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5.1 surround sound ("five-point one") is the common name forsurround sound audio systems. 5.1 is the most commonly used layout inhome theatres.[1] It uses five full-bandwidth channels and onelow-frequency effects channel (the "point one").[2]Dolby Digital, DolbyPro Logic II,DTS,SDDS, andTHX are all common 5.1 systems. 5.1 is also the standard surround sound audio component ofdigital broadcast and music.[3]
All 5.1 systems use the same speaker channels and configuration, having a Front Left (FL) and Front Right (FR), aCenter Channel (CNT), twosurround channels (Surround Left -SL and Surround Right -SR) and thelow-frequency effects (LFE) channel designed for asubwoofer.[4][5]
A prototype for five-channel surround sound, then dubbed "quintaphonic sound", was used in the 1975 filmTommy.[6]
5.1 dates back to 1976,[7] when Dolby Labs modified the track usage of the six analogue magnetic soundtracks onTodd-AO 70 mm film prints. The Dolby application of optical matrix encoding in 1976 (released on the filmLogan'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 withApocalypse Now. Instead of the five screen channels and one surround channel of the Todd-AO format,Dolby Stereo 70 mm Six Track provided three screen channels, two high-passed surround channels and a low-frequency surround channel monophonically blended with the two surround channels.
A system of digital 5.1 surround sound was also used in 1987 at the Parisian cabaret theMoulin Rouge, created by French engineer Dominique Bertrand. To achieve such a system in 1985, a dedicated mixing console had to be designed in cooperation withSolid State Logic, based on their 5000 series, and dedicated speakers in cooperation with APG.[8] The console included ABCDEF channels: respectively, A left, B right, C centre, D left rear, E right rear, F bass. The same engineer had already developed a similar 3.1 system in 1973, for use at the official International Summit of Francophone States inDakar.[citation needed]
Digital sound and the 5.1 format were introduced in 1990, byKodak and Optical Radiation Corporation, with releases ofDays of Thunder andThe Doors using the CDS (Cinema Digital Sound) format.
When digital sound was applied to 35 mm release prints, withBatman Returns in 1992, the 5.1 layout was adopted. The ability to provide 5.1 sound had been one of the key reasons for using 70 mm for prestige screenings. The provision of 5.1 digital sound on 35 mm significantly reduced the use of the very expensive 70 mm format.
5.1 digital surround, in the forms of Dolby Digital AC-3 and DTS, started appearing on several mid-1990sLaserDisc releases, among the earliest beingClear and Present Danger andJurassic Park (the latter having both AC3 and DTS versions). Many DVD releases have Dolby Digital tracks up to 5.1 channels, due to the implementation of Dolby Digital in the development of the DVD format. In addition, some DVDs have DTS tracks, with most being 5.1 channel mixes (a few releases, however, have 6.1 "matrixed" or even discrete 6.1 tracks).Blu-ray anddigital cinema both have eight-channel capability which can be used to provide either 5.1 or7.1 surround sound. 7.1 is an extension of 5.1 that uses four surround zones: two at the sides and two at the back.
The order of channels in a 5.1 file is different across file formats. The order inWAV files is (not complete) Front Left, Front Right, Center,Low-frequency effects, Surround Left, Surround Right.[9]
In music, the main goal of 5.1 surround sound is a proper localization and equability of all acoustic sources for a center-positioned audience. Therefore, ideally five matched speakers should be used.
For playback theInternational Telecommunication Union (ITU) recommends the following configuration (ITU-R BS 775):[10][5]