Editing Quadraphonic sound (section)

==Tape formats==

*[[Quadraphonic open reel tape|Q4 / quadraphonic reel to reel]] (1969)
*[[Quad-8|Quad-8 (Q8) / quadraphonic 8-track]] (1970)

Quadraphonic systems based on tape were also introduced, based on new equipment capable of playing four discrete channels. These recordings are all discrete 4–4–4 recordings released in [[reel-to-reel]] and [[8-track cartridge]] formats. Specially designed four channel machines were required to play these recordings. They are not compatible with stereo players.

=== Quadraphonic open reel tape (Q4) ===

[[File:TEAC 2340.jpg|thumb|A four-channel [[reel-to-reel tape]] unit from the 1970s, one of the few ways to achieve discrete four-channel sound at home]]

In these systems all four available tracks were recorded on the tape running in the same direction. Pre-recorded four channel reel-to-reel tapes were recorded at 7{{fraction|1|2}} inches per second (IPS), which is the fastest speed used for consumer grade reel-to-reel machines. By comparison stereo pre-recorded reel-to-reel tapes have 2 different programs with each running the opposite direction. Many stereo tapes were recorded at only 3{{fraction|3|4}} IPS, which is half of the full speed. The slower speed results in significantly poorer sound quality.<ref>{{Cite web|url=http://theartofsound.net/forum/showthread.php?1929-The-Official-Factory-Made-Reel-to-Reel-Tape-Thread&s=277907ddc0421c90b538c564d5d4f18f|title = The Official 'Factory-Made' Reel to Reel Tape Thread}}</ref>

=== Quadraphonic 8-track tape (Quad-8 and Q8) ===

[[RCA Records]] followed, in April 1970, with its announcement of a four-channel version of the [[8-track tape]], named ''[[Quad-8]]'' or ''Quadraphonic 8-track tape'' (later shortened to just '''Q8'''). These eventually appeared in staggered releases (70 Tapes) split by October, November, and December 1970.

The format was almost identical in appearance to stereo 8-tracks, except for a small sensing notch in the upper left corner of the cartridge. This signaled a quadraphonic 8-track player to combine the odd tracks as audio channels for program 1, and the even tracks as channels for program 2. The format was not backward-compatible with stereo or mono players; although quadraphonic players would play stereo 8-tracks, playing quadraphonic tapes on stereo players resulted in hearing only one-half the channels at a time.

The last release in the quadraphonic 8-track format was in 1978, although most had stopped appearing by the end of 1976.