Method and apparatus for reproducing sound having a realistic ambient field and acoustic image

• US 4,630,298 A
• Filed: 05/30/1985
• Issued: 12/16/1986
• Est. Priority Date: 05/30/1985
• Status: Expired due to Term

• Current Assignee: GE Business Financial Services, Inc. (Bank of America Corp.)
• Original Assignee: Colin B. Campbell, Matthew S. Polk
• Inventors: Campbell, Colin B., Polk, Matthew S.
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US06/739,452
• Time in Patent Office: 565 Days
• Field of Search: 381/1, 381/24, 381/99, 381/100, 381/17
• US Class Current: 381/1
• CPC Class Codes: H04S 3/00 Systems employing more than two channels, e.g. quadraphonic H04S5/00, H04S7/00 take precedence

Abstract

Apparatus for reproducing sound having a realistic ambient field and acoustic image is used in a stereophonic sound reproduction system having a left channel output and a right channel output. A right main speaker and a left main speaker are disposed at right and left main speaker locations, respectively, which are equidistantly spaced from a listening location along a listening axis perpendicular to a line joining the left and right main speakers. A right sub-speaker and a left sub-speaker are respectively disposed at right and left sub-speaker locations equidistantly spaced from the listening location, and further from the listening location than the main speaker. In one particular arrangement each main speaker includes a driver and a tweeter and each sub-speaker includes only a driver. The left and right channel outputs are respectively coupled to the left and right main speakers. A left channel minus right channel difference signal is coupled to the left sub-speaker and a right channel minus left channel difference signal is coupled to the right sub-speaker. In one embodiment, the main and sub-speakers for each channel are respectively incorporated in a common enclosure to fix the spacing therebetween. A technique for determining optimal spacing between the main and sub-speakers and between the various speakers and the listening location is set forth.

Claims

1. In a stereophonic sound reproduction system having a left channel output and a right channel output, apparatus for reproducing sound having a realistic ambient field and acoustic image comprising:

a right main speaker and a left main speaker disposed respectively 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 Δ

t_max'"'"' and the listening location being defined as the point on the ear axis equidistant to the right and left ears;

a right sub-speaker and a left sub-speaker disposed respectively at right and left sub-speaker locations equidistantly spaced from the listening location;

the right main speaker being separated from the right ear location by a sound distance t and being separated from the left ear by a sound distance t+Δ

t where Δ

t is the interaural sound distance spacing with respect to the right main speaker between the right ear location and the left ear location;

the right sub-speaker being separated from the right ear location by a sound distance t+Δ

t'"'"' where Δ

t'"'"' is the sound distance spacing with respect to the right ear location between the right main speaker location and right sub-speaker location;

the left main speaker being separated from the left ear location by a sound distance t and being separated from the right ear location by a sound distance t+Δ

t where Δ

t is the interaural sound distance with respect to the left main speaker between the left and right ear locations;

the left sub-speaker being separated from the left ear location by a sound distance t+Δ

t'"'"' where Δ

t'"'"' is the sound distance spacing with respect to the left ear location between the left main speaker location and left sub-speaker location;

each of said left and right main speakers comprising a driver and a tweeter, and wherein each of said main speaker tweeters are positioned physically further from the listening location than the main speaker drivers, each of said left and right sub-speakers consisting of only a driver which is positioned further from the listening location than the main speaker tweeter, cross-over networks for providing transition between the main speaker drivers and tweeters;

means coupling the right and left channel outputs, respectively, to said right and left main speakers;

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;

means limiting the acoustic output of said subspeakers to frequencies below approximately 1 kHz;

whereby sound reproduced by said apparatus as perceived by a listener whose head is located generally at the listening location has a realistic acoustic field and enhanced acoustic image.

2. In a stereophonic sound reproduction system having a left channel output and a right channel output, apparatus for reproducing sound having a realistic ambient field and acoustic image comprising:

right and left main speakers each comprising a driver and tweeter, said right and left main speaker drivers disposed respectively at right and left main speaker locations equidistantly spaced from a listening location, said right and left main speaker tweeters disposed a first predetermined distance from their respective associated drivers and further from the listening location than said main drivers;

right and left sub-speakers each consisting of only a driver spaced respectively from said right and left main speakers so as to be further from the listening location than the main speakers, said sub-speaker drivers being spaced a second predetermined distance respectively from the right and left main speaker drivers, said second predetermined distance being greater than said first predetermined distance;

coupling means including crossover networks for respectively coupling the right and left channel outputs to said right and left main speakers and for effecting a transition between the main speaker drivers and tweeters, means for coupling the left channel output minus the right channel output to said left sub-speaker and the right channel output minus the left channel output to said right sub-speaker;

means limiting the acoustic output of said subspeakers to frequencies below approximately 1 kHz.

3. Apparatus in accordance with claim 2 including a left enclosure commonly mounting said left main speaker and left sub-speaker, and a right enclosure commonly mounting said right main speaker and right sub-speaker.

4. Apparatus in accordance with claim 3 wherein said first predetermined distance is approximately 4 to 7.5 inches.

5. Apparatus in accordance with claim 4 wherein said second predetermined distance is approximately 7 to 12 inches.

6. A method for reproducing sound from a stereophonic source having a left channel output and a right channel output in which the reproduced sound has a realistic ambient field and acoustic image comprising the steps of:

disposing a right main speaker and left main speaker at right and left main speaker locations equidistantly spaced from a listening location, each of said main speakers comprising a driver and a tweeter with the tweeter spaced further from the listening location than the respective driver and separated from the respective driver by a first predetermined distance;

disposing right and left sub-speakers each consisting of only a driver at locations spaced respectively from the right and left main speaker locations so as to be further from the listening location than the main speaker locations by a second predetermined distance from respective main speaker locations;

coupling the right and left channel outputs to the respective right and left main speakers by cross-over networks for effecting transition between drivers and tweeter at a sound frequency of approximately 1 kHz;

coupling the left channel output minus the right channel output to the left sub-speaker and the right channel output minus the left channel output to the right sub-speaker;

limiting the acoustic output of said subspeakers to midrange and lower frequencies.

7. A method in accordance with claim 6 wherein the second predetermined distance is approximately 7 to 12 inches.

8. A method in accordance with claim 6 wherein the first predetermined distance is approximately 4 to 7.5 inches.

9. In a stereophonic sound reproduction system having a left channel output and a right channel output, apparatus for reproducing sound having a realistic ambient field and acoustic image comprising:

right and left main speakers disposed respectively at right and left main speaker locations equidistantly spaced from a listening location;

right and left sub-speakers spaced respectively from said right and left main speakers so as to be further from the listening location than the main speakers;

means for coupling the right and left channel outputs to said right and left main speakers and means for coupling the left channel output minus the right channel output to said left sub-speaker and the right channel output minus the left channel output to said right sub-speaker; and

means for limiting the acoustic output of said subspeakers to midrange and lower frequencies.