Patent Publication Number: US-11044553-B2

Title: Two-way quasi point-source wide-dispersion speaker

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This disclosure claims the benefit of priority to U.S. Provisional Application No. 62/824,518 filed Mar. 27, 2019, the disclosure of which is incorporated herein in its entirety. 
    
    
     BACKGROUND 
     Field of the Invention 
     The invention relates to an array of speakers disposed to propagate sound in a manner that simulates sound emanating from a point source. 
     Related Art 
     U.S. Pat. No. 8,249,268 relates to a woofer-less loudspeaker system that has a plurality of tweeter drivers arranged in a spherical or part spherical array so that each tweeter driver faces out from a center of the sphere and with the axis of symmetry of each tweeter driver defining a radius of the sphere. Sound energy then is directed radially out in all radial directions from the center of the sphere or in a number of radial directions corresponding to the part spherical array. The loudspeaker system disclosed in U.S. Pat. No. 8,249,268 is very effective in situations where it is desirable to have sound waves generated out uniformly in all directions or in a plurality of directions from an apparent single point source. 
     U.S. Pat. No. 8,917,881 relates to an audio speaker system with a plurality of tweeter drivers arranged in a spherical array so that each tweeter driver faces in toward the center of the sphere and with the axis of symmetry of each tweeter driver defining a radius of the sphere. Sound energy then is directed radially in all radial directions toward the center of the sphere. The sound waves from the spherical array of tweeter drivers merge at the center of the sphere, recombine and then are re-emitted outward in all directions as if the center point of the sphere is a point source of all outgoing soundwaves. It has been found that the speaker system disclosed in U.S. Pat. No. 8,917,881 is very effective in some environments but less effective in many other environments. For example, speakers often are mounted on or very close to one or more walls. In these situations, at least half of the re-emitted soundwaves emanating from the center of the sphere are directed toward the wall and reflect from the wall at a plurality of angles and a plurality of positions. Thus, the desired effect of having the sound waves appear to emanate from a point source is lost in the many situations where the spherical array of tweeter drivers are mounted in proximity to a wall. As a result, there are phase shifts in the sound waves reaching the listener due to the different distances that the sound waves travel from the respective tweeter drivers with or without reflections from the wall and from different points of reflection from the wall. The various waves form addition and cancellation interference with one another in those situations with a potentially significant reduction in the quality of the sound reaching the listener. 
     In view of the above, an object of the subject invention is to provide a speaker system configured to allow sound to be perceived by a listener as being directed outward from an apparent point source. 
     SUMMARY 
     The invention relates to a speaker system comprising at least one part-spherical array of speakers. Each speaker includes a front face from which sound is emitted and a rear face opposite the front face. An axis of symmetry extends concentrically through the front and rear faces of each speaker. The axes of symmetry of the speakers in the array extend radially through a center point of a sphere, and with the front face of each of the speakers facing toward the center point of the sphere. The speakers in the at least one array form part of a sphere. For example, the part spherical array of speakers may define a hemisphere or an array smaller or larger than a hemisphere. More particularly, an open area is formed in the spherical array. A plane passing through the center of the sphere and bisecting the open area may circumscribe a sector that spans an angle of 30°-180° or more. Sound energy emitted from the speakers will be directed toward the center of the sphere, will merge at the center, recombine and be emitted from the open area in a directional manner that is perceived as emanating from the center of the sphere. 
     The various speakers may be mounted in a structure intended to minimize vibration in the structure and thus minimizing any sound produced by such vibration. Additionally, the mounting structure for the speakers may have appropriate sealing material and/or insulation to minimize sound produced by the speakers from being transmitted through the mounting structure and in a direction away from the opening in the part spherical array. 
     In one embodiment, the speakers in the speaker array comprise or consist of tweeter drivers. In another embodiment, the speakers in the speaker array comprise tweeter drivers and midrange drivers. The tweeter drivers and the midrange drivers may be disposed at substantially identical radial distances from the center of the sphere. Additionally, the tweeter drivers and the midrange drivers may be disposed in a specified circumferential pattern, such as an alternating arrangement of tweeter drivers and midrange drivers. 
     The at least one part-spherical array of speakers may comprise at least first and second part-spherical arrays of speakers. The first part-spherical array of speakers may comprise speakers at a first radial distance from the center of the sphere, while the second part-spherical array of speakers may comprise speakers at a second radial distance from the center of the sphere, with the first and second radial distances being different from one another. The speakers in the first part spherical array may be different from the speakers in the second part-spherical array. For example, tweeter drivers may be disposed in the first part-spherical array, with the tweeter drivers being at a first radial distance from the center of the sphere. Midrange drivers may be disposed in the second part spherical array with the midrange drivers being at a second radial distance from the center of the sphere. The second radial distance may be greater than the first radial distance. Additionally, the drivers in the first and second part-spherical arrays are offset circumferentially from one another so that the drivers in the array closer to the center of the sphere do not impede sound energy emitted from the drivers in the second part spherical array. Thus, the sound energy emanating from both part-spherical arrays may reach the center point substantially unimpeded. This sound energy will merge and be emitted from the open area in the array. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of a part-spherical array of speaker drivers in accordance with a first embodiment. 
         FIG. 2  is a schematic cross-sectional view of a part-spherical array of speakers in accordance with a second embodiment. 
         FIG. 3  is a schematic cross-sectional view of a part-spherical array of speakers in accordance with a third embodiment. 
         FIG. 4  is a front elevational view of a variation of the third embodiment at an intermediate stage of manufacture. 
         FIG. 5  is a front elevational view of the embodiment illustrated in  FIG. 4  at a subsequent stage of manufacture. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a part-spherical speaker array  10  comprised of a plurality of drivers  12 . Each driver  12  has opposite front and rear faces  14  and  16  disposed along an axis  18 . The drivers  12  are oriented so that the axes  18  intersect a common center point and are oriented so that the front faces  14  of all of the drivers  12  face toward the common center point. The common center point is not visible in  FIG. 1 , but is visible in the second and third embodiments illustrated in  FIGS. 2 and 3  and described below. Additionally, in the embodiment of  FIG. 1 , the front faces  14  of the drivers  12  are at the same radial distance from the common center point. Thus, the front faces  14  of the drivers  12  are disposed in a spherically generated array. However, the array  10  of drivers do not form a complete sphere. Rather, the drivers  12  are disposed to leave an open area  22  for dispersion of sound from the drivers  12  of the array  10 . With this arrangement, sound energy produced from the plurality of drivers  12  is directed toward the center point of the part-spherical array  10 . The sound energy will merge at the center point, combine and be re-emitted from the open area  22  as if the sound all emanated from the center point of the part-spherical array  10 . 
       FIG. 2  illustrates a second embodiment that differs from the first embodiment with respect to the types of drivers that comprise the array. More particularly,  FIG. 2  illustrates a speaker array  10 A comprised of tweeter drivers  12 T and midrange drivers  12 MR. The axes  18  of the tweeter drivers  12 T and the midrange drivers  12 MR all are aligned radially with respect to the center point  20 A, and the front faces  14 T and  14 MR are equidistant from the center point  20 A to define a single part-spherical array  10 A. However, an open area  22 A is defined on one side of the part-spherical array  10 A and spans an angle of approximately 45°. Smaller or larger angles for the open area  22 A are possible. In most embodiments, the open area will span an angle of 180° or less. However, an open angle of greater than 180° is possible. As in the first embodiment, sound emitted from the tweeter drivers  12 T and midrange drivers  12 MR will meet at the center point  20 A, merge and be emitted from the open area  22 A while creating an acoustical impression that the sound all emanates from the center point  22 A. 
       FIG. 3  shows a third embodiment that is a variation of the second embodiment. More particularly,  FIG. 3  illustrates a part-spherical array  10 B comprised of tweeter drivers  12 T and midrange drivers  12 MR all of which have axes that form radii intersecting at a center point  20 B. However, the tweeter drivers  12 T have front faces  14 T spaced at a first radial distance from the center point  20 B, while the midrange drivers  12 MR have front faces  14 MR spaced at a second radial distance from the center point  20 B, with the second radial distance being greater than the first radial distance. As a result, the part-spherical array  10 B of the second embodiment has first and second part-spherical arrays  10 T and  10 MR. The tweeter drivers  12 T in the first part spherical array  10 T are at circumferential positions offset from the midrange drivers  12 MR in the second part-spherical array  10 MR. Thus, the tweeter drivers  12 T will not impede sound energy emitted from the midrange drivers  12 MR so that all of the sound energy will be directed to the center point  20 B. As in the previous embodiments, the sound energy will merge at the center point  20 B, recombine and exit via the open area  22 B. 
       FIGS. 4 and 5  illustrate various stages of manufacturing a part-spherical speaker array  10 B in accordance with one possible manufacturing approach. More particularly, a frame  30  substantially in the form of a part geodesic dome is formed from appropriate rigid materials such as wood or resin, as illustrated in  FIG. 4 . The tweeter drivers  12 T are affixed securely to inwardly facing surfaces of the frame  30 . The midrange drivers are affixed securely to outer surfaces of the frame  30 . The front faces of the tweeter drivers  12 T and the front faces of the midrange drivers  12 MR all face inward toward the center point  20 B. A sealing material and insulation  32  then is mounted to the frame  30  to prevent sound energy from the tweeter drivers  12 T and the midrange drivers  12 MR from emanating through areas between the tweeter drivers  12 T and the midrange drivers  12 MR. 
     The invention has been described with respect to certain specific embodiments. However, it is apparent that various changes can be made without departing from the scope of the invention. For example, the number and types of drivers can be varied. Additionally, the size of the open area from which the sound is emitted can be varied. Still further, the frame can take many different forms.