The Quad ESL - Patents

Quad Electrostatic Loudspeaker

The patents listed on this page do not, by any means, cover all patents ever granted in the area of electrostatic speakers. They concern the original Quad ESL in the main. Click the link above to see Quad ESL ‘63 patents. For example, I have deliberately left out significant work in the general field by Edelman (1930 - 31), and an ancient paper by Constantin Chilowsky and Paul Langevin [Sheet 1, Sheet 2] (yes, the famous French physicist), in the area of electrostatics. The papers and patents referred to herein are those which are directly related to the development of the Quad electrostatic loudspeaker, as quoted by Walker and WIlliamson. Where possible, 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 Patents are arranged below in chronological order by date of grant, not date of application. This will settle the confusion in some people's minds as to why the speaker is sometimes referred to as the ESL55 and sometimes as the ESL57. These are the years of filing for U.S. Patents 3,008,013 and 3,008,014 respectively. The speaker should simply be called the Quad Electrostatic Loudspeaker, as the designers called it.

Patent Dates	Details of Inventor, Title and Claims.
Filed: November 28, 1921 U.S. Patent 1,550,381 Granted: August 18, 1925	Joseph Masolle, Hans Vogt and Josef Engl assignors to Tri-Ergon Ltd., of Zurich, Switzerland "Electrostatic Telephone" [Claims 1-7]. [Diagrams1] [Diagrams 2] Referenced by Walker and Williamson in U.S. Pat. 3,008,014.
Filed: May 2, 1925 U.S. Patent 1,622,039 Granted: March 22, 1927	Frederick W. Lee, Owing Mills, Maryland. "Apparatus for and Method of Reproducing Sound". [Claims 1-5] [Claims 6-14]. Diagrams: [Sheet 1] [Sheet2] Referenced by Walker and Williamson in U.S. Pats. 3,008,013 & 3,008,014.
Filed: February 12, 1926 U.S. Patent 1,631,583 Granted: June 7, 1927	John Depew, of New York. "Capacitatively Actuated Loudspeaker". [Claims 1- 6].[Claim 6] Diagrams: [Sheet 1 ] Referenced by Walker and Williamson in U.S. Pat. 3,008,014
Filed: March 24, 1926 U.S. Patent 1,674,683 Granted: June 26, 1928	Walter Hahnemann, Kitzberg, Germany, assigned rights to Lorenz Aktiengesellschaft. "Arrangement for Uniform Electrical Sound Transmission". [Claims 1-3], Diagrams: [Sheet 1] [Sheet 2] Referenced by Walker and Williamson in U.S. Pat. 3,008,013
Filed: June 6, 1928 U.S. Patent 1,762,981 Granted: June 10, 1930	Ralph V.L. Hartley of South Orange, N.J. assigned rights to Bell Telephone Labs., N.Y. "Acoustic Device" [Claim 1], Diagrams: [Sheet 1] Referenced by Walker and Williamson in U.S. Pats. 3,008,013 & 3,008,014
Filed: Sept. 27, 1929 G.B. Patent 346,646 Granted: April 16, 1931	Edward Washburn Kellogg, Schenectady, N.Y. assigned rights to General Electric Co. N.Y. "Production of Sound" [Claim 1] [Claims 2-8], Diagrams: [Sheet 1] Indirectly Referenced by Walker and Williamson in U.S. Pats. 3,008,013 See also later, equivalent US Patent 1,983,377 on this page.
Filed: February 12, 1930 G.B. Patent 348,573 Granted: May 12, 1931	Albert Rauser and Wilhelm Steuer, of Kottbuser-Ufer 39/40, Berlin, S.O. 26 "Improvements Relating to Electrostatic Loud-speakers". [Claims 1-5], Diagrams: [Sheet 1] Referenced by Walker and Williamson in U.S. Pat. 3,008,014
Filed: June 1, 1931 G.B. Patent 370,248 Granted: April 7, 1932	Albert Rauser and Wilhelm Steuer, of Kottbuser-Ufer 39/40, Berlin, S.O. 26 "Improvements in Electrostatic Loud-speakers". [Claims 1-8], Diagrams: [Sheet 1] Referenced by Walker and Williamson in U.S. Pat. 3,008,014
Filed: Sept. 8, 1930 G.B. Patent 372,649 Granted: May 12, 1932	Hans Vogt, Genthinerstrasse 17, Berlin, W. 35, Germany. "Improvements Relating to the Insulation of Fixed Electrodes of Electrostatic Loudspeakers" [Claims 1-3] [Claims 4,5], Diagrams: [Sheet 1] Indirectly Referenced by Walker and Williamson in U.S. Pat. 3,008,014
Filed: Sept. 15, 1928 U.S. Patent 1,881,107 Granted: Oct. 4, 1932	Hans Vogt of Berlin-Wilmersdorf, Germany. "Sounding Condenser" [Claims 1-5], Diagrams: [Sheet 1] [Sheet 2] Referenced by Walker and Williamson in U.S. Pat. 3,008,013. Also ref: GB Patent 322,744 with 17 claims, granted December 10, 1929
Filed: July 30, 1930 U.S. Patent 1,930,518 Granted: October 17, 1933	Jurjen S. High of Camden, N.J. assigned rights to Westinghouse Electric and Manufacturing Co. Pennsylvania. "Electrostatic Loudspeaker" [Claims 1-6 ], Diagrams: [Sheet 1] [Sheet 2] Referenced by Walker and Williamson in U.S. Pats. 3,008,013 & 3,008,014
Filed: Sept. 27, 1929 U.S. Patent 1,983,377 Granted: December 4, 1934	Edward Washburn Kellogg, Schenectady, N.Y. assigned rights to General Electric Co., N.Y. "Production of Sound" [Claims 1-13], Diagrams: [Sheet 1] Referenced by Walker and Williamson in U.S. Pat. 3,008,013. Also ref: GB Patent 346,646 which pre-dates this grant of patent on the same device. See prior citation of E.W. Kellogg on this page.
Filed: April 9, 1946 G.B. Patent 610,297 Granted: Oct. 13, 1948	Etablissements S.M. Body Corporate of 26 Rue de Lagny, Paris. "Improvements in Electrostatic Microphones and Loud-speakers" [Claims 1-4], Diagrams: [Sheet 1 ] Referenced by Walker and Williamson in U.S. Pat. 3,008,013.
Filed: October 5, 1949 U.S. Patent 2,631,196 Granted: October 5, 1953	Arthur A. Janszen, Cambridge, Mass. "Electrostatic Loud-Speaker" [Claims 1-7 ], Diagrams: [Sheet 1] [Sheet 2] [Sheet 3] Referenced by Walker and Williamson in U.S. Pats. 3,008,013 & 3,008,014.
Filed: December 12, 1951 U.S. Patent 2,796,467 Granted: June 18, 1957	Winston E. Kock, Basking Ridge, N.J., assigned rights to Bell Telephone Labs., N.Y. "Directional Transducer" [Claim 1], Diagrams: [Sheet 1 ] Referenced by Walker and Williamson in U.S. Pats. 3,008,013 & 3,008,014.
Filed: December 11, 1953 U.S. Patent 2,855,467 Granted: October 7, 1958	Paul Curry, New Haven, Connecticut assigned rights to Curry Electronics Inc., New Haven, Conn. "Loudspeakers" [Claims 1-5] [Claims 6-10]. Diagrams:[Sheet 1] [Sheet2] Referenced by Walker and Williamson in U.S. Pat. 3,008,014.
Filed: November 29, 1954 U.S. Patent 2,864,899 Granted: December 16, 1958	Henry W. Parker, Flushing, N.Y. "Transducer" [Claim 1 ], Diagrams: [Sheet 1] Referenced by Walker and Williamson in U.S. Pat. 3,008,014.
Filed: July 15, 1955 U.S. Patent 3,008,013 Granted: November 7, 1961	David Theodore Nelson Williamson, Edinburgh, Scotland assigned rights to Ferranti Ltd., London. Peter James Walker of Huntingdon, England. "Electrostatic Loudspeakers" [Claims 1-3] [Claims 4-10]. Diagrams: [Sheet 1] [Sheet 2] [ Sheet 3] [Sheet 4]
Filed: September 12, 1957 U.S. Patent 3,008,014 Granted: November 7, 1961	David Theodore Nelson Williamson, Edinburgh, Scotland assigned rights to Ferranti Ltd., London. Peter James Walker of Huntingdon, England. "Electrostatic Loudspeakers" [Claims 1-15] [Claims 16,17], Diagrams: [Sheet 1] [Sheet 2]