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 70mm film, notably in 1979 with Apocalypse 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. 5.1 digital surround, in the forms of Dolby Digital AC3 and DTS, started appearing on several mid 90s Laserdisc releases, with among the earliest being Clear and Present Danger and Jurassic 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” tracks). Blu-ray and digital cinema both have eight-channel capability which can be used to provide either 5.1 or 7.1 surround sound. 7.1 is an extension of 5.1 that uses four surround zones: two at the sides and two at the back. Music Suggested configuration for 5.1 music listening . Regarding music, the main goal of 5.1 surround sound is a proper localization and equability of all acoustic sources for a centered positioned audience. Therefore, ideally five matched speakers should be used. For play-back of 5.1 music recommendations of the International Telecommunication Union (ITU) have been released and propose the following configuration (ITU-R BS 775): five speakers of the same size for front, center and surround identical distance from the listeners for all five speakers angle adjustment regarding viewing direction of audience: center 0°, front ±22.5° for movies ±30° for music, surround ±110°
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. 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. 5.1 digital surround, in the forms of Dolby Digital AC3 and DTS, started appearing on several mid-' 90s LaserDisc releases, among the earliest being Clear and Present Danger and Jurassic 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” tracks). Blu-ray and digital cinema both have eight-channel capability which can be used to provide either 5.1 or 7.1 surround sound. 7.1 is an extension of 5.1 that uses four surround zones: two at the sides and two at the back. Music Suggested configuration for 5.1 music listening 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 of 5.1 music , the International Telecommunication Union (ITU) recommends the following configuration (ITU-R BS 775): five speakers of the same size for front, center and surround identical distance from the listeners for all five speakers angle adjustment regarding viewing direction of audience: center 0°, front ±22.5° for movies ±30° for music, surround ±110°
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