System and method for sound field control with a spherical loudspeaker

Abstract

In at least one embodiment, a loudspeaker assembly is provided. The loudspeaker assembly includes a spherical enclosure and a first array of loudspeakers linearly positioned along the spherical enclosure. The assembly further includes a second array of loudspeakers linearly positioned along the spherical enclosure and a third array of loudspeakers linearly positioned along the spherical enclosure. The loudspeaker assembly further includes a common loudspeaker positioned with the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers. The common loudspeaker being configured to transmit a first audio output signal at a first frequency band into a listening environment that is higher than a frequency band of a remaining set of audio output signals provided by remaining loudspeakers that form the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers.

Description

[0001]SYSTEM AND METHOD FOR SOUND FIELD CONTROL WITH A SPHERICAL LOUDSPEAKER TECHNICAL FIELD Aspects disclosed herein generally relate to a system and method for providing sound field control with a spherical loudspeaker. These aspects and others will be discussed in more detail below. BACKGROUND Conventional box-shaped loudspeakers are designed or electronically equalized, to deliver flat and smooth frequency responses within a small listening area. The flat and smooth frequency responses may be centered around a perpendicular axis usually at tweeter height. An off-axis sound is radiated into the small listening area (or room) which may then reach a listener as reflected sound. It has been shown that for good perceived sound quality, not only the direct sound, but the indirect sound should equally exhibit a smooth and frequency-independent quality, free of resonances, peaks, or dips. Floyd E. Toole, “Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms”. AES publication, Focal Press, 3rdedition, 2017. SUMMARY In at least one embodiment, a loudspeaker assembly is provided. The loudspeaker assembly includes a spherical enclosure and a first array of loudspeakers linearly positioned along the spherical enclosure. The assembly further includes a second array of loudspeakers linearly positioned along the spherical enclosure and a third array of loudspeakers linearly positioned along the spherical enclosure. The loudspeaker assembly further includes a common loudspeaker positioned with the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers. The common loudspeaker being configured to transmit a first audio output signal at a first frequency band into a listening environment that is higher than a frequency band of a remaining set of audio output signals provided by remaining loudspeakers that form the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers. In at least one embodiment, a method is provided. The method includes positioning a first array of loudspeakers linearly along an enclosure and positioning a second array of loudspeakers linearly positioned along the enclosure. The method further includes positioning a third array of loudspeakers linearly positioned along the enclosure and positioning a common loudspeaker with the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers. The method further includes transmitting a first audio output signal by the common loudspeaker at a first frequency band into a listening environment that is higher than a frequency band of a remaining set of audio output signals provided by remaining loudspeakers that form the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers. In at least one embodiment, a loudspeaker assembly is provided. The loudspeaker assembly includes an enclosure and a first array of loudspeakers linearly positioned along the enclosure. The assembly further includes a second array of loudspeakers linearly positioned along the enclosure and a third array of loudspeakers linearly positioned along the enclosure. The loudspeaker assembly further includes a common loudspeaker positioned with the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers. The common loudspeaker being configured to transmit a first audio output signal at a first frequency band into a listening environment that is higher than a frequency band of a remaining set of audio output signals provided by remaining loudspeakers that form the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers. BRIEF DESCRIPTION OF THE DRAWINGS The embodiments of the present disclosure are pointed out with particularity in the appended claims. However, other features of the various embodiments will become more apparent and will be best understood by referring to the following detailed description in conjunction with the accompany drawings in which: FIGURE 1 depicts off-axis frequency responses of a high-quality two-way box loudspeaker; FIGURE 2 depicts off-axis frequency responses of a high-quality two-way box loudspeaker with a co-axial driver and rounded edges; FIGURE 3 depicts a first spherical loudspeaker system in accordance with one embodiment; FIGURE 4 depicts a cross-sectional view of the first spherical loudspeaker system of FIGURE 3; FIGURE 5 depicts frequency responses of high and low midrange speakers in between the arms of the first spherical loudspeaker system in accordance with one embodiment; FIGURE 6 depicts frequency responses for a tweeter of the first spherical loudspeaker system in accordance with one embodiment; FIGURE 7A depicts a method for selecting band-limiting functions in accordance with one embodiment; FIGURE 7B depicts a method for selecting beamforming filters in accordance with one embodiment. FIGURE 8 depicts various equalization filters employed for the first spherical loudspeaker system in accordance with one embodiment; FIGURE 9 depicts a first filter block employed for the first spherical loudspeaker system in accordance with one embodiment; FIGURE 10 depicts various frequency responses for combined beamforming / crossover filters, and off-axis responses in accordance with one embodiment; FIGUREs 11a and 11b depict a front view and a rear view of a second spherical loudspeaker system, respectively, in accordance with another embodiment; FIGURE 12 depicts a second filter block employed for the second spherical loudspeaker system in accordance with one embodiment; FIGURE 13 depicts various frequency responses for combined beamforming and crossover filters associated with the second spherical loudspeaker system, and resulting off-axis responses, in accordance with one embodiment; FIGURE 14 depicts a first sound projector in accordance with one embodiment; FIGURE 15 depicts a front view of the first sound projector of FIGURE 13 in accordance with one embodiment; FIGURE 16 depicts various steering angles associated with the first sound projector in accordance with one embodiment; FIGURE 17 depicts frequency responses associated with a narrow audio beam provided by the first sound projector in accordance with one embodiment; FIGURE 18 depicts frequency responses associated with a wide audio beam provided by the first sound projector in accordance with one embodiment; FIGURE 19 depicts frequency responses associated with an extra wide audio beam provided by the first sound projector in accordance with one embodiment; FIGURE 20 depicts frequency responses associated with a narrow audio beam at a first angle provided by the first sound projector in accordance with one embodiment; FIGURE 21 depicts frequency responses associated with a narrow audio beam at a second angle provided by the first sound projector in accordance with one embodiment; FIGURE 22 depicts frequency responses associated with a narrow audio beam at a third angle provided by the first sound projector in accordance with one embodiment; and FIGURE 23 depicts a second sound projector in accordance with one embodiment. DETAILED DESCRIPTION As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. Various box-shaped loudspeakers are designed or electronically equalized, to deliver flat and smooth frequency responses within a small listening area. The flat and smooth frequency responses may be centered around a perpendicular axis that is typically positioned at an overall height of a tweeter positioned in the loudspeaker. The loudspeaker may transmit an off-axis audio signal that is radiated into a small listening area (or room). Such an off-axis audio signal may reach a listener as reflected sound within the listening environment. It is known that for good perceived sound quality, not only should the direct sound, but the indirect sound should also equally exhibit a smooth and frequency-independent quality, free of resonances, peaks, or dips. FIGURE 1 depicts off-axis frequency responses of a high-quality two-way box loudspeaker. For example, FIGURE 1 illustrates measurements performed on audio outputs provided by a loudspeaker along a horizontal half-circle at 0, 30, 60, 90, and 180 degrees. The measurements that have been captured with respect to the noted angles are normalized to a frontal axis of such a loudspeaker. The loudspeaker of FIGURE 1 may be equipped with, for example, a 25-liter gross volume with sharp edges (e.g., Triangle BR03). In general, waveform 50 generally corresponds to the frequency response for the loudspeaker along a horizontal half-circle at 0 degrees. Waveform 50 is flat since the frequency responses are normalized. Waveform 60 generally corresponds to the frequency response for the loudspeaker along a horizontal half-circle at 30 degrees. Waveform 70 generally correspond to the frequency response for the loudspeaker along the horizontal half-circle at 60 degrees. Waveform 80 generally correspond to the frequency response for the loudspeaker along the horizontal half-circle at 90 degrees. Waveform 90 generally correspond to the frequency response for the loudspeaker along the horizontal half-circle at 180 degrees. FIGURE 2 depicts off-axis frequency responses of a high-quality two-way box loudspeaker with a co-axial driver and rounded edges. For example, FIGURE 2 also depicts measurements along a horizontal half-circle at 0, 30, 60, 90, and 180 degrees that are normalized to the frontal axis of the loudspeaker (e.g., see waveforms 50, 60, 70, 80, and 90, respectively). The loudspeaker used in connection with FIGURE 2 may be a 15-liter box with co-axial driver, curved baffle, and rounded edges (e.g., Kef LS50 meta). The loudspeakers noted in connection with FIGUREs 1 and 2 may be book shelve loudspeakers. The plots shown in FIGUREs 1 and 2 each reveal gross deviations from a desired flat and smooth frequency response off-axis, particularly at side and rear angles. An indicator of a good loudspeaker that features constant directivity with smooth and flat off-axis responses, is the loudspeaker’s imaging capability in a stereo panorama. Central phantom images, mostly vocals, maintain their apparent width and natural size throughout the frequency band. In addition, the vocal based signals generally do not widen at low frequencies or diffuse. U.S. Publication No.2023 / 0050161A to Horbach (the “161 publication”) discloses, inter alia, a first approach to solve the problem controlling off-axis responses (e.g., “generalized line array loudspeaker (GLA)”). Two or more long, vertical arrays of speaker drivers are placed next to each other, pointing at different room angles including 180° backwards. The ‘161 patent further discloses, inter alia, beamforming methods that were applied to loudspeaker arrays itself (i.e., vertical control), and to an ensemble (i.e., horizontal control). It can thus be seen that improved sound and stereo imaging quality were achieved over a conventional loudspeaker, at the expense of size and complexity. In the present disclosure, a simple approach may be provided that is equally effective and may be at a much lower cost in terms of transducer count and overall size when compared to conventional systems. For example, sphere-shaped loudspeakers exhibit much smoother and predictable off-axis responses when compared to cuboids or other geometric enclosure shapes. An arrangement of regular transducers such as tweeters, midranges, and woofers on a sphere as described herein is shown to produce spherically symmetric beams with full control at all angles. Beam shape and width can be specified in the form of target functions in the design process. The beam is predominantly forward-pointing, with defined attenuation behind the loudspeaker. This aspect allows adjustments of room interaction, or in technical terms, the ratio of direct to reflected sound. Another aspect as disclosed herein generally relates to sound projector. The sound projector generally includes a shallow loudspeaker with a dome-shaped spherical surface. The sound projector may steer a sound beam at any angle within its frontal hemisphere thereof. There are many use cases which involve one or more of the following: (i) distance rendering of sound objects by varying beamwidth and / or altering the ratio between direct sound and reflected sound, (ii) moving the stereo sweet spot to a desired off-axis location using a phone application as user interface, and (iii) using only one device for stereo reproduction, by generating multiple beams for center (0°), left channel (e.g. -60°), and right channel (+60°). In this case, the left and right channels are reflected from adjacent walls. An additional aspect noted in the present disclosure is the utilization of filters for the individual channels. Beam forming filters may be designed by an iterative method, such as for example, based on magnitude target functions for the beam shape. The resulting acoustic responses may be a linear phase at any point in the radiated sound field. Previous implementations may utilize a single off-axis attenuation factor that is specified for a vertical array. Various applications that may use aspects disclosed herein generally include stereo and home theater systems that employ multiple sphere speakers with or without subwoofer. Thus, in this regard, the present disclose provides superior sound and imaging quality in addition to better dialogue intelligibility. Compared with sound bars, the radiated sound field is controlled in all three dimensions, not only horizontal. In addition, aspects disclosed herein may be utilized in, for example, all-in-one stereo systems that utilize a single sound projector and for immersive sound systems that allow user interaction and user presence (e.g., augmented reality (AR) and mixed reality (MR)), by adjusting an apparent distance of individual sound objects, and arbitrary in-room positioning. Similarly, aspects disclosed herein may be used in, but not limited to, headrest stereo systems with spatial audio rendering that may be installed on a chair or in a car that utilizes miniaturized sphere (or spherical) loudspeakers. Spherical Three-Arm Array FIGURE 3 depicts a first spherical loudspeaker system 100 in accordance with one embodiment. In general, the system 100 includes a spherical shaped enclosure 102 and a plurality of loudspeaker arrays (or arms) 104a – 104c (or “104”) positioned within or on the enclosure 102. It is recognized that the number of loudspeaker arrays 104 positioned on the enclosure 102 may vary based on the desired criteria of a particular implementation. In general, each of the arrays 104a – 104c include loudspeaker 110 (e.g., a common loudspeaker 110). The loudspeaker 110 may be a tweeter (e.g., a center tweeter) that is configured to transmit audio in a frequency range (or frequency band) of 2 KHz to 20 KHz. The array 104a includes a portion of the loudspeaker 110, loudspeaker 112a, and loudspeaker 114a. The array 104b includes a portion of the loudspeaker 110, loudspeaker 112b, and loudspeaker 114b. The array 104c includes a portion of the loudspeaker 110, loudspeaker 112c, and loudspeaker 114c. In general, loudspeakers 114a, 114b, and 114c may be midrange (or woofer) loudspeakers configured to each transmit audio in a frequency range (or frequency band) of 250 Hz to 5000 KHz. The loudspeakers 114a, 114b, and 114c provide partially overlapping frequencies relative to the loudspeakers 110 and the loudspeakers 112a, 112b, and 112c., For example, see FIGURE 8, where waveform 290 corresponds to the frequency response for the loudspeaker 110, waveform 292 generally corresponds to the frequency response for the loudspeaker 112, waveform 294 generally corresponds to the frequency response for the loudspeaker 114, and waveform 296 generally corresponds to the frequency response for the loudspeaker 116). In addition, loudspeakers 112a, 112b, and 112c may also be woofer loudspeakers configured to each transmit audio in a frequency range (or frequency band) of 200 to 2000 Hz. Referring back to FIGURE 3, each of the arrays 104a, 104b, and 104c may be separated by one another at a predetermined angle while positioned on or in the spherical enclosure 102. In one example, the arrays 104a, 104b, and 104c may be separated at 120°- angles from one another. FIGURE 4 depicts a cross-sectional view of the spherical loudspeaker assembly 100. The enclosure 102 generally includes a first side 120 (e.g., front chamber), a second side 122 (e.g., a rear chamber), and a stand 124. The first side 120 is positioned opposite to the second side 122. A loudspeaker 116 is positioned on the second side 122 of the enclosure 102. The loudspeaker 116 may be a low-frequency woofer and is mounted in the rear chamber 122. The loudspeaker 116 located on the rear chamber 122 may be positioned directly opposite to the loudspeaker 110 located on the front chamber 120. The stand 124 defines a port channel 126 which is operably coupled to the loudspeaker 116. In another example, the rear chamber 122 may be sealed along with the stand 124. An overall diameter of the spherical enclosure 102 may be, for example, approximately 250 mm. It is recognized that at least one audio controller 130 (“the audio controller 130”) may be positioned within the enclosure 102 to provide audio input signals to the various loudspeaker arrays 104 and to the loudspeaker 116. The audio controller 130 may include a transceiver (not shown) for wireless receiving audio signal from an audio source 132 positioned exterior to the loudspeaker system 100. For example, the audio source 132 may be a mobile device, laptop, or any other suitable device programmed to provide audio signals to the loudspeaker assembly 100. The audio controller 130 and the audio source 132 may engage in bi-directional communication. For example, the audio controller 130 and the audio source 132 may communicate with one another via BLUETOOTH or other wireless communication standard. It is also recognized that the audio controller 130 and the audio source 132 may be hardwired coupled with one another such that the audio source 132 provides audio input signals to the audio controller 130 to playback the audio input signals via the arrays 104 into a listening environment 134. It is recognized that the audio controller 130 may include any number of digital signal processors (DSP), digital to analog (D / A) converters, and power amplifiers to process and provide the audio signals to the loudspeakers 110, 112, and 114 for transmissions into the listening environment 134. The various loudspeakers 110, 112, 114, 116 as positioned on the spherical enclosure 102 are operably (or electrically) coupled to the audio controller 130 via channels 1, 2, 3, and 4, respectively (see FIGURE 9). The loudspeaker system 100 utilizes arrays 104 with a sparse arrangement of loudspeakers 110, 112, 114, and 116 in which the arrays 104a, 104b, and 104c are separated by the predetermined angle (e.g., 120 degrees). The arrangement of the loudspeaker assembly 100 may be explained by applying a closed formula for the sound pressure field. For example, the sound pressure generated by a circular, radiating piston (e.g., a loudspeaker) on a sphere of radius a at an observation distance r and angle ϕ can be calculated as follows: ^^^^(^^^^,^^^^) = ∑∞^^^^^^^^(^^^^^^^^)^^^^=0�^^^^(^^^^−1)(^^^^^^^^^^^^ ∝) − ^^^^(^^^^+1)(^^^^^^^^^^^^ ∝)� ^^^^^′^^^ (^^^^^^^^)^^^^^^^^(^^^^^^^^^^^^^^^^) (Eq.1) ^^^^^′^^^, α angular spread (size) of the loudspeaker membrane, and k is the wave number. For convergence, n=0…40 may be selected. In general, equation 1 is used to compute the sound pressure at a distance r and observation angle φ. These aspects are illustrated in connection with Figures 5 and 6 where the sound pressure is provided over frequency. FIGURE 3 depicts various intermediate locations (1, 2, 2’, 3, 3) that are positioned on the enclosure 102. It is possible to calculate frequency responses at the intermediate locations 2->2’ and 3->3’ yields. In this regard, various curves corresponding to frequency curves may be shown in FIGURE 5. FIGURE 5 illustrates that the frequency responses are very smooth, and drop by less than 5dB at 3KHz, where the loudspeaker 110 (or center tweeter) takes over. FIGURE 5 also illustrates that a minor deviation from an ideal circular-symmetric polar response is present but nonetheless, tolerable. FIGURE 6 generally illustrates that the frequency response for the loudspeaker 110 (or center tweeter) is naturally attenuated at off-axis angles. This condition illustrates the shadowing effect of the spherical loudspeaker assembly 110. This is an effect that dominates beam forming at high frequencies. Combined Beamforming and Crossover Filter Design A classic loudspeaker design may start with choices of crossover filters to divide the frequency band into slices for the individual drivers. The loudspeaker assembly 100 as disclosed herein utilizes a different implementation with respect to filtering. For example, FIGURE 7A provides a method 200 for selecting band-limiting functions in accordance with one embodiment. In this regard, the method 200 may be considered an initial approach. In operation 202, at least one selection controller (not shown) may include an acoustic measurement device to measure four channels on axis for the loudspeaker assembly 100, thus providing four complex frequency responses ^^^^1…^^^^4. In general, the at least one selection controller may not be part of the audio controller as positioned on the loudspeaker assembly 100 and may be used separately from the loudspeaker assembly 100 to execute the various operations of the methods 200 and 222 during initial calibration and / or tuning of the loudspeaker assembly 110. It is recognized that at least one selection controller may include the acoustic measurement device may having any number of microphones and a signal generator in addition to any number of processors to measure the channels. Similarly, the at least one selection controller may include a tuning tool and / or execute algorithms in MATLAB or other simulations to predict behavior, etc. The at least one selection controller may be a PC based-system that also includes an audio interface. In operation 204, the at least one selection controller selects band-limiting functions ^^^^1…^^^^4to define the optimal operating bands for the loudspeakers 110, 112, 114, and 116 and to protect the loudspeakers 110, 112, 114, and 116. These functions are zero-phase (magnitude- only). In operation 206, a tuning tool of the at least one selection controller computes bandpass / EQ filters with the data of operation 202 using the functions Bi of operation 204 as target ^^^^^^^^_^^^^^^^^^^^^= ^^^^^^^^� ^^^^^^^^ , ^^^^ = 1 … 4. 110, 112, 114, and 116 noted in connection with the spherical loudspeaker assembly 100, the method 200 provides, for example: B1= HP1, a 6thorder Butterworth (BW) high pass (HP) with corner frequency fc=950 Hz (e.g., for the tweeter (or the loudspeaker 110)). B2 = HP2 LP1, HP2 a 6thorder BW HP with fc=350 Hz, and LP1 a 4thorder BW low pass (LP) at 3.5K (e.g., for the woofer (or the loudspeaker 114)). B3= HP3LP2, HP3a 6thorder BW HP with fc=250 Hz, and LP2a 4thorder BW low pass (LP) at 1.5K (e.g., for the woofer (or the loudspeaker 112)). B4 = LP3, a 4thorder BW LP at 200Hz for the loudspeaker 116. Note the large overlap between the bands, which is required for the following iteration to yield successful beam forming filters. Besides that, choice of frequency bands is widely arbitrary. The resulting filters (or equalizer filters) BP_EQi (or BP_EQ1 is shown as 304a, BP_EQ2 is shown as 304b, BP_EQ3 is shown as 304c, and BP_EQ4 is shown as 304d) are shown in a first filter block 300 of the controller 130 as depicted in Fig.9 for the above example. The at least one selection controller obtains the values for BP_EQi which are later stored on memory of the audio controller 130 of the loudspeaker assembly 100 for implementation and execution. FIGURE 7B depicts a method 220 for selecting beamforming filters in accordance with one embodiment. The method 200 aims to determine beam forming filters C1 (or 302a), C2 (or 302b), C3 (or 302c), and C4 (or 302d) that are utilized in the first filter block 300 of the controller 130 (see FIGURE 9). The at least one selection controller may determine the appropriate values for the beam forming filters as set forth in the method 220 and then later transmit such values to the memory of the audio controller 130 of the loudspeaker assembly 100 for implementation and execution. In operation 222, the at least one selection controller measures off-axis data in a non- echoic chamber, for example at 0°… 180° at tweeter (or loudspeaker 110) height in 30° steps. In operation 224, the at least one selection controller preconditions the data by applying gating and complex smoothing to remove remaining reflections. In this regard, the at least one selection controller includes tuning software stored in memory that is executable by one or more processors to execute the operations of the tuning software. Preconditioning generally includes smoothing of the data whereas gating eliminates remaining reflections in the measurement chamber. In operation 226, the at least one selection control also executes the tuning software to define a target function vector for the desired beam attenuation at the specified angles, for example at = [0 -4 -12 -18 -20] at angles [0306090180] °. In operation 228, the at least one selection controller provides the beam forming filters (e.g., 302a, 302b, 302c, and 302d) (see FIGURE 9) by executing a nonlinear bounded search algorithm that is stored on memory thereof. The measured, smoothed complex frequency responses can be written in matrix form as follows: ^^^^^^^^^^^^(^^^^, ^^^^), ^^^^ = 1 …^^^^, ^^^^ = 1 …^^^^. N is the FFT length, and M the number of angular measurements in an interval [0…180] °. One aspect provided herein is the design of ^^^^ beam forming filters ^^^^^^^^, r=1…P, where P is the number of driver channels (e.g., C1(or 302a), C2(or 302b), C3(or 302c), C4(or 302d)) as noted above in connection with the method 220. The following filter design iteration operates for each frequency point separately. It is possible to eliminate the frequency index for convenience and define: ^^^^(^^^^^^^^) ∶= ^^^^^^^^^^^^(^^^^, ^^^^)as the measured and normalized frequency response at discrete angles ^^^^^^^^. The acoustic frequency responses ^^^^(^^^^) of the array at angles ^^^^^^^^are given by the expression: ^^^^(^^^^) = ∑^^^^^^^^=1 ^^^^^^^^ ∙ ^^^^(^^^^^^^^) , where the unknown spectral filter values ^^^^^^^^for the beamforming filters (e.g., C1(or 302a), C2 (or 302b), C3 (or 302c), C4 (or 302d) can be obtained iteratively by minimizing the quadratic error function: ^^^^ =�∑^^^^ ^^^^(^^^^)(|^^^^(^^^^ | )2^^^^=1 ) / ^^^^ − ^^^^^^^^(^^^^) . and parameter a is an input parameter to be chosen. In this case at(k) specifies the array gain (or again): ^^^^^^^^^^^^^^^^^^^^ = 20 ∙ log (^^^^).Q is the number of angular target points. ^^^^(^^^^) is a weighting function that can be used if higher precision is required in a particular approximation point versus another (usually 0.1 < ^^^^ < 1).The variables to be optimized are ^^^^ complex filter values per frequency index ^^^^, ^^^^^^^^(^^^^), ^^^^ = 1 …^^^^ . Initially, a first frequency point in the band of interest may be obtained asfollows: ^^^^ = ^^^^1 =�^^^^1^^^^^^^^∙^^^^� where, for example, f1=100 Hz, and ^^^^^^^^ = 1 ∀ ^^^^ as a start solution. It isthen possible subsequently compute the filter values Cr for the beamforming filters 302a – 302d by incrementing the index each time until the last point ^^^^ = ^^^^^^^2^2=�^^^^^∙ ^^^^� (e.g., f2^^^ =10 KHz) isreached. Instead of real and imaginary part, a magnitude |^^^^^^^^(^^^^)| and phase arg�^^^^^^^^(^^^^)� =arctan (^^^^^^^^{^^^^^^^^(^^^^)}⁄ ^^^^^^^^{^^^^^^^^(^^^^)}) may be used for a nonlinear optimization routine as variables.This bounded, nonlinear optimization problem can be solved by the at least one selection controller that utilizes function “fmincon” of an optimization toolbox associated with MATLAB. The following bounds may be applied:^^^^^^^^^^^^^^^^ = 20 ∗ log(max(|^^^^^^^^|)),where ^^^^^^^^^^^^^^^^is the maximum allowed filter gain, and lower and upper limits for the magnitude values from one calculated frequency point to the next to be calculated point, specified by an input parameter ^^^^ |^^^^^^^^(^^^^)| ∙ (1 − ^^^^) < |^^^^^^^^(^^^^ + 1)| < |^^^^^^^^(^^^^)| ∙ (1 + ^^^^) to control smoothness of the resultingfrequency response. In general, the at least one selection controller may be implemented as a separate controller that is not part of the spherical loudspeaker assembly 100. The at least one selection controller may initially establish the filter values ^^^^^^^^for the beamforming filters (e.g., C1(or 302a), C2(or 302b), C3(or 302c), C4(or 302d) and the cutoff and / or corner frequencies for the equalizer filters 304a – 304d. FIGURE 10 depicts various frequency responses for combined beamforming / crossover filters 302a – 302d in accordance with one embodiment. As generally shown at 250, this graph illustrates combined filter responses for the respective transducers. As noted above, waveform 290 generally corresponds to the frequency response for the loudspeaker 110 (e.g., the tweeter). Waveform 292 generally corresponds to the frequency response for the loudspeaker 112 (e.g., the woofer). Waveform 294 generally corresponds to the frequency response for the loudspeaker 114 (e.g., the midrange or woofer). Waveform 296 generally corresponds to the frequency response for the loudspeaker 116 (e.g., the rear base or rear woofer). As generally shown at 252, this graph illustrates an overall performance for the first spherical loudspeaker system 100. The graphs as shown in 250 and 252 may be directly compared with the off-axis responses of the conventional loudspeakers as illustrated in connection with FIGUREs 1 and 2. The responses shown in 250 and 252 are smooth and extended. Similarly, these responses illustrate a widely frequency- independent attenuation up to 20 dB at 90° and 180°. Referring back to FIGURE 9 in which the first filter block 300 is shown in more detail. The audio controller 130 includes the first filter block 300. The audio controller 130 generally includes memory 272 and one or more processors 274 that are programmed to execute instructions stored in the memory 272 to perform the noted operations therein. As noted above, the audio controller 130 may receive an audio input signal the audio source 132. The various beamforming filters 302a – 302d may be implemented as, for example, finite impulse response (FIR) filters of having a length, for example, of 128 … 2048. In general, the beamforming filters 302a – 302d may shape the three-dimensional response of the loudspeaker assembly 100 based on a target function that specifies an amount of attenuation at various angles such as, for example, 0, 30, 60, 90, 120, 150, and 180 degrees. The equalizer filters 304a – 304d filter outputs provided by the beamforming filters 302a – 302d. As shown in FIGURE 9, the equalizer filter 304a provides a filtered audio output signal at a first frequency band to drive the loudspeaker 110 (e.g., the tweeter), the equalizer filter 304b provides a filtered audio output signal at a second frequency band to drive the loudspeakers 114a, 114b, 114c (e.g., a first woofer array), the equalizer filter 304c provides a filtered audio output signal at a third frequency band to drive the loudspeakers 112a, 112b, 112c, and the equalizer filter 304d provides a filtered audio output signal at a fixed frequency to drive the loudspeaker 116. The first frequency band may be higher than the second and third frequency bands. The equalizer filters 304a – 304d may be implemented as, for example, FIR filters. In general, it is desirable to assign band limiting to the equalizer filters 304 – 304d to define corner conditions (or corner frequencies). The equalizer filters 304a – 304d equalize the responses for each output thereof based on measurements of magnitude and phase in which a complex frequency number is provided as a result. The measurements yield an impulse response upon which a Fast Fourier Transform (FFT) operation is performed on the impulse response to obtain the complex frequency response. Then, it is possible to invert the complex frequency response by multiplying the same with the band limiting function provided by the equalizer filters 304a – 304d where it is then possible to take the inverse FFT to provide a time domain-based filter. FIGUREs 11a and 11b depict a front view and a rear view of a second spherical loudspeaker system 400, respectively, in accordance with another embodiment. In general, the system 400 includes a spherical shaped enclosure 402 and loudspeaker array (or arm) 404 positioned within or on the enclosure 402. It is recognized that the number of loudspeaker arrays 104 positioned on the enclosure 402 may vary based on the desired criteria of a particular implementation. In general, the array 404 includes a loudspeaker 410 (e.g., a common loudspeaker 410) and loudspeakers 412a – 412c. The loudspeaker 410 may be a tweeter (e.g., a center tweeter) that is configured to transmit audio in the frequency range (or frequency band) of 2 KHz to 20 KHz. In addition, the loudspeakers 412a, 412b, and 412c may be woofer loudspeakers configured to each transmit audio in a frequency range (or frequency band) of 40 to 5000 Hz. In general, each of the loudspeakers 412a, 412b, and 412c are required to provide an audio output that is up to 5000Hz to provide enough overlap as shown in FIGURE 13. Each of the loudspeakers 412a, 412b, and 412c are generally coupled to one another and operate at the same signal. The enclosure 402 generally includes a first side 420 (e.g., front chamber) and a second side 422 (e.g., a rear chamber). The first side 420 is positioned opposite to the second side 422. A loudspeaker 416 is positioned on the second side 422 of the enclosure 402. The loudspeaker 416 may be a low-frequency woofer and is mounted in the rear chamber 422. The loudspeaker 416 located on the rear chamber 422 may be positioned directly opposite to the loudspeaker 410 located on the front chamber 420. It is recognized that the system 400 may also include at least one audio controller 430 in addition to the filter bank 470. The audio controller 430 may operate in a similar manner to the audio controller 130 as described above. FIGURE 12 depicts a second filter block 500 employed for the second spherical loudspeaker system 400 in accordance with one embodiment. In general, the second filter block 500 is part of the audio controller 430. The audio controller 430 also includes memory 472 and one or more processors 474 that are programmed to execute instructions stored in the memory 472 to perform the noted operations therein. As noted above, the audio controller 430 may receive an audio input signal from the audio source 132. FIGURE 12 also includes the beamforming filters 302a – 302c and the equalizer filters 304a – 304c. FIGURE 13 depicts various frequency responses for combined beamforming and equalizer filters associated with the second spherical loudspeaker system 400 in accordance with one embodiment. In general, FIGURE 13 depicts the results for the off-axis responses. The frequency responses are within preferred margins and provide an improvement over those provided by a conventional loudspeaker. In general, the overall quality of the second spherical loudspeaker assembly 400 may be surprisingly close to the quality provided by the first spherical loudspeaker assembly 100 as shown in reference to FIGURE 10. FIGUREs 14 – 16 generally illustrate views for a first sound projector assembly 600 (or first sound projector 600) in accordance with one embodiment. The first sound projector assembly 600 may transmit sound along one or multiple directions. For example, the first sound projector assembly 600 may be used to render multichannel audio or redirect sound images to an off axis “sweet spot”. In general, the system 600 includes a dome (or disk) shaped enclosure 602 and a plurality of loudspeaker arrays (or arms) 604a – 604c (or “604”) positioned within or on the enclosure 602. It is recognized that the number of loudspeaker arrays 604 positioned on the enclosure 602 may vary based on the desired criteria of a particular implementation. In general, each of the arrays 604a – 604c include loudspeaker 610 (e.g., a common loudspeaker 610). The loudspeaker 610 may be a tweeter (e.g., a center tweeter) that is configured to transmit audio in a frequency range (or frequency band) of 2 KHz to 20 KHz. The array 604a includes a portion of the loudspeaker 610, loudspeaker 611a, loudspeaker 612a, and loudspeaker 614a. The array 604b includes a portion of the loudspeaker 610, loudspeaker 611b, loudspeaker 612b, and loudspeaker 614b. The array 604c includes a portion of the loudspeaker 610, loudspeaker 611c, loudspeaker 612c, and loudspeaker 614c. In general, loudspeakers 614a, 614b, and 614c may be midrange (or woofer) loudspeakers configured to each transmit audio in a frequency range (or frequency band) of 250 Hz to 5000 KHz. In addition, loudspeakers 612a, 612b, and 612c may be woofer loudspeakers configured to each transmit audio in a frequency range (frequency band) of 200 to 2000 Hz. The loudspeakers 611a, 611b, 611c may be tweeter loudspeakers (or frequency band) configured to each transmit audio in a frequency range of 1000 to 10000 Hz. Each of the arrays 604a, 604b, and 604c may be separated by one another at a predetermined angle while positioned on or in the dome-shaped enclosure 102. In one example, the arrays 604a, 604b, and 604c may be separated at 120°- angles from one another. The first sound projector 600 may be considered, for example, as a five-way “three-arm” driver layout (e.g., four-way loudspeaker assembly with an optional, external woofer). The enclosure 602 may be a disk of, for example, approximately 600 mm diameter and 80 mm depth, with a dome-shaped spherical surface. The first sound projector 600 may provide horizontal audio beams via the arrays 604a, 604b, 604c (or the loudspeaker 610, the loudspeaker 611a – 611c, the loudspeakers 612a – 612c, and the loudspeaker 614a - 614c). In general, each of the loudspeakers the loudspeaker 610, the loudspeaker 611a – 611c, the loudspeakers 612a – 612c, and the loudspeaker 614a - 614c may require a separate beam forming filter 302 and equalizer filter 304 to provide or allow beam steering at arbitrary angles. In other words, the first sound projector 600 requires a beam forming filter 302 and an equalizer filter 304 for each loudspeaker that is illustrated in FIGUREs 14 – 16. It is possible to reduce the number of beam forming filters 302 and equalizer filters 304 while providing only horizontal steering control. For example, in this arrangement, it is possible to provide a beam forming filter 302 and an equalizer filter 304 for the loudspeakers 611a and 611c. Similarly, it is possible to provide a beam forming filter 302 and an equalizer filter 304 for the loudspeakers 614a and 614c. Finally, it is possible to provide a beam forming filter 302 and an equalizer filter 304 for the loudspeakers 612a and 612c. The first sound projector 600 provides a target function that specifies beam direction and – shape, for example at = [-15 -20 -8 -200 -20 -8] at angles [030 -3060 -6090 -90] ° for a beam pointing at -60° (left). Since the first sound projector 600 is asymmetric in the horizontal plane (e.g., see FIGURE 16 where only the array 604b is positioned on the horizontal plane), the beam forming filters 302 may be arranged separately for left and right. Fig. 15 depicts that up- and downwards pointing beams at + / -60° (plane 2-6) and + / -120° (plane 3-5) are included by re- assigning the transducer or the loudspeaker channels. Any beams in between may be obtained by interpolation methods. Fig.17-19 depict results for frontal (0°) beams with narrow / wide and extra-wide target functions, respectively in connection with the first sound projector 600. As shown, the frequency responses are smoother and more accurate than conventional speaker designs. Fig. 20- - 22 illustrate the performance of some off-axis beams as examples (e.g., narrow, + / -30°, and +60°). In general, by collecting measurement data in finer angular steps, this enables the transmission of audio beams at any directions in between. FIGURE 23 depicts a second sound projector assembly 700 (or “second sound projector 700”) in accordance with one embodiment. In general, the system 700 includes a generally rectangular shaped enclosure 702 and a plurality of loudspeaker arrays (or arms) 704a – 704c (or “704”) positioned within or on the enclosure 702. It is recognized that the number of loudspeaker arrays 704 positioned on the enclosure 702 may vary based on the desired criteria of a particular implementation. In general, each of the arrays 704a – 704c include loudspeaker 710 (e.g., a common loudspeaker 710). The loudspeaker 710 may be a tweeter (e.g., a center tweeter) that is configured to transmit audio in a frequency range (or frequency band) of 2 KHz to 20 KHz. The array 704a includes a portion of the loudspeaker 710, loudspeaker 711a, loudspeaker 712a, and loudspeaker 714a. The array 704b includes a portion of the loudspeaker 710, loudspeaker 711b, loudspeaker 712b, and loudspeaker 714b. The array 704c includes a portion of the loudspeaker 710, loudspeaker 711c, loudspeaker 712c, and loudspeaker 714c. In general, loudspeakers 714a, 714b, and 714c may be midrange (or woofer) loudspeakers configured to each transmit audio in a frequency range (or frequency band) of 250 Hz to 5 KHz. In addition, loudspeakers 712a, 712b, and 712c may be woofer loudspeakers configured to each transmit audio in a frequency range of 200 to 2000 Hz. The loudspeakers 711a, 711b, 711c may also be tweeter loudspeakers configured to each transmit audio in a frequency range (or frequency band) of 1000 to 10000 Hz. The second sound projector 700 also includes loudspeakers 716a and 716b. The loudspeakers 716a and 716b may also be woofer loudspeakers each transmitting audio in a frequency range (or frequency band) of 40 to 200 Hz. In general, the arrays 804a, 804b, 804c be arranged in the form of a Y-shaped three-arm configuration. The array 704a and the array 704c may be separated by an angle of, for example, 135 degrees. Similarly, the array 704b and the array 704c may be separated by an angle of, for example, 135 degrees. The array 704a and the array 704b may be separated by an angle of + / - 90 degrees. It recognized that the controllers as disclosed herein may include various microprocessors, integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof), and software which co-act with one another to perform operation(s) disclosed herein. In addition, such controllers as disclosed utilizes one or more microprocessors to execute a computer- program that is embodied in a non-transitory computer readable medium that is programmed to perform any number of the functions as disclosed. Further, the controller(s) as provided herein includes a housing and the various number of microprocessors, integrated circuits, and memory devices ((e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM)) positioned within the housing. The controller(s) as disclosed also include hardware-based inputs and outputs for receiving and transmitting data, respectively from and to other hardware-based devices as discussed herein. While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.

Claims

WHAT IS CLAIMED IS:

1. A loudspeaker assembly comprising: a spherical enclosure; a first array of loudspeakers linearly positioned along the spherical enclosure; a second array of loudspeakers linearly positioned along the spherical enclosure; a third array of loudspeakers linearly positioned along the spherical enclosure; and a common loudspeaker positioned with the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers, the common loudspeaker being configured to transmit a first audio output signal at a first frequency band into a listening environment that is higher than a frequency band of a remaining set of audio output signals provided by remaining loudspeakers that form the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers.

2. The loudspeaker assembly of claim 1, wherein the first array of loudspeakers and the second array of loudspeakers are separated by one another by a first predetermined angle, wherein the first array of loudspeakers and the third array of loudspeakers are separated by one another by a second predetermined angle, and wherein the first predetermined angle is equal to the second predetermined angle.

3. The loudspeaker assembly of claim 1, wherein the common loudspeaker is positioned on a center location of the spherical enclosure.

4. The loudspeaker assembly of claim 1, wherein the loudspeaker assembly includes an audio controller positioned thereon and being programmed to (i) receive an audio input signal from an audio source, and (ii) provide the audio input signal to the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers to transmit the first audio output signal and the remaining set of audio output signals.

5. The loudspeaker assembly of claim 1 further comprising a plurality of beamforming filters, each of the plurality of beamforming filters being programmed to: receive an audio input signal; and shape a three-dimensional response for at least one of the first audio output signal and any one of the remaining set of audio output signals provided by at least one of the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers in response to the audio input signal.

6. The loudspeaker assembly of claim 5 further comprising a plurality of equalizer filters, each of the plurality of equalizer filters being programmed to: receive an output signal from a corresponding beamforming filter; and filter the output signal at corresponding corner frequencies to provide one of the first audio output signal and the any one of the remaining set of audio output signals.

7. The loudspeaker assembly of claim 1, wherein the spherical enclosure includes a first side and a second side, and wherein the common loudspeaker is positioned on the first side.

8. The loudspeaker assembly of claim 7 further comprising a first loudspeaker positioned on the second side and directly opposite to the common loudspeaker.

9. The loudspeaker assembly of claim 8, wherein the first frequency band at which the common loudspeaker transmits the first audio output signal is higher than a second frequency band at which the first loudspeaker transmits a second audio output signal.

10. A method comprising: linearly positioning a first array of loudspeakers linearly along an enclosure; linearly positioning a second array of loudspeakers linearly positioned along the enclosure;linearly positioning a third array of loudspeakers linearly positioned along the enclosure; and positioning a common loudspeaker with the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers; and transmitting a first audio output signal by the common loudspeaker at a first frequency band into a listening environment that is higher than a frequency band of a remaining set of audio output signals provided by remaining loudspeakers that form the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers.

11. The method of claim 10, wherein the first array of loudspeakers and the second array of loudspeakers are separated by one another by a first predetermined angle, wherein the first array of loudspeakers and the third array of loudspeakers are separated by one another by a second predetermined angle, and wherein the first predetermined angle is equal to the second predetermined angle.

12. The method of claim 10, wherein the common loudspeaker is positioned on a center location of the enclosure.

13. The method of claim 10 further comprising a plurality of beamforming filters, each of the plurality of beamforming filters being programmed to: receiving, at a plurality of beamforming filters, an audio input signal; and shaping a three-dimensional response for at least one of the first audio output signal and any one of the remaining set of audio output signals via the plurality of beamforming filter and provided by at least one of the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers in response to the audio input signal.

14. The method of claim 13 further comprising receiving an output signal, at one of a plurality of equalizer filters, from a corresponding beamforming filter; andfiltering the output signal at corresponding corner frequencies to provide one of the first audio output signal and the any one of the remaining set of audio output signals.

15. The method of claim 10, wherein the enclosure includes a first side and a second side, and wherein the common loudspeaker is positioned on the first side.

16. The method of claim 15 further comprising a first loudspeaker positioned on the second side and directly opposite to the common loudspeaker.

17. The method of claim 16, wherein the first frequency band at which the common loudspeaker transmits the first audio output signal is greater than a second frequency band at which the first loudspeaker transmits a second audio output signal.

18. The method of claim 10, wherein the enclosure is one of a sphere, a disc, or is generally rectangular.

19. A loudspeaker assembly comprising: an enclosure; a first array of loudspeakers linearly positioned along the enclosure; a second array of loudspeakers linearly positioned along the enclosure; a third array of loudspeakers linearly positioned along the enclosure; and a common loudspeaker positioned with the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers configured to transmit a first audio output signal at a first frequency band into a listening environment that is greater than a frequency band of a remaining set of audio output signals provided by remaining loudspeakers that form the first array of loudspeakers, the second array of loudspeakers, and the third array of loudspeakers.

20. The loudspeaker assembly of claim 19, wherein the enclosure is one of a sphere, a disc, or is generally rectangular.

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