TWO-CHANNEL, FOUR-COMPONENT STEREOPHONIC SYSTEM

• US 3,697,692 A
• Filed: 06/10/1971
• Issued: 10/10/1972
• Est. Priority Date: 06/10/1971
• Status: Expired due to Term

• Current Assignee: David Hafler
• Original Assignee: David Hafler
• Inventors: Hafler, David
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): D'Amico, Thomas
• Application Number:
  US05/151,790
• Time in Patent Office: 488 Days
• Field of Search: 179/15BT,1G,1GP,16.4ST,1.1TD
• US Class Current: 381/18
• CPC Class Codes: H04S 3/02 of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other

Abstract

A two-channel stereo signal including left and right channel responses (L and R, respectively), deriving from only two amplifiers, is fed to four speakers located approximately at the corners of a quadriliateral area, and are positioned to face toward the interior of the area. The network drives the speakers with four different signals so that sound from the speakers appears to a listener positioned interiorly of the area to come from the four sides of the area, rather than from the four corners. In one embodiment, speakers in the left and right front corners respond to (L + R/2 and (R + (L/2), respectively, while in a second embodiment these speakers respectively respond to (L) and (R), respectively. Speakers in the left and right rear corners (directed toward the listener'"'"''"'"'s back) respond to signals proportional to L - (R/2) and R - (L/2), respectively.

Claims

1. An audio reproduction system driving four speakers in response to only two left and right stereophonic audio power amplifiers, said amplifiers being left and right amplifiers and the audio signals provided by said amplifiers respectively having audio signal levels denominated as L and R, a different one of said speakers being positioned approximately at each of the four corners of a quadrilateral area, which may be occupied by a listener, said speakers directing sound towards the interior of the area, wherein first and second ones of the speakers are respectively positioned in the left and right rear corners of the area behind the listener and third and fourth ones of the speakers are positioned in the left and right front corners of the area facing the listener, each of said speakers including a signal and a ground terminal, comprising means responsive to said left amplifier for applying a first audio signal to said signal terminals of the front left and rear left speakers, means responsive to the other one of said amplifiers for applying a second audio signal to said signal terminals of the front right and rear right speakers, means grounding the second terminals of the two front speakers, and passive impedance network commonly in series with said rear speakers connecting the ground terminals of the two rear speakers to ground, the impedance of said impedance network having a substantiAl value capable of audibly modifying the relative amplitudes of the responses of the rear speakers relative each other.

2. The audio reproduction system of claim 1, wherein the value of said impedance network is selected so that the responses of the rear left and rear right speakers are respectively approximately proportional to (L - (R/2)) and (R - (L/2)).

3. The audio reproduction system of claim 2, wherein the impedance of said network has a value of the order of the impedance of each rear speaker.

4. The audio reproduction system of claim 2, wherein the first and second audio signals are respectively commensurate with (L + (R/2)) and (R + (L/2)), and the impedance network has an impedance approximately equal to four times the impedance of each rear speaker.

5. The audio reproduction system of claim 1, wherein said impedance network comprises a fifth speaker.

6. The audio reproduction system of claim 1, wherein the impedance network comprises a fifth speaker located at the front of the area approximately midway between the two front speakers.

7. The audio reproduction system of claim 1, wherein the impedance network comprises a fifth speaker located midway between said front speakers.

8. The audio reproduction system of claim 1, wherein said impedance network includes first, second and third variable resistors respectively connected, in the order recited, from the rear left speaker, and from the rear right speaker and as a common impedance extending from the first and second variable resistors to ground, and means for gang controlling the values of said resistors so that the first and second resistors always have approximately the same value and the third resistor has a value equal to that of one of the other resistors multiplied by a predetermined constant.

9. An audio reproduction system driving four speakers in response to only two stereophonic power amplifiers, said amplifiers being respectively denominated as left and right, a different one of said speakers being positioned approximately at each of the four corners of a quadrilateral area, said speakers directing sound towards the interior of the area, wherein first and second ones of the speakers are respectively positioned in the left and right rear corners of the area behind the listener and third and fourth ones of the speakers are positioned in the left and right front corners of the area facing the listener, said speakers each having a signal terminal and a ground terminal, comprising means responsive to one of the amplifiers for applying a first signal to the signal terminals of the front left and rear left corner speakers, means responsive to the other one of the amplifiers for applying an audio signal to the signal terminals of the front right and rear right corner speakers, means grounding the second terminals of the two front speakers, means connected to the second terminals of the two rear speakers for providing a common substantial resistance from the ground terminals of both rear speakers to ground, and means individually grounding the ground terminals of the front speakers.

10. An audio reproduction system driving four speakers in response to only left and right power amplifiers, a different one of said speakers being positioned approximately at each of the four corners of a quadrilateral area, said speakers directing sound towards the interior of the area, wherein first and second ones of the speakers are respectively positioned in the left and right rear corners of the area behind the listener and third and fourth ones of the speakers are positioned in the left and right front corners of the area facing the listener, said speakers each having a drive terminal and a ground terminal, comprising means responsive to the left and right amplifiers for deriving responses from the left and right front speakers respectively proportional to the outputs of said amplifiers, means responsive to said left and right amplifiers for deriving audio responses from the left and right rear speakers respectively proportional to (L - KR) and (R - KL), where K is a constant greater than zero and less than one, L is the output of the left amplifier and R is the output of the right amplifier.

11. The audio reproduction system of claim 10, where K is approximately 1/2.

12. The audio reproduction system of claim 11, wherein the means for deriving responses from the left and right rear speakers comprises a common impedance connecting the ground terminals of only the rear speakers to ground, said common impedance having a value approximately equal to the impedance of one of said rear speakers.

13. An audio reproduction system driving four speakers in response to only two stereophonic amplifiers, said amplifiers being respectively denominated as left and right, a different one of said speakers being positioned approximately at each of the four corners of a quadrilateral area, said speakers directing sound towards the interior of the area, wherein first and second ones of the speakers are respectively positioned in the left and right rear corners of the area behind the lister and third and fourth ones of the speakers are positioned in the left and right front corners of the area facing the listener, comprising means responsive to said amplifiers for deriving responses from the left and right front speakers respectively proportional to (L + K1R) and (R + K1L), means responsive to said amplifiers for deriving responses from the left and right rear speakers respectively proportional to (L - K2R) and (R - K2L), where K1 and K2 are constants greater than 0.25 and less than 0.75, where L is the audio output amplitude of the left amplifier and R is the audio output amplitude of the right amplifier.

14. The audio reproduction system of claim 13 wherein K1 K2 1/2 .

15. In a four speaker two amplifier stereophonic reproduction system, wherein left and right front speakers are connected to left and right amplifiers of said reproduction system, respectively, the combination wherein is provided left and right rear speakers connected respectively to be driven directly by said left and right amplifiers, and a passive circuit connected directly between said rear speakers and ground for introducing at least 25 percent of negative cross coupling of said rear speakers.

16. In a four speaker audio system having only left and right power amplifiers, four loudspeakers having each a signal input terminal and a grounding terminal, said loudspeakers being left front, right front, left rear, and right rear loudspeakers, respectively, means connecting said left power amplifier in parallel with the signal output terminals of said left front and left rear loudspeakers, means connecting said right power amplifier in parallel with the signal input terminals of said right front and rear loudspeakers, a switch normally connecting the grounding terminals of said rear loudspeakers to ground, a passive impedance network normally commonly connecting the grounding terminals of said rear speakers to ground via said switch, said impedance network comprising a common resistance connected with said rear speakers in parallel to audibly cross couple said rear loudspeakers.

17. The system according to claim 16 wherein is further provided control means for at will disconnecting only said signal input terminals of said rear speakers from said power amplifiers.

18. The system according to claim 16, wherein said impedance network is a resistive T-network including said common resistance and further separate resistances respectively connecting said grounding terminals of said rear speakers to said common resistance and thence via said switch to ground, and a gang control means for commonly adjusting all the resistances of said T-network.

19. The system according to claim 16, wherein said common impedance includes a fifth loudspeaker.

20. A four speaker stereophonic system driven solely from a left and a right power amplifier, said four speakers including left and right front speakers and left and right rear speakers, means driving said left speakers in multiple directly from said left amplifier, means driving said right speakers in multiple directly from said right amplifier, an adjustable resistive passive cross coupling network, said resistive cross coupling network being connected commonly between said rear loudspeakers and ground and providing at least 25 percent cross coupling between said rear loudspeakers.