Email Speaker History, Chapter 4
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Chapter 4: 1948 - 1975
Smaller Sizes for the Home and Studios
By Roy Johnson, loudspeaker designer, and Janet Lynn, Green Mountain Audio, Inc.
1948.
C.A. Ewaskio, of the Acoustics Research Laboratory, Harvard University, discusses the causes of electro-acoustic phase shift in loudspeakers and introduces the first accurate method for measuring phase shift.
1950.
Bozak introduces the model B-201, a 12", two-way speaker with minimum phase-shift.
1952.
Bartholomew N. Locanthi II applies elec- trical circuit analogies to solve loud- speaker mechanical problems. More >
1954.
American educator Edgar Villchur, Ms.Ed., former part-time electronics instructor at NYU, introduces the first bookshelf speaker, the Acoustic Research AR-1 (right), based on his acoustic suspension principle (later refined by Richard H. Small).
1954.
American electrical engineer and scientist Leo L. Beranek (right) publishes Acoustics, in which he presents mathematics which describe room acoustics as well as the acoustics inside a loudspeaker. More: (page 3) > More: Read the 1996 interview > American Academy of Arts & Sciences, 2000 >
1955.
Murlan S. Corrington presents a method of correlating transient measurements on speakers with listening tests. More >
1956.
E. J. ("Ted") Jordan publishes in Wireless World the mathematics for designing woofer enclosures with optimum bass performance. More >
1956.
Gerald Shirley, president of The Televex Company, Yonkers, N.Y., publishes the principles and mathematics behind the 'Corona wind' loudspeaker, invented by Dr. David M. Tombs of England. A working model is measured and analyzed. The speaker made sound with no moving parts.
1957.
Peter J. Walker, a former amplifier salesman for public address systems in England, builds the first wide-range electrostatic speaker, the Quad ESL. More >
1957.
Villchur designs the first dome tweeter (right). "Objective measurements in audio are primary, but they're useless unless they've been subjectively validated as predictors of musical accuracy," he says.
1958.
While working at the Banbury Aluminum Development Laboratory, England, Donald A. Barlow, a British metallurgist, suggests in a paper published in Wireless World that benefits might be gained from the use of a "foil-stressed" diaphragm in loudspeakers. He is contracted by the H.J. Leak & Co., Ltd., London to lead the development of a 'piston-action' speaker.
1959.
James F. Novak, an American electrical engineer and senior design engineer at the Jensen Manufacturing Company, presents the paper, "Performance of Enclosures for Low-Resonance High-Compliance Loudspeakers," in which he analyzes the low-frequency output of ported speakers versus sealed boxes. He concludes that the ported speaker can have greater acoustic output for a given amount of distortion than a sealed box of similar size.
1959.
While based at the University of Texas at Austin, James H. Craig of the Defense Research Laboratory and Lloyd A. Jeffress, American physicist, psychologist, and professor in the Department of Psychology, describe the effect of phase (pg. 22) on the quality of a two-component, unsymetrical, complex tone. More: Journal, Acoustic Society of America, 34, 1752, (1962); also see this link.
1960.
French physicist Leon N. Brillouin publishes a book on mathematics and the effects of phase shift and time delays on complex traveling waves, Wave Propagation in Periodic Structures. His works also include the book, Science and Information Theory and the manuscript, "Relativity Reexamined." More infoamerica.org > Google images results > More >
1961.
Australian mechancial and electrical engineer A. Neville Thiele publishes "Loudspeakers in Vented Boxes, Parts I and II" in the Amalgamated Wireless Australasia, Ltd., (AWA) Technical Review, in which he describes his mathematics and experimental results regarding the design of vented boxes for woofers. The papers will be published in the U.S. by the Audio Engineering Society and appear in its Journal in 1971. More: Audioxpress.com's interview >
1962.
American physicist Peter W. Tappan publishes research on reducing vibration of speaker cabinet walls in "Loudspeaker Enclosure Walls." He discusses acoustical requirements, typical wall behavior, and the effects on system performance of various wall properties.
1962.
Harold Leak (left) of the H.J. Leak & Co., Ltd, London introduces the "sandwich cone" speaker that was developed by Donald A. Barlow.
1962.
E. J. ("Ted") Jordan, chief designer for Goodmans Industries, Wembly, England, publishes Loudspeakers. It presents a mathematical analysis of loudspeaker theory and the first principle derivation of all speaker parameters, which will become known as the 'TM' parameters.
1962.
American electrical engineer J. Robert Ashley (right) describes his transient response of ideal crossover circuits.
1964.
Hilliard presents notes on how phase and delay distortions affect the quality of speech, music, and sound effects.
1965.
Raymond Edgar Cooke, a British electrical engineer and founder of Kent Engineering and Foundry, designs the K1, a three-way speaker, (right). The bass and midrange units have foil-stiffened, vacuum-formed, expanded polystyrene diaphragms, similar to the Leak 'sandwich' design of 1962.
1965.
Roy F. Allison, plant manager and former chief engineer at Villchur's Acoustic Research, shows a direct relationship between woofer efficiency and low-frequency response.
1965.
American electrical engineer Bill Hecht patents the soft-dome tweeter. More >
1966.
Ashley describes the causes of phase shift in audio systems.
1967.
Richard C. Heyser, an American electrical engineer at the Jet Propulsion Laboratory, California Institute of Technology, describes how to measure speakers with Time Delay Spectrometry. In addition to researching audio and acoustic measurements in a personal laboratory, Heyser's work involves communication and instrumentation design for major space programs, beginning with America's first satellite, Explorer I.
1968.
J.E. Benson, an Australian research engineer for AWA, publishes "Theory and Design of Loudspeaker Enclosures: Part I, Electro-Acoustical Relations and Generalized Analysis" in the company's Technical Review, of which he was editor from 1948 to 1974. Part I was the first of three articles in which he analyzes sealed, vented, and passive radiator designs. Part II will be published in 1971.
1968.
American electrical engineer Paul W. Klipsch presents a mathematical analysis of modulation distortion in speakers and measurement techniques. Results are shown on a spectrum analyzer.
1972.
Benson publishes "Theory and Design of Loudspeaker Enclosures, Part III: Introduction to Synthesis of Vented Systems," in the AWATechnical Review. Having provided the basis for the design of the loudspeaker systems installed by AWA in the Sydney Opera House, he shares in the Prince Philip Prize for Australian Design.
1973.
American civil engineer James K. Iverson presents "The Theory of Loudspeaker Cabinet Resonances." It is his research on the theory and nature of loudspeaker-cabinet panel resonances and a comparison of the effectiveness of various braces.
1973.
American electrical engineer Richard H. Small (on right, with Thiele) publishes a simplified method for vented-box woofer design, which combines Thiele's and Novak's work. Part 1 was published in June; Part 2, in July/August; Part 3 in September, and Part 4 was presented in October. Thiele's papers (originally published in Australia, 1961) together with Small's result in the development and acceptance of what will become known as the "Thiele-Small Parameters," a standard set of measurement criteria used to develop a test enclosure for any woofer or midrange driver. Audioxpress.com's interview with Thiele >
1973.
Benson publishes "An Introduction to the Design of Filtered Loudspeaker Systems" in the AWA Technical Review in which he describes analyses of the overall response and input impedance of second-order loudspeaker systems when fed through first- and second-order electrical filters. He establishes useful relationships applicable to crossover network design with loudspeaker terminations and which also lead to the synthesis of composite high-pass systems. Amazon.com: Benson, J.E., Theory and Design of Loudspeaker Enclosures >
1974.
Allison describes the destructive interference pattern that develops when a radiator is located one-quarter wavelength away from a reflective surface in his paper, "The Influence of Room Boundaries on Loudspeaker Power Output." His explanation of how room boundaries and loudspeaker power output interact will become known as the "Allison Effect."
1974.
American electrical engineer and physicist D. B. Keele, Jr. (left) presents an extremely simple method for measuring loudspeaker performance at low frequencies, which is used to this day. More >
1975.
At the Audio Engineering Society's Convention, Erik Baekgaard, manager of electronic engineering, R&D section, Bang & Olufsen, headquartered in Denmark, presents his paper, "Loudspeakers: The Missing Link" in which he describes a new test specification for loudspeakers that includes phase distortion. He states that low phase distortion is necessary.
1975.
Allison publishes "The Sound Field in Home Listening Rooms II," about room-boundary effects on bass response and presents experimental results of various woofer placements. More >
1975.
Two engineers working for the Nippon Gakki Company (Yamaha), located in Hamamatsu, Japan, present their paper, "The Beryllium Dome Diaphragm -- Its Use, Manufacture and Importance in Loudspeaker Systems" at the Audio Engineering Society Convention. Yasunori Yuasa and Stewart Greenberg discuss the application of beryllium metal, which will be seen in the midrange and tweeter of their own speaker, the NS1000M.
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