For example, the speaker of the present invention may be formed into various other shapes including a generally elliptical shape, a generally rectangular shape, a flat shape or the like.  
      As described above, the speaker device  1  of the present invention has the diaphragm  223  and the grille  4  provided in front of the diaphragm  223 . The grille  4  is formed in a position in front of the diaphragm  223 , and has the open area  41  in which the entire diameter of the diaphragm  223  is opened in the right ahead direction of the diaphragm  223 , also has the shield areas  42  formed on both sides of the open area  41  for shielding part of the diaphragm  223  viewed in an inclined direction, thereby making it possible to prevent a sound quality deterioration in the inclined direction using a simplified structure.  
      While there has been described what are at present considered to be preferred embodiments of the present invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.