PATENT DOCUMENT

Publication Number: US-10652650-B2
Application Number: US-201515513955-A
Country: US
Kind Code: B2

Title: Loudspeaker with reduced audio coloration caused by reflections from a surface

Abstract:
Loudspeakers are described that may reduce comb filtering effects perceived by a listener by either 1) moving transducers closer to a sound reflective surface (e.g., a baseplate, a tabletop or a floor) through vertical (height) or rotational adjustments of the transducers or 2) guiding sound produced by the transducers to be released into the listening area proximate to the reflective surface through the use of horns and openings that are at a prescribed distance from the reflective surface. The reduction of this distance between the reflective surface and the point at which sound emitted by the transducers is released into the listening area may lead to shorter reflected path that reduces comb filtering effects caused by reflected sounds that are delayed relative to the direct sound. Accordingly, the loudspeakers shown and described may be placed on reflective surfaces without severe audio coloration caused by reflected sounds.

Claims:
What is claimed is: 
     
       1. A loudspeaker, comprising:
 a cabinet; and 
 a plurality of audio transducers distributed radially about an interior of the cabinet, wherein each audio transducer in the plurality of audio transducers is acoustically coupled within the interior to an acoustic pathway that redirects audio generated by the audio transducer first downward and then radially outward through one or more sound output openings defined by the cabinet and into a listening area proximate the loudspeaker, and wherein each of audio transducer in the plurality of audio transducers is individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source. 
 
     
     
       2. The loudspeaker of  claim 1 , wherein a bottom of the cabinet is frusto conical, having a sidewall that joins an upper base and a lower base wherein the upper base is larger than the lower base, and wherein the audio transducers are mounted within a plurality of openings, respectively, formed in the sidewall in a ring formation. 
     
     
       3. The loudspeaker of  claim 1 , wherein a predefined distance between each of the audio transducers and a tabletop or floor upon which the loudspeaker rests is between 4.0 millimeters and 20.0 millimeters. 
     
     
       4. A loudspeaker, comprising:
 a cabinet; and 
 a plurality of audio transducers distributed radially about an interior of the cabinet, wherein each audio transducer in the plurality of audio transducers is acoustically coupled within the interior to an acoustic pathway that redirects audio generated by the audio transducer first downward and then radially outward through one or more sound output openings defined by the cabinet and into a listening area proximate the loudspeaker, and wherein each of audio transducer in the plurality of audio transducers is individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source, 
 wherein the audio transducers are tilted downward to make a predefined acute angle between a) a plane defined by an outside surface of a bottom end of the cabinet and b) a diaphragm of each of the audio transducers, such that a predefined distance is achieved between a center of the diaphragm and a tabletop or floor on which the bottom end of the cabinet is to rest. 
 
     
     
       5. The loudspeaker of  claim 4 , wherein the predefined acute angle is between 30.0° and 50.0°. 
     
     
       6. The loudspeaker of  claim 1 , wherein the cabinet is cylindrical, and the audio transducers are arranged in a ring around a bottom of the cabinet at a predefined distance, which is coaxial with a circumference of the cabinet. 
     
     
       7. A loudspeaker, comprising:
 a cabinet; and 
 a plurality of audio transducers distributed radially about an interior of the cabinet, wherein each audio transducer in the plurality of audio transducers is acoustically coupled within the interior to an acoustic pathway that redirects audio generated by the audio transducer first downward and then radially outward through one or more sound output openings defined by the cabinet and into a listening area proximate the loudspeaker, and wherein each of audio transducer in the plurality of audio transducers is individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source, 
 wherein a bottom of the cabinet is frusto conical, having a sidewall that joins an upper base and a lower base and wherein the upper base is larger than the lower base, wherein the acoustic pathway comprises:
 a plurality of horns mounted in the cabinet and coupled to guide sound from the audio transducers, respectively, to a plurality of sound output openings, respectively, that are formed in the sidewall of the cabinet. 
 
 
     
     
       8. The loudspeaker of  claim 7 , wherein a center point of each of the plurality of sound output openings is within a predefined distance from a tabletop or floor upon which the loudspeaker rests. 
     
     
       9. The loudspeaker of  claim 8 , wherein each of a set of diaphragms for the audio transducers is arranged in a first direction and the respective opening in the cabinet sidewall is arranged in a second direction different from the first direction to release sound produced by a diaphragm of a transducer into the listening area. 
     
     
       10. The loudspeaker of  claim 9 , wherein each of the plurality of horns is curved in order to bridge a difference between the first direction of the diaphragm of the transducer and the second direction of the respective opening such that sound produced by the transducer is released into the listening area through the respective opening. 
     
     
       11. The loudspeaker of  claim 3 , wherein the audio transducers are replicates, and wherein the loudspeaker is to be operated as an array. 
     
     
       12. The loudspeaker of  claim 3 , wherein the predefined distance is such that a) a transducer designed to emit sound with lower frequencies has a longer predefined distance than a transducer designed to emit sound with higher frequencies or b) a transducer with a larger diaphragm diameter has a longer predefined distance than a transducer with a smaller diaphragm diameter. 
     
     
       13. The loudspeaker of  claim 7 , further comprising:
 a phase plug used by each of the transducers to redirect high frequency sounds to reduce reflections off a tabletop or floor upon which the loudspeaker rests. 
 
     
     
       14. The loudspeaker of  claim 7 , further comprising:
 a resonator positioned along each of the plurality of horns, within at least one horn of the plurality of horns or proximate to the respective opening, to reduce an amount of sound reflections. 
 
     
     
       15. A loudspeaker, comprising:
 a cabinet; 
 a plurality of audio transducers disposed in a radial configuration within the cabinet, each audio transducer comprising a diaphragm, and each audio transducer being individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source; and 
 a baseplate to stabilize the cabinet in an upright position, wherein the baseplate is coupled to a bottom of the cabinet, 
 wherein a forward face of the diaphragm of each of the plurality of audio transducers faces a central region of the cabinet, the radial configuration being such that sound emitted by each transducer of the plurality of audio transducers is released from the cabinet into a listening area at a predefined distance from the baseplate. 
 
     
     
       16. The loudspeaker of  claim 15 , wherein the predefined distance as measured vertically between a center of the diaphragm of each of the transducers and the baseplate is between 4.0 millimeters and 20.0 millimeters. 
     
     
       17. A loudspeaker, comprising:
 a cabinet; 
 a plurality of audio transducers disposed in a radial configuration within the cabinet, each audio transducer comprising a diaphragm, and each audio transducer being individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source; and 
 a baseplate to stabilize the cabinet in an upright position, wherein the baseplate is coupled to a bottom of the cabinet, 
 wherein a forward face of the diaphragm of each of the plurality of audio transducers faces a central region of the cabinet, the radial configuration being such that sound emitted by each transducer of the plurality of audio transducers is released from the cabinet into a listening area at a predefined distance from the baseplate, 
 wherein the radial configuration of the transducers is tilted downward to make a predefined acute angle between, for each transducer, a) a plane in which a perimeter of a diaphragm lies and b) a horizontal plane at a top of the baseplate, such that the predefined distance is achieved between a center of the diaphragm and the horizontal plane at the top of the baseplate. 
 
     
     
       18. The loudspeaker of  claim 17 , wherein the predefined acute angle is between 30.0° and 50.0°. 
     
     
       19. A speaker, comprising:
 a cabinet; and 
 audio transducers radially distributed within an interior of the cabinet, each of the audio transducers comprising a diaphragm having a forward face oriented toward a central region of the cabinet, audio waves generated by the audio transducers being configured to exit the cabinet into a listening area proximate the cabinet, and wherein each of the audio transducers is individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source. 
 
     
     
       20. The speaker of  claim 19 , wherein the audio transducers are angled downward toward a bottom end of the cabinet at a predefined angle between 37.5° and 42.5°. 
     
     
       21. The speaker of  claim 20 , wherein the audio transducers are angled downward toward a bottom end of the cabinet at a predefined angle such that a distance between a center of at least one audio transducer of the audio transducers and a tabletop or floor upon which the speaker is resting is between 8.5 millimeters and 11.5 millimeters. 
     
     
       22. A speaker, comprising:
 a plurality of audio transducers to emit sound into a listening area, wherein each audio transducer in the plurality of audio transducers is individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source; 
 a cabinet to house the plurality of audio transducers, wherein the plurality of audio transducers is coupled to the cabinet and is entirely inside the cabinet, and the cabinet has a bottom end that is configured to rest on a tabletop or floor; 
 an opening in a side of the cabinet; and 
 a horn to redirect sound generated by the plurality of audio transducers first downward and then radially outward to the opening such that sound from the plurality of audio transducers is first released into the listening area through the opening at a predefined distance from the bottom end. 
 
     
     
       23. The speaker of  claim 22  wherein the predefined distance is between 8.0 millimeters and 13.0 millimeters. 
     
     
       24. The speaker of  claim 23 , wherein the bottom end of the cabinet is frusto conical, having a sidewall that joins an upper base and a lower base, and wherein the upper base is larger than the lower base. 
     
     
       25. A loudspeaker, comprising:
 a cabinet; and 
 a plurality of audio transducers distributed radially about an interior of the cabinet, wherein each audio transducer in the plurality of audio transducers is acoustically coupled within the interior to an acoustic pathway that redirects audio generated by the audio transducer first downward and then radially outward through one or more sound output openings defined by the cabinet and into a listening area proximate the loudspeaker, and wherein each of audio transducer in the plurality of audio transducers is individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source, 
 wherein the acoustic pathway is curved from an initial direction toward the interior of the cabinet to a final direction in which sound exits the cabinet in a downward and outward direction from a location along an angled sidewall of the cabinet. 
 
     
     
       26. The loudspeaker of  claim 1  further comprising a low frequency transducer disposed within the cabinet such that the plurality of audio transducers are positioned between the low frequency transducer and a bottom of the cabinet.

Description:
This application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application No. PCT/US2015/053,025, filed Sep. 29, 2015, which claims the benefit of U.S. Provisional Patent Application No. 62/057,992, filed Sep. 30, 2014; this application claims the benefit of the provisional&#39;s filing date under 35 U.S.C. § 119(e) and is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD 
     A loudspeaker is disclosed for reducing the effects caused by reflections off a surface on which the loudspeaker is resting. In one embodiment, the loudspeaker has individual transducers that are situated to be within a specified distance from the reflective surface, e.g., a baseplate which is to rest on a tabletop or floor surface, such that the travel distances of the reflected sounds and direct sounds from the transducers are nearly equivalent. Other embodiments are also described. 
     BACKGROUND 
     Loudspeakers may be used by computers and home electronics for outputting sound into a listening area. A loudspeaker may be composed of multiple electro-acoustic transducers that are arranged in a speaker cabinet. The speaker cabinet may be placed on a hard, reflective surface such as a tabletop. If the transducers are in close proximity to the tabletop surface, reflections from the tabletop may cause an undesirable comb filtering effect to a listener. Since the reflected path is longer than the direct path of sound, the reflected sound may arrive later in time than the direct sound. The reflected sound may cause constructive or destructive interference with the direct sound (at the listener&#39;s ears), based on phase differences between the two sounds (caused by the delay.) 
     The approaches described in this Background section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section. 
     SUMMARY 
     In one embodiment, a loudspeaker is provided with a ring of transducers that are aligned in a plane, within a cabinet. In one embodiment, the loudspeaker may be designed to be an array where the transducers are all replicates so that each is to produce sound in the same frequency range. In other embodiment, the loudspeaker may be a multi-way speaker in which not all of the transducers are designed to work in the same frequency range. The loudspeaker may include a baseplate coupled to a bottom end of the cabinet. The baseplate may be a solid flat structure that is sized to provide stability to the loudspeaker so that the cabinet does not easily topple over while the baseplate is seated on a tabletop or on another surface (e.g., the floor). The ring of transducers may be located at a bottom of the cabinet and within a predefined distance from the baseplate, or within a predefined distance from a a tabletop or floor (in the case where no baseplate is used and the bottom end of the cabinet is to rest on the tabletop or floor.) The transducers may be angled downward toward the bottom end at a predefined acute angle, so as to reduce comb filtering caused by reflections of sound from the transducer off of the tabletop or floor, in comparison to the transducers being upright. 
     Sound emitted by the transducers may be reflected off the baseplate or other reflective surface on which the cabinet is resting, before arriving at the ears of a listener, along with direct sound from the transducers. The predefined distance may be selected to ensure that the reflected sound path and the direct sound path are similar, such that comb-filtering effects perceptible by the listener are reduced. In some embodiments, the predefined distance may be selected based on the size or dimensions of a corresponding transducer or based on the set of audio frequencies to be emitted by the transducer. 
     In one embodiment, this predefined distance may be achieved through the angling of the transducers downward toward the bottom end of the cabinet. This rotation or tilt may be within a range of values such that the predefined distance is achieved without causing undesired resonance. In one embodiment, the transducers have been rotated or tilted to an acute angle, e.g., between 37.5° and 42.5°, relative to the bottom end of the cabinet (or if a baseplate is used, relative to the baseplate.) 
     In another embodiment, the predefined distance may be achieved through the use of horns. The horns may direct sound from the transducers to sound output openings in the cabinet that are located proximate to the bottom end. Accordingly, the predefined distance in this case may be between the center of the opening and the tabletop, floor, or baseplate, since the center of the opening is the point at which sound is allowed to propagate into the listening area. Through the use of horns, the predefined distance may be shortened without the need to move or locate the transducers themselves proximate to the bottom end or to the baseplate. 
     As explained above, the loudspeakers described herein may show improved performance over traditional loudspeakers. In particular, the loudspeakers described here may reduce comb filtering effects perceived by a listener due to either 1) moving transducers closer to a reflective surface on which the loudspeaker may be resting (e.g., the baseplate, or directly on a tabletop or floor) through vertical or rotational adjustments of the transducers or 2) guiding sound produced by the transducers so that the sound is released into the listening area proximate to the reflective surface, through the use of horns and through openings in the cabinet that are at the prescribed distance from the reflective surface. The reduction of this distance, between the reflective surface and the point at which sound emitted by the transducers is released into the listening area, reduces the reflective path of sound and may reduce comb filtering effects caused by reflected sounds that are delayed relative to the direct sound. Accordingly, the loudspeakers shown and described may be placed on reflective surfaces without severe audio coloration caused by reflected sounds. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one. Also, in the interest of conciseness and reducing the total number of figures, a given figure may be used to illustrate the features of more than one embodiment of the invention, and not all elements in the figure may be required for a given embodiment. 
         FIG. 1  shows a view of a listening area with an audio receiver, a loudspeaker, and a listener according to one embodiment. 
         FIG. 2A  shows a component diagram of the audio receiver according to one embodiment. 
         FIG. 2B  shows a component diagram of the loudspeaker according to one embodiment. 
         FIG. 3  shows a set of example directivity/radiation patterns that may be produced by the loudspeaker according to one embodiment. 
         FIG. 4  shows direct sound and reflected sound produced by a loudspeaker relative to a sitting listener according to one embodiment. 
         FIG. 5  shows a logarithmic sound pressure versus frequency graph for sound detected at one meter and at twenty degrees relative to the loudspeaker and the sitting listener according to one embodiment. 
         FIG. 6  shows direct sound and reflected sound produced by a loudspeaker relative to a standing listener according to one embodiment. 
         FIG. 7  shows a logarithmic sound pressure versus frequency graph for sound detected at one meter and at twenty degrees relative to the loudspeaker and the standing listener according to one embodiment. 
         FIG. 8  shows a contour graph illustrating comb filtering effects produced by the loudspeaker according to one embodiment. 
         FIG. 9A  shows a loudspeaker in which an integrated transducer has been moved toward the bottom end of the cabinet according to one embodiment. 
         FIG. 9B  shows the distance between a transducer and a reflective surface according to one embodiment. 
         FIG. 9C  shows a loudspeaker with an absorptive material located proximate to a set of transducers according to one embodiment. 
         FIG. 9D  shows a cutaway view of a loudspeaker with a screen located proximate a set of transducers according to one embodiment. 
         FIG. 9E  shows a close-up view of a loudspeaker with a screen located proximate a set of transducers according to one embodiment. 
         FIG. 10A  shows a contour graph for sound produced by a loudspeaker according to one embodiment. 
         FIG. 10B  shows a logarithmic sound pressure versus frequency graph for sound detected at one meter and at twenty degrees relative to the loudspeaker according to one embodiment. 
         FIG. 11A  shows the distances for three separate types of transducers according to one embodiment. 
         FIG. 11B  shows the distances for N separate types of transducers according to one embodiment. 
         FIG. 12  shows a side view of a loudspeaker according to one embodiment. 
         FIG. 13  shows an overhead cutaway view of a loudspeaker according to one embodiment. 
         FIG. 14A  shows a distance between a transducer directly facing a listener and a reflective surface according to one embodiment. 
         FIG. 14B  shows a distance between a transducer angled downward and a reflective surface according to one embodiment. 
         FIG. 14C  shows a comparison between a reflected sound path produced by a transducer directed at a listener and a transducer angled downward according to one embodiment. 
         FIG. 15A  shows a logarithmic sound pressure versus frequency graph for sound detected at one meter and at twenty degrees relative to the loudspeaker according to one embodiment. 
         FIG. 15B  shows a contour graph for sound produced by a loudspeaker according to one embodiment. 
         FIG. 16A  shows a cutaway side view of a cabinet for a loudspeaker that includes a horn, according to one embodiment in which no baseplate is provided. 
         FIG. 16B  shows a perspective view of a loudspeaker that has multiple horns for multiple transducers, according to one embodiment. 
         FIG. 17  shows a contour graph for sound produced by a loudspeaker according to one embodiment. 
         FIG. 18  shows a cutaway view of a cabinet for a loudspeaker in which the transducers are mounted through a wall of the cabinet according to another embodiment. 
         FIG. 19  shows a contour graph for sound produced by a loudspeaker according to one embodiment. 
         FIG. 20  shows a cutaway view of a cabinet for a loudspeaker in which the transducers are mounted inside the cabinet according to another embodiment. 
         FIG. 21  shows a contour graph for sound produced by a loudspeaker according to one embodiment. 
         FIG. 22  shows a cutaway view of a cabinet for a loudspeaker in which the transducers are located within the cabinet and a long narrow horn is utilized according to another embodiment. 
         FIG. 23  shows a contour graph for sound produced by a loudspeaker according to one embodiment. 
         FIG. 24  shows a cutaway view of a cabinet for a loudspeaker in which phase plugs are used to place the effective sound radiation area of the transducers closer to a reflective surface according to one embodiment. 
         FIG. 25  shows a loudspeaker with a partition according to one embodiment. 
         FIGS. 26A, 26B  illustrate the use of acoustic dividers in a multi-way loudspeaker or a loudspeaker array in accordance with yet another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Several embodiments are described with reference to the appended drawings are now explained. While numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known circuits, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1  shows a view of a listening area  101  with an audio receiver  103 , a loudspeaker  105 , and a listener  107 . The audio receiver  103  may be coupled to the loudspeaker  105  to drive individual transducers  109  in the loudspeaker  105  to emit various sound beam patterns into the listening area  101 . In one embodiment, the loudspeaker  105  may be configured and is to be driven as a loudspeaker array, to generate beam patterns that represent individual channels of a piece of sound program content. For example, the loudspeaker  105  (as an array) may generate beam patterns that represent front left, front right, and front center channels for a piece of sound program content (e.g., a musical composition or an audio track for a movie). The loudspeaker  105  has a cabinet  111 , and the transducers  109  are housed in a bottom  102  of the cabinet  111  and to which a baseplate  113  is coupled as shown. 
       FIG. 2A  shows a component diagram of the audio receiver  103  according to one embodiment. The audio receiver  103  may be any electronic device that is capable of driving one or more transducers  109  in the loudspeaker  105 . For example, the audio receiver  103  may be a desktop computer, a laptop computer, a tablet computer, a home theater receiver, a set-top box, or a smartphone. The audio receiver  103  may include a hardware processor  201  and a memory unit  203 . 
     The processor  201  and the memory unit  203  are generically used here to refer to any suitable combination of programmable data processing components and data storage that conduct the operations needed to implement the various functions and operations of the audio receiver  103 . The processor  201  may be an applications processor typically found in a smart phone, while the memory unit  203  may refer to microelectronic, non-volatile random access memory. An operating system may be stored in the memory unit  203  along with application programs specific to the various functions of the audio receiver  103 , which are to be run or executed by the processor  201  to perform the various functions of the audio receiver  103 . 
     The audio receiver  103  may include one or more audio inputs  205  for receiving multiple audio signals from an external or remote device. For example, the audio receiver  103  may receive audio signals as part of a streaming media service from a remote server. Alternatively, the processor  201  may decode a locally stored music or movie file to obtain the audio signals. The audio signals may represent one or more channels of a piece of sound program content (e.g., a musical composition or an audio track for a movie). For example, a single signal corresponding to a single channel of a piece of multichannel sound program content may be received by an input  205  of the audio receiver  103 , and in that case multiple inputs may be needed to receive the multiple channels for the piece of content. In another example, a single signal may correspond to or have encoded therein or multiplexed therein the multiple channels (of the piece of sound program content). 
     In one embodiment, the audio receiver  103  may include a digital audio input  205 A that receives one or more digital audio signals from an external device or a remote device. For example, the audio input  205 A may be a TOSLINK connector, or it may be a digital wireless interface (e.g., a wireless local area network (WLAN) adapter or a Bluetooth adapter). In one embodiment, the audio receiver  103  may include an analog audio input  205 B that receives one or more analog audio signals from an external device. For example, the audio input  205 B may be a binding post, a Fahnestock clip, or a phono plug that is designed to receive a wire or conduit and a corresponding analog signal. 
     In one embodiment, the audio receiver  103  may include an interface  207  for communicating with the loudspeaker  105 . The interface  207  may utilize wired mediums (e.g., conduit or wire) to communicate with the loudspeaker  105 , as shown in  FIG. 1 . In another embodiment, the interface  207  may communicate with the loudspeaker  105  through a wireless connection. For example, the network interface  207  may utilize one or more wireless protocols and standards for communicating with the loudspeaker  105 , including the IEEE 802.11 suite of standards, IEEE 802.3, cellular Global System for Mobile Communications (GSM) standards, cellular Code Division Multiple Access (CDMA) standards, Long Term Evolution (LTE) standards, and/or Bluetooth standards. 
     As shown in  FIG. 2B , the loudspeaker  105  may receive transducer drive signals from the audio receiver  103  through a corresponding interface  213 . As with the interface  207 , the interface  213  may utilize wired protocols and standards and/or one or more wireless protocols and standards, including the IEEE 802.11 suite of standards, IEEE 802.3, cellular Global System for Mobile Communications (GSM) standards, cellular Code Division Multiple Access (CDMA) standards, Long Term Evolution (LTE) standards, and/or Bluetooth standards. In some embodiments, the drive signals are received in digital form, and so in order drive the transducers  109  the loudspeaker  105  in that case may include digital-to-analog converters (DACs)  209  that are coupled in front of the power amplifiers  211 , for converting the drive signals into analog form before amplifying them to drive each transducer  109 . 
     Although described and shown as being separate from the audio receiver  103 , in some embodiments, one or more components of the audio receiver  103  may be integrated in the loudspeaker  105 . For example, as described below, the loudspeaker  105  may also include, within its cabinet  111 , the hardware processor  201 , the memory unit  203 , and the one or more audio inputs  205 . 
     As shown in  FIG. 1 , the loudspeaker  105  houses multiple transducers  109  in a speaker cabinet  111 , which may be aligned in a ring formation relative to each other, to form a loudspeaker array. In particular, the cabinet  111  as shown is cylindrical; however, in other embodiments the cabinet  111  may be in any shape, including a polyhedron, a frustum, a cone, a pyramid, a triangular prism, a hexagonal prism, a sphere, a frusto conical shape, or any other similar shape. The cabinet  111  may be at least partially hollow, and may also allow the mounting of transducers  109  on its inside surface or on its outside surface. The cabinet  111  may be made of any suitable material, including metals, metal alloys, plastic polymers, or some combination thereof. 
     As shown in  FIG. 1  and  FIG. 2B , the loudspeaker  105  may include a number of transducers  109 . The transducers  109  may be any combination of full-range drivers, mid-range drivers, subwoofers, woofers, and tweeters. Each of the transducers  109  may have a diaphragm or cone that is connected to a rigid basket or frame via a flexible suspension that constrains a coil of wire (e.g., a voice coil) that is attached to the diaphragm to move axially through a generally cylindrical magnetic gap. When an electrical audio signal is applied to the voice coil, a magnetic field is created by the electric current in the voice coil, making it a variable electromagnet. The coil and the transducers&#39;  109  magnetic system interact, generating a mechanical force that causes the coil (and thus, the attached cone) to move back and forth, thereby reproducing sound under the control of the applied electrical audio signal coming from an audio source, such as the audio receiver  103 . Although electromagnetic dynamic loudspeaker drivers are described for use as the transducers  109 , those skilled in the art will recognize that other types of loudspeaker drivers, such as piezoelectric, planar electromagnetic and electrostatic drivers are possible. 
     Each transducer  109  may be individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source (e.g., the audio receiver  103 ). By having knowledge of the alignment of the transducers  109 , and allowing the transducers  109  to be individually and separately driven according to different parameters and settings (including relative delays and relative energy levels), the loudspeaker  105  may be arranged and driven as an array, to produce numerous directivity or beam patterns that accurately represent each channel of a piece of sound program content output by the audio receiver  103 . For example, in one embodiment, the loudspeaker  105  may be arranged and driven as an array, to produce one or more of the directivity patterns shown in  FIG. 3 . Simultaneous directivity patterns produced by the loudspeaker  105  may not only differ in shape, but may also differ in direction. For example, different directivity patterns may be pointed in different directions in the listening area  101 . The transducer drive signals needed to produce the desired directivity patters may be generated by the processor  201  (see  FIG. 2A ) executing a beamforming process. 
     Although a system has been described above in relation to a number of transducers  109  that may be arranged and driven as part of a loudspeaker array, the system may also work with only a single transducer (housed in a cabinet  111 .) Thus, while at times the description below refers to the loudspeaker  105  as being configured and driven as an array, in some embodiments a non-array loudspeaker may be configured or used in a similar fashion described herein. 
     As shown and described above, the loudspeaker  105  may include a single ring of transducers  109  arranged to be driven as an array. In one embodiment, each of the transducers  109  in the ring of transducers  109  may be of the same type or model, e.g. replicates. The ring of transducers  109  may be oriented to emit sound “outward” from the ring, and may be aligned along (or lying in) a horizontal plane such that each of the transducers  109  is vertically equidistant from the tabletop, or from a top plane of a baseplate  113  of the loudspeaker  105 . By including a single ring of transducers  109  aligned along a horizontal plane, vertical control of sound emitted by the loudspeaker  105  may be limited. For example, through adjustment of beamforming parameters and settings for corresponding transducers  109 , sound emitted by the ring of transducers  109  may be controlled in the horizontal direction. This control may allow generation of the directivity patterns shown in  FIG. 3  along a horizontal plane or axis. However, by lacking multiple stacked rings of transducers  109  this directional control of sound may be limited to this horizontal plane. Accordingly, sound waves produced by the loudspeaker  105  in the vertical direction (perpendicular to this horizontal axis or plane) may expand outwards without limit. 
     For example, as shown in  FIG. 4 , sound emitted by the transducers  109  may be spread vertically with minimal limitation. In this scenario, the head or ears of the listener  107  are located approximately one meter and at a twenty degree angle relative to the ring of transducers  109  in the loudspeaker  105 . The spread of sound from the loudspeaker  105  may include sound emitted 1) downward and onto a tabletop on which the loudspeaker  105  has been placed and 2) directly at the listener  107 . The sound emitted towards the tabletop will be reflected off the surface of the tabletop and towards the listener  107 . Accordingly, both reflected and direct sound from the loudspeaker  105  may be sensed by the listener  107 . Since the reflected path is indirect and consequently longer than the direct path in this example, a comb filtering effect may be detected or perceived by the listener  107 . A comb filtering effect may be defined as the creation of peaks and troughs in frequency response that are caused when signals that are identical but have phase differences are summed. An undesirably colored sound can result from the summing of these signals. For example,  FIG. 5  shows a logarithmic sound pressure versus frequency graph for sound detected at one meter and at twenty degrees relative to the loudspeaker  105  (i.e., the position of the listener  107  as shown in  FIG. 4 ). A set of bumps or peaks and notches or troughs illustrative of this comb filtering effect may be observed in the graph shown in  FIG. 5 . The bumps may correspond to frequencies where the reflected sounds are in-phase with the direct sounds while the notches may correspond to frequencies where the reflected sounds are out-of-phase with the direct sounds. 
     These bumps and notches may move with elevation or angle (degree) change, as path length differences between direct and reflected sound changes rapidly based on movement of the listener  107 . For example, the listener  107  may stand up such that the listener  107  is at a thirty degree angle or elevation relative to the loudspeaker  105  as shown in  FIG. 6  instead of a twenty degree elevation as shown in  FIG. 4 . The sound pressure vs. frequency as measured at the thirty degree angle (elevation) is shown in  FIG. 7 . It can be seen that the bumps and notches in the sound pressure versus frequency behavior move with changing elevation, and this is illustrated in the contour graph of  FIG. 8  which shows the comb filtering effect of  FIGS. 5 and 7  as witnessed from different angles. The regions with darker shading represent high SPL (bumps), while the regions with lighter shading represent low SPL (notches). The bumps and notches shift over frequency, as the listener  107  changes angles/location relative to the loudspeaker  105 . Accordingly, as the listener  107  moves in the vertical direction relative to the loudspeaker  105 , the perception of sound for this listener  107  changes. This lack of consistency in sound during movement of the listener  107 , or at different elevations, may be undesirable. 
     As described above, comb filtering effects are triggered by phase differences between reflected and direct sounds caused by the longer distance the reflected sounds must travel en route to the listener  107 . To reduce audio coloration perceptible to the listener  107  based on comb filtering, the distance between reflected sounds and direct sounds may be shortened. For example, the ring of transducers  109  may be oriented such that sound emitted by the transducers  109  travels a shorter or even minimal distance, before reflection on the tabletop or another reflective surface. This reduced distance will result in a shorter delay between direct and reflected sounds, which consequently will lead to more consistent sound at locations/angles the listener  107  is most likely to be situated. Techniques for minimizing the difference between reflected and direct paths from the transducers  109  will be described in greater detail below by way of example. 
       FIG. 9A  shows a loudspeaker  105  in which an integrated transducer  109  has been moved closer to the bottom of the cabinet  111  than its top, in comparison to the transducer  109  in the loudspeaker  105  shown in  FIG. 4 . In one embodiment, the transducer  109  may be located proximate to a baseplate  113  that is fixed to a bottom end of the cabinet  111  of the loudspeaker  105 . The baseplate  113  may be a solid flat structure that is sized to provide stability to the loudspeaker  105  while the loudspeaker  105  is seated on a table or on another surface (e.g., a floor), so that the cabinet  111  can remain upright. In some embodiments, the baseplate  113  may be sized to receive sounds emitted by the transducer  109  such that sounds may be reflected off of the baseplate  113 . For example, as shown in  FIG. 9A , sound directed downward by the transducer  109  may be reflected off of the baseplate  113  instead of off of the tabletop on which the loudspeaker  105  is resting. The baseplate  113  may be described as being coupled to a bottom  102  of the cabinet  111 , e.g., directly to its bottom end, and may extend outward beyond a vertical projection of the outermost point of a sidewall of the cabinet. Although shown as larger in diameter than the cabinet  111 , in some embodiments, the baseplate  113  may be the same diameter of the cabinet  111 . In these embodiments the bottom  102  of the cabinet  111  may curve or cut inwards (e.g., until it reaches the baseplate  113 ) and the transducers  109  may be located in this curved or cutout section of the bottom  102  of the cabinet  111  such as shown in  FIG. 1 . 
     In some embodiments, an absorptive material  901 , such as foam, may be placed around the baseplate  113 , or around the transducers  109 . For example, as shown in  FIG. 9C , a slot  903  may be formed in the cabinet  111 , between the transducer  109  and the baseplate  113 . The absorptive material  901  within the slot  903  may reduce the amount of sound that has been reflected off of the baseplate  113  in a direction opposite the listener  107  (and that would otherwise then be reflected off of the cabinet  111  back towards the listener  107 ). In some embodiments, the slot  903  may encircle the cabinet  111  around the base of the cabinet  111  and may be tuned to provide a resonance in a particular frequency range to further reduce sound reflections. In some embodiments, the slot  903  may form a resonator coated with the absorptive material  901  designed to dampen sounds in a particular frequency range to further eliminate sound reflections off the cabinet  111 . 
     In one embodiment, as seen in  FIGS. 9D, 9E , a screen  905  may be placed below the transducers  109 . In this embodiment, the screen  905  may be a perforated mesh (e.g., a metal, metal alloy, or plastic) that functions as a low-pass filter for sound emitted by the transducers  109 . In particular, and as best seen in  FIG. 9D , the screen  905  may create a cavity  907  (similar to the slot  903  depicted in  FIG. 9C ) underneath the cabinet  111  between the baseplate  113  and the transducers  109 . High-frequency sounds emitted by the transducers  109  and which reflect off the cabinet  111  may be attenuated by the screen  905  and prevented from passing into the listening area  101 . In one embodiment, the porosity of the screen  905  may be adjusted to limit the frequencies that may be free to enter the listening area  101 . 
     In one embodiment, the vertical distance D between a center of the diaphragm of the transducer  109  and a reflective surface (e.g., the top of the baseplate  113 ) may be between 8.0 mm and 13.0 mm as shown in  FIG. 9B . For example, in some embodiments, the distance D may be 8.5 mm, while in other embodiments the distance D may be 11.5 mm (or anywhere in between 8.5 mm-11.5 mm). In other embodiments, the distance D may be between 4.0 mm and 20.0 mm. As shown in  FIGS. 9A and 9B , by being located proximate (i.e., a distance D) from the surface upon which sound is reflected (e.g., the baseplate  113 , or in other cases a tabletop or floor surface itself such as where no baseplate  113  is provided), the loudspeaker  105  may exhibit a reduced length of its reflected sound path. This reduced reflected sound path consequently reduces the difference between the lengths of the reflected sound path and the direct sound path, for sound originating from a transducer  109  integrated within the cabinet  111 , e.g., the difference, reflected sound path distance−direct sound path distance, approaches zero). This minimization or at least reduction in difference between the length of the reflected and direct paths may result in a more consistent sound (e.g., a consistent frequency response or amplitude response) as shown in the graphs of  FIG. 10A  and  FIG. 10B . In particular, the bumps and notches in both  FIG. 10A  and  FIG. 10B  have decreased in magnitude and moved considerably to the right and closer to the bounds of human perception (e.g., certain bumps and notches have moved above 10 kHz). Thus, comb filtering effects as perceived by the listener  107  may be reduced. 
     Although discussed above and shown in  FIGS. 9A-9C  for a single transducer  109 , in some embodiments each transducer  109  in a ring formation of multiple transducers  109  (e.g., an array of transducers) may be similarly arranged, along the side or face of the cabinet  111 . In those embodiments, the ring of transducers  109  may be aligned along or lie within a horizontal plane as described above. 
     In some embodiments, the distance D or the range of values used for the distance D may be selected based on the radius of the corresponding transducer  109  (e.g., the radius of the diaphragm of the transducer  109 ) or the range of frequencies used for the transducer  109 . In particular, high frequency sounds may be more susceptible to comb filtering caused by reflections. Accordingly, a transducer  109  producing higher frequencies may need a smaller distance D, in order to more stringently reduce its reflections (in comparison to a transducer  109  that produces lower frequency sounds.) For example,  FIG. 11A  shows a multi-way loudspeaker  105  with a first transducer  109 A used/designed for a first set of frequencies, a second transducer  109 B used/designed for a second set of frequencies, and a third transducer  109 C used/designed for a third set of frequencies. For instance, the first transducer  109 A may be used/designed for high frequency content (e.g., 5 kHz-10 kHz), the second transducer  109 B may be used/designed for mid frequency content (e.g., 1 kHz-5 kHz), and the third transducer  109 C may be used/designed for low frequency content (e.g., 100 Hz-1 kHz). These frequency ranges for each of the transducers  109 A,  109 B, and  109 C may be enforced using a set of filters integrated within the loudspeaker  105 . Since the wavelengths for sound waves produced by the first transducer  109 A are smaller than wavelengths of sound waves produced by the transducers  109 B and  109 C, the distance D A  associated with the transducer  109 A may be smaller than the distances D B  and D C  associated with the transducers  109 B and  109 C, respectively (e.g., the transducers  109 B and  109 C may be located farther from a reflective surface on which the loudspeaker  105  is resting, without notches associated with comb filtering falling within their bandwidth of operation). Accordingly, the distance D between transducers  109  and a reflective surface needed to reduce comb filtering effects may be based on the size/diameter of the transducers  109  and/or the frequencies intended to be reproduced by the transducers  109 . 
     Despite being shown with a single transducer  109 A,  109 B, and  109 C, the multi-way loudspeaker  105  shown in  FIG. 11A  may include rings of each of the transducers  109 A,  109 B, and  109 C. Each ring of the transducers  109 A,  109 B, and  109 C may be aligned in separate horizontal planes. 
     Further, although shown in  FIG. 11A  as including three different types of transducers  109 A,  109 B, and  109 C (i.e., a 3-way loudspeaker  105 ), in other embodiments the loudspeaker  105  may include any number of different types of transducers  109 . In particular, the loudspeaker  105  may be an N-way array as shown in  FIG. 11B , where N is an integer that is greater than or equal to one. Similar to  FIG. 11A , in this embodiment shown in  FIG. 11B , the distances D A -D N  associated with each ring of transducers  109 A- 109 N may be based on the size/diameter of the transducers  109 A- 109 N and/or the frequencies intended to be reproduced by the transducers  109 A- 109 N. 
     Although achieving a small distance D (i.e., a value within a range described above) between the center of the transducers  109  and a reflective surface may be achievable for transducers  109  with smaller radii by moving the transducers  109  closer to a reflective surface (i.e., arranging transducers  109  along the cabinet  111  to be closer to the baseplate  113 ), as transducers  109  increase in size the ability to achieve values for the distance D within prescribed ranges may be difficult or impossible. For example, it would be impossible to achieve a threshold value for D by simply moving a transducer  109  in the vertical direction along the face of the cabinet  111  closer to the reflective surface when the radius of the transducer  109  is greater than the threshold value for D (e.g., the threshold value is 12.0 mm and the radius of the transducer  109  is 13.0 mm). In these situations, additional degrees of freedom of movement may be employed to achieve the threshold value for D as described below. 
     In some embodiments, the orientation of the transducers  109  in the loudspeaker  105  may be adjusted to further reduce the distance D between the transducer  109  and the reflective surface, reduce the reflected sound path, and consequently reduce the difference between the reflected and direct sound paths. For example,  FIG. 12  shows a side view of a loudspeaker  105  according to one embodiment. Similar to the loudspeaker  105  of  FIG. 9 , the loudspeaker  105  shown in  FIG. 12  includes a ring of transducers  109  situated in or around the bottom of the cabinet  111  and near the baseplate  113 . The ring of transducers  109  may encircle the circumference of the cabinet  111  (or may be coaxial with the circumference), with equal spacing between each adjacent pairs of transducers  109  as shown in the overhead cutaway view in  FIG. 13 . 
     In the example loudspeaker  105  shown in  FIG. 12 , the transducers  109  are located proximate to the baseplate  113 , by being mounted in the bottom  102  of the cabinet  111 . The bottom in this example is frusto conical as shown having a sidewall that joins an upper base and a lower base, and wherein the upper base is larger than the lower base and the base plate  113  is coupled to the lower base as shown. Each of the transducers  109  in this case may be described as being mounted within a respective opening in the sidewall such that its diaphragm is essentially outside the cabinet  111 , or is at least plainly visible along a line of sight, from outside of the cabinet  111 . Note the indicated distance D being the vertical distance from the center of the diaphragm, e.g., the center of its outer surface, down to the top of the baseplate  113 . The sidewall (of the bottom  102 ) has a number of openings formed therein that are arranged in a ring formation and in which the transducers  109  have been mounted, respectively. As was noted above in relation to  FIGS. 9A and 9B , by positioning the transducers  109  close to a surface upon which sound from the transducers  109  is reflected, e.g., by minimizing the distance D while restricting the angle theta. 
     Referring to  FIG. 14 b   , the angle theta may be defined as depicted in that figure, namely as the angle between 1) a plane of the diaphragm of the transducer  109 , such as a plane in which a perimeter of the diaphragm lies, and 2) the tabletop surface, or if a baseplate  113  is used then a horizontal plane that touches the top of the base plate  113 .) The angle theta of each of the transducers  109  may be restricted to a specified range, so that the difference between the path of reflected sounds and the path of direct sounds may be reduced, in comparison to the upright arrangement of the transducer  109  shown in  FIG. 14 a   . A transducer  109  that is not angled downward is shown in  FIG. 14A , where it may be described as being upright or “directly facing” the listener  107 , defining an angle theta of at least ninety degrees, and a distance D 1  between the center of the transducer  109  and a reflective surface below, e.g., a tabletop or the top of the baseplate  113 . As shown in  FIG. 14B , angling the transducer  109  downward at an acute angle theta (θ) results in a distance D 2  between the center of the transducer  109  and a reflective surface, where D 2 &lt;D 1 . Accordingly, by rotating (tilting or pivoting) the transducer  109  “forward” and about its bottommost point, so that its diaphragm is more directed to the reflective surface, the distance D between the center of the transducer  109  and the reflective surface decreases (because the bottommost edge of the diaphragm remains fixed between  FIG. 14A  and  FIG. 14B , e.g., as close as possible to the reflective surface.) As noted above, this reduction in D results in a reduction in the difference between the direct and reflected sounds paths and a consequent reduction in audio coloration caused by comb filtering. The reduction in the reflected sound path may be seen in  FIG. 14C , where the solid line from the non-rotated transducer  109  is longer than the dashed line from the transducer  109  that is tilted by an angle theta, θ. Thus, to further reduce the distance D (e.g., the distance between the center of the transducer  109  and either the baseplate  113  or other reflective surface underneath the cabinet  111 ) and consequently reduce the reflected path, the transducer  109  may be angled downward toward the baseplate  113  as explained above and also as shown in  FIG. 12 . 
     As described above, the distance D is a vertical distance between the diaphragm of each of the transducers  109  and a reflective surface (e.g., the baseplate  113 ). In some embodiments, this distance D may be measured from the center of the diaphragm to the reflective surface. Although shown with both protruding diaphragms and flat diaphragms, in some embodiments inverted diaphragms may be used. In these embodiments, the distance D may be measured from the center of the inverted diaphragm, or from the center as it has been projected onto a plane of the diaphragm along a normal to the plane, where the diaphragm plane may be a plane in which the perimeter of the diaphragm lies. Another plane associated with the transducer may be a plane that is defined by the front face of the transducer  109  (irrespective of the inverted curvature of its diaphragm). 
     Although tilting or rotating the transducers  109  may result in a reduced distance D and a corresponding reduction in the reflected sound path, over rotation of the transducers  109  toward the reflective surface may result in separate unwanted effects. In particular, rotating the transducers  109  past a threshold value may result in a resonance caused by reflecting sounds off the reflective surface or the cabinet  111  and back toward the transducer  109 . Accordingly, a lower bound for rotation may be employed to ensure an unwanted resonance is not experienced. For example, the transducers  109  may be rotated or tilted between 30.0° and 50.0° (e.g., θ as defined above in  FIG. 14B  may be between 30.0° and 50.0°). In one embodiment, the transducers  109  may be rotated between 37.5° and 42.5° (e.g., θ may be between 37.5° and 42.5°). In other embodiments, the transducers  109  may be rotated between 39.0° and 41.0°. The angle theta of rotation of the transducers  109  may be based on a desired or threshold distance D for the transducers  109 . 
       FIG. 15A  shows a logarithmic sound pressure versus frequency graph for sound detected at a position (of the listener  107 ) along a direct path that is one meter away from the loudspeaker  105 , and twenty degrees upward from the horizontal—see  FIG. 4 . In particular, the graph of  FIG. 15A  represents sound emitted by the loudspeaker  105  shown in  FIG. 12  with a degree of rotation theta of the transducers  109  at 45°. In this graph, sound levels are relatively consistent within the audible range (i.e., 20 Hz to 10 kHz). Similarly, the contour graph of  FIG. 15B  for a single transducer  109  shows relative consistency in the vertical direction, for most angles at which the listener  107  would be located. For instance, a linear response is shown in the contour graph of  FIG. 15B  for a vertical position of the listener  107  being 0° (the listener  107  is seated directly in front of the loudspeaker  105 ) and for a vertical position between 45° and 60° (the listener  107  is standing up near the loudspeaker  105 ). In particular, notches in this counter graph have been mostly moved outside the audible range, or they have been moved to vertical angles where the listener  107  is not likely to be located (e.g., the listener  107  would not likely be standing directly above the loudspeaker  105 , at the vertical angle of 90°). 
     As noted above, rotating the transducers  109  achieves a lower distance D between the center of the transducers  109  and a reflective surface (e.g., the baseplate  113 ). In some embodiments, the degree of rotation or the range of rotation may be set based on the set of frequencies and the size or diameter of the transducers  109 . For example, larger transducers  109  may produce sound waves with larger wavelengths. Accordingly, the distance D needed to mitigate comb filtering for these larger transducers  109  may be longer than the distance D needed to mitigate comb filtering for smaller transducers  109 . Since the distance D is longer for these larger transducers  109  in comparison to smaller transducers  109 , the corresponding angle θ at which the transducers are tilted, as needed to achieve this longer distance D, may be larger (less tilting or rotation is needed), in order avoid over-rotation (or over-tilting). Accordingly, the angle of rotation θ for a transducer  109  may be selected based on the diaphragm size or diameter of the transducers  109  and the set of frequencies desired to be output by the transducer  109 . 
     As described above, positioning and angling the transducers  109  along the face of the cabinet  111  of the loudspeaker  105  may reduce a reflective sound path distance, reduce a difference between a reflective sound path and a direct sound path, and consequently reduce comb filtering effects. In some embodiments, horns may be utilized to further reduce comb filtering. In such embodiments, a horn enables the point at which sound escapes from (an opening in) the cabinet  111  of the loudspeaker  105  (and then moves along respective direct and reflective paths toward the listener  107 ) to be adjusted. In particular, the point of release of sound from the cabinet  111  and into the listening area  101  may be configured during manufacture of the loudspeaker  105  to be proximate to a reflective surface (e.g., the baseplate  113 ). Several different horn configurations will be described below. Each of these configurations may allow use of larger transducers  109  (e.g., larger diameter diaphragms), or a greater number or a fewer transducers  109 , while still reducing comb filtering effects and maintaining a small cabinet  111  for the loudspeaker  105 . 
       FIG. 16A  shows a cutaway side view of the cabinet  111  of the loudspeaker  105  having a horn  115  and no baseplate  113 .  FIG. 16B  shows an elevation or perspective view of the loudspeaker  105  of  FIG. 16A  configured as, and to be driven as, an array having multiple transducers  109  arranged in a ring formation. In this example, the transducer  109  is mounted or located further inside or within the cabinet  111  (rather than within an opening in the sidewall of the cabinet  111 ), and a horn  115  is provided to acoustically connect the diaphragm of the transducer  109  to a sound output opening  117  of the cabinet  111 . In contrast to the embodiment of  FIG. 9D  where the transducer  109  is mounted within an opening in the sidewall of the cabinet  111  and is visible from the outside, there is no “line of sight” to the transducer  109  in  FIGS. 16A, 16B  from outside of the cabinet  111 . The horn  115  extends downward from the transducer  109 , to the opening  117 , which is formed in the sloped sidewall of the bottom  102  of the cabinet  111  which lies on a tabletop or floor. In this example, the bottom  102  is frusto conical. The horn  115  directs sound from the transducer  109  to an inside surface of the sidewall of the cabinet  111  where the opening  117  is located, at which point the sound is then released into the listening area through the opening  117 . As shown, although the transducer may still be closer to the bottom end of the cabinet  111  than it top end, the transducer  109  is in a raised position (above the bottom end) in contrast to the embodiment of  FIG. 12 . Nevertheless, sound emitted by the transducer  109  can still be released from the cabinet  111  at a point that is “proximate” or close enough to the reflective surface underneath. That is because the sound is released from an opening  117  which itself is positioned in close proximity to the baseplate  113 . In some embodiments, the opening  117  may be positioned and oriented to achieve the same vertical distance D that was described above in connection with the embodiments of  FIGS. 9B, 12, 14B  (in which the distance D was being measured between the diaphragm and the reflective surface below the cabinet  111 .) For the horn embodiment here, the predefined vertical distance D (from the center of the opening  117  vertically down to the tabletop or floor on which the cabinet  111  is resting) may be for example between 8.0 millimeters and 13.0 millimeters. In the case of the horn embodiment here, the distance D may be achieved in part by inclining the opening  117  (analogous to the rotation or tilt angle theta of  FIG. 14B ), for example, appropriately defining the angle or slope of the sidewall of the frusto-conical bottom  102  (of the cabinet  111 ) in which the opening  117  is formed. 
     The horn  115  and the opening  117  may be formed in various sizes to accommodate sound produced by the transducers  109 . In one embodiment, multiple transducers  109  in the loudspeaker  105  may be similarly configured with corresponding horns  115  and openings  117  in the cabinet  111 , together configured, and to be driven as, an array. The sound from each transducer  109  is released from the cabinet  111  at a prescribed distance D from the reflective surface below the cabinet  111  (e.g., a tabletop or a floor on which the cabinet  111  is resting, or a baseplate  113 ). This distance D may be measured from the center of the opening  117  (vertically downward) to the reflective surface. Since sound is thus being emitted proximate to the baseplate  113 , reflected sound may travel along a path similar to that of direct sound as described above. In particular, since sound only travels a short distance from the opening  117  before being reflected, the difference in the reflected and direct sound paths may be small, which results in a reduction in comb filtering effects perceptible to the listener  107 . For example, the contour graph of  FIG. 17  corresponding to the loudspeaker  105  shown in  FIGS. 16A and 16B  shows a smooth and consistent level difference across frequencies and vertical angles (which are angles that define the possible vertical positions of the listener  107 ), in comparison to the comb filtering effect shown in  FIG. 8 . 
       FIG. 18  shows a cutaway view of the cabinet  111  of the loudspeaker  105 , according to another horn embodiment. In this example, the transducers  109  are mounted to or through the sidewall of the cabinet  111 , but are pointed inward (rather than outward as in the embodiment of  FIG. 9D , for example. In other words, the forward faces of their diaphragms are facing into the cabinet  111 . Corresponding horns  115  are acoustically coupled to the front faces of diaphragms of the transducers  109 , respectively, and extend downward along respective curves to corresponding openings  117 . In this embodiment, although the transducers  109  are facing a first direction, the curvature of the horns  115 A allow sound to be emitted from the openings  117 , which are aimed to emit sound into the listening area  101  in a second direction (different than the first direction). The openings  117  of the cabinet  111  in this embodiment may be positioned and oriented the same as described above in connection with the horn embodiments of  FIGS. 16A, 16B . Additionally, a phase plug  119  may be added into the acoustic path between the transducer  109  and its respective opening  117 , as shown, so as to redirect high frequency sounds to avoid reflections and cancellations. The contour graph of  FIG. 19  corresponding to the loudspeaker  105  of  FIG. 18  shows a smooth and consistent level difference across frequencies and vertical listening positions (vertical direction angles), in comparison to the undesirable comb filtering effects shown in  FIG. 8 . 
       FIG. 20  shows a cutaway view of the cabinet  111  of the loudspeaker  105 , according to yet another embodiment. In this example, the transducers  109  are also mounted within the cabinet  111  but they are pointed downwards (rather than sideways as in the embodiment of  FIG. 18  in which the transducers  109  may be mounted to the sidewall of the cabinet  111 ). This arrangement may enable the use of horns  115  that are shorter than those in the embodiment of  FIG. 18 . As shown in the contour graph of  FIG. 21 , the shorter horns  115  may contribute to a smoother response by this embodiment, in comparison to the other embodiments that also use horns  115  (described above.) In one embodiment, the length of the horns  115  may be between 20.0 mm and 45.0 mm. The openings  117  of the cabinet  111  in this embodiment may also be formed in the sloped sidewall of the frusto-conical bottom  102  of the cabinet  111 , and may be positioned and oriented the same as described above in connection with the horn embodiments of  FIGS. 16A,16B  to achieve a smaller distance D relative to the reflective surface, e.g., the top surface of the baseplate  113 . 
       FIG. 22  shows a cutaway view of the cabinet  111  in the loudspeaker  105 , according to yet another embodiment. In this example, each of the transducers  109  is mounted within the cabinet  111 , e.g., similar to  FIG. 20 , but the horn  115  (which directs sound emitted from its respective transducer  109  to its respective opening  117 ) is longer and narrower than in  FIG. 20 . In some embodiments, a combination of one or more Helmholtz resonators  121  may be used for each respective transducer  109  (e.g., an 800 Hz resonator, a 3 kHz resonator, or both) along with phase plugs  119 . The resonators  121  may be aligned along the horn  115  or just outside the opening  117 , for absorbing sound and reducing reflections. As shown in the contour graph of  FIG. 23 , the longer, narrower horns  115  of this embodiment, together with 800 Hz and 3 kHz Helmholtz resonators  121  may result in a smooth frequency response (at various angles in the vertical direction). 
       FIG. 24  shows a cutaway or cross section view taken of a combination transducer  109  and its phase plug  119 , in the cabinet  111  of the loudspeaker  105 , according to another embodiment. In this embodiment, the phase plug  119  is placed adjacent to its respective transducer  109 , and each such combination transducer  109  and phase plug  119  may be located entirely within (inward of the sidewall of) the cabinet  111  as shown. In one embodiment, a shielding device  2401  that is coupled to the outside surface of the cabinet  111  or also to the baseplate  113  may hold the phase plug  119  in position against its transducer  109 . The shielding device  2401  may extend around the perimeter or circumference of the cabinet  111 , forming a ring that serves to hold all of the phase plugs  119  of all of the transducers  109  (e.g., in the case of a loudspeaker array). The phase plug  119  may be formed as several fins  2403  that extend from a center hub  2405 . The fins  2403  may guide sound (through the spaces between adjacent ones of the fins  2403 ) from the diaphragm of the corresponding transducer  109  to an aperture  2407  formed in the shielding device  2401 . Accordingly, the phase plug  119  may be shaped to surround the transducer  109 , including a diaphragm of the transducer  109  as shown, such that sound may be channeled from the transducers  109  to the aperture  2407 . By also guiding the sound from the transducers  109  to the openings  117 , respectively, the phase plugs  119  of this embodiment are also able to place the effective sound radiation area of the transducers  109  closer to the reflective surface (e.g., the baseplate  113 , or a tabletop on which the loudspeaker  105  is resting). As noted above, by positioning the sound radiation area or sound-radiating surface of the transducers  109  closer to a reflective surface, the loudspeaker  105  in this embodiment may reduce the difference between reflective and direct sound paths, which in turn may reduce comb filtering effects. 
     Turning now to  FIG. 25 , in this embodiment, the loudspeaker  105  has a partition  2501 . The partition  2501  may made of a rigid material (e.g., a metal, metal alloy, or plastic) and extends from the outside surface of the cabinet  111  over the bottom  102  of the cabinet  111 , to partially block the transducers  109 —see  FIG. 12  which shows an example of the bottom  102  of the cabinet  111  and the transducers  109  therein, which would be blocked by the partition  2501  of  FIG. 25 . The partition  2501  in this example is a simple cylinder (extending straight downward) but it could alternatively have a different curved shape, e.g., wavy like a skirt or curtain, to encircle the cabinet  111  and partially block each of the transducers  109 . In one embodiment, the partition  2501  may include a number of holes  2503  formed in its curved sidewall as shown which may be sized to allow the passage of various desired frequencies of sound. For example, one group or subset of the holes  2503  which are located farthest from the baseplate  113  may be sized to allow the passage of low-frequency sounds (e.g., 100 Hz-1 kHz) while another group or subset of holes  2503  that lies below the low-frequency holes may be sized to allow the passage of mid-frequency sounds (e.g., 1 kHz-5 kHz). In this embodiment, high-frequency sounds may pass between a gap  2505  created between the bottom end of the partition  2501  and the baseplate  113 . Accordingly, high-frequency content is pushed closer to the baseplate  113  by restricting this content to the gap  2505 . This movement of high-frequency content closer to the baseplate  113  (i.e., the point of reflection) reduces the reflected sound path and consequently reduces the perceptibility of comb filtering for high-frequency content, which as noted above is particularly susceptible to this form of audio coloration. 
     Turning now to  FIGS. 26A, 26B , these illustrate the use of acoustic dividers  2601  in a multi-way version, or in an array version, of the loudspeaker  105 , in accordance with yet another embodiment of the invention. The divider  2601  may be a flat piece that forms a wall joining the bottom  102  of the cabinet  111  to the baseplate  113 , as best seen in the side view of  FIG. 26B . The divider  2601  begins at the transducer  109  and extends outward lengthwise, e.g., until a horizontal length given by the radius r, which extends from a center of the cabinet (through which a vertical longitudinal axis of the cabinet  111  runs—see  FIG. 26 b   . The divider  2601  need not reach the vertical boundary defined by the outermost sidewall of the cabinet  111 , as shown. A pair of adjacent dividers  2601  on either side of a transducer  109  may, together with the surface of the bottom  102  of the cabinet  111  and the top surface of the baseplate, act like a horn for the transducer  109 . 
     As explained above, the loudspeakers  105  described herein when configured and driven as an array provide improved performance over traditional arrays. In particular, the loudspeakers  105  provided here reduce comb filtering effects perceived by the listener  107  by either 1) moving transducers  109  closer to a reflective surface (e.g., the baseplate  113 , or a tabletop) through vertical or rotational adjustments of the transducers  109  or 2) guiding sound produced by the transducers  109  to be released into the listening area  101  proximate to a reflective surface through the use of horns  115  and openings  117  that are the prescribed distance from the reflective surface. The reduction of this distance between the reflective surface and the point at which sound emitted by the transducers  109  is released into the listening area  101  consequently reduces the reflective path of sound and reduces comb filtering effects caused by reflected sounds that are delayed relative to the direct sound. Accordingly, the loudspeakers  105  shown and described may be placed on reflective surfaces without severe audio coloration caused by reflected sounds. 
     As also described above, use of an array of transducers  109  arranged in a ring may assist in providing horizontal control of sound produced by the loudspeaker  105 . In particular, sound produced by the loudspeaker  105  may assist in forming well-defined sound beams in a horizontal plane. This horizontal control, combined with the improved vertical control (as evidenced by the contour graphs shown in the figures) provided by the positioning of the transducers  109  in close proximity to the sound reflective surface underneath the cabinet  111 , allows the loudspeaker  105  to offer multi-axis control of sound. However, although described above in relation to a number of transducers  109 , in some embodiments a single transducer  109  may be used in the cabinet  111 . In these embodiments, it is understood that the loudspeaker  105  would be a one-way or multi-way loudspeaker, instead of an array. The loudspeaker  105  that has a single transducer  109  may still provide vertical control of sound through careful placement and orientation of the transducer  109  as described above. 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. The description is thus to be regarded as illustrative instead of limiting.

Metadata:
Filing Date: 20150929
Publication Date: 20200512
Grant Date: 20200512
Priority Date: 20140930
Inventors: JOHNSON, MARTIN E.
PORTER, SIMON K.
HARDY, SUZANNE
Sheerin, John H.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R1/288", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/403", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/2803", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2803", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/403", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2201/401", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/403", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2803", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R3/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2811", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R3/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/288", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2811", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2201/401", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2803", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/403", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/403", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 54291705