EP3292701B1

EP3292701B1 - Omni-directional speaker system and related devices and methods

Info

Publication number: EP3292701B1
Application number: EP16750576.7A
Authority: EP
Inventors: Donna Marie Sullivan; Wontak Kim
Original assignee: Bose Corp
Current assignee: Bose Corp
Priority date: 2016-07-28
Filing date: 2016-07-29
Publication date: 2019-05-22
Anticipated expiration: 2036-07-29
Also published as: EP3292701A1; WO2018022086A1; JP6530496B2; CN107980224B; JP2018530171A; CN107980224A

Description

BACKGROUND

Conventional acoustic deflectors in speaker systems can exhibit artifacts in the acoustic spectrum due to acoustic modes present between an acoustic driver and an acoustic deflector. This disclosure relates to an acoustic deflector for equalizing the resonant response for an omni-directional speaker system.
US 6 064 744 , US 2009/245561 , US 2012/201403 , DE 10 2011 016326 and US 6 026 928 disclose prior art speaker systems.

SUMMARY

The present invention relates to an omni-directional speaker system as recited in claim 1. Advantageous embodiments are recited in dependent claims.
In one example, an omni-directional speaker system includes a deflector sub-assembly and a pair of acoustic sub-assemblies. The deflector sub-assembly includes a pair of diametrically opposed acoustic deflectors. Each of the acoustic sub-assemblies includes an acoustic driver for radiating acoustic energy toward an associated one of the acoustic deflectors. The acoustic sub-assemblies are coupled together via the deflector sub-assembly.
In some implementations, each of the acoustic sub-assemblies includes an acoustic enclosure, and the deflector sub-assembly is coupled to the acoustic sub-assemblies so as to enable formation of respective acoustic seals at respective junctions between associated ones of the acoustic drivers and the acoustic enclosures.
In certain implementations, the pair of acoustic sub-assemblies includes a first acoustic sub-assembly. The first acoustic sub-assembly includes a first acoustic driver and a first acoustic enclosure. The first acoustic driver is coupled to the first acoustic enclosure via a first pair of fasteners partially forming a first acoustic seal at a junction between the first acoustic driver and the first acoustic enclosure. The deflector sub-assembly is coupled to the first acoustic sub-assembly via a second pair of fasteners so as to complete the first acoustic seal.
In some examples, each fastener of the second pair of fasteners passes through respective holes in the deflector sub-assembly and the first acoustic driver, and threadingly engages the first acoustic enclosure.
In certain examples, the pair of acoustic sub-assemblies also includes a second acoustic sub-assembly. The second acoustic sub-assembly includes a second acoustic driver and a second acoustic enclosure. The second acoustic driver is coupled to the second acoustic enclosure via a third pair of fasteners partially forming a second acoustic seal at a junction between the second acoustic driver and the second acoustic enclosure. The deflector sub-assembly is coupled to the second acoustic sub-assembly via a fourth pair of fasteners so as to complete the second acoustic seal.
In some cases, each fastener of the fourth pair of fasteners passes through respective holes in the second acoustic enclosure and the second acoustic driver, and threadingly engages the deflector sub-assembly.
In certain cases, the deflector sub-assembly includes a plurality of vertical legs, and the deflector sub-assembly is coupled to the acoustic sub-assemblies via the vertical legs.
In some implementations, the deflector sub-assembly is coupled to a first one of the acoustic sub-assemblies via a first diametrically opposed pair of the vertical legs, and the deflector sub-assembly is coupled to a second one of the acoustic sub-assemblies via a second diametrically opposed pair of the vertical legs.
In certain implementations, the pair of diametrically opposed acoustic deflectors together define a common (shared) acoustic chamber.
In some examples, the deflector sub-assembly includes an acoustically absorbing member disposed within the acoustic chamber.
In certain examples, the acoustically absorbing member is held in a compressed state by the pair of diametrically opposed acoustic deflectors.
In some cases, the compression of the acoustically absorbing member changes an acoustic property of the acoustically absorbing member.
Another aspect provides an acoustic deflector sub-assembly that includes a pair of diametrically opposed omni-directional acoustic deflectors, and a first pair of vertical legs for mounting to a first acoustic sub-assembly such that a first one of the acoustic deflectors is arranged to deflect acoustic energy radiated from the first acoustic sub-assembly. The acoustic deflector sub-assembly also includes a second pair of vertical legs for mounting to a second acoustic sub-assembly such that a second one of the acoustic deflectors is arranged to deflect acoustic energy radiated from the second acoustic sub-assembly.
Each of the omni-directional acoustic deflectors includes an acoustically reflective body that has a truncated conical shape including a substantially conical outer surface, a top surface, and a cone axis. Each acoustically reflective body has an opening in the top surface centered on the cone axis. An acoustically absorbing material may be disposed at the openings in the top surfaces of the acoustically reflective bodies.
In certain implementations, the respective cone axes of the omni-directional acoustic deflectors are coaxial.
According to yet another aspect, an acoustic deflector sub-assembly includes a pair of diametrically opposed omni-directional acoustic deflectors. Each of the omni-directional acoustic deflectors includes an acoustically reflective body have a truncated conical shape including a substantially conical outer surface, a top surface and a cone axis. Each acoustically reflective body having an opening in the top surface centered on the cone axis. The acoustically reflective bodies together define a shared acoustic chamber that is acoustically coupled to the openings in the top surfaces of the acoustically reflective bodies.
In some implementations, the acoustically reflective bodies include recesses disposed about their respective substantially conical outer surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an acoustic assembly for an omni-directional speaker system.
FIG. 1B is a cross-sectional side view of the acoustic assembly of FIG. 1A.
FIGS. 2A through 2F are perspective assembly views illustrating a step-wise assembly of an omni-directional sound system including the acoustic assembly of FIG. 1A.
FIG. 3 is a cross-sectional side view of an omni-directional speaker system.
FIG. 4 is a perspective view of the omni-directional speaker system of FIG. 3.

DETAILED DESCRIPTION

Multiple benefits are known for omni-directional speaker systems. These benefits include a more spacious sound image when the speaker system is placed near a boundary, such as a wall within a room, due to reflections. Another benefit is that the speaker system does not have to be oriented in a particular direction to achieve optimum high frequency coverage. This second advantage is highly desirable for mobile speaker systems where the speaker system and/or the listener may be moving.
FIGS. 1A and 1B are perspective and cross-sectional views, respectively, of an acoustic assembly 100 for an omni-directional speaker system. The acoustic assembly includes a pair of diametrically opposing acoustic sub-assemblies 102a, 102b (collectively referenced as 102), which are coupled together via a common deflector sub-assembly 104. Each of the acoustic sub-assemblies 102 includes an acoustic enclosure 106a, 106b (collectively referenced as 106) and an acoustic driver 108a, 108b (collectively referenced as 108).
Each acoustic enclosure 106 includes a base 110a, 110b (collectively referenced as 110) and a plurality of sidewalls 112a, 112b, (collectively referenced as 112) which extend from the base to an opposing, open end. The associated acoustic driver 108 is secured to the open end such that a rear radiating surface of the driver radiates acoustic energy into the acoustic enclosure 106, and such that acoustic energy radiated from an opposing, front radiating surface of the acoustic driver 108 propagates toward the deflector sub-assembly 104.
The deflector sub-assembly 104 includes a pair of diametrically opposing omni-directional acoustic deflectors 114a, 114b (collectively 114). Each of the acoustic deflectors 114 has four vertical legs 116 to which a corresponding one of the acoustic sub-assemblies 102 is mounted. The acoustic sub-assemblies 102 are mounted such that the motion axes of their respective acoustic drivers 108 are coaxial.
Acoustic energy generated by the acoustic drivers 108 propagates toward the deflector sub-assembly 104 and is deflected into a substantially horizontal direction (i.e., a direction substantially normal to the motion axes of the acoustic drivers 108), by respective substantially conical outer surfaces of the acoustic deflectors 114. There are eight substantially rectangular openings 120. Each opening 120 is defined by one of the acoustic sub-assemblies, a base 122 of the deflector sub-assembly 104, and a pair of the vertical legs 116. These eight openings 120 are acoustic apertures which pass the horizontally propagating acoustic energy. It should be understood that the propagation of the acoustic energy in a given direction includes a spreading of the propagating acoustic energy, for example, due to diffraction.
As shown in FIG. 1B, each of the acoustic deflectors 114 has a substantially truncated conical shape. In other examples, the respective slopes of the conical outer surfaces, between the base and the vertex of the cone, are not constant. For example, one or both of the outer surfaces of the acoustic deflectors 114 may have a non-linear slant profile such as a parabolic profile or a profile described by a truncated hyperboloid of revolution. The bodies of the acoustic deflectors 114 can be made of any suitably acoustically reflective material. For example, the bodies may be formed from plastic, stone, metal, or other rigid materials.
In the illustrated example, each of the omni-directional acoustic deflectors 114 includes two features which may contribute to an improvement of the acoustic spectrum. First, there are acoustically absorbing regions disposed along the acoustically reflecting surface. As shown in FIG. 1B, each of these regions is arranged at an opening 124a, 124b (collectively 124), centered on the cone axis at the top of the truncated cone of the corresponding one of the acoustic deflectors 114, in which acoustically absorbing material 126 is disposed. This acoustically absorbing material 126 attenuates the energy present near or at the peak of the lowest order circularly symmetric resonance mode. In some implementations, the respective diameters of the openings 124 are chosen so that the resulting attenuation of the acoustic energy by the acoustic drivers 108 is limited to an acceptable level while achieving a desired level of smoothing of the acoustic spectrum.
In the illustrated implantation, the acoustically absorbing material 126 is foam (e.g., melamine foam). Notably, the bodies of the acoustic deflectors 114 together form a common body cavity 128 (a/k/a acoustic chamber), which, in the illustrated example, is filled with a single volume of foam such that the foam is adjacent to, or extends into, the openings. Alternatively, a separate foam element may be disposed at each opening so that only a portion of the body cavity 128 is occupied by foam. In one implementation, the foam present at each of the central openings 124 is at one end of a cylindrically-shaped foam element disposed within the body cavity 128. In some cases, the foam element is oversized and is compressed between the bodies of the acoustic deflectors 114 to achieve the desired acoustic properties (e.g., the desired acoustic absorptivity).
The body cavity 128, together with the openings 124, serves as a Helmholtz resonator (i.e., a shared, or dual, Helmholtz resonator) for attenuating a certain acoustic mode. By combining the volume between the two acoustic deflectors, there is more volume to work with in terms of trapping of the energy making the Helmholz resonator work. So sharing a common acoustic chamber effectively increases the volume that is available to each one of the deflectors individually, thereby increasing the amount of volume to kill the acoustic mode.
The second feature of the acoustic deflectors 114 that contribute to an improvement in the acoustic spectrum is the presence of recesses 130a, 130b (a/k/a collectively 130), shown as ring shaped troughs, located along the circumferences of the substantially conical outer surfaces. In one example, the recesses 130 are each arranged at a circumference at a peak of the second harmonic of the resonance mode. In another example, one or both of the recesses 130 may be arranged at a radius that is approximately one-half of the base radius of the cone.
Alternatively or additionally, the recesses 130 may correspond with/to features of the acoustic driver. That is the recesses may be included to accommodate movement of features of the acoustic driver (e.g., movement of a diaphragm of the acoustic driver) relative to the omni-directional acoustic deflectors.
FIGS. 2A through 2F illustrate a step-wise assembly of an omni-directional speaker system that includes the acoustic assembly 100. Beginning with FIG. 2A, the bodies of the acoustic deflectors 114 are brought together, e.g., in a welding operation, to define the body cavity 128 (FIG. 1B) therebetween. In some examples, a hot plate welding procedure is employed to form a weld seam 132 (FIG. 1B) that couples the deflector bodies together and acoustically seals the body cavity 128 at the junction between the two deflector bodies. The weld seam 132 may be formed by a rib (e.g., a plastic rib) that is heated during a hot plate welding operation. A cylindrical piece of acoustically absorbing material 126 (e.g., foam) is disposed between the bodies and is compressed during the assembly operation to provide finished deflector sub-assembly 102 with the desired acoustic absorbing property.
FIG. 2B illustrates the assembly of the first acoustic sub-assembly 102a. A first end of electrical wiring 200 is passed through an aperture 202 in the first acoustic enclosure 106a, via a grommet 204, and is connected to terminals (not shown) on the first acoustic driver 108a. The electrical wiring 200 provides electrical signals to the first acoustic driver 108a for driving the first acoustic driver 108a. The grommet 204 helps to assure that the aperture 202 in the first acoustic enclosure 106a is acoustically sealed in the final assembly.
The first acoustic driver 108a is then secured to the first acoustic enclosure 106a via a pair of fasteners 206 that pass through holes in a mounting bracket of the first acoustic driver 108a and threadingly engage the first acoustic enclosure 106a. In that regard, the fasteners 206 may engage pre-formed threaded holes in the first acoustic enclosure 106a, or they may form threaded holes as they engage the first acoustic enclosure 106a. A peripheral gasket 208 is provided at the open end of the first acoustic enclosure 106a to help provide an acoustic seal at the junction between the first acoustic driver 108a and the first acoustic enclosure 106a. Assembly of the second acoustic sub-assembly 102b (FIG. 1A) is substantially identical to that of the first acoustic sub-assembly 102a, and, thus, is not described for the sake of conciseness.
Next, referring to FIG. 2C, the deflector sub-assembly 104 is secured to the first acoustic sub-assembly 102a via a pair of fasteners 210 which pass through holes in a first pair of diametrically opposed ones of the vertical legs 116, then pass through holes in the mounting bracket of the first acoustic driver 108a, and then threadingly engage the first acoustic enclosure 106a. In that regard, the fasteners 210 may engage pre-formed threaded holes in the first acoustic enclosure 106a, or they may form threaded holes as they engage the first acoustic enclosure 106a. This completes the coupling of the deflector sub-assembly 104 to the first acoustic sub-assembly 102a and completes the acoustic seal at the junction between the first acoustic driver 108a and the first acoustic enclosure 106a.
Referring to FIG. 2D, once the deflector sub-assembly 104 is fastened to the first acoustic sub-assembly 102a, the second acoustic sub-assembly 102b is coupled to the deflector sub-assembly 104 via another pair of fasteners 212 (one shown) which pass through holes in the second acoustic enclosure 106b, then pass through holes in a mounting bracket of the second acoustic driver 108b, and then threadingly engage a second pair of diametrically opposed ones of the vertical legs 116. In that regard, the fasteners 212 may engage pre-formed threaded holes in the vertical legs116, or they may form threaded holes as they engage the vertical legs 116. This completes the coupling of the second acoustic sub-assembly 102b to the deflector sub-assembly 104 and completes the acoustic seal at the junction between the second acoustic driver 108b and the second acoustic enclosure 106b. Coupling the acoustic sub-assemblies 102 through the deflector sub-assembly 104 in this manner can help to eliminate the need for visible fasteners in the finished assembly.
With reference to FIG. 2E, the second, free ends of the electrical wiring 200 for the acoustic drivers are attached to a printed wiring board (PWB 214), which also supports an electrical connector 216 for providing external electrical connection (e.g., to a source of audio signals (not shown)). The PWB 214 is arranged adjacent to the base 110b of the second acoustic enclosure 106b. A compliant member 218 (e.g., a piece of foam) is disposed between the base 110b of the second acoustic enclosure 106b and the PWB 214. As described below, the compliant member 218 serves to bias the PWB 214 against an end cap (item 230b, FIG. 2F) in the finished assembly.
Referring to FIGS. 2F and 3, a band of vibration absorbing material 220 is wrapped around each of the acoustic sub-assemblies 102, and then a hollow outer sleeve 222 is slid over the acoustic assembly 100. The sleeve 222 is slid over the acoustic assembly from the second acoustic sub-assembly 102b toward the first acoustic sub-assembly 102a, such that a first recess 224 (FIG. 3) formed at a first open end of the sleeve 222 comes to rest above a lip 226 formed around the base 110a of the first acoustic enclosure 106a. In that regard, the lip 226 is only used as a hard stop for drop - there is a gap for buzz prevention. The sleeve 222 may be formed from a rigid material, such as plastic or metal (e.g., aluminum), and includes regions 228 of perforations which align with the openings 120 in the acoustic assembly 100 to permit the passage of the acoustic energy that is radiated from the acoustic drivers 108 and deflected by the deflector sub-assembly 104. The vibration absorbing material 220 helps to inhibit buzzing (undesirable noise) that may otherwise be caused by relative movement of the acoustic assembly 100 and the sleeve 222 during operation of the omni-directional speaker system 300 (FIG.3).
Finally, first and second end caps 230a, 230b are arranged at first and second open ends of the sleeve 222, respectively, to provide a finished appearance. In that regard, a first end cap 230a is coupled to the base 110a of the first acoustic enclosure 106a (e.g., via adhesive such as a pressure sensitive adhesive), and the second end cap 230b is coupled to the sleeve 222 at the second open end of the sleeve 222 and the second acoustic enclosure 106b (e.g., via adhesive such as hot melt polyethylene).
The second end cap 230b includes apertures 232 to permit terminals 234 of the electrical connector 216 to pass therethrough. As mentioned above, the compliant member 218 biases the PWB 214 against the second end cap 230b to help ensure that the terminals 234 protrude through the apertures 232 a sufficient distance the enable a sufficient electrical connection and with enough pre-load to prevent buzz.
As shown in FIG. 4, the assembled omni-directional speaker system 300 has a smooth outer appearance with an absence of seams along the length of the sleeve and no visible mechanical fasteners.
In general, omni-directional acoustic deflectors according to principles described herein act as an acoustic smoothing filter by providing a modified acoustic resonance volume between the acoustic driver and the acoustic deflector. It will be appreciated that adjusting the size and locations of the acoustically absorbing regions allows for the acoustic spectrum to be tuned to modify the acoustic spectrum. Similarly, the profile of the acoustically reflecting surface may be non-linear (i.e., vary from a perfect conical surface) and defined so as to modify the acoustic spectrum. In addition, non-circularly symmetric extensions in the acoustically reflecting surface, such as the radial extensions described above, can be utilized to achieve an acceptable acoustic spectrum.

Claims

An omni-directional speaker system (100), comprising:
a deflector sub-assembly (104) comprising a pair of opposed omni-directional acoustic deflectors (114a, 114b); and

a pair of acoustic sub-assemblies (102a,102b) each comprising an acoustic driver (108a,108b) arranged to radiate acoustic energy toward an associated one of the acoustic deflectors,

wherein the acoustic sub-assemblies (102a, 102b) are coupled together via the deflector sub-assembly (104);

wherein each of the omni-directional acoustic deflectors (114a, 114b) comprises an acoustically reflective body having a truncated conical shape including a substantially conical outer surface, a top surface and a cone axis, each acoustically reflective body having an opening (124a, 124b) in the top surface centered on the cone axis,

wherein the acoustically reflective bodies together define a shared acoustic chamber that is acoustically coupled to the openings in the top surfaces of the acoustically reflective bodies,

wherein the acoustically reflective bodies include ring shaped recesses (130a, 130b) disposed along circumferences of the conical outer surface,

the recesses being each arranged at a circumference at a peak of a second harmonic of a resonance mode or

one or two of the recesses being each arranged at a radius that is approximately one-half of a base radius of the cone of an associated acoustically reflective body or

the recesses being each arranged to accommodate movement of features of the acoustic drivers relative to the omni-directional acoustic deflectors.
The omni-directional speaker system (100) of claim 1, wherein the recesses (130a, 130b) are arranged to accommodate movement of a diaphragm of the acoustic drivers relative to the omni-directional acoustic deflectors.
The omni-directional speaker system of claim 1, wherein the pair of acoustic sub-assemblies (102a, 102b) comprises a first acoustic sub-assembly (102a) comprising a first acoustic driver (108a) and a first acoustic enclosure (106a), wherein the first acoustic driver (108a) is coupled to the first acoustic enclosure (106a) via a first pair of fasteners (206) partially forming a first acoustic seal at a junction between the first acoustic driver (108a) and the first acoustic enclosure (106a), and wherein the deflector sub-assembly (104) is coupled to the first acoustic sub-assembly (102a) via a second pair of fasteners (210) so as to complete the first acoustic seal.
The omni-directional speaker system of claim 3, wherein each fastener of the second pair of fasteners (210) passes through respective holes in the deflector sub-assembly and the first acoustic driver (108a), and threadingly engages the first acoustic enclosure (106a).
The omni-directional speaker system of claim 4, wherein the pair of acoustic sub-assemblies further comprises a second acoustic sub-assembly (102b) comprising a second acoustic driver (108b) and a second acoustic enclosure (106b) wherein the second acoustic driver (108b) is coupled to the second acoustic enclosure (106b) via a third pair of fasteners partially forming a second acoustic seal at a junction between the second acoustic driver and the second acoustic enclosure, and wherein the deflector sub-assembly (104) is coupled to the second acoustic sub-assembly (102b) via a fourth pair of fasteners (212) so as to complete the second acoustic seal.
The omni-directional speaker system of claim 5, wherein each fastener of the fourth pair of fasteners (212) passes through respective holes in the second acoustic enclosure (106b) and the second acoustic driver (108b), and threadingly engages the deflector sub-assembly (104).
The omni-directional speaker system of claim 1, wherein the deflector sub-assembly (104) comprises a plurality of vertical legs (116), and wherein the deflector sub-assembly is coupled to the acoustic sub-assemblies via the vertical legs.
The omni-directional speaker system of claim 7, wherein the deflector sub-assembly (104) is coupled to a first one of the acoustic sub-assemblies via a first opposed pair of the vertical legs (116), and wherein the deflector sub-assembly (104) is coupled to a second one of the acoustic sub-assemblies via a second opposed pair of the vertical legs (116).
The omni-directional speaker system of claim 1, wherein the deflector sub-assembly (104) comprises an acoustically absorbing member (126) disposed within the shared acoustic chamber.
The omni-directional speaker system of claim 9, wherein the acoustically absorbing member (126) is held in a compressed state by the pair of opposed omni-directional acoustic deflectors (114a, 114b).
The omni-directional speaker system of claim 10, wherein the compression of the acoustically absorbing member is configured to change an acoustic property of the acoustically absorbing member.