Patent ID: 12207048

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

In one or more embodiments, an omnidirectional loudspeaker is disclosed which utilizes a compression driver for efficiently and effectively generating sound in a generally horizontal 360° radiation pattern. As compared with direct-radiating dome speakers, use of compression driver in the omnidirectional loudspeaker disclosed herein results in a ten-fold increase in efficiency and sensitivity, as well as an increase in maximum sound pressure level.

With reference first toFIG.1, an exploded perspective view of a compression driver100is illustrated which includes a magnet assembly102, an annular flexural diaphragm104, and a phasing plug106disposed coaxially along a central axis108. In one or more embodiments, the magnet assembly102may comprise an annular permanent magnet110disposed between an annular top plate112and a back plate114, although the magnet assembly102is not limited to this construction. As is known in the art, the magnet assembly102provides a permanent magnetic field for electrodynamic coupling with a voice coil (not shown), wherein the voice coil is coupled to the diaphragm104and produces movement of the flexible portion of the diaphragm104.

There are two major types of compression drivers, the first utilizing a dome diaphragm and the other using an annular flexural diaphragm104as disclosed herein. One advantage of annular diaphragms is the smaller radial dimensions of the moving part of the diaphragm compared to dome diaphragms having the same diameter of the moving voice coil. In a compression driver, the diaphragm104is loaded by a compression chamber116(FIG.6), which is a thin layer of air separating the diaphragm104from the phasing plug106. The volume of air entrapped in the compression chamber116is characterized by an acoustical compliance which is proportional to the volume of compression chamber116. The small radial dimension of the annular diaphragm104corresponds to the small radial dimensions of the matching compression chamber116, which shifts undesirable air resonances (cross-modes) in the chamber to higher frequencies, sometimes above the audio range. Since the annular diaphragm104has two clamping perimeters, inside and outside of the moving part of the diaphragm104, the annular diaphragm104has a better dynamic stability and it is less prone to the rocking modes compared to a dome diaphragm that has only external clamping. The diaphragm104may include a profiled section such as a V-shaped section118, or may have other suitable configurations.

With continuing reference toFIG.1as well as with reference toFIGS.2-4, the phasing plug106includes a base portion120and a raised portion122extending upwardly from the base portion120and disposed generally symmetrically about the central axis108. The raised portion122may have a generally constant height above the base portion120, and the raised portion122may be integrally formed with the base portion120or may be attached to the base portion122by any suitable means. The base portion120may be generally circular or may have any other suitable geometry.

The base portion120includes a first side124(FIGS.2-3) and an opposing second side126(FIG.4) generally facing the diaphragm104. The base portion120further includes one or more apertures128that extend as passages through the base portion120from the first side124to the second side126through which sound waves created by the diaphragm104may travel. In the embodiments depicted herein, the apertures128may be arranged generally circumferentially about the central axis108, generally forming a circle with respect to a center of the phasing plug106.

In the embodiment shown inFIGS.1-4, the apertures128are configured as a plurality of diagonal slots. The slots are generally positioned end-to-end, such as in a “zig-zag” or sawtooth type pattern. Such a meandering pattern of axially-oriented slots may “smear” the resonance effects produced by a combination of mechanical and acoustical modes (resonances) in the compression chamber116, providing averaging, randomization, and integration of sound pressure in the compression chamber116in such a way that the overall frequency response of the compression driver100becomes smoother. Instead of substantially linear or rectangular slots, the apertures128may include a plurality of curved slots, such as with the slots generally positioned end-to-end in a smoothed “zig-zag” or sinusoidal type pattern. Still further, a plurality of circular or square apertures128could be utilized, for example. It is understood that the apertures128are not limited to the embodiments depicted herein and may include other suitable shapes and configurations. For example, the plurality of slots could be uninterrupted so as to form a continuous sawtooth or sinusoidal arrangement of apertures128. The configuration of apertures128described herein makes it possible to provide reflection-free propagation of sound waves from the compression chamber116to the exit of the compression driver100.

In one or more embodiments, the raised portion122may have a central section130and a plurality of arms132extending outwardly therefrom. The apertures128may be disposed along or form an edge134of the central section130, with an arm132extending between each adjacent pair of apertures128. Said another way, an arm132may be disposed on each side of an aperture128. In a top view, each arm132may be generally triangular in shape. In one or more embodiments, first arms132ahaving a wider width along a circumferential direction of the phasing plug106may alternate with second arms132bhaving a relatively narrower width along a circumferential direction of the phasing plug106. With the triangular shape, the arms132are widest adjacent the edge134of the central section130and taper in width toward a perimeter136of the base portion120. Of course, it is understood that the phasing plug106is not limited to the embodiments depicted herein, and that the base portion120and raised portion122may include other suitable shapes and configurations.

With reference toFIGS.2and3, each aperture128is therefore acoustically connected to a corresponding radially-expanding channel138defined between each pair of adjacent arms132and the base portion120. The radial channels138have expanding width and merge at the perimeter136of the base portion120, and thus of the compression driver100. The channels138may function to ensure even distribution of sound pressure around the entirety of the compression driver100for achieving omnidirectional radiation of sound. In addition to the embodiments depicted herein, it is also contemplated that the phasing plug106could include a lesser or greater number of channels138, or alternatively could be configured without radially-expanding air channels.

As best shown inFIGS.1and4, the phasing plug106may include a mounting member140on the second side126that depends downwardly from the base portion120. The mounting member140may have any configuration suitable for coupling the phasing plug106to the magnet assembly102or to the rear section of the compression driver100. In one embodiment, the mounting member140may be provided in the form of a cylinder. The magnet assembly102, the diaphragm104, and the phasing plug106may be connected together by fasteners through mounting apertures142.

FIG.5is an exploded view of an omnidirectional loudspeaker200according to one more embodiments including the compression driver100and an exponential horn which includes a first or lower horn member202and a second or upper horn member204. The lower horn member202may be generally bowl-shaped with a generally convex, upwardly-facing outer wall206and a generally concave, downwardly-facing inner wall208defining a lower cavity210. Correspondingly, the upper horn member204may be generally bowl-shaped with a generally convex, downwardly-facing outer wall212and a generally concave, upwardly-facing inner wall214defining an upper cavity216. Both the upper and lower horn members202,204may be rotationally symmetric about the central axis108.

At least one of the lower and upper horn members202,204includes a recess218which may be generally cylindrical and sized to at least partially receive the compression driver100. The recess218may be defined by a generally planar floor member220and an upstanding wall structure222connected to and at least partially surrounding the floor member220, where the recess218includes an opening224adjacent the outer wall206,212of the corresponding horn member202,204. The compression driver100may be disposed or mounted within the recess218, such as by one or more fasteners engaging the floor member220, for generating sound energy and directing it in an axial direction.

FIG.6is a cross-sectional view of the assembled omnidirectional loudspeaker200including the compression driver100and the lower and upper horn members202,204. In this instance where the compression driver100is received in the lower horn member202, the upper horn member204is mounted on and secured to the compression driver100by fasteners, such as mounting screws, through assembly holes or apertures226. Of course, if the compression driver100is received in the upper horn member204, then the lower horn member202may be secured to the compression driver100. When assembled, the compression driver100is generally centrally-located within the omnidirectional loudspeaker200, and the lower and upper horn members202,204are spaced apart, such as by the raised portion122of the phasing plug106. The sound waves generated by the diaphragm104propagate through the apertures128into an annular waveguide that expands in the radial direction, the waveguide formed by the radially-expanding air channels138of the raised portion122of the phasing plug106and the outer walls206,212of the lower and upper horn members202,204.

With continuing reference toFIG.6, the compression chamber116is located in the space between the diaphragm104and the second side126of the phasing plug base portion120. In practice, the height of the compression chamber116may be quite small (e.g., approximately 0.5 mm or less) such that the volume of the compression chamber116is also small. The actuation of the diaphragm104generates high sound-pressure acoustical signals within the compression chamber116, and the signals travel as sound waves through the base portion120of the phasing plug106via the apertures128that provide passages from the second side126to the first side124. With the apertures128, the area of the entrance to the phasing plug106is significantly smaller than the area of the diaphragm104. The air paths of the phasing plug106are essentially the beginning of the horn which functions to control directivity (i.e., coverage of sound pressure over a particular listening area) and to increase reproduced sound pressure level over a certain frequency range. The overall acoustical cross-sectional area of the air paths, including the apertures128and outwardly radiating channels138, in the phasing plug106and then of the horn members202,204gradually increase to provide a smooth transition of sound waves. From the apertures128, the sound waves radiate outward along the radially-expanding channels138, through the passageway228between the compression driver100and the horn members202,204, and propagate omnidirectionally into the ambient environment.

The lower horn member202limits the propagation of sound energy in a first axial direction (i.e., downwardly), and the upper horn member204limits the propagation of sound energy in a second axial direction (i.e., upwardly). The lower and upper horn members202,204thus provide acoustical loading for the compression driver100and control of the directivity in the vertical plane. In combination, the lower and upper horn members202,204define a passageway228therebetween to direct the flow of sound energy radially, where the acts like a radial horn providing omnidirectional coverage, extending 360° about the central axis108to direct the flow of sound energy generated by the compression driver100to radiate 360° outwardly horizontally in all directions.

Of course, it is understood that directional identifiers such as upper and lower and upwardly and downwardly used herein are not intended to be limiting, and are simply used to provide an exemplary environment for the components of the omnidirectional loudspeaker200as disclosed herein.

FIG.7is a cross-sectional view of an embodiment of the omnidirectional loudspeaker200which includes dual compression drivers100. As shown, a first compression driver100ais disposed within the lower horn member202and a second compression driver100bis disposed within the upper horn member204in an opposed axial orientation, where the first and second compression drivers100a,100bare secured to each other. As such, the first compression driver100agenerates sound in a first axial direction and the second compression driver100bgenerates sound in a second or opposite axial direction. This configuration further increases the sound pressure output and maximum sound pressure level of the omnidirectional loudspeaker200, where the compression drivers100a,100bare vertically arranged in a very compact space in opposing recesses218.

FIG.8is a cross-sectional view of an embodiment of the omnidirectional loudspeaker200with compression drivers100a,100bof different sizes and frequency ranges. In the example shown, a high frequency driver100ais disposed within the lower horn member202and a midrange driver100bis disposed within the upper horn member204, although the omnidirectional loudspeaker200is not limited to this type and placement of drivers100a,100b. Again, the compression drivers100a,100bare vertically arranged in a very compact space in opposing recesses218and their output is blended, where the drivers100a,100bcan be secured directly to one another or both joined to an intermediate plate230. In this configuration, two compression drivers100a,100bhaving different-sized voice coils and diaphragms can be coupled such that a summation of the signals is provided at the exits of the phasing plugs106, and the outputs of both drivers100a,100bpass through the passageway228formed between the horn members202,204and are then uniformly radiated in the horizontal plane for uniform sound distribution in a 360° pattern. As such, the omnidirectional loudspeaker200functions as a two-way system, and therefore its frequency range is expanded.

Each omnidirectional loudspeaker200is suitable as a stand-alone acoustical unit but, if a system of higher sound pressure level output is desired, a plurality of omnidirectional loudspeakers200may be assembled or vertically stacked in modular fashion, one above the other, to form an omnidirectional speaker array300as illustrated inFIG.9. The lower and upper horn members202,204each have a generally circular circumferential edge232,234surrounding the cavity210,216, such that adjacent horn members202,204may be connected, such as via fasteners or adhesive, at their respective circumferential edges232,234to form the speaker array300. The modularity of the omnidirectional loudspeaker200disclosed herein advantageously allows for the construction of loudspeaker systems having a wide range of potential intensities by assembling an appropriate number of loudspeaker units200, each having the same size, engagement and mounting surfaces, and fastening structures.

The ends of the speaker array300can be left open as illustrated inFIG.9, or the lower and upper cavities210,216of the end lower and upper horn members202,204, respectively, may each be enclosed with a cover236as shown inFIG.10. In one or more embodiments, the cover236may be generally bowl-shaped and may correspond to the size and shape of the horn members202,204. In other embodiments, the cover236may be generally spherical or conical, for example, or have other configures which would all provide slightly different acoustical behavior from the standpoint of diffraction.

FIG.10depicts an omnidirectional loudspeaker200with covers236enclosing the lower and upper horn members202,204. As shown, a support stand238, which may include support legs, can be mounted or integrally formed with the lower cover236for supporting the omnidirectional loudspeaker200or speaker array300on a surface.FIG.11is a perspective view of a loudspeaker assembly400which includes an omnidirectional loudspeaker200(such as the configuration shown inFIG.10) mounted on an enclosure402including a woofer404, for example.

FIG.12is a graph of directivity response of the omnidirectional loudspeaker200and incorporated compression driver100in the vertical plane, the compression driver100including a 1.5″ diameter voice coil and polymer flexural annular diaphragm104. The axisymmetric horn created by the lower and upper horn members202,204provides acoustical loading equivalent to that of an exponential horn.

Applications for the compression driver100, omnidirectional loudspeaker200and speaker array300described herein include, but are not limited to, landscape sound systems, Hi-Fi systems, home lifestyle loudspeaker systems, public address systems, alarm and warning sound systems, portable audio Bluetooth-based loudspeakers, high-powered pendant speakers, negative directivity ceiling speakers, or other applications where omnidirectionality is desired or required. Compared with direct-radiating dome speakers, use of the compression driver100in the omnidirectional loudspeaker200disclosed herein results in a ten-fold increase in efficiency and sensitivity, as well as an increase in maximum sound pressure level. The compression driver100and omnidirectional loudspeaker200provide uniform sound radiation at all frequencies over a full 360° coverage area, are easily scalable for different sizes of voice coils and diaphragms, and provide a modular system for the construction of customized speaker arrays.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.