Patent Description:
Loudspeaker arrays are often used by computers and home electronics for outputting sound into a listening area. Each loudspeaker array may be composed of multiple transducers that are arranged on a single plane or surface of an associated cabinet or casing. Acoustic horns may be used along with transducers to increase the efficiency by which these transducers output sound. In particular, horns may provide (<NUM>) extra acoustic gain in one or more frequency bands and (<NUM>) directivity control. Further background information can be found in the following documents:.

Although horns may provide some efficiency improvements, horns may also lead to aliasing issues between transducers. In particular, horns may increase the distance between the points where sound from adjacent transducers in a loudspeaker array is mixed. This distance defines the aliasing frequency above which sound may become distorted based on sound mixing between proximate transducers.

Further, traditional horn designs suffer from sharp cutoff frequencies caused by the shape and dimensions of the horn. Accordingly, sound produced by a transducer below this frequency is cut off or inconsistently modified in comparison to higher frequency content.

The invention is as set out in the appended set of claims. In an embodiment useful for understanding the invention, an audio system operating within a listening area is described. The audio system may include an audio receiver and a loudspeaker array. The audio receiver may be coupled to the loudspeaker array to drive individual transducers in the loudspeaker array to emit various sound beam or radiation patterns into the listening area for a listener. In one embodiment, the loudspeaker array may include a continuously open circumferential horn for controlling sound produced by the transducers. In this embodiment, one or more transducers may be coupled proximate to a throat of the horn. The continuously open circumferential horn may <NUM>) improve the power efficiency of the transducers without unwanted aliasing effects in audible frequency ranges and/or <NUM>) provide vertical control for sound emitted by the transducers.

In particular, by providing an unobstructed and open cavity for sound emitted by the transducers to mix, the continuously open circumferential horn may decrease a mixing distance between adjacent transducers (e.g., transducers that are directly adjacent in the ring of transducers) such that a corresponding aliasing frequency is increased. This aliasing frequency describes the highest frequency that may be emitted by the transducers without generation or production of aliasing effects caused by mixing of sound between transducers. Accordingly, by decreasing the mixing distance, the continuously open circumferential horn increases the maximum frequency that may be produced by the transducers without unwanted effects.

Further, the continuously open circumferential horn may provide improved directional control for sound produced by the transducers, including both horizontal and vertical control. For example, the outer corners of the continuously open circumferential horn may be curved. These curved corners more uniformly improve gain across frequency ranges in comparison to horns that are abruptly cutoff at the mouth of the horn.

The above summary does not include an exhaustive list of all aspects of the present invention.

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.

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> shows a view of an audio system <NUM> operating within a listening area <NUM> according to one embodiment. The audio system <NUM> may include an audio receiver <NUM> and a loudspeaker array <NUM>. The audio receiver <NUM> may be coupled to the loudspeaker array <NUM> to drive individual transducers <NUM> in the loudspeaker array <NUM> to emit various sound beam/radiation patterns into the listening area <NUM> for a listener <NUM>. In one embodiment, the loudspeaker array <NUM> may include a continuously open circumferential horn <NUM> for controlling sound produced by the transducers <NUM>. In this embodiment, one or more transducers <NUM> may be coupled proximate to a throat <NUM> of the horn <NUM>. As will be described in greater detail below, the continuously open circumferential horn <NUM> may <NUM>) improve the power efficiency of the transducers <NUM> without unwanted aliasing effects in audible frequency ranges and/or <NUM>) provide vertical control for sound emitted by the transducers <NUM>.

In some embodiments, the transducers <NUM> of the array <NUM> may be configured to generate beam patterns. The beam patterns may represent individual channels of a piece of sound program content. For example, the loudspeaker array <NUM> 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).

Each element of the audio system <NUM> shown in <FIG> will be described below by way of example. In other embodiments, the audio system <NUM> may include additional components than those described below and shown in <FIG>.

<FIG> shows a component diagram of the audio receiver <NUM> according to one embodiment. The audio receiver <NUM> may be any electronic device that is capable of driving one or more transducers <NUM> in the loudspeaker array <NUM>. For example, the audio receiver <NUM> may be a desktop computer, a laptop computer, a tablet computer, a home theater receiver, a set-top box, and/or a mobile device (e.g., a smartphone). The audio receiver <NUM> may include a hardware processor <NUM> and a memory unit <NUM>.

The processor <NUM> and the memory unit <NUM> are 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 <NUM>. The processor <NUM> may be an applications processor typically found in a smart phone, while the memory unit <NUM> may refer to microelectronic, non-volatile random access memory. An operating system may be stored in the memory unit <NUM> along with application programs specific to the various functions of the audio receiver <NUM>, which are to be run or executed by the processor <NUM> to perform the various functions of the audio receiver <NUM>.

The audio receiver <NUM> may include one or more audio inputs <NUM> for receiving audio signals from an external device, e.g., a remote device. For example, the audio receiver <NUM> may receive audio signals from a remote server of a streaming media service. 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 <NUM> of the audio receiver <NUM>. In another example, a single signal may correspond to multiple channels of a piece of sound program content, which are multiplexed onto the single signal. The processor <NUM> of the audio receiver <NUM> may receive as inputs multiple audio channel signals simultaneously, and processes these to produce multiple acoustic transducer drive signals (to render the audio content in the input signals as sound), e.g., as a beamforming process to control relative phases and gains for each of the signals used to drive the transducers such that the transducers generate an acoustic beam pattern along the horizontal plane.

In one embodiment, the audio receiver <NUM> may include a digital audio input 205A that receives digital audio signals from an external device and/or a remote device. For example, the audio input 205A may be a TOSLINK connector or a digital wireless interface (e.g., a wireless local area network (WLAN) adapter or a Bluetooth adapter). In one embodiment, the audio receiver <NUM> may include an analog audio input 205B that receives analog audio signals from an external device. For example, the audio input 205B 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 another embodiment, the processor <NUM> may obtain its input audio channel signals by decoding an encoded audio file, e.g., an MPEG file.

In one embodiment, the audio receiver <NUM> may include an interface <NUM> for communicating with the loudspeaker array <NUM>. The interface <NUM> may utilize wired mediums (e.g., conduit or wire) to communicate with the loudspeaker array <NUM>, as shown in <FIG>. In another embodiment, the interface <NUM> may communicate with the loudspeaker array <NUM> through a wireless connection. For example, the network interface <NUM> may utilize one or more wireless protocols and standards for communicating with the loudspeaker array <NUM>, including the IEEE <NUM> suite of standards, IEEE <NUM>, cellular Global System for Mobile Communications (GSM) standards, cellular Code Division Multiple Access (CDMA) standards, Long Term Evolution (LTE) standards, and/or Bluetooth standards.

<FIG> shows a component diagram for the loudspeaker array <NUM> according to one embodiment. As shown in <FIG>, the loudspeaker array <NUM> may include an interface <NUM> for receiving drive signals from the audio receiver <NUM>. The drive signals may be used for driving each of the transducers <NUM> in the loudspeaker array <NUM>. As with the interface <NUM>, the interface <NUM> may utilize wired protocols and standards and/or one or more wireless protocols and standards, including the IEEE <NUM> suite of standards, IEEE <NUM>, 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 embodiment, the loudspeaker array <NUM> may include power amplifiers <NUM> for amplifying the drive signals sent to each of the transducers <NUM> in the loudspeaker array <NUM>, as well as digital to analog converters (DACs) <NUM> for converting the drive signals from digital domain into analog domain, both of which may be integrated into the speaker cabinet <NUM>. Although described and shown as being separate from the audio receiver <NUM>, in some embodiments, one or more components of the audio receiver <NUM> may be integrated within a housing of the loudspeaker array <NUM>. For example, the loudspeaker array <NUM> may include the hardware processor <NUM>, the memory unit <NUM>, and the one or more audio inputs <NUM>.

<FIG> shows a side view of a loudspeaker array <NUM> according to one embodiment. As shown in <FIG>, the loudspeaker array <NUM> houses multiple transducers <NUM> in a cabinet <NUM>. The cabinet <NUM> may be a loudspeaker cabinet or loudspeaker enclosure composed of two frusto conical sections 117A and 117B rotated in relation to each other by <NUM>°, and joined to each other at their respective smaller base regions, to form a waist region in which the transducers <NUM> are positioned. An interior volume of the cabinet <NUM> may be used to house associated electronic hardware such as amplifiers and crossover circuits that are mounted inside the cabinet <NUM>, but its primary role may be to prevent sound waves generated by rearward facing surfaces of diaphragms of the transducers <NUM> (not visible in <FIG>), interacting with sound waves generated off the front facing surfaces of the diaphragms of the transducers <NUM> (which are visible as illustrated in <FIG>) and emanating sideways and outward from the frusto conical sections 117A, 117B. As will be described in greater detail below, these frusto conical sections 117A and 117B (as joined) form a continuously open circumferential horn <NUM> at the waist region, which may be used for improving performance of integrated transducers <NUM> or for providing vertical sound control for the loudspeaker array <NUM>. One or both of the larger base regions of the frusto conical sections 117A, 117B may be joined to a respective outer wall, depicted as outer walls 127A, 127B in <FIG> below.

Although described in relation to frusto conical sections 117A and 117B, in other embodiments, the cabinet <NUM> may be composed of any shapes or sections that provide a narrow inner circumference (or waist), to define a throat <NUM> of the continuously open circumferential horn <NUM>, and a flared or wider outer section that defines a mouth <NUM> of the horn <NUM>. For example, in other embodiments the cabinet <NUM> may be composed of one or more frustums, cones, pyramids, triangular prisms, spheres, or any other similar shape.

In some embodiments, the cabinet <NUM> may be defined by a hyperboloid shape that is similar to the cabinet <NUM> formed by the frusto conical sections 117A and 117B described above. In this embodiment, the cabinet <NUM> may include upper and lower sections that are wider than a middle or waist section. The upper and lower sections may taper inwards to meet the narrower middle section to form the throat <NUM> of the continuously open circumferential horn <NUM>. In each of these embodiments, a horizontal cross-section of the cabinet <NUM>, which lies in a horizontal plane that is perpendicular to the page showing <FIG> and that is positioned to cut through the middle section, may be circular such that the continuously open circumferential horn <NUM> uniformly extends around the entire perimeter of the cabinet <NUM>.

In some embodiments, the cabinet <NUM> may be at least partially hollow and may allow for the mounting of transducers <NUM> on an inside surface of the cabinet <NUM> with sound output holes formed in a cylindrical wall of the waist section, each of the output holes being aligned with the diaphragm of a respective one of the transducers, or on an outside surface of the cabinet <NUM> (e.g., where each transducer is mounted such that its diaphragm is positioned outside or spaced outward of the cylindrical surface of the waist section). The cabinet <NUM> may be made of any material, including metals, metal alloys, plastic polymers, or some combination thereof.

As shown in <FIG> and <FIG> and described above, the loudspeaker array <NUM> may include a set of transducers <NUM>. The transducers <NUM> may be any combination of full-range drivers, mid-range drivers, subwoofers, woofers, and tweeters, although in one embodiment they may all be replicates of each other. Each of the transducers <NUM> may use a lightweight diaphragm, or cone, connected to a rigid basket, or frame, via a flexible suspension that constrains a coil of wire (e.g., a voice coil) to move axially through a 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' <NUM> 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 <NUM>. Although electromagnetic dynamic loudspeaker drivers are described for use as the transducers <NUM>, those skilled in the art will recognize that other types of loudspeaker drivers, such as piezoelectric, planar electromagnetic and electrostatic drivers are possible. As shown in <FIG> and <FIG>, in one embodiment, the rear face of the diaphragm of each transducer <NUM> faces inward (into the ring formed by the entire group of transducers <NUM>) while the front face is facing outward.

Referring back to <FIG>, each transducer <NUM> may be individually and separately driven using the power amplifiers <NUM> to produce sound in response to separate and discrete audio drive signals received from an audio source (e.g., the audio receiver <NUM> - see <FIG>). By allowing the transducers <NUM> in the loudspeaker array <NUM> to be individually and separately driven according to different parameters and settings (including delays and voltage levels), the loudspeaker array <NUM> may produce numerous directivity or beam radiation patterns that accurately represent each channel of a piece of sound program content received from the audio receiver <NUM>. In some embodiments, digital filtering techniques may be used that impart variable gains and phases (relative to each other) upon the individual drive signals for the transducers <NUM>, in the digital domain, e.g., by the processor <NUM> which may be part of the audio receiver <NUM> (see <FIG>). A beamforming process may be performed upon a give set of two or more input audio channels, e.g., by the processor <NUM>, to produce a number of desired acoustic output patterns, which are rendered by transferring the individual transducer drive signals (in digital form) to the DACs <NUM> via the interface <NUM>.

For example, in one embodiment, the loudspeaker array <NUM> may produce one or more of the directivity or radiation patterns shown in <FIG> along a horizontal plane that is perpendicular to the upright stance of the cabinet <NUM> as seen in the earlier figures (or that is perpendicular to the central upright axis <NUM>). In <FIG>, an omnidirectional pattern is shown on the right (having a low directivity index, DI), a hypercardiod pattern is shown on the right (having a high DI), while a cardiod pattern is shown in the middle. <FIG> shows a top view of a loudspeaker array <NUM> emitting a forward (or right) facing cardioid radiation pattern in a horizontal plane using a set of transducers <NUM> according to one embodiment. Simultaneous directivity patterns produced by the loudspeaker array <NUM> may not only differ in shape, but may also differ in the direction of their respective reference axes. For instance, different directivity patterns may be "pointed" in different directions in the listening area <NUM> to represent separate channels or separate pieces of sound program content for separate zones or separate listeners <NUM>.

Power or gain performance from the transducers <NUM> may be lacking, if the transducers <NUM> have to be made smaller in order to fit into a smaller cabinet <NUM>. To improve the performance of the transducers <NUM>, a horn may be used at the primary sound output opening of each transducer <NUM> (or selected ones of the transducers <NUM>). In particular, an acoustic horn may be used to <NUM>) increase the efficiency of a transducer <NUM> (e.g., add acoustic gain for sound output by a transducer <NUM>) and/or <NUM>) to control the direction in which the sound is radiated into the listening area <NUM>.

For example, as shown in <FIG>, a single transducer <NUM> is connected to the throat <NUM> of a horn <NUM>, and the cross sectional area of the horn <NUM> increases with distance from the throat <NUM> to the mouth <NUM> of the horn <NUM>. The change in cross section with distance and the detailed shape of the horn <NUM> may be chosen to add a specified level of gain to sound emitted by the transducer <NUM> for a specified frequency range of operation. In this sense, the horn <NUM> may be considered an acoustic transformer that provides impedance matching between the diaphragm material of the transducer <NUM> and the less-dense air surrounding the loudspeaker array <NUM>. The result is greater acoustic output power from transducer <NUM>. The shape of the horn <NUM> may also be designed to give different passive directivity properties.

Historically, horns were very useful in increasing acoustic gain when amplifiers were not yet available. Although amplifiers are now readily available, horns may continue to be useful as they still improve the gain performance of transducers <NUM> in particular frequency ranges and may provide passive directional control. Accordingly, horns may allow the use of smaller transducers <NUM> in mobile or other compact devices where amplifiers may not be suitable options (e.g., size or thermal considerations).

In an example not covered by the scope of the claims, but useful for understanding the invention, the horn <NUM> shown in <FIG> is used with multiple transducers <NUM> arranged alongside each other. For example, as shown in <FIG>, multiple horns <NUM> may be used with multiple transducers <NUM>, respectively, that are positioned side by side in a ring or circular formation. In this embodiment, sound from each transducer <NUM> travels through a corresponding throat <NUM> of its horn <NUM>, and mixes with sound from adjacent transducers <NUM> upon exiting at the mouth <NUM> of its horn <NUM>. Accordingly, the horn <NUM> in this arrangement provides a sound barrier between adjacent transducers <NUM>, where this barrier extends from the throat <NUM>, which is proximate and coupled to the transducer <NUM>, to the mouth <NUM> such that sound from adjacent transducers <NUM> is not permitted to mix until after escaping the horn <NUM>.

The distance D shown in <FIG> represents the separation between points where sounds from adjacent transducers <NUM> are allowed to mix together (i.e., the point in this case where sounds leave respective horns <NUM>). The horns <NUM> shown in <FIG> draw sound outward and away from the transducers <NUM> (using a set of barriers or walls that define the shape of the horns <NUM>) before a sound can be mixed with sound from other transducers <NUM>, and this may dictate the distance D. In particular, since the horn <NUM> flares outward, as the design of the horn <NUM> increases in length (e.g., calculated from the throat <NUM> to the mouth <NUM>), the horns <NUM> and their corresponding transducers <NUM> may need to be more greatly separated from each other. This increased distance or spacing between the transducers <NUM> results in a similar increase to the mixing distance D between adjacent horns <NUM>. For simplicity and consistency, this distance D may be measured (for each adjacent pair of horns <NUM>) along any suitable, mathematically defined curve that connects the centers of the mouths <NUM> of adjacent horns <NUM>. Similarly, for the embodiment of <FIG>, the mixing distance D may be measured along a suitable, mathematically defined curve (in front of the transducers <NUM>) that connects the centers of the diaphragms of adjacent transducers <NUM>.

In some cases, mixing of sounds produced by transducers <NUM> may cause aliasing issues. Aliasing may be restricted to particular frequency bands based on the distance D. For example, aliasing may occur when a wavelength of sound produce by the transducers <NUM> is smaller than the mixing distance D. In other words, the sound produced by adjacent transducers <NUM> (and as heard by the listener <NUM>) may exhibit aliasing at wavelengths that are smaller than a threshold wavelength (or equivalently at frequencies that are higher than a threshold frequency. ) Since higher frequency sounds have shorter wavelengths in comparison to lower frequency sounds, as the distance D increases the frequencies of sound that may be produced by the transducers <NUM> without aliasing effects decreases (e.g., an inverse relationship between the mixing distance D and the aliasing frequency). In other words, the "aliasing frequency" (the frequency above which there is substantial aliasing in the sound that may be heard at a position of the listener <NUM>) drops, as the mixing distance D increases. Accordingly, to ensure that sounds may be produced at higher frequencies by the loudspeaker array <NUM> without the occurrence of aliasing effects, the mixing distance D should be decreased.

In one embodiment, the loudspeaker array <NUM> described herein reduces the distance D by providing a continuously open circumferential horn <NUM>. As described above and shown in <FIG>, the continuously open circumferential horn <NUM> may include a throat <NUM>, a mouth <NUM>, and a set of inner walls 123a, 123b. The throat <NUM> is defined by the narrowest end of the horn <NUM> and is proximate or coupled to the ring of transducers <NUM>. In contrast, the mouth <NUM> is formed at the opposite end of the horn <NUM> and is defined by the widest end of the horn <NUM>. The inner walls 123a, 123b mark the upper and lower halves, or upper and lower bounds, respectively, of the horn <NUM> and may provide a tapered or angled connection between the throat <NUM> and the mouth <NUM> such that the horn <NUM> flares outwards (i.e., increases in diameter moving from the throat <NUM> to the mouth <NUM>).

The combined throat <NUM>, mouth <NUM>, and inner walls <NUM> may extend the entire circumference or perimeter of the cabinet <NUM> (e.g., <NUM>° around a center upright axis <NUM> of the cabinet <NUM>) such that the horn <NUM> is circumferentially open and no barriers are present between transducers <NUM>. In comparison to the arrangement in <FIG> in which each individual horn <NUM> creates a sound barrier for each corresponding transducer <NUM>, the continuously open circumferential horn <NUM> depicted in <FIG> may allow the placement of multiple transducers <NUM> side by side at the throat <NUM>, without barriers between each transducer <NUM>. Although the inner walls <NUM> form upper and lower barriers for sound produced by the transducers <NUM>, these inner walls <NUM> do not restrict mixing of sound between transducers <NUM>. For example, <FIG> shows a top view of an arrangement of as in <FIG>, in which the transducers <NUM> are side by side around the throat <NUM> of the continuously open circumferential horn <NUM>. Since in this embodiment no barriers are present between each adjacent pair of the transducers <NUM>, sound from each of the transducers <NUM> may be mixed together soon after being produced or emitted by the transducers <NUM> (e.g., they are mixed in the throat <NUM> of the horn <NUM>). In particular, the mixing distance D at which sound from adjacent transducers <NUM> is mixed may be reduced in comparison to the distance D shown in <FIG>.

Based on this reduced mixing distance D between sounds from adjacent transducers <NUM> entering into the same environment (e.g., see <FIG>, the throat <NUM> of the horn <NUM>) and being allowed to mix together, the aliasing frequency may be increased when using the continuously open circumferential horn <NUM>. As noted above, the aliasing frequency is the frequency at which higher frequency sounds may cause undesirable aliasing effects, based on the mixing distance D. Accordingly, since the continuously open circumferential horn <NUM> provides a higher aliasing frequency based on the reduced mixing distance D in comparison to the closed or segmented horns <NUM> shown in <FIG>, the transducers <NUM> in <FIG> and <FIG> may be driven with higher frequency sounds without the presence of aliasing effects. Further, the continuously open circumferential horn <NUM> may still provide efficiency improvements (i.e., improved gain performance) and vertical sound control similar to traditional horn designs.

In one embodiment, the continuously open circumferential horn <NUM> may be formed using components of the cabinet <NUM>. For example, as described above, the cabinet <NUM> may be formed of the two frusto conical sections 117A and 117B, which are joined together as shown in <FIG>. In particular, one of the two frusto conical sections 117A and 117B may be rotated <NUM>° in relation to the other and then joined to form a generally hourglass or hyperboloid shape for the cabinet <NUM>. The bottom of the lower section 117B may be flat so as to enable the cabinet <NUM> to stably rest on a flat surface such as a tabletop as shown in the example of <FIG>, or on a floor. This generally hourglass or hyperboloid shape has a narrow or tapered section that defines the throat <NUM> of the horn <NUM> and a wide or flared section that defines the mouth <NUM> of the horn <NUM>. Although described as being formed of separate sections 117A and 117B that are joined or otherwise coupled together, the cabinet <NUM> may be made in different ways such as two or more vertically or horizontally continuous pieces that are joined together. The continuously open circumferential horn <NUM> may have a curved surface at the corners 125A, 125B of its mouth <NUM> so that the cabinet <NUM> has a true hyperboloid shape, as depicted in <FIG>, for example.

In one embodiment, the ring of transducers <NUM> may be located around the throat <NUM> of the continuously open circumferential horn <NUM>. As shown in <FIG> and <FIG>, the transducers <NUM> may be aligned in a horizontal plane, around the throat <NUM>, such that each of the transducers <NUM> is vertically equidistant from the larger base of the upper section 117A and is vertically equidistant from the larger base of the lower section 117B of the cabinet <NUM>.

Although as shown in <FIG> and <FIG> and described above the transducers <NUM> are arranged uniformly at the throat <NUM> of the horn <NUM> with their diaphragms oriented substantially vertically, in other embodiments the transducers <NUM> may be differently arranged around or about the throat <NUM> of the horn <NUM>. For example, since the throat <NUM> of the continuously open circumferential horn <NUM> is formed at a narrowest or waist section of the cabinet <NUM>, arranging all of the transducers <NUM> along this section, with their diaphragms in a vertical orientation, may be difficult. Namely, the constricted space provided by the throat <NUM> may not allow the use of large, more powerful transducers <NUM> (unless the diameter of the throat is made larger, and the top and bottom sections 117a, 117b of the cabinet are also made larger. ) The limited space may also result in heat issues caused by poor thermal dissipation in a confined area with a high density of transducers <NUM>. To alleviate these space constraints, some or all of the transducers <NUM> (that together may form a ring) may instead be located within a hollow portion of the upper section 117A, which is above the throat <NUM> (and below a top of the upper section 117a) as shown in <FIG>. Since the horn <NUM> tapers such that the throat <NUM> is the narrowest element of the cabinet <NUM> (from a side view, as in <FIG>), any portion of the progressive widening upper section 117A above the throat <NUM> may afford more space for the placement or mounting of the transducers <NUM>, and in particular their motors which are directly behind, and attached to drive, their respective diaphragms, in comparison to mounting of the transducers <NUM> at the throat <NUM>, e.g., all oriented vertically as shown in <FIG> and <FIG>. In the example of <FIG>, which is an example not covered by the scope of the claims, but useful for understanding the invention, sound produced by the transducers <NUM> may be directed to flow into the continuously open circumferential horn <NUM> through the slots <NUM>. The slot <NUM> may be a passageway that extends into the cabinet <NUM>, from the outer surface of a side wall of the upper section 117A, and that acoustically joins the front surface of the diaphragm of each respective transducer <NUM> to the throat <NUM> (of the continuously open circumferential horn <NUM>. ) In some embodiments, one or more of the slots <NUM> may include one or more bends or curves. The bends or curves allow the transducers <NUM> to be placed or mounted in different positions and orientations within the cabinet <NUM> while still allowing for sound produced by each transducer <NUM> to reach the throat <NUM> of the continuously open circumferential horn <NUM>. In the version shown in <FIG>, the slots <NUM> are such that they enable their respective transducers <NUM> to be oriented so that their diaphragms are substantially horizontal (instead of vertical as in <FIG><FIG>thereby allowing more space for their respective motors within the upper section 117a. Since the slots <NUM> deliver sound produced by corresponding transducers <NUM> at the same point around the throat <NUM> as when the transducers <NUM> are mounted at the throat <NUM> as shown in <FIG>, the mixing distance D between adjacent transducers <NUM> may remain the same or nearly identical. Given that the mixing distance D remains small (in comparison to the horns <NUM> shown in <FIG>), the aliasing frequency for the loudspeaker array <NUM> shown in <FIG> may remain high as described above, such that high frequency sounds may be emitted by the transducers <NUM> without the presence or occurrence of aliasing effects.

Although as described above and shown in <FIG> all of the transducers <NUM> are housed entirely within the upper section 117A, in another embodiment all of the transducers <NUM> (together still forming a ring) may be similarly placed or mounted entirely within the lower section 117B. In some other examples not covered by the scope of the claims, but useful for understanding the invention, the transducers <NUM> are alternately placed within (alternating between) the top and lower sections 117A and 117B as shown in <FIG>. Within each top or bottom section 117a, 117b, there is even more space between adjacent ones of the transducers <NUM> that are within the same section 117a, 117b of the cabinet <NUM> for mounting, since the transducers <NUM> are alternately placed above and below the throat <NUM>. Similar to the loudspeaker array <NUM> shown in <FIG>, the loudspeaker array <NUM> shown in <FIG> may utilize slots <NUM> to direct sound from the transducers <NUM> to the throat <NUM> of the continuously open circumferential horn <NUM>.

As described above, the continuously open circumferential horn <NUM> reduces aliasing effects between adjacent transducers <NUM> in the loudspeaker array <NUM>. In particular, the mixing distance D between adjacent transducers <NUM> (e.g., transducers <NUM> that are directly adjacent in the ring of transducers <NUM>) may be decreased such that a corresponding aliasing frequency is increased. This aliasing frequency describes the highest frequency that may be emitted by the transducers <NUM> without generation or production of aliasing effects caused by mixing of sound between transducers <NUM>. Accordingly, by decreasing the mixing distance D, the continuously open circumferential horn <NUM> increases the range of frequencies that may be produced by the transducers <NUM> without unwanted effects.

As shown in <FIG> and <FIG> and described above, the loudspeaker array <NUM> may include a single ring of transducers <NUM> that are positioned side by side as shown. In one embodiment, each of the transducers <NUM> in the ring of transducers <NUM> may be of the same type or model, e.g., replicates. The ring of transducers <NUM> may be aligned along or in a horizontal plane such that each of the transducers <NUM> is vertically equidistant from a planar, larger base of the top frusto conical section 117A and is vertically equidistant from a planar, larger base of the bottom frusto conical section 117B of the cabinet <NUM>. Further, this horizontal plane may be perpendicular to the upright stance of the cabinet <NUM> (as it is shown in the figures). Although a single ring of transducers <NUM> aligned along a horizontal plane may provide dynamic horizontal beam control through adjustment of relative gains and phases of drive signals applied to each transducer <NUM>, vertical control of sound emitted by the loudspeaker array <NUM> may be limited. In particular, by lacking multiple stacked rings of transducers <NUM>, dynamic directional control of sound may be limited to this horizontal plane.

Since dynamic vertical control of sound produced by the single ring of transducers <NUM> may not be possible, more passive solutions may be used. For example, the continuously open circumferential horn <NUM> may be used to assist in controlling the vertical spread of sound from the ring of transducers <NUM> into the listening area <NUM>. As shown in <FIG>, the continuously open circumferential horn <NUM> may be flared to control the direction of sound along a vertical axis. The horn <NUM> may be adjusted during manufacture to accommodate for different performance requirements of the loudspeaker array <NUM>. For example, the angle of the upper and lower inner walls 123a, 123b (relative to the horizontal plane) and the corresponding size of the mouth <NUM> may be adjusted to create a larger or smaller vertical spread of sound into the listening area <NUM> (see <FIG>. ) In other embodiments, the corners 125a, 125b that connect the inner walls 123a, 123b to the outer walls 127a, 127b, respectively, and which define the entrance of the mouth <NUM>, may be curved or rounded as shown in <FIG>. This curvature may provide a more consistent frequency response in comparison to a sharp or abrupt corner <NUM> such as depicted in <FIG>.

Although the design of the horn <NUM> in <FIG> may reduce aliasing effects as described above, its sharp corners <NUM> may apply an inconsistent improvement or increase in gain across all frequencies. Instead, the sharp corners <NUM> may lead to peak improvements in gain across some frequencies while providing less or no increases in gain in other frequency ranges (e.g., particularly with low frequency content). This inconsistent response across frequencies may create undesirable changes to sound produced by the loudspeaker array <NUM>. In contrast, the curved corners <NUM> of the horn <NUM> shown in <FIG> may provide a more desirable horn design that is less likely to have reduced gain at low frequencies. In particular, in the horn <NUM> of <FIG> the sidewall 123a may gradually flare off at the corner 125a and join the vertically oriented outer wall <NUM>; similarly, the sidewall 123b flares off at the corner 125b and joins the vertically oriented outer wall 127b. A more consistent frequency response for sound produced by the transducers <NUM> using these curved corners <NUM> may be expected.

Although shown in <FIG> as being identical, the angle and shape of the inner wall 123a (along or defined by the upper section 117A) may, alternatively, be different in comparison to the angle and shape of the inner wall 123b (along or defined by the lower section 117B. ) For example, as shown in <FIG>, the inner wall 123b along the lower section 117B may be planar and perpendicular relative to the vertically oriented center upright axis <NUM>, e.g., entirely horizontal, while the inner wall 123a along the upper section 117A remains similar as in the earlier embodiments, such as <FIG>, that is not planar and sloped upward (in relation to the horizontal plane. ) Further, the corner 125b of the lower section 117B may be sharper in comparison to the corner 125a of the upper section 117A, as shown. In this embodiment, the lack of slope to the inner wall 123b and the sharply angled corner 125b (of the lower section 117B) may assist the horn <NUM> in directing sound away from a possibly reflective surface upon which the loudspeaker array <NUM> may be situated (e.g., a table or a floor). The upward slope of the inner wall 123a and curved corner 125a of the upper section 117A may direct sound produced by the transducers <NUM> towards the listener <NUM>. In other embodiments, the upper and lower sections 117A and 117B of the horn <NUM> (cabinet <NUM>) may be formed in different fashions to provide desired vertical control of sound output.

Although described above in relation to a single ring of identical transducers <NUM>, the loudspeaker array <NUM> may include additional transducers arranged along and within the cabinet <NUM>. For example, <FIG> shows a loudspeaker array <NUM> with a first set of transducers 109A used for producing, or designed to be driven by, a first set of audio frequencies (where the first set of transducers 109A may be a single ring of transducers such as the transducers <NUM> depicted in <FIG>, a second set of transducers 109B used for producing, or designed to be driven by a second set of frequencies, and a third set of transducers 109C used for producing, or designed to be driven by a third set of frequencies. In this example, there is a group of transducers 109B, 109C that are housed within the section of the cabinet <NUM> that is below the horn <NUM> and defined by the outer wall 127B, and another group of transducers 109B, 109C that are housed within the section of the cabinet <NUM> that is above the horn <NUM> and defined by the outer wall 127A. For instance, the first set of transducers 109A may be used or designed for high frequency content (e.g., <NUM>-<NUM>), the second set of transducers 109B may be used or designed for mid frequency content (e.g., <NUM>-<NUM>), and the third set of transducers 109C may be used or designed for low frequency content (e.g., <NUM>-<NUM>). These frequency ranges for driving each of the transducers 109A, 109B, and 109C may be enforced using a set of filters that may be integrated within the loudspeaker array <NUM> (not shown). Since the wavelengths for sound waves produced by the first transducers 109A are smaller than wavelengths of sound waves produced by the transducers 109B, the mixing distance D associated with these transducers 109A (see <FIG>) should be designed to be smaller than the mixing distance D associated with the transducers 109B. In particular, to prevent aliasing effects the mixing distance D for the transducers 109A should be small enough such that the small wavelengths produced by high frequency content are not smaller than the distance D. However, since the transducers 109B produce lower frequency content (i.e., mid frequency content) with larger wavelengths, the distance D for transducers 109B may be made larger, e.g. the transducers 109B do not need to be as tightly packed as the transducers 109A. Similarly, the transducers 109C may be arranged to have a larger mixing distance D than both the transducers 109A and the transducers 109B. Since the mixing distances D for the transducers 109B and the transducers 109C may be made larger without the occurrence of aliasing effects, a continuously open circumferential horn <NUM> that enables a reduction in the distance D may not be necessary for these transducers 109B and 109C. In these embodiments, a traditional horn <NUM>, such as those shown in <FIG>, may be added to one or more of the transducers 109B, 109C, if gain efficiency improvements or directional control for these rings of transducers 109B and 109C are desired.

Although the open circumferential horn <NUM> is described above as a "completely open" circumferential horn <NUM>, in an example not falling under the scope of the claims a divider <NUM> is added or placed between an adjacent pair of transducers <NUM> as shown in <FIG>. A divider <NUM> may be a flat, rigid piece or segment that extends outward from the throat <NUM> between an adjacent pair of transducers <NUM>, generally transverse to or perpendicular to the inner walls 123a, 123b, along a of the horn <NUM> (in the case where the horn <NUM> defines a circular mouth <NUM>. ) Although not shown in the drawings, the divider <NUM> may be joined to both of the inner walls 123a, 123b and may widen in the vertical direction (as it extends outward and along the inner walls 123a, 123b. ) An adjacent pair of the dividers <NUM> may be viewed as partitioning =a portion of the mouth <NUM> of the horn <NUM> for each transducer <NUM>. The length dimension of the divider <NUM>, e.g., measured along the radius (r) taken from the center of a circular mouth <NUM> which may be concentric with a circular throat <NUM> as shown in <FIG>, may be selected to trade off between the frequency where aliasing begins and the amount of directivity control that may be achieved at lower frequencies for a given amplifier power and transducer <NUM> excursion. For example, a set of the dividers <NUM> as shown in <FIG>, for all of the transducers <NUM>, may each be between <NUM> millimeters and <NUM> millimeters long between its inner end point at the throat <NUM> and its outer end point. Alternatively, the dividers <NUM> extend the entire distance from the mouth <NUM> to the throat <NUM> (of the otherwise continuously open circumferential horn <NUM>. ) The dividers <NUM> may be sized (as in <FIG>) to extend to only a fraction of the distance from the mouth <NUM> to the throat <NUM>.

Additionally, the dividers <NUM> may provide an effective "short horn" for the sound emerging from the transducers <NUM> prior to being mixed within the shared space of the circumferential horn <NUM> (that is within the boundary of mouth <NUM> depicted in <FIG>). Providing a short horn section before mixing can have the effect of smoothing out particle velocity across the exits of the short horns formed by the dividers <NUM> such that aliasing effects are reduced. For example, a set of small transducers <NUM>, wherein each adjacent pair is spaced a distance d apart from each other (e.g., a straight line that joint a center of the diaphragm of one to the center of the diaphragm of another, and noting that this may not be the mixing distance D referred to above), may have worse aliasing effects than a set of larger transducers <NUM> (wherein each adjacent pair is also spaced the same distance d apart), due to the additional empty spaces between the smaller transducers <NUM>. <FIG> shows two example velocity profiles A and B that may be produced by rings of small and large transducers. In both situations, aliasing occurs at the same frequency, but profile A (of the ring of smaller transducers) has worse aliasing effects than profile B. The short horns created by the dividers <NUM> have the effect of making the velocity profile of a set of small transducers <NUM> as illustrated by profile A look more like profile B such that aliasing effects are reduced.

Claim 1:
A loudspeaker array (<NUM>), comprising:
a cabinet (<NUM>) including a vertically oriented central axis and forming an open circumferential horn (<NUM>) including a throat (<NUM>) and a mouth (<NUM>), wherein the open circumferential horn (<NUM>) flares outward from the throat (<NUM>) to the mouth (<NUM>); and
a plurality of first transducers (109A) integrated within the cabinet (<NUM>) circumferentially around the vertically oriented central axis, wherein the plurality of first transducers (109A) include respective diaphragms having respective front surfaces arranged in a ring formation at the throat (<NUM>) and facing radially outward from the vertically oriented central axis to emit sound circumferentially into the throat (<NUM>) and through the throat (<NUM>) and the mouth (<NUM>) into a listening area, wherein no barriers are present between the first transducers (109A) in the circumferential horn (<NUM>).