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GENIUS! #18: Michael Gerzon and Ambisonics

"Stereo: An obsolescent term meaning a hi-fi system in which two speakers are missing"

Tragically, Michael Gerzon did not live long enough to see his greatest achievement, Ambisonics, become part of the quest for a truly immersive audio experience.

Born in Birmingham at the end of 1945, Gerzon had, like many geniuses, many interests and brought his undoubtedly immense intelligence to bear on other areas of audio. He was involved in the early development of digital compression and processing that formed the basis of Waves’ first products. But it is his work on Ambisonics that cements Gerzon’s place in the sound pantheon.

Gerzon was both a mathematician and a recording engineer. His father, David, who had studied physics and chemistry, gave the shy, introverted Michael his first reel-to-reel tape recorder, which both helped in his school studies and began a life-long interest.

While studying mathematics at Corpus Christi College, Oxford, Gerzon joined the University Tape Recording Society (OUTRS) with like-minded fellow student Peter Craven, who would work with him on future developments. It was the now defunct Studio Sound magazine that published Gerzon’s tongue-in-cheek glossary of audio terms, including his observation that stereo was an obsolete format with two loudspeakers missing.

Gerzon was dismissive of the quadrophonic systems that were produced in the early to mid-70s. Working with others, including Professor Peter Berners Fellgett of the University of Reading, he set out to overcome the technical and acoustic shortcomings of quad and create something that captured and reproduced an accurate sound picture.

His conclusion was that proper spatial imaging could only be achieved if the actual acoustical signals contained in the recording environment were recorded. He defined the soundfield as comprising the absolute sound pressure level and the three pressure gradients: left/right, front/back and up/down.

Having calculated such a system, which was named Ambisonics (both syllables from Latin, ‘ambi’ for ‘around’ or ‘surround’ and sonic for sound), Gerzon and his colleagues (pictured above right: Michael Gerzon, Paul Hodges, Peter Craven, Stephen Hornton) needed a specialist microphone to record the necessary information. The resultant Soundfield microphone, which has four capsules mounted on the faces of a tetrahedron, was manufactured first by Calrec Audio, then SoundField and now TSL PPL SoundField.

The Core Sound TetraMic is also based on Gerzon’s patents and for some time both it and the Soundfield were the only practical realisations of Ambisonics. Despite enthusiasm for it among studios and record companies, the recording and mastering format itself faded away in the early 1980s.

Gerzon was downhearted at this, something not helped by persistent ill health and stays in hospital. His later work with Waves raised his spirits, and supplied necessary income. The irony is that multichannel systems such as Dolby Digital and DTS were becoming established for the cinema when Gerzon died in May 1996.

Nearly twenty years after his death Ambisonics has a new lease of life as today’s researchers attempt to produce a fully immersive soundscape. The SoundField mic (with a capital ‘F’) also continues to evolve. As its current designer, Pieter Schillebeeckx, says, Michael Gerzon was a genius because of his wide range of interests, including Ambisonics, lossless compression, music recording and poetry, which gave him core visions beyond just mathematical equations, although he did ultimately use mathematics to solve the technical problems he faced.

Hail to the boffins! Genius! is all about celebrating those clever people whose inventions have transformed the world of professional audio. Mailed out with the February print edition of PSNEurope, the 36-page supplement is also available to read in handy digital-edition form. Read it online, or download as a PDF, at

With thanks to Michael Gerzon: Beyond Psychoacoustics by Robert Charles Alexander (Dora Media Production 2008;; and Paul Hodges for the use of his photographs