Integrated info @ Audio Encoding, Enhancement technologies as DOLBY, DTS, SDDS, DATASAT & THX Technologies etc.
5.1 Channel Surround (3-2 Stereo) (digital discrete: Dolby Digital, DTS, SDDS, Penteo)
Delivers Five discrete audio channels and 1 LFE channel from a 6 channel source:
Two channels for speakers at the front—left (L) and right (R).
One channel for speaker at the center—center (C).
Two channels for surround speakers at the rear—surround left (LS) and surround right (RS).
One low-frequency effects channel (LFE).
Describes the Dolby Digital, Digital Theater System (DTS), and Sony Dynamic Digital Sound (SDDS) systems. Source media, usually DVD and sometimes Laser Disc or satellite/digital cable is often branded with "Dolby Digital" and/or DTS logos.
Although DTS uses a higher data rate than Dolby Digital, this doesn't mean that the fidelity is higher.
5.1 surround sound may also be referred to as 3-2 stereo. This defines the configuration that has been standardised for numerous surround sound applications. The term 3-2 refers to 3 front speakers and 2 rear speakers.
Placement: 5.1 speaker layouts should conform to the ITU-R BS.775 standard, despite the myth that music and video content require different placements. The ITU standard states that the left and right speakers are located at ±30°, while the rear speakers should be positioned approximately ±110°. There is speculation that rear loudspeakers at ±150° provide "more exciting surround effects".