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 Quad ESL '63
The patents discussed on this page cover all the materials examined formally by Peter Walker in his own Patent Application U.S. 3,773,984 for the speaker that became known as the ESL '63. Where relevant, both the GB and US patents are referred to, assuming that they exist. Some US patents have no GB equivalent, and vice versa. If any reader of this page has knowledge of other interesting and directly related technical papers on this subject I would be glad to hear of these. The series of references is very eclectic, covering not only feedback as it applies to amplifier systems (the Quad '63 uses a form of feedback), but one paper, by Stolaroff, on magnetic recording. There are, naturally, references to other electrostatic speaker patents, including the monumental Patent granted to William W. Wright of Dayton-Wright fame.
The Patents are arranged below in chronological order by date of grant, not date of application. This will create confusion in some people's minds as to why the speaker is referred to as the ESL63, as Peter Walker's patent was granted on November 20, 1973. For the unitiated, it is called the ESL '63 because that is when Peter Walker made the first entries in his note book about this new speaker. The technology has not really change in the 988-989 series of speakers, whcih still employ the ESL '63 annular ring schema and the constant current drive system, with the addition of high quality electrostatic woofers.
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Patent Dates
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Details of Inventor, Title and Claims.
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Filed: September 27, 1929
U.S. Patent 1,983,377
Granted: December 4, 1934
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Edward W. Kellogg "Production of Sound"
[Claims 1-13 ], Diagrams: [Sheet 1]
Referenced by Walker in U.S. Pat. 3,773,984.
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Filed: February 21, 1940
G.B. Patent 537,931
Granted: July 14, 1941
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Donovan Ernest Lea Shorter
"Improvements in Electrostatic Loudspeakers"
[Claims 1-10], Diagrams: [Sheet 1]
Referenced by Walker U.S. Pats. 3,773,984.
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Filed: January 28, 1941
U.S. Patent 2,302,493
Granted: November 17, 1942
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Robert B. Dome, Bridgeport, Connecticut
"Amplifying System".
[ Claims 1-6], [Claims 7 -15 ], [Claim 16]; Diagrams: [Sheet 1] Referenced by Walker in U.S. Pat. 3,773,984.
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Filed: June 24, 1943
U.S. Patent 2,387,845
Granted: October 30, 1945
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William R. Harry, Summit, New Jersey
"Electroacoustic Transducer".
[Claims 1-7], [Claims 8,9]. Diagrams: [Sheet 1]
Referenced by Walker U.S. Pat. 3,773,984.
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Filed: December 18, 1948
U.S. Patent 2,634,335
Granted: April 7, 1953
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Myron B. Stolaroff, Redwood City, California assignor to Ampex Corporation
"Magnetic Recording System with Negative Feedback System."
[Claims 1-4], [Claim 5]. Diagrams [Sheet 1]
Referenced by Walker U.S. Pat. 3,773,984.
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Filed: May 19, 1954
U.S. Patent 2,843,671
Granted: July 15, 1958
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Charles A. Wilkins and Herbert Sullivan, New York
"Feed Back Amplifiers"
[Claim 1], [Claim 2 ]. Diagrams: [Sheet 1], [Sheet 2]
Referenced by Walker in U.S. Pats. 3,773,984
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Filed: August 29, 1956
U.S. Patent 2,905,761
Granted: September 22, 1959
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Charles A. Wilkins, New York.
"Control of Amplifier Source Resistance"
[Claim 1],[Claims 2-10 ],[Claim 10]. Diagrams: [Sheet 1]
[Sheet 2]
Referenced by Walker in U.S. Pat. 3,773,984
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Filed: September 9, 1958
U.S. Patent 3,061,675
Granted: October 30, 1962
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James Ross Macdonald
"Loudspeaker Improvement"
[Claims 1-5], [Claim 5 ]. Diagrams:[Sheet 1] [Sheet 2]
Referenced by Walker in U.S. Pat. 3,773,984.
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Filed: December 10, 1958
U.S. Patent 3,135,838
Granted: June 2, 1964
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William M. Wright, Boston Mass.
"Electrostatic Loudspeaker"
[Claims 1-10], [Claims 11-25 ]. Diagrams: [Sheet 1] [Sheet2] [Sheet 3] [Sheet 4 ] [Sheet 5] [Sheet 6]
Referenced by Walker in U.S. Pat. 3,773,984.
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Filed: May 18, 1967
U.S. Patent 3,542,952
Granted: November 24, 1970
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Chien San Wang, Denver, Colorado
"Low Distortion Signal Reproduction Apparatus"
[Claim 1] [Claims 2-8]. Diagrams: [Sheet 1]
Referenced by Walker in U.S. Pat. 3,773,984.
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Filed: November 3, 1970
U.S. Patent 3,773,984
Granted: November 20, 1973
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Peter James Walker of Huntingdon, England.
"Electrostatic Loudspeaker with Constant Current Drive"
[Claims 1-7]. Diagrams: [Sheet 1]
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