Head related transfer function equalization and transducer aiming of stereo dimensional array (SDA) loudspeakers

Abstract

An enhanced Stereo Dimensional Array loudspeaker system 250 preferably including a mirror image pair of loudspeaker enclosures 280L, 280R configurable by a user or installer as a left-channel loudspeaker and a right channel loudspeaker each having a driver array aiming configuration with first and second angled baffle facets carrying main and effects drivers on separate facets and a Head Shadow filter signal processing system and method for driving the main and effects drivers to achieve a psycho-acoustically expanded image breadth by Head Shadow filter compensated inter-aural crosstalk cancellation.

Claims

1. A sound reproduction system having a left channel output and a right channel output, apparatus for reproducing sound having an expanded and stable acoustic field and acoustic image, comprising: (a) a first loudspeaker system enclosure or tower disposed in a first loudspeaker system enclosure location along a speaker axis spaced from a listening location, the listening location being a place in a space for accommodating a listener's head having a right ear location and a left ear location spaced along an ear axis, said first loudspeaker system enclosure having a multi-faceted or multi-planar front baffle surface comprising a first front baffle surface or facet which is angled rearwardly to recede at a selected angle in the range of 10 to 30 degrees from a vertical plane aligned with the speaker axis on the left side, and a second front baffle surface or facet which is angled rearwardly to recede at a selected angle in the range of 10 to 30 degrees from a vertical plane aligned with the speaker axis on the right side, where the first and second baffle surfaces define loudspeaker driver supporting and aiming structures aligned along substantially vertical planes; (b) wherein the first baffle surface or facet carries and aims a first midrange driver having a midrange driver acoustic center and a first tweeter driver having a tweeter driver acoustic center which is substantially vertically aligned with said first midrange driver acoustic center; (c) wherein the second baffle facet carries and aims a second midrange driver and a second tweeter driver, wherein said second midrange driver has its acoustic center spaced laterally from said first midrange driver by a selected distance DW in the range of 6 to 6.5 inches, and wherein said second tweeter driver has a tweeter driver acoustic center which is substantially vertically aligned with said second midrange driver acoustic center and spaced laterally from said first tweeter driver by said selected distance DW in the range of 6 to 6.5 inches; (d) said first loudspeaker system enclosure or tower having external terminals for Main (+) connection and main () connection signal inputs, and a Stereo Dimensional Array signal input terminal and a Stereo Dimensional Array signal output terminal; and (e) said first enclosure signal processing circuitry including a crossover with input terminals for said Main (+) connection, said main () connection, said Stereo Dimensional Array signal input terminal and said Stereo Dimensional Array signal output terminal, wherein said crossover is configured to generate (i) a main tweeter signal (ii) a main midrange signal, (iii) a Head Shadow Filter compensated Stereo Dimensional Array dimensional effect tweeter signal, and a Head Shadow Filter compensated Stereo Dimensional Array dimensional effect midrange signal; and (f) wherein said signal processing circuitry communicates said Stereo Dimensional Array dimensional effect tweeter signal and said Stereo Dimensional Array dimensional effect midrange signal to a Stereo Dimensional Array dimensional effect radiating array including said first tweeter driver and said first midrange driver which are aimed by said first front baffle surface or facet away from the listening position.

2. The sound reproduction system of claim 1, wherein said signal processing circuitry communicates said main tweeter signal and said main midrange signal to a main radiating array comprising said second tweeter driver and said second midrange driver which are aimed by said second front baffle surface or facet toward the listening position.

3. The sound reproduction system of claim 2, further including: (g) a second loudspeaker system enclosure or tower disposed in a second loudspeaker system location which is spaced from and aligned along a speaker axis with said first loudspeaker system location and spaced from said listening location, said second loudspeaker system enclosure having a multi-faceted or multi-planar front baffle surface comprising a first front baffle surface or facet which is angled rearwardly to recede at a selected angle in the range of 10 to 30 degrees from a vertical plane aligned with the speaker axis on the left side, and a second front baffle surface or facet which is angled rearwardly to recede at a selected angle in the range of 10 to 30 degrees from a vertical plane aligned with the speaker axis on the right side, where the first and second baffle surfaces define loudspeaker driver supporting and aiming structures aligned along substantially vertical planes; (h) wherein the second enclosure first baffle surface or facet carries and aims a first midrange driver having a midrange driver acoustic center and a first tweeter driver having a tweeter driver acoustic center which is preferably substantially vertically aligned with said first midrange driver acoustic center; (i) wherein the second enclosure second baffle surface or facet carries and aims a second midrange driver and a second tweeter driver, wherein said second midrange driver has its acoustic center spaced laterally from said first midrange driver by a selected distance DW in the range of 6 to 6.5 inches, and wherein said second tweeter driver has a tweeter driver acoustic center which is preferably substantially vertically aligned with said second midrange driver acoustic center and spaced laterally from said first tweeter driver by said selected distance DW in the range of 6 to 6.5 inches; (j) said second loudspeaker system enclosure or tower having external terminals for Main (+) connection and main () connection; signal inputs, a Stereo Dimensional Array signal input terminal and a Stereo Dimensional Array signal output terminal; (k) second enclosure signal processing circuitry including a second enclosure crossover with input terminals for said Main (+) connection, said main () connection, said Stereo Dimensional Array signal input terminal and said Stereo Dimensional Array signal output terminal, wherein said second enclosure crossover is configured to generate (i) a second main tweeter signal (ii) a second main midrange signal, (iii) a second Head Shadow Filter compensated Stereo Dimensional Array dimensional effect tweeter signal, and a second Head Shadow Filter compensated Stereo Dimensional Array dimensional effect midrange signal; and (l) wherein said second enclosure signal processing circuitry communicates said second Stereo Dimensional Array dimensional effect tweeter signal and said second Stereo Dimensional Array dimensional effect midrange signal to a second Stereo Dimensional Array dimensional effect radiating array including said second enclosure second tweeter driver and said second enclosure second midrange driver which are aimed by said second enclosure second front baffle away from the listening position.

4. The sound reproduction system of claim 3, wherein said second enclosure signal processing circuitry communicates said second main tweeter signal and said second main midrange signal to a second main radiating array comprising said second enclosure first tweeter driver and said second enclosure first midrange driver which are aimed by said second enclosure first front baffle surface or facet toward the listening position.

5. The sound reproduction system of claim 1, further including: a user or installer selectable signal connection configurable to make said first loudspeaker system enclosure function as either a left-side enhanced SDA speaker system or a right-side enhanced SDA speaker system, wherein said user or installer selectable signal connection comprises a single-throw multi-pole switch or a tether connection system.

6. In a stereophonic sound reproduction system having a left channel output and a right channel output, an improved apparatus for reproducing sound having a realistic ambient field and a larger, more stable acoustic image, comprising: a right main speaker and a left main speaker disposed respectively at right and left main speaker locations spaced apart along a speaker axis, with a listening location located generally along a listening axis perpendicular to the speaker axis and intersecting the speaker axis at a point midway between the right and left main speaker locations; means coupling the right and left channel outputs, respectively, to said right and left main speakers; a right sub-speaker positioned on the speaker axis at a right sub-speaker location spaced a predetermined distance from the right main speaker location and further from the listening axis than said right main speaker location; a left sub-speaker positioned on the speaker axis at a left sub-speaker location spaced a predetermined distance from the right main speaker location and further from the listening axis than said left main speaker location; means connected to the right and left channel outputs for developing a left channel minus right channel signal and a right channel minus left channel signal; means coupling said left channel minus right channel signal to said left sub-speaker and said right channel minus left channel signal to said right sub-speaker; whereby sound reproduced by said apparatus as perceived by a listener located generally along the listening axis has a realistic acoustic field and enhanced acoustic image; the improvement comprising: said left main speaker is aimed toward the listening position at a selected main driver aiming angle from a line parallel to said listening axis, said selected main driver aiming angle being between 10 degrees and 30 degrees and wherein said left sub speaker is aimed away from the listening position at a selected sub driver aiming angle from a line parallel to said listening axis which is substantially equal in magnitude to said main driver aiming angle.

7. The improved apparatus for reproducing sound having a realistic ambient field and a larger, more stable acoustic image of claim 6, wherein said left main speaker is aimed toward the listening position at a selected main driver aiming angle from a line parallel to said listening axis, said selected main driver aiming angle being 15 degrees and wherein said left sub speaker is aimed away from the listening position at a selected sub driver aiming angle from a line parallel to said listening axis which is 15 degrees away from the listener's position and said line parallel to said listening axis.

8. In a stereophonic sound reproduction system having a left channel output and a right channel output, an improved apparatus for reproducing sound having a realistic ambient field and a larger, more stable acoustic image, comprising: a right main speaker and a left main speaker disposed respectively at right and left main speaker locations spaced apart along a speaker axis, with a listening location located generally along a listening axis perpendicular to the speaker axis and intersecting the speaker axis at a point midway between the right and left main speaker locations; means coupling the right and left channel outputs, respectively, to said right and left main speakers; a right sub-speaker positioned on the speaker axis at a right sub-speaker location spaced a predetermined distance from the right main speaker location and further from the listening axis than said right main speaker location; a left sub-speaker positioned on the speaker axis at a left sub-speaker location spaced a predetermined distance from the right main speaker location and further from the listening axis than said left main speaker location; means connected to the right and left channel outputs for developing a left channel minus right channel signal and a right channel minus left channel signal; means coupling said left channel minus right channel signal to said left sub-speaker and said right channel minus left channel signal to said right sub-speaker; whereby sound reproduced by said apparatus as perceived by a listener located generally along the listening axis has a realistic acoustic field and enhanced acoustic image; the improvement comprising: said left main speaker is a left main midrange driver which is vertically aligned with a left main tweeter to provide a left main driver array aimed toward the listening position at a selected left main driver array aiming angle from a line parallel to said listening axis, said selected left main driver array aiming angle being between 10 degrees and 30 degrees and wherein said left sub speaker is a left sub midrange driver which is vertically aligned with a left sub tweeter to provide a left sub driver array aimed away from the listening position at a selected left sub driver array aiming angle from a line parallel to said listening axis which is substantially equal in magnitude to said main driver aiming angle.

9. The improved apparatus for reproducing sound having a realistic ambient field and a larger, more stable acoustic image of claim 8, wherein said left main driver array is aimed toward the listening position at a selected main driver aiming angle from a line parallel to said listening axis, said selected main driver aiming angle being 15 degrees and wherein said left sub driver array is aimed away from the listening position at a selected sub driver aiming angle from a line parallel to said listening axis which is 15 degrees away from the listener's position and said line parallel to said listening axis.

10. In a stereophonic sound reproduction system having a left channel output and a right channel output, an improved apparatus for reproducing sound having a realistic ambient field and a larger, more stable acoustic image, comprising: a right main speaker and a left main speaker disposed respectively at right and left main speaker locations spaced apart along a speaker axis, with a listening location located generally along a listening axis perpendicular to the speaker axis and intersecting the speaker axis at a point midway between the right and left main speaker locations; means coupling the right and left channel outputs, respectively, to said right and left main speakers; a right sub-speaker positioned on the speaker axis at a right sub-speaker location spaced a predetermined distance from the right main speaker location and further from the listening axis than said right main speaker location; a left sub-speaker positioned on the speaker axis at a left sub-speaker location spaced a predetermined distance from the right main speaker location and further from the listening axis than said left main speaker location; means connected to the right and left channel outputs for developing a left channel minus right channel signal and a right channel minus left channel signal; means coupling said left channel minus right channel signal to said left sub-speaker and said right channel minus left channel signal to said right sub-speaker; whereby sound reproduced by said apparatus as perceived by a listener located generally along the listening axis has a realistic acoustic field and enhanced acoustic image; the improvement comprising: said means connected to the right and left channel outputs for developing a left channel minus right channel signal and a right channel minus left channel signal including signal processing circuitry including a crossover with input terminals for a Main (+) connection, a main () connection, a Stereo Dimensional Array In connection and a Stereo Dimensional Array Out connection, wherein said crossover is configured to generate (i) a main tweeter signal (ii) a main midrange signal, (iii) a Head Shadow Filter compensated Stereo Dimensional Array dimensional effect tweeter signal, and a Head Shadow Filter compensated Stereo Dimensional Array dimensional effect midrange signal, and wherein said left sub speaker comprises an array with a sub tweeter driver which is spaced from and vertically aligned with a sub midrange driver, wherein said Head Shadow Filter compensated Stereo Dimensional Array dimensional effect tweeter signal is communicated with said sub tweeter driver.

11. The improved apparatus for reproducing sound having a realistic ambient field and a larger, more stable acoustic image of claim 10, wherein said left main speaker includes a left main driver array which is aimed toward the listening position at a selected main driver aiming angle from a line parallel to said listening axis, said selected main driver aiming angle in the range of 10 to 30 degrees and wherein said left sub driver array is aimed away from the listening position at a selected sub driver aiming angle from a line parallel to said listening axis which is in the range of 10 to 30 degrees away from the listener's position and said line parallel to said listening axis.

12. The improved apparatus for reproducing sound having a realistic ambient field and a larger, more stable acoustic image of claim 10, wherein said Head Shadow Filter comprises an inductance in parallel with a resistance to provide a shelf filter.

13. An improved method for reproducing sound from a nonbinaural recorded stereophonic source having a left channel output and a right channel output in which the reproduced sound has an expanded acoustic image comprising the steps of: disposing a right main speaker and a left main speaker at right and left main speaker locations equidistantly spaced from a listening location, the listening location being a place in space for accommodating a listener's head facing the main speakers and having a right ear location and a left ear location along an ear axis, with the right and left ear locations separated along the ear axis by a maximum interaural sound distance of tmax, and the listening location being defined as the point on the ear axis equidistant to the right and left ears, the listening location being spaced from the main speakers and defining a listening angle with respect thereto to result in an interaural time delay t of the right and left ear locations along the listening angle to the left and right main speakers; disposing at least one right sub-speaker and at least one left sub-speaker at right and left sub-speaker locations equidistantly spaced from the listening location; selecting the right and left sub-speaker locations such that the inter-speaker delay of the right sub-speaker over the right main speaker with respect to the right ear location and the inter-speaker delay of the left sub-speaker over the left main speaker with respect to the left ear location are each approximately the same as the interaural time delay t; coupling the right and left channel outputs to the right and left main speakers, respectively; deriving from the right and left channel outputs an inverted right channel signal and an inverted left channel signal; and coupling the inverted right channel signal to the at least one left sub-speaker and coupling the inverted left channel signal to the at least one right sub-speaker; the improvement comprising: deriving a head shadow compensated inverted right channel signal and a head shadow compensated inverted left channel signal and coupling the head shadow compensated inverted right channel signal to the at least one left sub-speaker and coupling the head shadow compensated inverted left channel signal to the at least one right sub-speaker.

14. The improved method in accordance with claim 13 wherein the main speaker locations and sub-speaker locations are selected to be on non-parallel baffle segments aiming at least one right sub-speaker away from a speaker axis which is parallel to the ear axis.

15. The improved method in accordance with claim 13 including the step of high pass filtering the inverted right and left channel signals prior to applying them to the at least one left and at least one right sub-speakers, respectively.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1A is a diagram illustrating Mathew Polk's original SDA loudspeaker system and method, with a stereo pair of main left and right channel speakers (LMS, RMS) each including a corresponding sub speaker (LSS, RSS), where all four loudspeaker drivers are aligned along a speaker axis in front of a listening location, in accordance with the prior art.

(2) FIG. 1B illustrates Polk Audio's original SDA1 loudspeaker system and setup method, with a pair of loudspeaker enclosures including the main left and right channel speakers (LMS, RMS) each including a corresponding sub or SDA effects speaker (LSS, RSS), where all four loudspeaker drivers are aligned along a planar front baffle surface aligned on the speaker axis in front of a listening location, in accordance with the prior art.

(3) FIGS. 1C and 1D illustrate the setup method for Polk Audio's original SDA1 loudspeaker system, in accordance with the prior art.

(4) FIG. 2A is a spectral plot illustrating plots received at the listener's left ear, right ear and the acoustic sum, for an SDA effect generating speaker which does not include a head shadow compensating filter in the speaker's crossover.

(5) FIGS. 2B and 2C are diagram illustrating the new approach for generating a head shadow filter enhanced SDA effect for a listener, in accordance with the structure and method of the present invention.

(6) FIG. 3 illustrates an SPL v. frequency plot for an exemplary HRTF curve (or head shadow) target response curve developed as part of the present invention for a crosstalk cancelling (or dimensional SDA effect) loudspeaker, in accordance with the structure and method of the present invention.

(7) FIG. 4 illustrates an SPL v. frequency plot for a prototype crosstalk cancelling driver array or SDA effect section of the loudspeaker, in accordance with the structure and method of the present invention.

(8) FIG. 5. illustrates a crossover circuit schematic for an initial prototype wherein the rightmost section illustrates connections for the crosstalk cancelling or dimensional SDA effect speakers and where R6 and L6 define a shelf filter section which comprises the head shadow mimicking portion, in accordance with the structure and method of the present invention.

(9) FIGS. 6A and 6B illustrate early prototypes for a preferred embodiment of the user or installer configurable, single SKU, multi-faceted or multi-baffle SDA loudspeaker system, in accordance with the structure and method of the present invention.

(10) FIG. 7 is a diagram and schematic which, taken together, illustrate how the user or installer configurable multi-faceted or multi-baffle SDA loudspeaker system of FIGS. 2-6B may be set up for use as either a left main stereo speaker or a right main stereo speaker, in accordance with the structure and method of the present invention.

(11) FIG. 8A illustrates another preferred embodiment of the system of the present invention including left and right multi-faceted or multi-baffle SDA loudspeaker system enclosures, in accordance with the structure and method of the present invention.

(12) FIG. 8B is a diagram illustrating the new SDA loudspeaker system and method, with a stereo pair of left and right channel loudspeaker system enclosures, where both loudspeaker system enclosures are aligned along the speaker axis in front of a listening location and each loudspeaker system enclosure faces forward and in so doing, orients one baffle surface toward the listener and another baffle surface laterally outside of and away from the listener

(13) FIGS. 9A-9E, are several views of the new SDA loudspeaker system and method, in accordance with the present invention.

(14) FIG. 10 illustrates a crossover circuit schematic for another embodiment of the new SDA loudspeaker system and method wherein the middle section illustrates connections for the crosstalk cancelling or dimensional SDA effect signals for the SDA tweeter and SDA midrange speakers including a shelf filter section which comprises the head shadow mimicking portion, in accordance with the structure and method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(15) Turning now to FIGS. 2A-10, the present invention comprises an enhanced or improved SDA main stereo pair loudspeaker system 250 including a left tower enclosure 280L and a right tower enclosure 280R which overcomes the issues encountered with the original SDA system (e.g., 50).

(16) FIG. 2A illustrates part of the problem with the SDA systems described above. In this development effort, applicants recognized that, as shown in FIG. 2A, the SDA effect was created with a band-limited interaural crosstalk cancelling inverted signal from each sub speaker which was typically not effective for crosstalk at frequencies above about 2 Khz., so this compromise became a focus of the development effort. An improvement in SDA effect bandwidth was sought to generate an enhanced crosstalk cancelling signal which is more effective in cancelling crosstalk at frequencies in the range of 2 KHz to about 5 KHz. FIG. 2A is a diagram which illustrates applicant's early prototype design considerations for generating an enhanced SDA effect for a listener. The principal differences between the system and method of the present invention (now referred to as the Challenger SDA system 250) and the SDA systems of the prior art (e.g., 50) are (a) a new implementation of a Head-Shadow filter, optimized for use with (b) first and second angled or divergently aimed baffles carrying a main tweeter/midrange driver array on a first baffle beside a dimensional or SDA cancellation effect tweeter/midrange driver array on a second baffle, where each tower enclosure has the paired angled baffles aiming at selected angles from a reference plane projecting in parallel to the listening axis and perpendicularly to the speaker axis (best seen in FIG. 8B).

(17) FIG. 4 illustrates an SPL v. frequency plot for an improved Headshadow compensating crosstalk cancelling section of the loudspeaker, in accordance with the structure and method of the present invention. The new SDA loudspeaker enclosure configuration includes first and second angled baffles segments or facets (e.g., 192, 194) and the SDA baffle midrange driver (e.g., in the prototype illustrated in FIG. 6B) is a 4 midrange while the tweeter is a 1 ring radiator tweeter. The transducers must have the necessary bandwidth to create the Head Shadow compensating effect as described below. Alternatively, the selected transducers for the Main or SDA baffles could be single full range transducers. FIG. 5. illustrates a crossover schematic for an initial prototype crossover 140 where the rightmost section illustrates connections for the crosstalk cancelling speakers and R6 and L6 define a Shelf filter section which comprises the head shadow compensating (or mimicking) portion, in accordance with the structure and method of the present invention. The shelf filter section shown in FIG. 5 is better suited for use in this system than a Low Pass filter section because it can render the Head shadow compensating filter response shape more effectively (in comparison, a similar Low Pass Filter would roll off high frequencies excessively and change the tonal balance adversely).

(18) An Improved SDA system (e.g., 250) includes a matched pair of tower-shaped loudspeaker enclosures, 280 with a front baffle 290 having a first angled upper segment or facet 292 and a second diverging angled upper segment or facet 294 (best seen in FIGS. 9A, 9C and 9D). First or upper left segment 292 is oriented to aim a selected angle (e.g., 15 degrees) to the left and second or upper right segment 294 is oriented to aim at the same selected angle (e.g., 15 degrees) but diverges to the right, so neither baffle segment or facet points straight ahead.

(19) Each upper baffle segment or facet is preferably substantially planar and includes first and second driver receiving apertures configured to support and aim a pair of mounted loudspeaker drivers which are preferably aligned on a centered vertical axis (as seen in FIGS. 9A, 9C and 9D). Each upper baffle segment or facet 292, 294 thus aims a tweeter driver 338 and a midrange driver 329 which are aligned on a vertical axis within the baffle segment's planar surface and the drivers in each array are time-aligned by the orientation of the baffle segment surface and the mounting depth within the mounting baffle's thickness (e.g., 25 mm thick MDF). So each enclosure 280 has on its front baffle 290 an angled upper left baffle segment or facet 292 which aims a vertically aligned left side driver array including left array tweeter driver 338L and left array midrange driver 329L. Enclosure front baffle 290 also includes non-parallel, diverging right baffle segment or facet 294 which aims a vertically aligned right side driver array including right array tweeter driver 338R and right array midrange driver 329R.

(20) The angled facets or baffle segments 292, 294 support and aim their driver arrays such that the main or stereo tweeter for each channel (e.g., 338R for left speaker tower 280L) is now pointing almost directly at the listening location. The main or stereo midrange (e.g., 329R for left speaker tower 280L) is also mounted on the same angled baffle (e.g., 294L for left speaker tower 280L) and aimed at the listening location so that the combination of the main tweeter and main midrange create a better dispersion pattern with a more pleasing overall tonal balance due to that baffle (294L) being effectively toed in toward the listening location.

(21) Once the crossovers are installed in the enclosures, the system 250 becomes a pair of matched enclosures 280L, 280R, so left speaker system enclosure 280L has it's main tweeter and midrange drivers 338, 329 aligned vertically in an array aimed from the upper right inwardly angled baffle segment 294L (aimed at the listening location, see FIG. 8B) and also has an effects or SDA dimensional cancellation effect generating midrange and tweeter driver array 338, 329 on the upper left segment 292L, where the SDA dimensional baffle segment or facet 292L is angled or slanted to aim the SDA midrange and the SDA tweeter away from the listening location.

(22) Following the same acoustic principles, when system 250 is installed in the listening space, the mirror-imaged right speaker system 280R has its main tweeter and midrange drivers 338, 329 on the upper left angled segment 292R aimed at the listening location and also has its effects or SDA dimensional midrange and tweeter drivers 338, 329 arrayed on the upper right segment 294R, where the SDA dimensional baffle 294R is angled or slanted to aim the SDA midrange and the SDA tweeter away from the listening location.

(23) Referring again to FIG. 8B, when setting up the new SDA system 250, a stereo pair of loudspeaker enclosures 280L 280R is configured in a listening space with a listening location, each loudspeaker system's enclosure 280 has the dual array aiming beveled or faceted front baffle 290 which carries and aims first and second midrange and tweeter arrays, with a new crossover (see, e.g., FIGS. 5 and 10) which provides appropriately filtered signals to the each of the drivers in each array.

(24) In an early prototype loudspeaker system tower 90 shown in FIG. 6A, a first midrange driver 90ML is mounted on a first angled baffle surface or facet and a second midrange driver 90MR is mounted on a second angled baffle surface or baffle, and a single tweeter 90T is mounted near (e.g., just above) both angled baffle surfaces on the loudspeaker's front baffle. This early prototype incorporated a crossover network similar to that shown in FIG. 5 (but without the crossover portion for the SDA effect tweeter) and was not really effective enough at presenting the advantages sought in applicants' development work.

(25) In a second early embodiment of the improved SDA loudspeaker system 100 (as shown in FIG. 6B), a first midrange driver and first tweeter are aligned along a vertical axis on a first angled baffle surface or facet 192 and a second midrange driver and second tweeter are aligned along a vertical axis on a second angled baffle surface or baffle 194, where both angled baffle surfaces are part of the loudspeaker's front baffle 190. This second embodiment tower 100 provides an enhanced SDA main stereo pair loudspeaker product which more effectively overcomes the problems/issues with the original SDA (including perceived phasiness and a narrow sweet spot) in a loudspeaker system having a left speaker tower and a right speaker tower (not shown) which can be easily set up in a listening space by a listener, user or installer.

(26) The vertical axes and aligned acoustic centers of the drivers on left angled baffle 192 and the right angled baffle 194 are preferably spaced apart laterally at a distance (W, which is a function of t.sub.max) of approximately 6.5 inches. In the preferred embodiment, each tweeter/midrange array is aligned along its substantially vertical axis which is centered on its angled baffle segment, so, for a left loudspeaker tower enclosure, the main tweeter was mounted directly above the main midrange driver on the upper right angled segment 194 and aimed at the listener and the effects or SDA dimensional tweeter was above and vertically aligned with the effects or SDA midrange on the upper left segment 192, where the SDA dimensional baffle (192, for a left side tower enclosure, similar to 280L, in FIG. 8B) is angled or slanted to aim the SDA midrange and the SDA tweeter away from the listening position. This prototype loudspeaker tower 100 incorporates a crossover network 140 (FIG. 5) and the connections to drivers made in a specific enclosure render that enclosure either a Left channel tower or a Right channel tower. Referring again to FIG. 5, for a Right channel tower, the main array connections are made (a) from K2-LMD to the midrange driver on upper left baffle segment 192 and (b) from K1-LTW to the tweeter driver also on upper left baffle segment 192; following this method, the SDA or dimensional array connections are made (a) from K5-RMD to the midrange driver on upper right baffle segment 194 and (b) from K4-RTW to the tweeter driver also on upper right baffle segment 194.

(27) In the exemplary embodiment of FIG. 6B, the angled wall segments recede symmetrically to the rear at an aiming angle of 15 degrees, but these baffles need not be symmetrical and can recede at selected aiming angles in the range of 10-30 degrees, and those angles may vary to accommodate drivers with different radiation patterns. For this exemplary embodiment, the acoustic centers separating the left angled baffle tweeter and right angled baffle tweeter are preferably approximately 6.5 apart, and the acoustic centers separating the left angled baffle midrange and right angled baffle midrange drivers are also that same distance (e.g., preferably approximately 6.5) apart.

(28) When two of the loudspeaker system enclosures (e.g., towers 100 or 280) of the present invention are placed in a typical stereo-listening arrangement in a listener's space or room (e.g., as seen in FIG. 8B), the inner-baffle set of drivers (e.g., on baffle segments 294L and 292R) are oriented toward a baffle aiming axis and generally toward the centered listener or listening location. When installed and in use, those inner facing baffle-mounted driver arrays play the standard (or main stereo) left and right signals from an amplifier (e.g., 54). The outer-baffle sets of drivers (e.g., on baffle segments 292L and 294R) are oriented away from the listening axis and generate the crosstalk cancellation or SDA dimensional effect sounds. Crosstalk cancellation (or SDA dimensional effect) signals are generated by crossover circuits (e.g., 140 in FIG. 5 or 440 in FIG. 10) connecting the loudspeakers to one or more amplifiers (e.g., 54) such that the left tower gets an L-R signal and the right tower gets an R-L signal communicated via an SDA interconnect (e.g., 266) connecting a crossover in a left speaker (e.g., 280L) to a crossover in its paired right speaker (e.g., 280R). The crossover networks (e.g., 440) of right speaker 280R and left speaker 280L are connected to one another through connections labelled SDA Out and SDA In and an inverted right channel signal (R) with the low frequency components attenuated is developed and coupled to the left dimensional effect or SDA speaker via the SDA interconnect cable 266. And an inverted left channel signal (L) with the low frequency components attenuated is developed and coupled to the right dimensional effect or SDA speaker also via SDA interconnect cable 266, and these connections are used to make the crosstalk cancelling signals used to drive the dimensional or SDA effect tweeter/midrange driver array by matching the main tweeter/midrange driver array's signal and compensating for the headshadow. In the prototype a simple R-L shelf circuit (see, in FIG. 10, parallel circuit elements L7 and R8) was used to achieve this.

(29) Turning now to FIG. 7 a user or installer configurable multi-faceted or multi-baffle SDA loudspeaker system (e.g., 100) may include a switching or multiplexing system and be set up for use as either a left main stereo SDA speaker or a right main stereo SDA speaker, in accordance with the structure and method of the present invention. This optional feature allows product manufacturers SDA compatible loudspeaker products that can be user configured to be left channel or right channel SDA speakers, but, at the time of sale have a single product or Stock Keeping Unit SKU identifiers. The addition of a tweeter on the crosstalk cancelling side of the new SDA loudspeaker (e.g., 100 or 280) now allows the speaker (as a product or SKU) to be symmetrical, thereby providing an option for resolving this issue (using, e.g., the system illustrated in FIG. 7). The result is a loudspeaker system front baffle with two diverging arrays, each mounted on conjoined, preferably planar left and right side baffle segments or facets which diverge a selected angle (e.g., 15 degrees) from a transverse vertical plane defined along what, in FIG. 1A would otherwise been have been the speaker axis. In the illustrated embodiments, the symmetrically angled conjoined intersecting left and right side baffles (e.g., 192, 194) can intersect in a forward-facing or distal edge to define left and right side angled baffle planes or facets meeting at an acute angle of, preferably 150 degrees (as seen from within the loudspeaker enclosure) or defining an outside corner of two planes which meet at an angle of 210 degrees, as seen from the listener's position, in front of the speaker(s). The baffle aiming angle described and illustrated in these embodiments as being (preferably) 15 degrees to the left and right of a central axis parallel to the listening axis, but could be rendered (effectively enough, with crossover changes) using baffles angled symmetrically back from a horizontal plane in any angle within the range of 10 degrees and 30 degrees. The angled first and second upper baffle segment arrays are then are then fed signals from a crossover (e.g., 140, 440) which is optionally configurable using switches or jumpers (as illustrated in FIG. 7) such that either (e.g., left baffle or right baffle) array can be selected by the user or installer as being (a) the main array or (b) SDA/effects array by rerouting signals through a switch or a jumper block.

(30) Enhanced Crosstalk Cancellation Using the Head Shadow:

(31) Referring again to FIGS. 2A, 2B, 2C and 8B, cancellation of cross talk requires computing and accounting for the time delay () for sound travelling between speakers and the listener's ears. It is important that the dimensional SDA effect cancellation signal's acoustical energy arrive at the ear at the same time as the original stereo (e.g., main) signal's acoustical energy, since they are summed at the ear. To accomplish this, the distance between main and effects arrays (W or DW) must be roughly the distance between the ears, or about 6. In the development process for this invention, the sound arriving at each ear was considered as an acoustic sum where:

(32) $\begin{array}{cc}{L}_{\mathrm{ear}}=L_{\mathrm{Main}}+L_{\mathrm{SDA}}*{}_1+R_{\mathrm{SDA}}*\frac{{\mathrm{HRTF}}_{-30}}{{\mathrm{HRTF}}_{+30}}*{}_2\mathrm{And}& \left(\mathrm{Eq}.1\right)\\ R_{\mathrm{ear}}=L_{\mathrm{Main}}*\frac{{\mathrm{HRTF}}_{-30}}{{\mathrm{HRTF}}_{+30}}*{}_3+L_{\mathrm{SDA}}*\frac{{\mathrm{HRTF}}_{-30}}{{\mathrm{HRTF}}_{+30}}*{}_2+R_{\mathrm{SDA}}*{}_1& \left(\mathrm{Eq}.2\right)\end{array}$
The term (HRTF.sub.30/HRTF.sub.+30) is the difference between the signal arriving at the near ear and signal arriving at the far ear. This is often referred to as the Head Shadow, so in the following equations, HS=(HRTF.sub.30/HRTF.sub.+30). FIG. 3 illustrates an approximation or modelled spectral response known as the KEMAR Head Shadow (+30 vs 30 degrees) for a standard head shape and this response was used in generating the following. So, for the Right side ear:
R.sub.ear=L.sub.Main*HS*.sub.3+L.sub.SDA*HS*.sub.2+R.sub.SDA*.sub.1(Eq. 3)

(33) If one assumes there is only left signal (i.e. signal is completely panned left), then, for the right ear, there should be no signal. (so R.sub.ear=0).

(34) If, for example, if delay 3=1 these two assumptions can be plugged into the equation, and upon rearranging terms, one gets:
L.sub.main*HS*.sub.1=L.sub.SDA*HS*.sub.2+R.sub.SDA*.sub.1(Eq. 4)

(35) Ignoring the L.sub.SDA term:
L.sub.Main*HS*.sub.1=R.sub.SDA*.sub.1(Eq. 5)

(36) And this observation lead to how a head shadow effect generating filter may be approximated. If the R.sub.SDA (dimensional or SDA effect crosstalk cancelling) signal can be filtered in such a way as to mimic or compensate for the head shadow, then it will more completely cancel the L.sub.Main signal's crosstalk. Applicant's development work has led to the discovery that this can be approximated by a simple filter and one can then effectively multiply SDA array's signal by the effect of this filter.
R.sub.ear=L.sub.Main*HS*.sub.3+L.sub.SDA*HS*HS*.sub.2+R.sub.SDA*HS*.sub.1(Eq. 6)
Because it is known that R.sub.SDA=L.sub.Main (electrically), the expression for the filter as written in Eq. 6 can be simplified to:
R.sub.ear=L.sub.SDA*HS*HS*.sub.2(Eq. 7)

(37) So, the remainder of the acoustic summation at the right ear is the L.sub.SDA signal, filtered by the electrical filter and also the physical head shadow itself, plus a delay, which means cancellation of crosstalk is more effective than the prior art SDA system.

(38) In improved SDA system 250, the SDA crosstalk cancellation effect is significantly increased by using crossover networks (e.g., 140 or 340 with Shelf filter sections in the SDA part of the crossover network) that compensate for a listener's Head Shadow, thereby making the dimensional or SDA crosstalk cancellation more effective over a broader spectrum.

(39) Referring next to FIGS. 8A and 8B, sound reproduction system 250 having a left channel output and a right channel output includes apparatus for reproducing sound having an expanded and more stable acoustic field and acoustic image and includes a first or left loudspeaker system enclosure or tower 280L disposed in a first loudspeaker system enclosure location (FIG. 8B) spaced a selected distance (e.g., 6-20 feet) from a listening location for left channel playback, where the listening location is a place in a space for accommodating a listener's head having a right ear location and a left ear location spaced along an ear axis. System 250 preferably includes a second or right side loudspeaker system enclosure 280R which is configured for right channel playback and is wired to function as a mirror image or cooperating loudspeaker.

(40) The left loudspeaker system enclosure 280L has a multi-faceted or multi-planar front baffle surface (see e.g., FIGS. 9A-9E) comprising a first front baffle surface or facet 292L which is angled rearwardly to recede at a selected (e.g., 10-30 degree, preferably 15 degree) angle from a vertical plane aligned with the speaker axis on the left side, and a second front baffle surface or facet 294L which is angled rearwardly to recede at a selected (e.g., 15 degree) angle from a vertical plane aligned with the speaker axis on the right side, where the first and second baffle surfaces 292L, 294L define loudspeaker driver supporting and aiming structures aligned along substantially vertical planes (e.g., as shown in FIGS. 9A-9E). As described above, that first baffle facet 292L carries and aims a first midrange driver 329L having a midrange driver acoustic center and a first tweeter driver 338L having a tweeter driver acoustic center which is preferably substantially vertically aligned with said first midrange driver acoustic center along a vertical axis centered within and in the vertical plane defined by facet surface 292. The second baffle facet 294 carries and aims a second midrange driver 329R and a second tweeter 338R, and that second midrange driver 329R has its acoustic center spaced laterally from the first midrange driver 329L by a selected distance DW (see, e.g. FIG. 9D, about 6-6.5 inches), and the second tweeter driver 338R has a tweeter driver acoustic center which is preferably substantially vertically aligned with the acoustic center of second midrange driver 329R and spaced laterally from the first tweeter driver's acoustic center by the same selected distance DW (e.g., about 6-6.5 inches). First loudspeaker system enclosure or tower 280L has external terminals (e.g., via input panel 316) for Main (+) and () signal inputs, and an SDA signal input/output terminal (as shown in FIG. 10) where signal processing circuitry including crossover circuit 440 has bi-amp or bi-wire compatible (HI and LO) input terminals for the Main (+) connection, the Main () connection, an SDA In connection and an SDA Out connection, where crossover 440 is configured to generate (i) a main tweeter signal (ii) a main midrange signal, (iii) a Head Shadow Filter compensated SDA dimensional effect tweeter signal, and a Head Shadow Filter compensated SDA dimensional effect midrange signal. The signal processing circuitry including crossover 440 (or crossover 140) communicates the SDA dimensional effect tweeter signal and the SDA dimensional effect midrange signal to an SDA dimensional effect radiating array (mounted on facet 292) including first tweeter 338L and first midrange 329L which are aimed by first front baffle or facet 292 away from the listening position and away from the listening axis (as shown in FIG. 8B).

(41) Sound reproduction system 250 has signal processing circuitry (e.g., in crossover circuit 440) that communicates the Main Tweeter signal and the Main Midrange signal to the main radiating array comprising second tweeter 338R and second midrange 329R which are aimed by said second front baffle 294 toward the listening position. As shown in FIG. 8B, sound reproduction system 250 also of claim 2, further includes a second loudspeaker system enclosure or tower 280R disposed in a second loudspeaker system location which is spaced laterally from and aligned along a speaker axis with the location of first loudspeaker system 280L and the spacing between left tower 280 L and right tower 280 R is preferably in the range of 6 to 20 feet. Second tower or right side SDA speaker assembly 280R is preferably spaced from the listening location by a distance substantially equal to the spacing between the listening location and the first loudspeaker system 280L. Second loudspeaker system enclosure 280R, is physically configured as a tower enclosure assembly (e.g., 280, FIGS. 9A-9E), and differs from left or first enclosure 280L in how its crossover (e.g., 440) is connected.

(42) Second loudspeaker system enclosure 280R also has a multi-faceted or multi-planar front baffle surface 290 comprising a first front angled baffle surface or facet 292R which is angled rearwardly to recede at a selected (e.g., 10-30 degree, preferably 15 degree) angle from a vertical plane aligned with the speaker axis on the left side, and a second front baffle surface or facet 294R which is angled rearwardly to recede at a selected (e.g., 15 degree) angle from a vertical plane aligned with the speaker axis on the right side, where the first and second baffle surfaces 292R, 294R define loudspeaker driver supporting and aiming structures aligned along substantially vertical planes.

(43) Turning again to FIGS. 9A-9E, and specifically to FIG. 9E which provides an exploded perspective view of the tower loudspeaker enclosure 280 used in making left side enclosure 280L and 280R, it is shown that braced MDF loudspeaker cabinet 301 includes internal 18 mm MDF bracing and is supported upon base 302 which is made of 50 mm thick MDF. The cabinet's entire front baffle 290 (including facets 292 and 294) and top 303 are preferably made of 25 mm MDF. In the preferred embodiment, a pair of 5.25 inch midrange drivers 329 are positioned beside one another on the diverging adjacent baffle or facet surfaces 292, 294. The front baffle 290 is covered by and supports a detachable grill assembly 311 and in the bottom segment includes vertically aligned circular openings configured to support and aim first and second 10 woofers 304 above an aperture or port defined by port trim insert member 306. An optional removable top cover 305 allows future installation and use of up-firing (e.g., Dolby Atmos system) drivers. As noted above, each tower enclosure assembly 280 includes first and second tweeters 338 mounted with tweeter trim panels 312. In a bass cavity section behind and in fluid communication with the back side of woofers 304, a tuned port assembly includes port flare 313 and MDF doughnut 314 on cylindrical cardboard port tube 315.

(44) The connections to the crossover (e.g., 140 or 440) are made through an aluminum input plate 316. Two SDA interconnect conductors (preferably bundled into an SDA interconnect cable assembly 266) are preferably made up as red and black jumper wires, one red, one black, each 12AWG, and each with a gold plated spade terminal on one end and a banana plug pin connector on the opposite end. The crossover assembly 345 is preferably a printed circuit board assembly (e.g., with conductors and circuit elements for crossover circuit 440, as shown in FIG. 10) and preferably has plastic standoffs for attachment near the bottom of the cabinet's interior volume. Crossover assembly 345 preferably has polarized Faston-style connectors on all connections. Input plate 316 carries preferably three binding post assemblies 359 for a bi-wireable main connection to one or more amplifiers (e.g., 54) and optionally to a source for an elevation module (e.g., Atmos) signal to drive an optional ATMOS assembly (not shown).

(45) Turning to the crossover circuit 440 illustrated in FIG. 10, the Main In portion of the crossover is configured for use with a biwire or biamp setup, and so is divided into Hi and Lo sections which may be used with conductive jumpers connecting terminals shown as HI In+ to LO In+ and HI In to LO In, where the terminals labeled LO In are connected to the woofer portion of the crossover circuit and the terminals labeled HI In are connected to the midrange and tweeter portions of the crossover circuit. Crossover 440 is a three-way crossover with five main sections, namely:

(46) 1) Main Tweetera third order high pass with level resistor and notch;

(47) 2) Main Midrangea third order high pass, third order low pass, notch and a level resistor;

(48) 3) Woofera third order low pass;

(49) 4) SDA Tweetera third order high pass with level resistor and notch;

(50) 5) SDA Midrangea third order high pass, third order low pass, notch and a level resistor, where

(51) 6) The SDA sections are preceded by a first order low pass shelf circuit (the paralleled circuit of L7 and R8).

(52) The SDA Input/Output terminals are used to connect the SDA portion of the crossover to the other speaker in the stereo pair (e.g., 280L and 280R) and enable the improved head-shadow compensating SDA crosstalk cancellation to function as intended. An optional Elevation module input (not shown in FIG. 10, but possibly included in crossover assembly 345) connects a set of wires up to an optional elevation module which might be installed in the top of the speaker (e.g., replacing cover 305). Returning to FIG. 10, the critical passive electrical components shown in crossover 440 have selected tolerances which are typically measured at 1 kHz, and the specifics for those components are included in the Table 1:

(53) TABLE-US-00001 TABLE 1 Power, Voltage or Current DCR(Inductors Nominal Rating or & Switches) Part Value Tol. Wire Gauge DF (Capacitors) Material C1, C9 10 F 5% 100 V 1% Polyester metal film C2, C10 30 F 5% 100 V 1% Polyester metal film C3, C11 2.0 F 5% 100 V 1% Polyester metal film C4, C5, 68 F @ 120 Hz 5% 200 V 5% Electrolytic C12, C13 C6, C14 1.0 F 5% 100 V 1% Polyester metal film C7, C15 18 F 5% 100 V 1% Polyester metal film C8, C16 30 F 5% 100 V 5% Electrolytic C17 4.7 F 5% 100 V 5% Electrolytic C18 82 F 5% 100 V 5% Electrolytic L1, L8 0.3 mH 5% 1.0 mm 0.25 Air Core; copper wire L2, L9 1.0 mH 5% 0.5 mm 2.0 Air Core; copper wire L3, L10 2.0 mH 5% 1.0 mm 0.25 Steel laminate I-Core; copper wire on plastic bobbin L4, L11 1.0 mH 5% 1.0 mm 0.15 Steel laminate U-Core (min 9.5 mm square); copper wire on plastic bobbin L5, L12 0.5 mH 5% 1.0 mm 0.1 Steel laminate U-Core (min 9.5 mm square); copper wire on plastic bobbin L6, L13 3.0 mH 5% 0.8 mm 0.6 Steel laminate I-Core; copper wire on plastic bobbin L7 1.2 mH 5% 1.0 mm 0.2 Steel laminate U-Core (min 9.5 mm square); copper wire on plastic bobbin L14 3.0 mH @ 120 Hz 5% 1.2 mm 0.2 Steel laminate I-Core; copper wire on plastic bobbin L15 2.0 mH @ 120 Hz 5% 1.2 mm 0.15 Steel laminate I-Core; copper wire on plastic bobbin R5, R13 15 5% 5 W Sand Cast R6, R14 1.0 5% 5 W Sand Cast R7, R15 4.0 5% 10 W Sand Cast R8 8.0 5% 10 W Sand Cast R16 15 5% 5 W Sand Cast R17 1.0 5% 10 W Sand Cast

(54) Referring again to FIGS. 9A and 10, the connections to drivers made in a specific enclosure (e.g. 280R) render that enclosure either a Left channel tower or a Right channel tower. So for a Right channel tower (e.g. 280R), the main array connections for the driver array on left facet surface 292R are made (a) from connector P2, terminals 3 (+) and 4 to the midrange driver 329L on upper left baffle segment 292 and (b) from connector P2, terminals 1 (+) and 2 to the tweeter driver also on upper left baffle segment 292; following this method, the SDA or dimensional array connections are made (a) from connector 2X2, terminals 2 and 4 to the midrange driver 329R on upper right baffle segment 294 and (b) from connector 2X2, terminals 1 and 3 to the tweeter driver 338R also on upper right baffle segment 294.

(55) The system 250 and method of the present invention provide specific improvements on this applicants' prior work on the well-known SDA speaker systems, and persons of skill in the art will appreciate that those improvements include a new and more effective SDA effect generating apparatus in system 250 with a left speaker (e.g., 329R) in enclosure 280L which is aimed (e.g., by facet 294L) toward the listening position at a selected main driver aiming angle (diverging from a straight ahead line parallel to the listening axis, where the selected main driver aiming angle is between 10 degrees and 30 degrees (e.g., 15 degrees) and where the left sub or SDA effect generating speaker(s) (e.g., 329L and 338L) are aimed away from the listening position at a selected symmetrical mirror-image diverging sub/SDA effect driver aiming angle to that straight ahead reference line which is parallel to the listening axis, where the sub/SDA effect driver aiming angle is substantially equal in magnitude to the main driver aiming angle (best seen in FIGS. 8B, 9C and 9D).

(56) Another improvement in selected embodiments of new and improved SDA loudspeaker system (e.g., 250) is that a left main speaker may comprise a left main midrange driver which is vertically aligned with a left main tweeter (e.g., on angled baffle surface 292R) to provide a left main driver array aimed toward the listening position at a selected left main driver array aiming angle from a line parallel to the listening axis (as seen in FIGS. 8B and 9C), where that selected left main driver array aiming angle is between 10 degrees and 30 degrees (e.g., 15 degrees) and where the left sub or SDA effects speaker includes a left sub midrange driver 329R which is vertically aligned with a left sub tweeter to provide a left sub driver array aimed (e.g., by facet 294R away from the listening position at a selected left sub driver array aiming angle, diverging from that imaginary straight ahead line parallel to the listening axis which is substantially equal in magnitude to the main driver aiming angle (as best seen in FIG. 9C).

(57) Yet another improvement in selected embodiments of new and improved SDA loudspeaker system (e.g., 250) is that the SDA jumper connection 266 connecting the crossovers in each of the speakers (e.g., 280L, 280R) provides a connection to the right and left channel outputs for developing a left channel minus right channel signal and a right channel minus left channel signal which now includes signal processing circuitry included in each crossover (e.g., 140, 440) with input terminals for a Main (+) connection, a main () connection, an SDA In connection and an SDA Out connection, where that crossover (e.g., 140 or 440) is configured to generate (i) a main tweeter signal (ii) a main midrange signal, (iii) a Head Shadow Filter compensated SDA dimensional effect tweeter signal, and a Head Shadow Filter compensated SDA dimensional effect midrange signal. In addition, the left sub (or SDA effect) speaker now comprises an array with an effects generating (or sub) tweeter driver which is spaced from and vertically aligned with a sub midrange driver, so that the Head Shadow Filter compensated SDA dimensional effect tweeter signal is communicated with the SDA effect generating (or sub) tweeter.

(58) The improved method of operating and using system 250 of the present invention comprises the steps of: disposing a right main speaker (e.g., on baffle segment 292R) and a left main speaker (e.g., on baffle segment 294L) at right and left main speaker locations equidistantly spaced from the listening location which, as seen in FIG. 8B is a place in space for accommodating a listener's head facing the main speakers and having a right ear location and a left ear location along an ear axis, with the right and left ear locations separated along the ear axis by a maximum interaural sound distance of tmax, and the listening location being defined as the point on the ear axis equidistant to the right and left ears, the listening location being spaced from the main speakers and defining a listening angle with respect thereto to result in an interaural time delay t of the right and left ear locations along the listening angle to the left and right main speakers; the next step is disposing at least one right sub-speaker (e.g., on baffle segment 294R) and at least one left sub-speaker (e.g., on baffle segment 292L) at right and left sub-speaker locations equidistantly spaced from the listening location; the next step is selecting the right and left sub-speaker locations such that the inter-speaker delay of the right sub-speaker over the right main speaker with respect to the right ear location and the inter-speaker delay of the left sub-speaker over the left main speaker with respect to the left ear location are each approximately the same as the interaural time delay t; and then coupling the right and left channel outputs to the right and left main speakers, respectively (via crossovers 140 or 440 and SDA cable 266); next, using crossover 140 or 440, deriving from the right and left channel outputs an inverted right channel signal and an inverted left channel signal for use in generating the cross talk cancellation effect; and coupling the inverted right channel signal to the at least one left sub-speaker and coupling the inverted left channel signal to the at least one right sub-speaker. Here, we note that the Improved Method of the present invention also comprises deriving a head shadow compensated inverted right channel signal and a head shadow compensated inverted left channel signal and coupling the head shadow compensated inverted right channel signal to the at least one left sub-speaker (e.g., on baffle segment 292L) and coupling the head shadow compensated inverted left channel signal to the at least one right sub-speaker (e.g., on baffle segment 294R). This improved method also includes selecting main speaker locations and sub-speaker locations to be on non-parallel baffle segments (e.g., on baffle segments 292L and 292R) aiming at least one left or right sub-speaker away from a speaker axis which is parallel to the ear axis. Optionally, the method may include high pass filtering the inverted right and left channel signals prior to applying them to the at least one left and at least one right sub-speakers, respectively.

(59) Having described preferred embodiments of a new and improved loudspeaker system (e.g., 250) and SDA signal processing method, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teachings set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the present invention as set forth in the following claims.