Patent Publication Number: US-11395063-B2

Title: Speaker and sound diffuser thereof

Description:
BACKGROUND 
     Technical Field 
     This application relates to a speaker and a sound diffuser thereof, and in particular, to a speaker that has both a tweeter and a woofer and a sound diffuser thereof. 
     Related Art 
     A sound diffuser is used for a driver of a loudspeaker, and is used to change sound transmission paths that are various of frequency ranges and that are generated by different drivers. It helps better radiating sounds to a free field around a loudspeaker, thereby increasing sound pressure levels and sound radiation efficiency in various frequency bands with 360 degrees directions. 
     Currently, loudspeakers with sound diffusers are basically designed with corresponding drivers for different sound frequency bands. It separately designs corresponding sound diffusers and dedicated sound production space locations. Generally, a sound radiation surface of a bass sound diffuser is mainly a spherical surface, and a sound radiation surface of a treble sound diffuser is mainly a pointed cone surface. As shown in the GB2459338A, sound production spaces of treble and bass speakers are separately designed, so that there is a distance between a treble sound production space and a bass sound production space. 
     However, when a loudspeaker with a plurality of drivers integrated into a box needs to be designed, if each driver respectively has one sound production space, a relatively large space of the loudspeaker is occupied. This is not acceptable for a speaker that has a limited space. Therefore, a sound diffuser shared by a plurality of drivers needs to be developed, and a speaker system needs also to be improved to achieve an optimal acoustic characteristic. 
     SUMMARY 
     In view of this, this disclosure provides a sound diffuser used in a speaker. The sound diffuser is coaxially located between a first driver and a second driver, and the sound diffuser includes a first diffusion surface and a second diffusion surface. The first diffusion surface faces toward a first driver, and has a first central area that is a circular protrusion, a first outer ring region, and a first concave ring region located between the first central area and the first outer ring region. The second diffusion surface faces toward a second driver, and is a circular dish surface protuberant from center outwards. 
     This disclosure further provides an embodiment, where the second diffusion surface has a second central area, which is a circular protrusion, and a diameter of the first central area of the first diffusion surface is greater than the second central area of the second diffusion surface. 
     In an embodiment, the second diffusion surface has a second concave ring surface, and a diameter of the second concave ring surface is less than a diameter of the first concave ring region of the first diffusion surface. 
     This disclosure further provides an embodiment, where the second diffusion surface has a second central area, which is protuberant in a pointed cone. 
     In an embodiment, the second diffusion surface has a second central area, which is protuberant in a straight cone. 
     This disclosure further provides an embodiment, where the second diffusion surface has a second central area, which is protuberant in a circular convex cone. 
     In an embodiment, the sound diffuser is hollow, and the first diffusion surface has a plurality of openings. 
     In another embodiment, inner surfaces or outer surfaces of the plurality of openings of the first diffusion surface have damping layers. 
     This disclosure further provides a speaker, including a first driver, a second driver, and the sound diffuser according to embodiments of this application. A sound production frequency of the second driver is different from that of the first driver. The sound diffuser includes a first diffusion surface and a second diffusion surface. The first diffusion surface faces toward a first driver, and has a first central area that is a circular protrusion, a first outer ring region, and a first concave ring region located between the first central area and the first outer ring region. The second diffusion surface faces toward a second driver, and is a circular dish surface protuberant from center outwards. 
     The speaker and the sound diffuser thereof according to the embodiments of this application can enable sound production spaces of the first driver and the second driver to become smaller, and can still simultaneously diffuse sound waves that are from the first driver and the second driver. A single sound diffuser can reduce mutual impact between sound fields in the sound production spaces of the first driver and the second driver to the minimum, and can improve a direction of a sound (for example, traveling in a horizontal direction), to achieve an optimal acoustic characteristic for a speaker. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the present invention, and where: 
         FIG. 1  is a schematic sectional diagram of a speaker and a sound diffuser thereof according to an embodiment of this application; 
         FIG. 2  is a schematic sectional diagram of the sound diffuser in  FIG. 1 ; 
         FIG. 3A  is a schematic sectional diagram of a speaker and a sound diffuser thereof according to another embodiment of this application; 
         FIG. 3B  is a schematic sectional diagram of the sound diffuser in  FIG. 3A ; 
         FIG. 4A  is a schematic sectional diagram of a speaker and a sound diffuser thereof according to still another embodiment of this application; 
         FIG. 4B  is a schematic sectional diagram of the sound diffuser in  FIG. 4A ; 
         FIG. 5A  is a schematic sectional diagram of a speaker and a sound diffuser thereof according to yet another embodiment of this application; 
         FIG. 5B  is a schematic sectional diagram of the sound diffuser in  FIG. 5A ; 
         FIG. 6  is a frequency-response curve diagram of simulating the sound diffuser in  FIG. 2A , 
         FIG. 3B ,  FIG. 4B , and  FIG. 5B ; 
         FIG. 7A  is a stereoscopic appearance diagram of a sound diffuser according to another embodiment of this application; 
         FIG. 7B  is a stereoscopic sectional view of a sound diffuser according to another embodiment of this application; 
         FIG. 7C  is a stereoscopic sectional view of a sound diffuser according to another embodiment of this application; 
         FIG. 7D  is a stereoscopic sectional view of a sound diffuser according to another embodiment of this application; 
         FIG. 8  is a frequency-response curve diagram of simulating a (treble) second driver; and 
         FIG. 9  is a frequency-response curve diagram of measuring a (treble) second driver. 
     
    
    
     DETAILED DESCRIPTION 
     To facilitate reading, this document points out “upper”, “lower”, “left”, and “right” according to the figures. Its objective is to point out relative reference locations of components, but not to limit this application. 
       FIG. 1  is a schematic sectional diagram of a speaker  1  and a sound diffuser  30  thereof according to an embodiment of this application. The speaker  1  in this application mainly includes a first driver  10 , a second driver  20 , and a sound diffuser  30 . The first driver  10  and the second driver  20  are mutually coaxially disposed, and the sound diffuser  30  is also coaxially disposed between the upper first driver  10  and the lower second driver  20 . 
     The first driver  10  is disposed inside a hollow first cavity  11 , the second driver  20  is disposed inside a hollow second cavity  21 , and the sound diffuser  30  is disposed between the first cavity  11  and the second cavity  21 . The sound diffuser  30  to be coaxially disposed between the upper first driver  10  and the lower second driver  20 . For the convenience of description, a support (not shown) that fastens the sound diffuser  30  between the first driver  10  (the first cavity  11 ) and the second driver  20  (the second cavity  21 ) is not displayed may be implemented by using any structure design that can accommodate the sound diffuser  30  in this application and satisfy a sound diffusion function requirement thereof. 
     For example, the first driver  10  may be a woofer, and a sound production direction of the woofer faces toward the sound diffuser  30 . In an embodiment, a sound frequency range of the first driver  10  is approximately 40 Hz to 2,000 Hz. The first driver  10  has a first vibration film  13 , and at a location close to its outter edge, there is a coaxially disposed round first folding ring  131  that protrudes toward the sound diffuser  30 . A sound production frequency of the second driver  20  is different that of the first driver  10 . For example, the second driver  20  may be a tweeter, and a sound production direction thereof faces toward the sound diffuser  30 . In an embodiment, a sound frequency range of the second driver  20  is approximately 2,000 Hz to 20,000 Hz. The second driver  20  has a second vibration film  23 , and at a location close to its outter edge, there is a coaxially disposed round second folding ring  231  that protrudes toward the sound diffuser  30 . 
       FIG. 2  is a schematic cross-sectional diagram of the sound diffuser in  FIG. 1 . Refer to both  FIG. 1  and  FIG. 2 . Between the first cavity  11  and the second cavity  21  are sound production spaces of the first driver  10  and the second driver  20 . The sound diffuser  30  separates the sound production spaces, so that sound waves from both the first driver  10  and the second driver  20  can be simultaneously diffused. The influences between sound fields in the two sound production spaces of the first driver  10  and the second driver  20  can be reduced to the minimum, thereby reducing or even eliminating intermodulation distortion generated between the sound fields in two sound production frequency bands. The sound diffuser  30  may be in the shape of a circular dish protuberant from center outwards. The sound diffuser  30  is configured to change a diffusion direction of a sound wave. The sound diffuser  30  includes a first diffusion surface  31  and a second diffusion surface  32 . The first diffusion surface  31  faces toward the first driver  10 , the second diffusion surface  32  faces toward the second driver  20 , and surface curvatures of the first diffusion surface  31  and the second diffusion surface  32  are different. 
     The first diffusion surface  31  has a first central area  310  that is a circular protrusion, a first outer ring region  312  that is approximately horizontal flat, and a first concave ring region  311  located between the first central area  310  and the first outer ring region  312 . The first central area  310 , the first concave ring region  311 , and the first outer ring region  312  of the first diffusion surface  31  smoothly transit at adjacent locations thereof, and are mutually coaxially disposed corresponding to the first vibration film  13  of the first driver  10 . At least one part of the first central area  310  of the first diffusion surface  31  is corresponding to a cambered surface of the first vibration film  13  of the first driver  10 . A location of the first diffusion surface  31  is a maximum physical stroke location corresponding to the first vibration film  13  of the first driver  10 , that is, a vertical distance between the first diffusion surface  31  and the first folding ring  131  is equal to or greater than a maximum physical stroke generated by the first folding ring  131 . 
     The second diffusion surface  32  is in the shape of a circular dish surface protuberant from center outwards. The second diffusion surface  32  has a second central area  320  that is a circular protrusion, an approximately horizontal second outer ring region  322  and a second concave ring region  321  located between the second central area  320  and the second outer ring region  322 . The second central area  320 , the second concave ring region  321 , and the second outer ring region  322  of the second diffusion surface  32  smoothly transit at adjacent locations thereof, and are mutually coaxially disposed corresponding to the second vibration film  23  of the second driver  20 . 
     A sound wave (for example, a bass sound wave) that is toward the sound diffuser  30  from the first driver  10  is diffused outward (for example, horizontally diffused outward), and the first diffusion surface  31  of the sound diffuser  30  changes a direction of the sound wave. Similarly, a sound wave (for example, a treble sound wave) that is toward the sound diffuser  30  from the second driver  20  is diffused outward (for example, horizontally diffused outward), and the second diffusion surface  32  of the sound diffuser  30  changes a direction of the sound wave. 
     Referring to both  FIG. 1  and  FIG. 2 , in an embodiment, a diameter of the first concave ring region  311  of the first diffusion surface  31  is less than or equal to a diameter of the first folding ring  131  of the first driver  10 . In another embodiment, a diameter of the second concave ring surface  321  of the second diffusion surface  32  of the sound diffuser  30  is less than a diameter of the first concave ring region  311  of the first diffusion surface  31 . In some embodiments, a diameter of the first central area  310  of the first diffusion surface  31  of the sound diffuser  30  is greater than the second central area  320  of the second diffusion surface  32 . 
     Referring to both  FIG. 3A  and  FIG. 3B ,  FIG. 3A  is a schematic sectional diagram of a speaker and a sound diffuser thereof according to another embodiment of this application, and  FIG. 3B  is a schematic sectional diagram of the sound diffuser in  FIG. 3A . In addition to the foregoing embodiments, there are also other implementations in which preferable acoustic characteristic performance of the speaker and the sound diffuser thereof in this application is achieved. In  FIG. 3A  and  FIG. 3B , a structure of the first diffusion surface  31  of the sound diffuser  30  is the same as that in  FIG. 1  and  FIG. 2 . A difference is that, in  FIG. 3A  and  FIG. 3B , the second central area  320  of the second diffusion surface  32  of the sound diffuser  30  is a protuberant pointed cone formed by a concave surface, and the second diffusion surface  32  outside the second central area  320  is an approximately flat surface. 
     Referring to both  FIG. 4A  and  FIG. 4B ,  FIG. 4A  is a schematic sectional diagram of a speaker and a sound diffuser thereof according to still another embodiment of this application, and  FIG. 4B  is a schematic sectional diagram of the sound diffuser in  FIG. 4A . In addition to the foregoing embodiments, there are also other implementations in which preferable acoustic characteristic performance of the speaker and the sound diffuser thereof in this application is achieved. In  FIG. 4A  and  FIG. 4B , a structure of the first diffusion surface  31  of the sound diffuser  30  is the same as that in  FIG. 1  and  FIG. 2 . A difference is that, in  FIG. 4A  and  FIG. 4B , the second central area  320  of the second diffusion surface  32  of the sound diffuser  30  is a protuberant straight cone formed by a flat surface. 
     Referring to both  FIG. 5A  and  FIG. 5B ,  FIG. 5A  is a schematic sectional diagram of a speaker and a sound diffuser thereof according to yet another embodiment of this application, and  FIG. 5B  is a schematic sectional diagram of the sound diffuser in  FIG. 5A . In addition to the foregoing embodiments, there are also other implementations in which preferable acoustic characteristic performance of the speaker and the sound diffuser thereof in this application is achieved. In  FIG. 5A  and  FIG. 5B , a structure of the first diffusion surface  31  of the sound diffuser  30  is the same as that in  FIG. 1  and  FIG. 2 . A difference is that, in  FIG. 5A  and  FIG. 5B , the second central area  320  of the second diffusion surface  32  of the sound diffuser  30  is a protuberant circular convex cone formed by a round surface. 
       FIG. 6  is a frequency-response curve diagram of the sound diffuser in  FIG. 2A ,  FIG. 3B ,  FIG. 4B , and  FIG. 5B , simulating a frequency response of the second driver  20  (for example, a tweerter) at a location which is one meter away from a horizontal middle location of the sound diffuser  30 . A dotted line “ . . . ” indicates the sound diffuser  30 , shown in  FIG. 3B , whose second central area  320  is a pointed cone; a solid line “-” indicates the sound diffuser  30  shown in  FIG. 2 ; a dashed line “---” indicates the sound diffuser  30 , shown in  FIG. 4B , whose second central area  320  is a straight cone; a dot dash line “-.-” indicates the sound diffuser  30 , shown in  FIG. 5B , whose second central area  320  is a circular convex cone. 
     It can be learned from  FIG. 6  that, when a frequency is less than 10 kHz, trends of four sound pressure level curves are slightly different, and all have one valley at 2.3 kHz and one valley at 5.4 kHz, and frequency bandwidth of the valleys is approximately 500 Hz; in a frequency band of 10 kHz to 20 kHz, a sound pressure level curve of the sound diffuser  30 , shown in  FIG. 5B , whose second central area  320  is a circular convex cone is most flat. Overall, treble acoustic characteristic performance of the sound diffuser  30 , shown in  FIG. 5B , whose second central area  320  is a circular convex cone is optimal. The second diffusion surface  32  of the sound diffuser  30  mainly affects a sound pressure level curve of a frequency band equal to or greater than 10 kHz. 
     Referring to  FIG. 7A  and  FIG. 7B ,  FIG. 7A  and  FIG. 7B  are a stereoscopic appearance diagram and a stereoscopic sectional view of a sound diffuser according to another embodiment of this application. To eliminate valleys at 2.3 kHz and 5.4 kHz, another embodiment of this application further provides a hollow sound diffuser  30  with porous. As shown in  FIG. 7A  and  FIG. 7B , the sound diffuser  30  is hollow having six openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e  provided in the first central area  310  of the first diffusion surface  31  (bass) of the sound diffuser  30 . In an embodiment, for example, the openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e  may be circular, equal in diameter, and symmetrically arranged. The sound diffuser  30  is equivalent to a Helmholtz resonator. The Helmholtz resonator usually has relatively narrow sound absorption bandwidth, and absorbs maximum energy at a resonance frequency. Sound absorption performance of the Helmholtz resonator at a non-resonance frequency rapidly decreases, and the Helmholtz resonator is suitable for controlling over narrow band sound transmission. When a size of the Helmholtz resonator is far less than a wavelength of a sound wave of its resonance frequency, all gas particles within the neck may be considered as “mass blocks”, and gas within a cavity is considered as a “spring”, thereby forming a spring-mass system, that is, a classic concentrated parameter model. Then, a mechanical model of the Helmholtz resonator may be simplified as a concentrated mass-spring system with a single degree of freedom. A theoretical resonance frequency formula of the sound diffuser  30  that is used as the Helmholtz resonator in  FIG. 7A  and  FIG. 7B  is as follows: 
     
       
         
           
             f 
             = 
             
               
                 c 
                 
                   2 
                   ⁢ 
                   π 
                 
               
               ⁢ 
               
                 
                   S 
                   
                     L 
                     * 
                     V 
                   
                 
               
             
           
         
       
     
     where, c is a sound speed, S is areas of openings in the neck (that is, areas of the individual openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e ), L is an effective length of the neck (that is, a depth of the individual openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e ), and V is a volume of a cavity (that is, a hollow volume of the sound diffuser  30 ). 
     In  FIG. 7A  and  FIG. 7B , the total area of the openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e  of the sound diffuser  30  at the first diffusion surface  31  (bass) needs to be properly coordinated with the hollow volume of the sound diffuser, and damping layer(s)  314 ,  314 ′ (shown in  FIG. 7C  and  FIG. 7D ) are added to locations of inner surfaces or outer surfaces of the openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e . The damping layers  314 ,  314 ′ may be implemented by respectively disposing mesh cloths on the openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e , and the mesh cloths used as the damping layers  314 ,  314 ′ cover the inner surfaces or the outer surfaces of the openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e . To adjust the damping coefficient of the damping layers, the ratio of the openings of the mesh cloths used as the damping layers may be adjusted and the sizes of the openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e  may be adjusted. In this way, a proper resonance frequency and the Helmholtz resonator with damping may be designed to serve as the sound diffuser  30 . 
     By performing a simulated test by replacing the sound diffuser  30  in  FIG. 1  with the hollow porous sound diffuser  30  in  FIG. 7A  and  FIG. 7B , which shows a comparison of a frequency response of the second driver  20  (treble) between a perforated sound diffuser  30  and an imperforate sound diffuser  30  at a location that is one meter away from a horizontal middle point, as shown in  FIG. 8  and  FIG. 9 ,  FIG. 8  is a frequency-response curve diagram of simulating a (treble) second driver  30 . A solid line “-” indicates the hollow porous sound diffuser  30  with damping layers in  FIG. 7A  and  FIG. 7B ; a dashed line “---” indicates the imperforate sound diffuser  30  in  FIG. 1 .  FIG. 9  is a frequency-response curve diagram of measuring a (treble) second driver  20 . A solid line “-” indicates the hollow porous sound diffuser  30  with damping layers in  FIG. 7A  and  FIG. 7B ; a dashed line “---” indicates the imperforate sound diffuser  30  in  FIG. 1 . 
     It can be learned from simulated sound pressure level curves in  FIG. 8  that, the hollow porous sound diffuser with damping layers can effectively eliminate a valley at 2.3 kHz and improve a valley at 5.4 kHz, so that the sound pressure level curves are easier, thereby helping to design the sound diffuser  30  of the speaker  1 . It may be learned from the measured curve in  FIG. 9  that a measurement result is basically consistent with a simulation result. It can be learned from a further analysis that the valleys at 2.3 kHz and 5.4 kHz are caused by coupling sound fields of treble and bass at the outer diameter of the sound diffuser  30 . The openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e  are provided in the first diffusion surface  31  (bass) of the sound diffuser  30 , and damping layers are added, so that the sound diffuser  30  becomes a Helmholtz resonator with damping layers, a sound transmission path of a sound production space of the first driver  10  (bass) is changed, and then the valley at 2.3 kHz is eliminated and the valley at 5.4 kHz is improved. It is noteworthy that damping control at locations of the openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e  in the first diffusion surface  31  of the sound diffuser  30  is very important. The optimal control effect cannot be achieved if the damping force is excessively large or excessively small. If the damping force is excessively large, it means that the first diffusion surface  31  (bass) of the sound diffuser  30  is rigid, and a sound cannot enter into the sound diffuser  30 ; if the damping force is excessively small, most of the sound radiated into the sound diffuser  30  is radiated back into an original sound field, effective coupling cannot occur, and the optimal effect cannot be achieved. Therefore, the damping at the locations of the openings  313   a ,  313   b ,  313   c ,  313   d ,  313   f , and  313   e  needs to be properly adjusted, so as to achieve the optimal effect. 
     According to the speaker  1  and the sound diffuser  30  thereof of this disclosure, sound waves from both the first driver  10  and the second driver  20  can be simultaneously diffused, and the mutual impact between sound fields in the two sound production spaces of the first driver  10  and the second driver  20  can be reduced to the minimum, so that an optimal acoustic characteristic is achieved for the speaker  1 . 
     Although this application is disclosed above by using the embodiments, the embodiments are not used for limiting this application. Any person skilled in the art may perform some modifications and improvements without disobeying the spirit and scope of this application. Therefore, the protection scope of this application should be subject to the scope defined by the claims.