Taming the room
Feedback, equalisation and measurement
Between the 1950s and the 1990s, tuning a sound system moved from ears and notch filters to transfer-function measurement.
1930s onward
Early equalisers
RCA’s John Volkman is credited with the first external variable equaliser, in a 1930s cinema, and Art Davis’s Type 7080 at Cinema Engineering with the first active graphic equaliser.
Sources, summarised in our own words
- RaneNote 122, “Operator Adjustable Equalizers: An Overview” (Dennis Bohn, 1990) · Rane · link pending
1960s
Notching out feedback
C. P. Boner, a physics professor at the University of Texas, built his equalisation method on the fact that feedback starts at one frequency. His passive notch filters, about 5 Hz wide, were wired 100 to 150 sections at a time; his former student Gifford White built them, founding White Instruments.
Sources, summarised in our own words
- RaneNote 122, “Operator Adjustable Equalizers: An Overview” (Dennis Bohn, 1990) · Rane · link pending
1967–68
One-third octave
Altec’s Acousta-Voice set of passive one-third-octave filters, developed by Art Davis, Jim Noble and Don Davis, offered a broadband alternative. Rane’s history dates it to 1967; Don and Carolyn Davis’s own account dates the prototype and its AES presentation to 1968.
Sources, summarised in our own words
- RaneNote 122, “Operator Adjustable Equalizers: An Overview” (Dennis Bohn, 1990) · Rane · link pending
- A Conversation with Audio Pioneers, SynAudCon Founders Don & Carolyn Davis · ProSoundWeb · link pending
1967–1983
Measuring in time
Richard Heyser of the Jet Propulsion Laboratory published time-delay spectrometry in the Journal of the AES in 1967. It let engineers separate the direct sound from room reflections. Crown’s Techron division turned it into the TEF analyser in the early 1980s.
Sources, summarised in our own words
- Audio Breakthroughs with TEF Analysis · TV Technology · link pending
1973
Teaching the craft
After leaving Altec, Don and Carolyn Davis founded Syn-Aud-Con in 1973, taking sound-system seminars on the road; their Sound System Engineering first appeared that year. Yamaha’s Sound Reinforcement Handbook by Gary Davis and Ralph Jones, published by Hal Leonard, became a standard text; its second edition appeared in 1988.
Sources, summarised in our own words
- A Conversation with Audio Pioneers, SynAudCon Founders Don & Carolyn Davis · ProSoundWeb · link pending
- The Sound Reinforcement Handbook, 2nd ed. (ISBN 978-0881889000), listing · AbeBooks · link pending
1986–1996
