5.1 ("five point one") is the common name for six channel surround sound multichannel audio systems.
5.1 is now the most commonly used layout in both commercial cinemas and home theaters.
It uses five full bandwidth channels and one low-frequency effects channel (the "point one").
Dolby Digital, Dolby Pro Logic II, DTS, and SDDS 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 and right, a center channel, two surround channels and a subwoofer. 5.1 surround sound - Wikipedia, the free encyclopedia