In 1969, Dynaco introduced a system to ‘derive’ surround sound from stereophonic LPs by using a passive electronic circuit called a Hafler Circuit. This was designed by Dave Hafler of Dynaco in the early 1960s and required four speakers in a diamond configuration for derived quadraphonic (2:2:4) sound.
Around 1970, Dynaco introduced the Dynaquad system for encoding matrixed quadraphonic sound (4:2:4). The system was similar to EV Stereo-4 (EV-4) introduced in 1970, and was broadly compatible.
A sampler disc for the Dynaquad system was released in 1971 on the Vanguard Records label, and by this time it was suggested that the four speakers were placed in the four corners of the room rather than the diamond configuration.
Very few records appear to have used Dynaquad encoding. The 1970 eponymous album by The Flame may have used Dynaquad, along with some of the ‘Environments’ series by Syntonic Research. There were also some LPs and 7-inch singles produced by KL Recordings in the mid-1970s.