Patent Publication Number: US-10785560-B2

Title: Waveguide for a height channel in a speaker

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application No. 62/333,673, filed on May 9, 2016, hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     One or more embodiments relate generally to loudspeakers, and in particular, to a waveguide for a height channel in a speaker. 
     BACKGROUND 
     A loudspeaker reproduces audio when connected to a receiver (e.g., a stereo receiver, a surround receiver, etc.), a television (TV) set, a radio, a music player, an electronic sound producing device (e.g., a smartphone), video players, etc. A loudspeaker may comprise one or more height channels that forward most of the acoustic energy reproduced towards the ceiling. 
     SUMMARY 
     One embodiment provides a speaker device comprising a first housing including a first top surface comprising a first opening, a first recessed mounting surface spaced below the first opening, and a first recessed sidewall extending upwardly from the first recessed mounting surface to the first opening to form a first waveguide. The speaker device further comprises a first upward-facing driver mounted into the first recessed mounting surface. The first waveguide shapes propagation of acoustic energy generated by the first upward-facing driver to project the acoustic energy out of the speaker device in an upwardly inclined direction. 
     Another embodiment provides a method for producing a waveguide for a speaker device. The method comprises determining at least one waveguide property suitable for enhancing an amount of acoustic energy projected by an upward-facing driver of the speaker device in an upwardly inclined direction, and fabricating a housing of the speaker device based on the at least one waveguide property. The housing includes the waveguide defined by an opening included in a top surface of the housing, a recessed mounting surface of the housing spaced below the opening, and a recessed sidewall extending upwardly from the recessed mounting surface to the opening. The upward-facing driver is mounted into the recessed mounting surface. The waveguide shapes propagation of the acoustic energy to project the acoustic energy out of the speaker device in the upwardly inclined direction. 
     One embodiment provides a method for enhancing an amount of acoustic energy projected by an upward-facing driver of the speaker device in an upwardly inclined direction. The method comprises generating, utilizing the upward-facing driver, the acoustic energy, and shaping propagation of the acoustic energy utilizing a waveguide of the speaker device to project the acoustic energy out of the speaker device in the upwardly inclined direction. The waveguide is defined by an opening included in a top surface of a housing of the speaker device, a recessed mounting surface of the housing spaced below the opening, and a recessed sidewall extending upwardly from the recessed mounting surface to the opening. The upward-facing driver is mounted into the recessed mounting surface. 
     These and other features, aspects and advantages of the one or more embodiments will become understood with reference to the following description, appended claims and accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a cross-section of a side view of an example height channel speaker in a speaker device, in accordance with one embodiment, in accordance with one embodiment; 
         FIG. 1B  illustrates a top view of the height channel speaker in  FIG. 1A , in accordance with one embodiment; 
         FIG. 2A  illustrates a top, front perspective view of an example soundbar, in accordance with one embodiment; 
         FIG. 2B  illustrates a front view of the soundbar in  FIG. 2A , in accordance with one embodiment; 
         FIG. 2C  illustrates a top view of the soundbar in  FIG. 2A , in accordance with one embodiment; 
         FIG. 3A  illustrates different measures of sound quality of audio reproduced by the soundbar in  FIG. 2A , in accordance with one embodiment; 
         FIG. 3B  is an example graph illustrating sound power levels of audio reproduced by the soundbar in  FIG. 2A  over a frequency domain, in accordance with one embodiment; 
         FIG. 4A  illustrates a top, front perspective view of an example speaker device, in accordance with one embodiment; 
         FIG. 4B  illustrates a front view of the speaker device in  FIG. 4A , in accordance with one embodiment; 
         FIG. 4C  illustrates a top view of the speaker device in  FIG. 4A , in accordance with one embodiment; 
         FIG. 5A  illustrates a top, front perspective view of an example speaker device comprising a height channel speaker having a straight waveguide with a circular exit, in accordance with one embodiment; 
         FIG. 5B  is an example graph illustrating sound power levels of audio reproduced by the speaker device in  FIG. 5A  over a frequency domain, in accordance with one embodiment; 
         FIG. 6A  illustrates a top, front perspective view of an example speaker device comprising a height channel speaker having a straight waveguide with an elliptical exit, in accordance with one embodiment; 
         FIG. 6B  is an example graph illustrating sound power levels of audio reproduced by the speaker device in  FIG. 6A  over a frequency domain, in accordance with one embodiment; 
         FIG. 7A  illustrates a cross-section of an example horn-shaped waveguide that forms a tangency angle of about 2 degrees with a top plate, in accordance with one embodiment; 
         FIG. 7B  illustrates a cross-section of an example horn-shaped waveguide that forms a tangency angle of about 5 degrees with a top plate, in accordance with one embodiment; 
         FIG. 7C  illustrates a cross-section of an example horn-shaped waveguide that forms a tangency angle of about 15 degrees with a top plate, in accordance with one embodiment; 
         FIG. 7D  illustrates a cross-section of an example horn-shaped waveguide that forms a tangency angle of about 30 degrees with a top plate, in accordance with one embodiment; 
         FIG. 7E  illustrates a cross-section of an example horn-shaped waveguide that forms a tangency angle of about 45 degrees with a top plate, in accordance with one embodiment; 
         FIG. 7F  illustrates a cross-section of an example horn-shaped waveguide that forms a tangency angle of about 90 degrees with a top plate, in accordance with one embodiment; 
         FIG. 8A  is an example graph illustrating sound power levels projected by the waveguide in  FIG. 7A  over a frequency domain, in accordance with one embodiment; 
         FIG. 8B  is an example graph illustrating sound power levels projected by the waveguide in  FIG. 7B  over a frequency domain, in accordance with one embodiment; 
         FIG. 8C  is an example graph illustrating sound power levels projected by the waveguide in  FIG. 7C  over a frequency domain, in accordance with one embodiment; 
         FIG. 8D  is an example graph illustrating sound power levels projected by the waveguide in  FIG. 7D  over a frequency domain, in accordance with one embodiment; 
         FIG. 8E  is an example graph illustrating sound power levels projected by the waveguide in  FIG. 7E  over a frequency domain, in accordance with one embodiment; 
         FIG. 8F  is an example graph illustrating sound power levels projected by the waveguide in  FIG. 7F  over a frequency domain, in accordance with one embodiment; 
         FIG. 9A  illustrates a top, front perspective view of an example speaker device comprising a height channel speaker having a horn-shaped waveguide that smoothly transitions to a circular exit, in accordance with one embodiment; 
         FIG. 9B  illustrates a cross-section of a side view of the speaker device in  FIG. 9A , in accordance with one embodiment; 
         FIG. 9C  is an example graph illustrating sound power levels of audio reproduced by the speaker device in  FIG. 9A  over a frequency domain, in accordance with one embodiment; 
         FIG. 10A  illustrates a top, front perspective view of an example speaker device comprising a height channel speaker having a horn-shaped waveguide that smoothly transitions to a quadrilateral exit, in accordance with one embodiment; 
         FIG. 10B  illustrates a cross-section of a side view of the speaker device in  FIG. 10A , in accordance with one embodiment; 
         FIG. 10C  is an example graph illustrating sound power levels of audio reproduced by the speaker device in  FIG. 10A  over a frequency domain, in accordance with one embodiment; 
         FIG. 11A  illustrates a top, front perspective view of an example speaker device comprising a height channel speaker having a horn-shaped waveguide that smoothly transitions to an elliptical exit, in accordance with one embodiment; 
         FIG. 11B  illustrates a cross-section of a side view of the speaker device in  FIG. 11A , in accordance with one embodiment; 
         FIG. 11C  is an example graph illustrating sound power levels of audio reproduced by the speaker device in  FIG. 11A  over a frequency domain, in accordance with one embodiment; 
         FIG. 12A  illustrates a top, front perspective view of an example speaker device comprising a height channel speaker having a horn-shaped waveguide that smoothly transitions to a circular exit, in accordance with one embodiment; 
         FIG. 12B  illustrates a cross-section of a side view of the speaker device in  FIG. 12A , in accordance with one embodiment; 
         FIG. 12C  is an example graph illustrating sound power levels of audio reproduced by the speaker device in  FIG. 12A  over a frequency domain, in accordance with one embodiment; 
         FIG. 13A  illustrates a top, front perspective view of an example speaker device comprising a height channel speaker having a deeply set driver and a horn-shaped waveguide that smoothly transitions to a circular exit, in accordance with one embodiment; 
         FIG. 13B  illustrates a cross-section of a side view of the speaker device in  FIG. 13A , in accordance with one embodiment; 
         FIG. 13C  is an example graph illustrating sound power levels of audio reproduced by the speaker device in  FIG. 13A  over a frequency domain, in accordance with one embodiment; 
         FIG. 14A  illustrates a top, front perspective view of an example speaker device comprising a height channel speaker having a cup-shaped waveguide that smoothly transitions to a circular exit, in accordance with one embodiment; 
         FIG. 14B  is an example graph illustrating sound power levels of audio reproduced by the speaker device in  FIG. 14A  over a frequency domain, in accordance with one embodiment; 
         FIG. 15A  illustrates a top, front perspective view of an example speaker device comprising a height channel speaker having a cone-shaped waveguide that smoothly transitions to a circular exit, in accordance with one embodiment; 
         FIG. 15B  is an example graph illustrating sound power levels of audio reproduced by the speaker device in  FIG. 15A  over a frequency domain, in accordance with one embodiment; 
         FIG. 16  is an example flowchart for producing a waveguide for a speaker device, in accordance with one embodiment; 
         FIG. 17  is an example flowchart for enhancing an amount of acoustic energy projected by an upward-facing driver of a speaker device towards a ceiling, in accordance with one embodiment; 
         FIG. 18A  illustrates a top view of an example height channel speaker in a speaker device, in accordance with one embodiment; and 
         FIG. 18B  illustrates a cross-section of a side view of the height channel speaker in a speaker device, in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is made for the purpose of illustrating the general principles of one or more embodiments and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations. Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. 
     For expository purposes, the term “speaker device” as used herein generally refers to any type of audio speaker device/system. Examples of different types of audio speaker devices/systems include, but are not limited to, a loudspeaker, a soundbar, a subwoofer, or any other type of audio speaker device/system. 
     One or more embodiments relate generally to loudspeakers, and in particular, to a waveguide for a height channel in a speaker. One embodiment provides a speaker device comprising a first housing including a first top surface comprising a first opening, a first recessed mounting surface spaced below the first opening, and a first recessed sidewall extending upwardly from the first recessed mounting surface to the first opening to form a first waveguide. The speaker device further comprises a first upward-facing driver mounted into the first recessed mounting surface. The first waveguide shapes propagation of acoustic energy generated by the first upward-facing driver to project the acoustic energy out of the speaker device in an upwardly inclined direction. 
     Another embodiment provides a method for producing a waveguide for a speaker device. The method comprises determining at least one waveguide property suitable for enhancing an amount of acoustic energy projected by an upward-facing driver of the speaker device in an upwardly inclined direction, and fabricating a housing of the speaker device based on the at least one waveguide property. The housing includes the waveguide defined by an opening included in a top surface of the housing, a recessed mounting surface of the housing spaced below the opening, and a recessed sidewall extending upwardly from the recessed mounting surface to the opening. The upward-facing driver is mounted into the recessed mounting surface. The waveguide shapes propagation of the acoustic energy to project the acoustic energy out of the speaker device in the upwardly inclined direction. 
     One embodiment provides a method for enhancing an amount of acoustic energy projected by an upward-facing driver of the speaker device in an upwardly inclined direction. The method comprises generating, utilizing the upward-facing driver, the acoustic energy, and shaping propagation of the acoustic energy utilizing a waveguide of the speaker device to project the acoustic energy out of the speaker device in the upwardly inclined direction. The waveguide is defined by an opening included in a top surface of a housing of the speaker device, a recessed mounting surface of the housing spaced below the opening, and a recessed sidewall extending upwardly from the recessed mounting surface to the opening. The upward-facing driver is mounted into the recessed mounting surface. 
     Some speaker devices may comprise height channels, such as soundbars, front/surround/rear speakers outfitted with drivers for height channels, etc. Height channels in a speaker device aim sound generated by a sound source (e.g., transducer) of the speaker device at the ceiling (or other surface at a height above a listener or position from which sound is intended to be directed), allowing the sound to be reflected off the ceiling to create an impression of the sound coming from “above” the listener. One embodiment enhances an amount of acoustic energy directed towards the ceiling over an amount of acoustic energy towards a listener (i.e., leaked towards the listener instead of directed towards the ceiling). 
     Specification for Dolby Atmos speaker layouts require a driver of a height channel speaker to be structurally and acoustically occluded from a listener. The driver is acoustically occluded if a majority of acoustic energy coming from the height channel speaker is not directed to the listener via a direct path; instead the majority of the acoustic energy is directed towards the ceiling at an upwardly inclined direction that is substantially 70 degrees off a horizontal plane (i.e., substantially 20 degrees from a vertical plane), such that the majority of the acoustic energy reaches the listener via a reflection off the ceiling. The specification also requires a difference in sound level between sound towards the listener and sound reflected off the ceiling to be within a specified limit. 
     A conventional soundbar may utilize digital signal processing, such as beamforming, to direct sound from the soundbar towards the ceiling. A conventional height channel speaker may have height channels at a 20 degree inclined plane, the height channels having cylindrical wedge-like cutouts or simple square cutouts. Conventional height channel speakers typically produce a Directivity Index (DI) of a Height Listening Window (Height WDW) curve with peaks and dips in a critical frequency range of 1 kHz-8 kHz. Based on listening tests, listeners prefer speakers that have very smooth Directivity Index (DI) curves. A DI curve is characterized as a smooth DI curve if the curve exhibits one or more of the following properties: (1) the curve has less than a predefined number of peaks and/or dips, and/or (2) the curve has peaks and/or dips with slopes or derivatives that are (2a) within a predefined range, (2b) less than a predefined number, or (2c) greater than the predefined number. A speaker that has a smooth DI curve provides enhanced/improved sound quality. 
     One embodiment provides a waveguide that results in a very smooth DI curve. The waveguide satisfies requirements of the specification for Dolby Atmos speaker layouts. The waveguide structurally and acoustically occludes a driver from the listener, and enhances acoustic energy reflected off the ceiling. In one embodiment, the waveguide optimizes acoustic sound reflected off the ceiling. One embodiment provides a waveguide for a soundbar that begins at a 20 degree inclined plane in which a driver is mounted to a top plane of the soundbar to achieve a smooth DI Height WDW curve. The smooth DI Height WDW curve is psycho-acoustically much superior to a DI Height WDW curve with peaks and dips for a conventional speaker device. In one example implementation, the waveguide has a horn-like shape, and the waveguide ends substantially tangentially at the top plane of the soundbar. In one example implementation, the waveguide has an elliptic exit shape at the top plane of the soundbar. Compared to conventional height channel speakers, the waveguide improves sound quality, improves sound perception, improves ratio of acoustic energy reflected from the ceiling to acoustic energy towards to the listener, and does not require digital signal processing. 
       FIG. 1A  illustrates a cross-section of a side view of an example height channel speaker  103  in a speaker device  100 , in accordance with one embodiment. The speaker device  100  comprises a speaker housing  102  including one or more sound sources (e.g., a speaker driver, etc.). Specifically, a top plane (i.e., a top surface)  102 T of the speaker housing  102  comprises a height channel speaker  103 . The height channel speaker  103  comprises an upward-facing speaker driver  106  (e.g., a tweeter, a woofer, etc.) disposed within a recessed area  102 R of the top plane  102 T. In one embodiment, the driver  106  lies flush inside the recessed area  102 R. 
     The driver  106  is positioned/mounted axially in a recessed mounting surface  110  that defines a base of the recessed area  102 R. Let  0  denote an angle of inclination of the driver  106  relative to a vertical axis  10  (i.e., an angle at which the recessed mounting surface  110  is inclined relative to the vertical axis  10 ). In one embodiment, the angle θ is in the range of 0 degrees to 60 degrees. In a preferred embodiment, the angle θ is about 20 degrees. 
     In one embodiment, the driver  106  is positioned in the mounting surface  110  at about a center of the mounting surface  110 . In another embodiment, the driver  106  is positioned in the mounting surface  110  off-center (i.e., the driver  106  is positioned in the mounting surface  110  towards a top/bottom of the mounting surface  110 ). 
     One or more recessed sidewalls  108 S of the recessed area  102 R connecting the mounting surface  110  to the top plane  102 T form a waveguide  108 . In this example, the waveguide  108  is formed by a single recessed sidewall  108 S. The waveguide  108  has an exit  104  defined as a cutout/opening in the top plane  102 T where the recessed sidewalls  108 S join/meet the top plane  102 T. During operation of the speaker device  100 , the waveguide  108  shapes propagation of acoustic energy reproduced by the driver  106  to project the acoustic energy out of the exit  104  in an upwardly inclined direction. 
     As described in detail later herein, a shape of the exit  104  may be circular, quadrilateral (e.g., a trapezoid, a square, a rectangle, etc.), elliptical, polygonal, or any other shape. A shape of the waveguide  108  may be straight or substantially curved (e.g., horn-shaped, cone-shaped, cup-shaped, etc.), depending on a shape of each recessed sidewall  108 S. A waveguide may comprise one or more sidewall segments (e.g., straight, curved, etc.) that together form the waveguide. For example, a substantially curved waveguide may comprise a smooth curved segment, a number of straight segments that together form an approximately curved section, or a combination thereof. 
     In one embodiment, the top plane  102 T is substantially parallel to a horizontal axis  20 . In another embodiment, the top plane  102 T is slanted or curved. A forward slanted top plane  102 T decreases acoustical occlusion as a forward-facing part of the waveguide  108  is shortened. This reduces a ratio of acoustic energy reflected off the ceiling to acoustic energy leaked to a listener, thereby reducing perception of height in sound. 
     In one embodiment, multiple drivers  106  may be positioned inside one waveguide  108  (see  FIGS. 18A-18B ). 
     In one embodiment, the exit  104  may have an asymmetric shape. For example, to steer acoustic energy laterally, a center of the exit  104  need not be located in the same vertical plane as a center of the driver  106 . 
     In one embodiment, a shape of the mounting surface  110  may be circular, elliptical, or any other shape. In one embodiment, the mounting surface  110  may have the same shape as the exit  104  (e.g., both the mounting surface  110  and the exit  104  are elliptical, as shown in  FIG. 6A ). In another embodiment, the mounting surface  110  may have a different shape than the exit  104  (e.g., the mounting surface  110  is circular whereas the exit  104  is elliptical, as shown in  FIG. 11A ; other configurations are possible). 
     In one embodiment, the speaker device  100  may have a preferred sound direction. As shown in  FIG. 3A , the preferred sound direction may be towards a listener  30  ( FIG. 3A ) positioned in front of and within proximity of the speaker device  100 . A front  102 F of the speaker housing  102  is directed towards the preferred sound direction, whereas a back  102 B of the speaker housing  102  is directed towards another direction that is opposite of the preferred sound direction. 
     In one embodiment, the speaker device  100  may comprise one or more additional speaker housings. An additional speaker housing may include a respective top surface comprising a respective opening, a respective recessed mounting surface spaced below the respective opening, and a respective recessed sidewall extending upwardly from the respective recessed mounting surface to the respective opening to form an additional waveguide. An additional upward-facing driver may be mounted into the respective recessed mounting surface of the additional speaker housing. The additional waveguide shapes propagation of acoustic energy generated by the additional upward-facing driver to project the acoustic energy out of the speaker device in an upwardly inclined direction. In one example implementation, respective shapes of the waveguide  108  and each additional waveguide are at least partially distinct (e.g., the same general shape but different sizes, or vice versa). In one example implementation, respective shapes of openings of the waveguide  108  and each additional waveguide are at least partially distinct. 
       FIG. 1B  illustrates a top view of the height channel speaker  103 , in accordance with one embodiment. Let d 0  denote a diameter of the driver  106 , let eA denote a minor radius of the exit  104 , and let eB denote a major radius of the exit  104 . If a shape of the exit  104  is circular, eA=eB. In one embodiment, if a shape of the exit  104  is elliptical, eB&gt;eA. In another embodiment, if a shape of the exit  104  is elliptical, eB&lt;eA. 
     In one embodiment, the diameter d 0  is about 60 mm, the minor radius eA is about 50 mm, and the major radius eB is in the range of 50 mm to 150 mm, depending on a design or application of the speaker device  100 . 
     In one embodiment, one or more parameters/properties of the height channel speaker  103  may be varied/configured to achieve a smooth DI curve. Example parameters/properties of the height channel speaker  103  include, but are not limited to, a shape of the exit  104 , a shape of the waveguide  108 , narrowness of the waveguide  108  at the base, depth of the recessed area  102 R, etc. In one embodiment, a smooth DI curve is attainable without using other means (i.e., varying/configuring parameters/properties of the height channel speaker  103  is enough); examples of other means include, but are not limited to, adding materials to the height channel speaker  103  (e.g., foam material), using digital signal processing techniques, etc. 
     In one embodiment, the height channel speaker  103  may be incorporated into any type of speaker device, such as a soundbar in a home theater setup. 
       FIG. 2A  illustrates a top, front perspective view of an example soundbar  200 , in accordance with one embodiment.  FIG. 2B  illustrates a front view of the soundbar  200  (which is one type of speaker, speaker device, speaker system, etc.), in accordance with one embodiment.  FIG. 2C  illustrates a top view of the soundbar  200 , in accordance with one embodiment. As shown in  FIGS. 2A and 2C , the soundbar  200  comprises a left height channel speaker  201 L and a right height channel speaker  201 R that are spaced apart on a top plane  200 T of the soundbar  200 . The top plane  200 T is substantially parallel to the horizontal axis  20 . 
     Each height channel speaker  201 L,  201 R is an example implementation of the height channel speaker  103  described above. The left height channel speaker  201 L comprises a first upward-facing driver  203 L disposed within a first recessed area  202 L in the top plane  200 T. One or more recessed sidewalls of the first recessed area  202 L form a first waveguide  204 L for shaping propagation of acoustic energy reproduced by the first upward-facing driver  203 L to project the acoustic energy out of the soundbar  200  in an upwardly inclined direction. The right height channel speaker  201 R comprises a second upward-facing driver  203 R disposed within a second recessed area  202 R in the top plane  200 T. One or more recessed sidewalls of the second recessed area  202 R form a second waveguide  204 R for shaping propagation of acoustic energy reproduced by the second upward-facing driver  203 R to project the acoustic energy out of the soundbar  200  in an upwardly inclined direction. 
     As further shown in  FIGS. 2A and 2B , a front side  200 F of the soundbar  200  comprises a first set  205 L of forward-facing speakers for a left channel, a second set  205 C of forward-facing speakers for a center channel, and a third set  205 R of forward-facing speakers for a right channel. In one embodiment, each set  205 L,  205 C, and  205 R comprises at least one tweeter  206 A and at least one mid-base woofer  206 B (e.g., two mid-base woofers and one tweeter). In another embodiment, each set  205 L,  205 C, and  205 R comprises a single driver/transducer (i.e., a full range speaker). 
     In one embodiment, an exit of each waveguide  204 L,  204 R may have an asymmetric shape. For example, to steer acoustic energy laterally, a center of an exit of each waveguide  204 L,  204 R need not be located in the same vertical plane as a center of a driver  203 L,  203 R. A listener could perceive a wider sound image if an exit of the first waveguide  204 L is shifted to the left of its base, and an exit of the second waveguide  204 R is shifted to the right of its base. 
       FIG. 3A  illustrates different measures of sound quality of audio reproduced by the soundbar  200 , in accordance with one embodiment. Assume a geometrical shape such as a sphere  50  surrounding the soundbar  200 , wherein a surface of the sphere  50  is centered on the soundbar  200 , such that all points on the surface of the sphere  50  are an equal distance away from the soundbar  200 . The soundbar  200  is positioned in front of and within proximity of a listener  30 . A majority of acoustic energy reproduced by the upward-facing drivers  203 L,  203 R of the soundbar  200  is directed in an upwardly inclined direction towards a ceiling  60 . 
     In this specification, let the term “listening window” (LSTWDW) generally refer to an area  51  of the sphere  50  that is located symmetrically around the vertical axis  10  and the horizontal axis  20 . The listening window  51  covers physical positions that one or more listeners  30  are most likely to occupy in an environment surrounding the soundbar  200  (e.g., a home environment, etc.). Typically, most listeners  30  will occupy a space inside the listening window  51 . The listening window  51  represents propagation of acoustic energy reproduced by the soundbar  200  towards one or more listeners  30 . For example, a majority of acoustic energy reproduced by the sets  205 L,  205 C,  205 R of forward-facing speakers of the soundbar  200  is directed towards the listener  30 . The listening window  51  spans between −35 degrees to +35 degrees horizontally about the horizontal axis  20 , and −15 degrees to +15 degrees vertically about the vertical axis  10 . 
     In this specification, let the term “height window” generally refer to an area  52  of the sphere  50  that is located symmetrically around the vertical axis  10  and the horizontal axis  20 . The height window  52  represents propagation of acoustic energy reproduced by the soundbar  200  in an upwardly inclined direction towards the ceiling  60 ; the acoustic energy are reflected off the ceiling  60 , causing the listener  30  to perceive the acoustic energy as coming from the ceiling. The height window  52  may be a cone of about 10 degrees around an inclined axis  40  pointing in a direction about 70 degrees vertically above the horizontal axis  20 . 
     In this specification, let the term “total sound power” generally refer to an average energy of sound pressure levels (SPL) measured on the entire sphere  50 . 
     In this specification, let the term “height directivity index” generally refer to a ratio of sound power (in Watt units) averaged over the height window  52  in comparison to an amount of total sound power averaged over the entire sphere  50 . As sound power is often expressed in decibel (dB) units (i.e., sound power levels), the height directivity index also refers to a difference between sound power levels (in dB units) averaged over the height window  52  and an amount of total sound power levels averaged over the entire sphere  50 . The waveguides  204 L,  204 R of the soundbar  200  increases a difference between sound power levels averaged over the height window  52  and sound power levels average over the listening window  51 , thereby causing the listener  30  to perceive sound as coming more from the ceiling  60 . 
     In this specification, one or more of the following curves representing different measures of sound quality may be included in a graph illustrating sound power levels of audio reproduced by a speaker device over a frequency domain: (1) a sound power curve representing an amount of total sound power levels reproduced by the speaker device, (2) a listening window curve representing sound power levels averaged over a listening window for the speaker device, (3) a height window curve representing sound power levels averaged over a height window for the speaker device, (4) a height DI curve representing a height DI for the speaker device, (5) a difference curve representing a difference between sound power levels averaged over the height window and sound power levels averaged over the listening window, and (6) a specification (“spec”) curve representing a pre-specified limit for a difference between sound power levels averaged over a height window for a speaker device and sound power levels averaged over a listening window for the speaker device. 
     In one embodiment, a pre-specified limit represented by a spec curve is specified in spec for Dolby Atmos speaker layouts. A speaker device receives Dolby certification if a difference between sound power levels averaged over a height window for the speaker device and sound power levels averaged over a listening window for the speaker device is always greater than the pre-specified limit. 
       FIG. 3B  is an example graph  400  illustrating sound power levels of audio reproduced by the soundbar  200  over a frequency domain, in accordance with one embodiment. The graph  400  comprises a sound power curve  401  (“SNDPWR”), a second listening window curve  402  (“LSTWDW”), a height window curve  403  (“HEIGHT WDW”), (4) a height DI curve  404  (“DI HEIGHT WDW”), a difference curve  405  (“HEIGHT WDW−LSTWDW”), and a spec curve  406  (“Dolby Spec”). A horizontal axis  400 A represents frequency values of the frequency domain expressed in Hertz (Hz) units. A left vertical axis  400 C represents sound power levels of the curves  401 - 403  expressed in dB units. A right vertical axis  400 B represents sound power levels of the curves  404 - 406  expressed in dB units. 
     A smooth height DI curve over a frequency domain correlates with improved perception of sound by a listener  30 . Any local dips or local peaks in a height DI curve correlates with a degradation in sound quality. If a listener  30  receives a majority of acoustic energy reproduced by a speaker device directly through a listening window rather than reflected off a ceiling through a height window, the listener  30  will not perceive sound as coming from above (e.g., from the ceiling). The listener  30  is more likely to perceive sound as coming from above (e.g., from the ceiling) if a difference between sound power levels averaged over the height window and sound power levels averaged over the listening window is increased. 
     In one embodiment, the speaker device  100  is implemented as a front, center, surround, or rear speaker in a home theater setup. 
       FIG. 4A  illustrates a top, front perspective view of an example speaker device  300 , in accordance with one embodiment.  FIG. 4B  illustrates a front view of the speaker device  300 , in accordance with one embodiment.  FIG. 4C  illustrates a top view of the speaker device  300 , in accordance with one embodiment. The speaker device  300  may be utilized as a front, center, surround, or a rear speaker in a home theater setup. As shown in  FIGS. 4A and 4C , a top plane  300 T of the speaker device  300  comprises a height channel speaker  301 . The top plane  300 T is substantially parallel to the horizontal axis  20 . The height channel speaker  301  is an example implementation of the height channel speaker  103  described above. The height channel speaker  301  comprises an upward-facing driver  302  disposed within a recessed area  300 R in the top plane  300 T. One or more recessed sidewalls of the recessed area  300 R form a waveguide  303  for shaping propagation of acoustic energy reproduced by the driver  302  to project the acoustic energy out of the speaker device  300  in an upwardly inclined direction. In one embodiment, the waveguide  303  is formed by combining multiple recessed sidewalls. In another embodiment, the waveguide  303  is formed by a single recessed sidewall. 
     As further shown in  FIGS. 4A and 4B , a front side  300 F of the speaker device  300  comprises one or more forward-facing speakers  305  (e.g., at least one mid-base woofer and/or at least one tweeter). 
       FIG. 5A  illustrates a top, front perspective view of an example speaker device  500  comprising a height channel speaker  503  having a straight waveguide  508  with a circular exit  504 , in accordance with one embodiment. The speaker device  500  comprises a speaker housing  502  including one or more sound sources. Specifically, a top plane (i.e., a top surface)  502 T of the speaker housing  502  comprises a height channel speaker  503 . The top plane  502 T is substantially parallel to the horizontal axis  20 . The height channel speaker  503  comprises an upward-facing speaker driver  506  disposed within a recessed area  502 R of the top plane  502 T. In one embodiment, the driver  506  lies flush inside the recessed area  502 R. 
     The driver  506  is positioned/mounted axially in a recessed mounting surface  510  that defines a base of the recessed area  502 R. 
     One or more recessed sidewalls of the recessed area  502 R comprises one or more straight walls connecting the mounting surface  510  to the top plane  502 T form a straight waveguide  508 . The straight waveguide  508  has circular exit  504  defined as a circular cutout/opening in the top plane  502 T where the recessed sidewalls join/meet the top plane  502 T. As the recessed sidewalls are straight, the recessed sidewalls form an edge at the circular exit  504 . During operation of the speaker device  500 , the waveguide  508  shapes propagation of acoustic energy reproduced by the driver  506  to project the acoustic energy out of the circular exit  504  in an upwardly inclined direction. 
       FIG. 5B  is an example graph  550  illustrating sound power levels of audio reproduced by the speaker device  500  over a frequency domain, in accordance with one embodiment. The graph  550  comprises a sound power curve  551 , a listening window curve  552 , a height window curve  553 , a height DI curve  554 , a difference curve  555 , and a spec curve  556 . A horizontal axis  550 A represents frequency values of the frequency domain expressed in Hz units. A left vertical axis  550 C represents sound power levels of the curves  551 - 553  expressed in dB units. A right vertical axis  550 B represents sound power levels of the curves  554 - 556  expressed in dB units. 
     As shown in  FIG. 5B , the height DI curve  554  exhibits a substantially large dip at about 6 kHz frequency, which may be undesirable in certain circumstances. 
       FIG. 6A  illustrates a top, front perspective view of an example speaker device  600  comprising a height channel speaker  603  having a straight waveguide  608  with an elliptical exit  604 , in accordance with one embodiment. The speaker device  600  comprises a speaker housing  602  including one or more sound sources. Specifically, a top plane (i.e., a top surface)  602 T of the speaker housing  602  comprises a height channel speaker  603 . The top plane  602 T is substantially parallel to the horizontal axis  20 . The height channel speaker  603  comprises an upward-facing speaker driver  606  disposed within a recessed area  602 R of the top plane  602 T. In one embodiment, the driver  606  lies flush inside the recessed area  602 R. 
     The driver  606  is positioned/mounted axially in a recessed mounting surface  510  that defines a base of the recessed area  602 R. 
     One or more recessed sidewalls of the recessed area  602 R comprises one or more straight walls connecting the mounting surface  610  to the top plane  602 T form a straight waveguide  608 . The straight waveguide  608  has an elliptical exit  604  defined as an elliptical cutout/opening in the top plane  602 T where the recessed sidewalls join/meet the top plane  602 T. As the recessed sidewalls are straight, the recessed sidewalls form an edge at the elliptical exit  604 . During operation of the speaker device  600 , the waveguide  608  shapes propagation of acoustic energy reproduced by the driver  606  to project the acoustic energy out of the elliptical exit  604  in an upwardly inclined direction. 
       FIG. 6B  is an example graph  650  illustrating sound power levels of audio reproduced by the speaker device  600  over a frequency domain, in accordance with one embodiment. The graph  650  comprises a sound power curve  651 , a listening window curve  652 , a height window curve  653 , a height DI curve  654 , a difference curve  655 , and a spec curve  656 . A horizontal axis  650 A represents frequency values of the frequency domain expressed in Hz units. A left vertical axis  650 C represents sound power levels of the curves  651 - 653  expressed in dB units. A right vertical axis  650 B represents sound power levels of the curves  654 - 656  expressed in dB units. 
     Compared to the speaker device  600 , the height DI curve  654  exhibits relatively smaller dips, indicating that the speaker device  600  provides improved/enhanced sound quality. 
     In one embodiment, a waveguide of a speaker device may be horn-shaped, wherein a top portion (i.e., an ending portion) of the waveguide transitions to a top plate of the speaker device at an angle about an exit of the waveguide. Let a denote a tangency angle that a top portion of a waveguide of a speaker device forms with a top plate of the speaker device, such that the top portion of the waveguide ends substantially tangential to the top plate. In one embodiment, the waveguide ends substantially tangential to the top plate if the tangency angle α is less than about 45 degrees. In another embodiment, the waveguide ends substantially tangential to the top plate if the tangency angle α is less than about 30 degrees. In yet another embodiment, the waveguide ends substantially tangential to the top plate if the tangency angle α is less than about 15 degrees. 
       FIGS. 7A-7F  illustrate different horn-shaped waveguides, in accordance with one or more embodiments. Specifically,  FIG. 7A  illustrates a cross-section of an example horn-shaped waveguide  108 A that forms a tangency angle of about 2 degrees with a top plate  102 T, in accordance with one embodiment.  FIG. 7B  illustrates a cross-section of an example horn-shaped waveguide  108 B that forms a tangency angle of about 5 degrees with a top plate  102 T, in accordance with one embodiment.  FIG. 7C  illustrates a cross-section of an example horn-shaped waveguide  108 C that forms a tangency angle of about 15 degrees with a top plate  102 T, in accordance with one embodiment.  FIG. 7D  illustrates a cross-section of an example horn-shaped waveguide  108 D that forms a tangency angle of about 30 degrees with a top plate  102 T, in accordance with one embodiment.  FIG. 7E  illustrates a cross-section of an example horn-shaped waveguide  108 E that forms a tangency angle of about 45 degrees with a top plate  102 T, in accordance with one embodiment.  FIG. 7F  illustrates a cross-section of an example horn-shaped waveguide  108 F that forms a tangency angle of about 90 degrees with a top plate  102 T, in accordance with one embodiment. 
       FIGS. 8A-8F  illustrate different graphs illustrating sound power levels projected by different waveguides with substantially curved shapes over a frequency domain, in accordance with one or more embodiments.  FIG. 8A  is an example graph  400 A illustrating sound power levels projected by the waveguide  108 A over a frequency domain, in accordance with one embodiment.  FIG. 8B  is an example graph  400 B illustrating sound power levels projected by the waveguide  108 B over a frequency domain, in accordance with one embodiment.  FIG. 8C  is an example graph  400 C illustrating sound power levels projected by the waveguide  108 C over a frequency domain, in accordance with one embodiment.  FIG. 8D  is an example graph  400 D illustrating sound power levels projected by the waveguide  108 D over a frequency domain, in accordance with one embodiment.  FIG. 8E  is an example graph  400 E illustrating sound power levels projected by the waveguide  108 E over a frequency domain, in accordance with one embodiment.  FIG. 8F  is an example graph  400 F illustrating sound power levels projected by the waveguide  108 F over a frequency domain, in accordance with one embodiment. Each graph  400 A- 400 F comprises a sound power curve, a listening window curve, a height window curve, a height DI curve, a difference curve, and a spec curve. 
     In one embodiment, a tangency angle α formed between a top portion of a waveguide of a speaker device forms with a top plate of the speaker device is small enough to eliminate any drops in a height DI curve for the speaker device. 
     Small design or aesthetic features (e.g., steps, gaps, ribs, or other features less than 2 mm in size) included in a top portion of a waveguide or a top plate may be neglected when determining a tangency angle α between the waveguide and the top plate as these features do not alter sound quality significantly. Design or aesthetic features larger than 2 mm, however, may result in degradation of sound quality as these features obstruct/prevents the top portion of the waveguide from ending substantially tangential to the top plate. 
     In one embodiment, a shape of a waveguide for a height channel speaker has the following characteristics: (1) a bottom portion (i.e., a base) of the waveguide begins/starts close to an upward-facing driver of the height channel speaker (i.e., a mounting surface that the driver is positioned/mounted axially to is narrow, such that a diameter of the mounting surface is close to a diameter of the driver), and (2) a top portion of the waveguide smoothly transitions to a top plate of the height channel speaker, such that the top portion of the waveguide ends substantially tangential to the top plate. 
       FIG. 9A  illustrates a top, front perspective view of an example speaker device  700  comprising a height channel speaker  703  having a horn-shaped waveguide  708  that smoothly transitions to a circular exit  704 , in accordance with one embodiment.  FIG. 9B  illustrates a cross-section of a side view of the speaker device  700 , in accordance with one embodiment. The speaker device  700  comprises a speaker housing  702  including one or more sound sources. Specifically, a top plane (i.e., a top surface)  702 T of the speaker housing  702  comprises a height channel speaker  703 . The top plane  702 T is substantially parallel to the horizontal axis  20 . The height channel speaker  703  comprises an upward-facing speaker driver  706  disposed within a recessed area  702 R of the top plane  702 T. In one embodiment, the driver  706  lies flush inside the recessed area  702 R. 
     The driver  706  is positioned/mounted axially in a recessed mounting surface  710  that defines a base of the recessed area  702 R. In one embodiment, the driver  706  has a surround suspension element  706 A (i.e., an edge) that the mounting surface  710  is shaped to receive and engage with for maintaining the driver  706  within the recessed area  702 R. For example, the surround suspension element  706 A may comprise a surround roll. 
     One or more recessed sidewalls  708 S of the recessed area  702 R connecting the mounting surface  710  to the top plane  702 T form a horn-shaped waveguide  708 . The waveguide  708  has a circular exit  704  defined as a circular cutout/opening in the top plane  702 T where the recessed sidewalls  708 S join/meet the top plane  702 T. The waveguide  708  smoothly ends at the circular exit  704 . During operation of the speaker device  700 , the waveguide  708  shapes propagation of acoustic energy reproduced by the driver  706  to project the acoustic energy out of the circular exit  704  in an upwardly inclined direction. A bottom portion  708 A of the waveguide  708  begins at an upper point A 1  and a lower point A 2  along a plane  75  that is parallel to a diaphragm of the driver  706  (e.g., a plane inclined at 20 degrees from the horizontal axis). Let φ denote an angle formed between a recessed sidewall of a recessed area (e.g., a recessed sidewall  708 S) and the plane  75 . In one embodiment, an angle φ formed between a recessed sidewall  708 S and the plane  75  is about 90 degrees. 
     Let d 1  denote a distance between a recessed sidewall of a recessed area (e.g., a recessed sidewall  708 S) and a surround suspension element (i.e., an edge of a driver, such as the surround suspension element  706 A), and let d 2  denote a diameter of the surround suspension element. As shown in  FIG. 9B , a distance d 1  between a recessed sidewall  708 S and the surround suspension element  706 A is substantially greater than a diameter d 2  of the surround suspension element  706 , thereby providing the waveguide  708  with a wide base that is distant from the driver  706 . A top portion  708 B of the waveguide  708  smoothly ends at the circular exit  704  at points B 1  and B 2  in the top plane  702 T. The recessed sidewalls  708 S end substantially tangential to the top plane  702 T. The recessed sidewalls  708 S transition smoothly and continually between the points A 1  and A 2  along the plane  75  and the points B 1  and B 2  in the top plane  702 T. 
     In one embodiment, a diameter of a surround suspension element for a driver (e.g., the surround suspension element  706 A) may be in the range of 2 mm to 20 mm (e.g., the diameter is smaller if the driver comprises a tweeter, the diameter is larger if the driver comprises a woofer, etc.). In one embodiment, to prevent local dips and peaks below 8 kHz resulting from a wide base, d 1  is less than 3-4 mm. 
     In one embodiment, the base of the waveguide has a space d 1  between the driver and the front wall of the waveguide. 
       FIG. 9C  is an example graph  750  illustrating sound power levels of audio reproduced by the speaker device  700  over a frequency domain, in accordance with one embodiment. The graph  750  comprises a sound power curve  751 , a listening window curve  752 , a height window curve  753 , a height DI curve  754 , a difference curve  755 , and a spec curve  756 . A horizontal axis  750 A represents frequency values of the frequency domain expressed in Hz units. A left vertical axis  750 C represents sound power levels of the curves  751 - 753  expressed in dB units. A right vertical axis  750 B represents sound power levels of the curves  754 - 756  expressed in dB units. 
     As shown in  FIG. 9C , the height DI curve  754  exhibits a dip between 5 kHz frequency and 7 kHz frequency, which may negatively influence perceived sound quality. 
       FIG. 10A  illustrates a top, front perspective view of an example speaker device  800  comprising a height channel speaker  803  having a horn-shaped waveguide  808  that smoothly transitions to a quadrilateral exit  804 , in accordance with one embodiment.  FIG. 10B  illustrates a cross-section of a side view of the speaker device  800 , in accordance with one embodiment. The speaker device  800  comprises a speaker housing  802  including one or more sound sources. Specifically, a top plane (i.e., a top surface)  802 T of the speaker housing  802  comprises a height channel speaker  803 . The top plane  802 T is substantially parallel to the horizontal axis  20 . The height channel speaker  803  comprises an upward-facing speaker driver  806  disposed within a recessed area  802 R of the top plane  802 T. In one embodiment, the driver  806  lies flush inside the recessed area  802 R. 
     The driver  806  is positioned/mounted axially in a recessed mounting surface  810  that defines a base of the recessed area  802 R. In one embodiment, the driver  806  has a surround suspension element  806 A (i.e., an edge) that the mounting surface  810  is shaped to receive and engage with for maintaining the driver  806  within the recessed area  802 R. For example, the surround suspension element  806 A comprises a surround roll. 
     One or more recessed sidewalls  808 S of the recessed area  802 R connecting the mounting surface  810  to the top plane  802 T form a horn-shaped waveguide  808 . The waveguide  808  has a quadrilateral exit  804  defined as a quadrilateral cutout/opening in the top plane  802 T where the recessed sidewalls  808 S join/meet the top plane  802 T. As shown in  FIG. 10A , the quadrilateral exit  804  has a trapezoidal shape. In another embodiment, the quadrilateral exit  804  has another quadrilateral shape, such as a square, a rectangle, etc. In yet another embodiment, the waveguide  808  has a polygonal exit instead (i.e., the exit has a polygonal shape). The waveguide  808  smoothly ends at the quadrilateral exit  804 . During operation of the speaker device  800 , the waveguide  808  shapes propagation of acoustic energy reproduced by the driver  806  to project the acoustic energy out of the quadrilateral exit  804  in an upwardly inclined direction. A bottom portion  808 A of the waveguide  808  begins at an upper point A 1  and a lower point A 2  along a plane  75  that is parallel to a diaphragm of the driver  806  (e.g., a plane inclined at 20 degrees from the horizontal axis). In one embodiment, an angle φ formed between a recessed sidewall  808 S and the plane  75  is about 90 degrees. 
     As shown in  FIG. 10B , a distance d 1  between a recessed sidewall  808 S and the surround suspension element  806 A is substantially smaller than a diameter d 2  of the surround suspension element  806 A, thereby providing the waveguide  808  with a narrow base that is close to the driver  806 . In one embodiment, d 1  is about 0 mm. In one embodiment, d 1  is about 1 mm to account for manufacturing/positioning tolerance. A top portion  808 B of the waveguide  808  smoothly ends at the quadrilateral exit  804  at points B 1  and B 2  in the top plane  802 T. The recessed sidewalls  808 S end substantially tangential to the top plane  802 T. The recessed sidewalls  808 S transition smoothly and continually between the points A 1  and A 2  along the plane  75  and the points B 1  and B 2  in the top plane  802 T. 
       FIG. 10C  is an example graph  850  illustrating sound power levels of audio reproduced by the speaker device  800  over a frequency domain, in accordance with one embodiment. The graph  850  comprises a sound power curve  851 , a listening window curve  852 , a height window curve  853 , a height DI curve  854 , a difference curve  855 , and a spec curve  856 . A horizontal axis  850 A represents frequency values of the frequency domain expressed in Hz units. A left vertical axis  850 C represents sound power levels of the curves  851 - 853  expressed in dB units. A right vertical axis  850 B represents sound power levels of the curves  854 - 856  expressed in dB units. 
     As shown in  FIG. 10C , the height DI curve  854  exhibits a dip at about 2 kHz frequency. Compared to the height DI curve  754  for the speaker device  700 , the height DI curve  854  is smoother. 
       FIG. 11A  illustrates a top, front perspective view of an example speaker device  900  comprising a height channel speaker  903  having a horn-shaped waveguide  908  that smoothly transitions to an elliptical exit  904 , in accordance with one embodiment.  FIG. 11B  illustrates a cross-section of a side view of the speaker device  900 , in accordance with one embodiment. The speaker device  900  comprises a speaker housing  902  including one or more sound sources. Specifically, a top plane (i.e., a top surface)  902 T of the speaker housing  902  comprises a height channel speaker  903 . The top plane  902 T is substantially parallel to a horizontal axis  20 . The height channel speaker  903  comprises an upward-facing speaker driver  906  disposed within a recessed area  902 R of the top plane  902 T. In one embodiment, the driver  906  lies flush inside the recessed area  902 R. 
     The driver  906  is positioned/mounted axially in a recessed mounting surface  910  that defines a base of the recessed area  902 R. In one embodiment, the driver  906  has a surround suspension element  906 A (e.g., a surround roll) that the mounting surface  910  is shaped to receive and engage with for maintaining the driver  906  within the recessed area  902 R. 
     One or more recessed sidewalls  908 S of the recessed area  902 R connecting the mounting surface  910  to the top plane  902 T form a horn-shaped waveguide  908 . The waveguide  908  has an elliptical exit  904  defined as an elliptical cutout/opening in the top plane  902 T where the recessed sidewalls  908 S join/meet the top plane  902 T. The waveguide  908  smoothly ends at the elliptical exit  904 . During operation of the speaker device  900 , the waveguide  908  shapes propagation of acoustic energy reproduced by the driver  906  to project the acoustic energy out of the elliptical exit  904  in an upwardly inclined direction. A bottom portion  908 A of the waveguide  908  begins at an upper point A 1  and a lower point A 2  along a plane  75  that is parallel to a diaphragm of the driver  906  (e.g., a plane inclined at 20 degrees from the horizontal axis). In one embodiment, an angle φ formed between a recessed sidewall  908 S and the plane  75  is about 90 degrees. 
     As shown in  FIG. 11B , a distance d 1  between a recessed sidewall  908 S and the surround suspension element  906 A is substantially smaller than a diameter d 2  of the surround suspension element  906 A, thereby providing the waveguide  908  with a narrow base that is close to the driver  906 . A top portion  908 B of the waveguide  908  smoothly ends at the elliptical exit  904  at points B 1  and B 2  in the top plane  902 T. The recessed sidewalls  908 S end substantially tangential to the top plane  902 T. The recessed sidewalls  908 S transition smoothly and continually between the points A 1  and A 2  along the plane  75  and the points B 1  and B 2  in the top plane  902 T. 
       FIG. 11C  is an example graph  950  illustrating sound power levels of audio reproduced by the speaker device  900  over a frequency domain, in accordance with one embodiment. The graph  950  comprises a sound power curve  951 , a listening window curve  952 , a height window curve  953 , a height DI curve  954 , a difference curve  955 , and a spec curve  956 . A horizontal axis  950 A represents frequency values of the frequency domain expressed in Hz units. A left vertical axis  950 C represents sound power levels of the curves  951 - 953  expressed in dB units. A right vertical axis  950 B represents sound power levels of the curves  954 - 956  expressed in dB units. 
     Compared to the height DI curve  754  for the speaker device  700 , the height DI curve  954  is smoother. 
       FIG. 12A  illustrates a top, front perspective view of an example speaker device  1100  comprising a height channel speaker  1103  having a horn-shaped waveguide  1108  that smoothly transitions to a circular exit  1104 , in accordance with one embodiment.  FIG. 12B  illustrates a cross-section of a side view of the speaker device  1100 , in accordance with one embodiment. The speaker device  1100  comprises a speaker housing  1102  including one or more sound sources. Specifically, a top plane (i.e., a top surface)  1102 T of the speaker housing  1102  comprises a height channel speaker  1103 . The top plane  1102 T is substantially parallel to a horizontal axis  20 . The height channel speaker  1103  comprises an upward-facing speaker driver  1106  disposed within a recessed area  1102 R of the top plane  1102 T. In one embodiment, the driver  1106  lies flush inside the recessed area  1102 R. 
     The driver  1106  is positioned/mounted axially in a recessed mounting surface  910  that defines a base of the recessed area  1102 R. In one embodiment, the driver  1106  has a surround suspension element  1106 A (e.g., a surround roll) that the mounting surface  910  is shaped to receive and engage with for maintaining the driver  1106  within the recessed area  1102 R. 
     One or more recessed sidewalls  1108 S of the recessed area  1102 R connecting the mounting surface  910  to the top plane  1102 T form a horn-shaped waveguide  1108 . The waveguide  1108  has a circular exit  1104  defined as a circular cutout/opening in the top plane  1102 T where the recessed sidewalls  1108 S join/meet the top plane  1102 T. The waveguide  1108  smoothly ends at the circular exit  1104 . During operation of the speaker device  1100 , the waveguide  1108  shapes propagation of acoustic energy reproduced by the driver  1106  to project the acoustic energy out of the circular exit  1104  in an upwardly inclined direction. A bottom portion  1108 A of the waveguide  1108  begins at an upper point A 1  and a lower point A 2  along a plane  75  that is parallel to a diaphragm of the driver  1106  (e.g., a plane inclined at 20 degrees from the horizontal axis). In one embodiment, an angle φ formed between a recessed sidewall and the plane  75  is about 90 degrees. 
     As shown in  FIG. 12B , a distance d 1  between a recessed sidewall and the surround suspension element  1106 A is substantially smaller than a diameter d 2  of the surround suspension element  1106 A, thereby providing the waveguide  1108  with a narrow base that is close to the driver  1106 . A top portion  1108 B of the waveguide  1108  smoothly ends at the circular exit  1104  at points B 1  and B 2  in the top plane  1102 T. The recessed sidewalls  1108 S end substantially tangential to the top plane  1102 T. The recessed sidewalls  1108 S transition smoothly and continually between the points A 1  and A 2  along the plane  75  and the points B 1  and B 2  in the top plane  1102 T. A transition region  1007  is formed between the recessed sidewalls  1108 S and the top plane  1102 T. 
     In one embodiment, x 1  is about 10 mm, and x 2  is about 30 mm (i.e., x 1  is about 33% of x 2 ). 
       FIG. 12C  is an example graph  1150  illustrating sound power levels of audio reproduced by the speaker device  1100  over a frequency domain, in accordance with one embodiment. The graph  1150  comprises a sound power curve  1151 , a listening window curve  1152 , a height window curve  1153 , a height DI curve  1154 , a difference curve  1155 , and a spec curve  1156 . A horizontal axis  1150 A represents frequency values of the frequency domain expressed in Hz units. A left vertical axis  1150 C represents sound power levels of the curves  1151 - 1153  expressed in dB units. A right vertical axis  1150 B represents sound power levels of the curves  1154 - 1156  expressed in dB units. 
     As shown in  FIG. 12C , the height DI curve  1154  does not exhibit any dips, indicating that the speaker device  1100  provides good sound quality. 
       FIG. 13A  illustrates a top, front perspective view of an example speaker device  1000  comprising a height channel speaker  1003  having a deeply set driver  1006  and a horn-shaped waveguide  1008  that smoothly transitions to a circular exit  1004 , in accordance with one embodiment.  FIG. 13B  illustrates a cross-section of a side view of the speaker device  1000 , in accordance with one embodiment. The speaker device  1000  comprises a speaker housing  1002  including one or more sound sources. Specifically, a top plane (i.e., a top surface)  1002 T of the speaker housing  1002  comprises a height channel speaker  1003 . The top plane  1002 T is substantially parallel to a horizontal axis  20 . The height channel speaker  1003  comprises an upward-facing speaker driver  1006  disposed within a recessed area  1002 R of the top plane  1002 T. In one embodiment, the driver  1006  lies flush inside the recessed area  1002 R. 
     The driver  1006  is positioned/mounted axially in a recessed mounting surface  1010  that defines a base of the recessed area  1002 R. In one embodiment, the driver  1006  has a surround suspension element  1006 A (e.g., a surround roll) that the mounting surface  1010  is shaped to receive and engage with for maintaining the driver  1006  within the recessed area  1002 R. 
     One or more recessed sidewalls  1008 S of the recessed area  1002 R connecting the mounting surface  1010  to the top plane  1002 T form a horn-shaped waveguide  1008 . In one embodiment, the waveguide  1008  has a circular exit  1004  defined as a circular cutout/opening in the top plane  1002 T where the recessed sidewalls  1008 S join/meet the top plane  1002 T. In another embodiment, the waveguide  1008  has an exit having another shape, such as an elliptical shape, a quadrilateral shape (e.g., a trapezoid, a square, a rectangle, etc.), a polygonal shape, etc. 
     A smooth transition region  1007  is formed between the recessed sidewalls  1008 S and the top plane  1002 T. In one embodiment, the transition region  1007  is formed along a perimeter of the circular exit  1004 . In another embodiment, the transition region  1007  is formed along a portion of the perimeter of the circular exit  1004 , wherein the portion of the perimeter is on a side of a listener  30  (i.e., facing a front of the speaker device  1000 ). Compared to the transition region  1107  in  FIG. 12B , the transition region  1007  is less curved (i.e., more smooth). 
     The waveguide  1008  smoothly ends at the circular exit  1004 . During operation of the speaker device  1000 , the waveguide  1008  shapes propagation of acoustic energy reproduced by the driver  1006  to project the acoustic energy out of the circular exit  1004  in an upwardly inclined direction. A bottom portion  1008 A of the waveguide  1008  begins at an upper point A 1  and a lower point A 2  along a plane  75  that is parallel to a diaphragm of the driver  1006  (e.g., a plane inclined at 20 degrees from the horizontal axis). In one embodiment, an angle φ formed between a recessed sidewall  1008 S and the plane  75  is about 100 degrees. 
     As shown in  FIG. 13B , a distance d 1  between a recessed sidewall  1008 S and the surround suspension element  1006 A is substantially smaller than a diameter d 2  of the surround suspension element  1006 A, thereby providing the waveguide  1008  with a narrow base. A top portion  1008 B of the waveguide  1008  smoothly ends at the circular exit  1004  at points B 1  and B 2  in the top plane  1002 T. The recessed sidewalls  1008 S end substantially tangential to the top plane  1002 T. The recessed sidewalls  1008 S transition smoothly and continually between the points A 1  and A 2  along the plane  75  and the points B 1  and B 2  in the top plane  1002 T. 
     The driver  1006  is set deeply into the speaker housing  1002  such that an upper portion of the driver  1006  is positioned a substantial distance below an exterior surface  1002 T (i.e., an outer surface) of the speaker housing  1002  and the waveguide  1008  has a rear portion. Let x 1  denote a distance between the upper point A 1  along the plane  75  and the top plane  1002 T. Let x 2  denote a distance between the lower point A 2  along the plane  75  and the top plane  1002 T. In one embodiment, the upper point A 1  is positioned below the top plane  1002 T by a distance x 1  that is at least about 40% of a distance x 2 . In another embodiment, the upper point A 1  is positioned below the top plane  1002 T by a distance x 1  that is at least about 50% of a distance x 2 . In yet another embodiment, the upper point A 1  is positioned below the top plane  1002 T by a distance x 1  that is at least about 60% of a distance x 2 . 
     In one embodiment, x 1  is about 20 mm, and x 2  is about 40 mm (i.e., x 1  is about 50% of x 2 ). 
       FIG. 13C  is an example graph  1050  illustrating sound power levels of audio reproduced by the speaker device  1000  over a frequency domain, in accordance with one embodiment. The graph  1050  comprises a sound power curve  1051 , a listening window curve  1052 , a height window curve  1053 , a height DI curve  1054 , a difference curve  1055 , and a spec curve  1056 . A horizontal axis  1050 A represents frequency values of the frequency domain expressed in Hz units. A left vertical axis  1050 C represents sound power levels of the curves  1051 - 1053  expressed in dB units. A right vertical axis  1050 B represents sound power levels of the curves  1054 - 1056  expressed in dB units. 
     As shown in  FIG. 13C , the height DI curve  1054  does not exhibit any dips, indicating that the speaker device  1000  provides good sound quality. 
       FIG. 14A  illustrates a top, front perspective view of an example speaker device  1200  comprising a height channel speaker  1203  having a cup-shaped waveguide  1208  that smoothly transitions to a circular exit  1204 , in accordance with one embodiment. The speaker device  1200  comprises a speaker housing  1202  including one or more sound sources. Specifically, a top plane (i.e., a top surface)  1202 T of the speaker housing  1202  comprises a height channel speaker  1203 . The top plane  1202 T is substantially parallel to the horizontal axis  20 . The height channel speaker  1203  comprises an upward-facing speaker driver  1206  disposed within a recessed area  1202 R of the top plane  1202 T. In one embodiment, the driver  1206  lies flush inside the recessed area  1202 R. 
     The driver  1206  is positioned/mounted axially in a recessed mounting surface  1210  that defines a base of the recessed area  1202 R. 
     One or more recessed sidewalls of the recessed area  1202 R connecting the mounting surface  1210  to the top plane  1202 T form a cup-shaped waveguide  1208 . The waveguide  1208  has a circular exit  1204  defined as a circular cutout/opening in the top plane  1202 T where the recessed sidewalls join/meet the top plane  1202 T. During operation of the speaker device  1200 , the waveguide  1208  shapes propagation of acoustic energy reproduced by the driver  1206  to project the acoustic energy out of the circular exit  1204  in an upwardly inclined direction. 
       FIG. 14B  is an example graph  1250  illustrating sound power levels of audio reproduced by the speaker device  1200  over a frequency domain, in accordance with one embodiment. The graph  1250  comprises a sound power curve  1251 , a listening window curve  1252 , a height window curve  1253 , a height DI curve  1254 , a difference curve  1255 , and a spec curve  1256 . A horizontal axis  1250 A represents frequency values of the frequency domain expressed in Hz units. A left vertical axis  1250 C represents sound power levels of the curves  1251 - 1253  expressed in dB units. A right vertical axis  1250 B represents sound power levels of the curves  1254 - 1256  expressed in dB units. 
     As shown in  FIG. 14B , the height DI curve  1254  exhibits small dips, which may negatively influence perceived sound quality. 
       FIG. 15A  illustrates a top, front perspective view of an example speaker device  1300  comprising a height channel speaker  1303  having a cone-shaped waveguide  1308  that smoothly transitions to a circular exit  1304 , in accordance with one embodiment. The speaker device  1300  comprises a speaker housing  1302  including one or more sound sources. Specifically, a top plane (i.e., a top surface)  1302 T of the speaker housing  1302  comprises a height channel speaker  1303 . The top plane  1302 T is substantially parallel to the horizontal axis  20 . The height channel speaker  1303  comprises an upward-facing speaker driver  1306  disposed within a recessed area  1302 R of the top plane  1302 T. In one embodiment, the driver  1306  lies flush inside the recessed area  1302 R. 
     The driver  1306  is positioned/mounted axially in a recessed mounting surface  1310  that defines a base of the recessed area  1302 R. 
     One or more recessed sidewalls of the recessed area  1302 R connecting the mounting surface  1310  to the top plane  1302 T form a cone-shaped waveguide  1308 . The waveguide  1308  has a circular exit  1304  defined as a circular cutout/opening in the top plane  1302 T where the recessed sidewalls join/meet the top plane  1302 T. During operation of the speaker device  1300 , the waveguide  1308  shapes propagation of acoustic energy reproduced by the driver  1306  to project the acoustic energy out of the circular exit  1304  in an upwardly inclined direction. 
       FIG. 15B  is an example graph  1350  illustrating sound power levels of audio reproduced by the speaker device  1300  over a frequency domain, in accordance with one embodiment. The graph  1350  comprises a sound power curve  1351 , a listening window curve  1352 , a height window curve  1353 , a height DI curve  1354 , a difference curve  1355 , and a spec curve  1356 . A horizontal axis  1350 A represents frequency values of the frequency domain expressed in Hz units. A left vertical axis  1350 C represents sound power levels of the curves  1351 - 1353  expressed in dB units. A right vertical axis  1350 B represents sound power levels of the curves  1354 - 1356  expressed in dB units. 
     As shown in  FIG. 15B , the height DI curve  1354  exhibits small dips, which may negatively influence perceived sound quality. 
       FIG. 16  is an example flowchart  1400  for producing a waveguide for a speaker device, in accordance with one embodiment. In process block  1401 , determine at least one waveguide property suitable for enhancing an amount of acoustic energy projected by an upward-facing driver of the speaker device towards a ceiling. In process block  1402 , fabricate a housing of the speaker device based on the at least one waveguide property, wherein the housing includes a waveguide for shaping propagation of the acoustic energy generated by the driver to project the acoustic energy out of the speaker device in an upwardly inclined direction towards the ceiling. 
     In one example implementation, the acoustic energy may be projected out of the speaker device in the upwardly inclined direction at an angle that is substantially seventy degrees relative to a horizontal plane to reflect the acoustic energy off the ceiling. 
     In one example implementation, the waveguide may be defined by an opening included in a top surface of a housing of the speaker device, a recessed mounting surface of the housing spaced vertically downwards from the top surface, and a recessed sidewall extending upwardly from the recessed mounting surface to the opening. The driver is mounted into the recessed mounting surface. 
     In one example implementation, determining at least one waveguide property may comprise determining a shape of the opening, determining a shape of the recessed sidewall, determining one or more dimensions of the recessed mounting surface, and determining a depth of the waveguide. 
     In one example implementation, the waveguide has a substantially straight shape defined by one or more straight walls of the recessed sidewall. In another example implementation, the waveguide has a substantially curved shape defined by one or more curved segments of the recessed sidewall. 
     In one example implementation, an end of the recessed sidewall is substantially tangential to the top surface. 
     In one example implementation, the shape of the opening is one of substantially circular, substantially elliptical, or substantially quadrilateral. 
       FIG. 17  is an example flowchart  1500  for enhancing an amount of acoustic energy projected by an upward-facing driver of a speaker device towards a ceiling, in accordance with one embodiment. In process block  1501 , generate, utilizing the driver, the acoustic energy. In process block  1502 , shape propagation of the acoustic energy utilizing a waveguide of the speaker device to project the acoustic energy out of the speaker device in an upwardly inclined direction towards the ceiling. 
     In one example implementation, the acoustic energy may be projected out of the speaker device in the upwardly inclined direction at an angle that is substantially seventy degrees relative to a horizontal plane to reflect the acoustic energy off the ceiling. 
     In one example implementation, the waveguide may be defined by an opening included in a top surface of a housing of the speaker device, a recessed mounting surface of the housing spaced vertically downwards from the top surface, and a recessed sidewall extending upwardly from the recessed mounting surface to the opening. The driver is mounted into the recessed mounting surface. 
       FIG. 18A  illustrates a top view of an example height channel speaker  153  in a speaker device  150 , in accordance with one embodiment.  FIG. 18B  illustrates a cross-section of a side view of the height channel speaker  103  in the speaker device  100 , in accordance with one embodiment. The speaker device  150  comprises a speaker housing  152  including one or more sound sources (e.g., a speaker driver, etc.). Specifically, a top plane (i.e., a top surface)  152 T of the speaker housing  152  comprises a height channel speaker  153 . The height channel speaker  153  comprises multiple upward-facing speaker drivers disposed within a recessed area  152 R of the top plane  152 T. For example, as shown in  FIGS. 18A-18B , the height channel speaker  153  comprises a first driver  156 A and a second driver  156 B. In one embodiment, each driver  156 A,  156 B lies flush inside the recessed area  152 R. 
     In one embodiment, the drivers  156 A and  156 B are partially distinct in that both drivers  156 A and  156 B may have the same general shape, but different sizes (or vice versa). As shown in  FIGS. 18A-18B , in one example implementation, the drivers  156 A and  156 B have the same general shape, but different physical dimensions (e.g., the driver  156 A is smaller than the driver  156 B). In another example implementation, the drivers  156 A and  156 B have substantially similar physical dimensions, but different shapes. 
     Each driver  156 A,  156 B is positioned/mounted axially in a recessed mounting surface  160  that defines a base of the recessed area  152 R. The drivers  156 A and  156 B are spaced apart in the mounting surface  160 . For example, as shown in  FIGS. 18A-18B , the first driver  156 A is positioned in the mounting surface  160  towards a top of the mounting surface  160 , whereas the second driver  156 B is positioned in the mounting surface  160  towards a bottom of the mounting surface  160 . The drivers  156 A and  156 B may be positioned in the mounting surface  160  in accordance with other spatial arrangements. 
     One or more recessed sidewalls  158 S of the recessed area  152 R connecting the mounting surface  160  to the top plane  152 T form a waveguide  158 . The drivers  156 A and  156 B are be positioned inside the same waveguide  158 . The waveguide  158  has an exit  154  defined as a cutout/opening in the top plane  152 T where the recessed sidewalls  158 S join/meet the top plane  152 T. During operation of the speaker device  150 , the waveguide  158  shapes propagation of acoustic energy reproduced by the drivers  156 A and  156 B to project the acoustic energy out of the exit  154  in an upwardly inclined direction. A shape of the exit  154  may be circular, quadrilateral (e.g., a trapezoid, a square, a rectangle, etc.), elliptical, polygonal, or any other shape. A shape of the waveguide  158  may be straight or substantially curved (e.g., horn-shaped, cone-shaped, cup-shaped, etc.), depending on a shape of each recessed sidewall  158 S. 
     In one embodiment, the top plane  152 T is substantially parallel to a horizontal axis  20 . In another embodiment, the top plane  152 T is slanted or curved. A forward slanted top plane  152 T decreases acoustical occlusion as a forward-facing part of the waveguide  158  is shortened. This reduces a ratio of acoustic energy reflected off the ceiling to acoustic energy leaked to a listener, thereby reducing perception of height in sound. 
     Though the embodiments have been described with reference to certain versions thereof; however, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.