Audio Engineering Society
Chicago
Meeting Review, April 11, 2006
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4/11/06
Meeting Highlights Constant-Directivity Horn Development, TEF
Measurements, And The Nearfield Paper� by veteran loudspeaker design and test engineer and
Academy Award winner Don Keele. About 35 attendees were treated to an audio history
lesson, including several highlights of Mr. Keele�s own 34-year career. The presentation started with the first
generation of constant-directivity horns, beginning with the Electro-Voice HR models (also known as the
�white horns�) and the TL Bass Boxes. The HR line was a new direction in horn design,
making its public debut in 1974. In 1975 Mr. Keele presented on the technology at the 51st Convention
of the AES. The TL line was also developed around the same time, and was initially only sold
as plans except for one model. In 1976, Altec
Lansing started producing its Manta Ray line of Horns, about which Cliff Henricksen and Mark Ureda
presented at the 58th Convention of the AES in 1977. Having some advantages and disadvantages over previous
designs, one practical advantage was ease of manufacture due to the lack of curved surfaces. The
JBL Bi-Radial line was the last of the first generation of CD horns, with production starting in
the late 1970�s. Mr. Keele reviewed two patents he received during this period. The next part of the presentation covered
the early history of Time-Energy-Frequency (TEF) measurements, and its implementation with
the test products developed by the Tecron Division of Crown, International. This prompted a
spirited, sentimental group discussion about the TEF System 10 of the early 1980�s. Mr. Keele
concluded with a brief recounting of the history behind his 1974 AES Journal
paper titled Low Frequency Loudspeaker Assessment
by Nearfield Sound Pressure Measurement, being sure to give credit to Ray Newman,
who inspired the work but declined to co-author the paper. The lesson was a valuable reminder of how
audio technology was advanced back when computational power was rare, so the analysis was
fundamental out of necessity. This resulted in practical, elegant designs that remain the roots of
many of today�s products. |
