Draft:ABC System
Matrix 4-channel quadraphonic sound system
From Wikipedia, the free encyclopedia
The ABC System was a short‑lived quadraphonic matrix sound format developed in the Soviet Union in the late 1970s and early 1980s. Developed by a team headed by musician Yuriy Berendyukov at the Leningrad Electrotechnical Institute of Communications, the system was adopted experimentally by the state‑owned Melodiya label.[1] Its encoding method was intended to create a panoramic, concert‑hall‑like sound field, in contrast to the discrete four‑corner presentation common in Western quadraphonic formats.[2]
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Design
According to a design description published in the Soviet electronics magazine Radio, discrete quadraphonic systems such as CD‑4 were regarded as too complex and costly for widespread use, since they required entirely new recording and playback equipment. The article further stated that matrix formats like SQ and QS offered only limited spatial realism, and that attempts to improve their performance through logic‑based gain‑control circuits introduced audible distortions while increasing system complexity and cost. After extensive experimental work on loudspeaker placement and listener position, the developers introduced what they termed a “panoramic encoding method” as the basis of the ABC system.
Through the use of a panoramic encoding device, multiple input sources were converted into weighted signal pairs that determined their position within the perceived 360‑degree soundfield. Because the method relied on simple summation of the inputs, the resulting two encoded channels occupied the same bandwidth as a normal stereo recording and could be handled by standard equipment. During playback, the recommended loudspeaker arrangement placed the four speakers at the corners of an isosceles trapezoid, with the listener positioned near or at the rear base. The rear loudspeakers were not advised to be spaced more than six meters apart.[3]
The system's name refers to the three primary phantom image zones created between the speaker pairs: zone A between the front speakers, zone B between the front-left and rear-left speakers, and zone C between the front-right and rear-right speakers. The recommended loudspeaker geometry and listening position were considered essential for maintaining these images. Moving toward the center of the trapezoid, such as in a traditional quadraphonic seating position, caused the side images to collapse and disrupt the continuity of the panorama.[4]
Surround Matrix
Although no encoding documentation has been published, the decoding matrix was published in the following form:
| ABC System decoding matrix[4] | Left Front | Right Front | Left Back | Right Back |
|---|---|---|---|---|
| Left Total | 1.0 | 0 | 1.0 | -0.7 |
| Right Total | 0 | 1.0 | -0.7 | 1.0 |
Known Recordings
Квадра. Демонстрационная Квадрафоническая Пластинка По Системе ABC — Melodiya, КА90‑11199‑200 (1978) ABC System at Discogs
Яблоко – Кантри‑Фолк‑Рок‑Группа «Яблоко» — Melodiya, C60‑15499‑500 (1980) ABC System at Discogs