5.1 surround sound ("five-point one") is the common name for surround sound audio systems. 5.1 is the most commonly used layout in home theatres. It uses five full bandwidth channels and one low-frequency effects channel (the "point one"). Dolby Digital, Dolby Pro Logic II, DTS, SDDS, and THX are all common 5.1 systems. 5.1 is also the standard surround sound audio component of digital broadcast and music.

All 5.1 systems use the same speaker channels and configuration, having a Front Left (FL) and Front Right (FR), a Center Channel (CNT), two surround channels (Surround Left - SL and Surround Right - SR) and the low-frequency effects (LFE) channel designed for a subwoofer.

History

A prototype for five-channel surround sound, then dubbed "quintaphonic sound", was used in the 1975 film Tommy.

5.1 dates back to 1976, when Dolby Labs modified the track usage of the six analogue magnetic soundtracks on Todd-AO 70 mm film prints. The Dolby application of optical matrix encoding in 1976 (released on the film Logan's Run) did not use split surrounds, and thus was not 5.1. Dolby first used split surrounds with 70 mm film, notably in 1979 with Apocalypse Now.