1.mono*
2.Stereo
2.1 2.0**
2.2 2.1**
3.Multichannel Audio
3.1. 4.0 surround
3.2. 4.0 Quard
3.3. 4.1
3.4. 5.1
3.5 5.1 side***
3.6 6.1
3.7 7.1 Front
3.8 7.1 Surround
3.9 9.1 surround
3.10 10.2
3.11 22.2
4.Virtual Surround sound
5.ambisonic surround sound
5.1 panor-ambisonic
(*) For historical reasons, when using (1.0) mono sound, often in technical implementations the first (left) channel is used, instead of the center speaker channel, in many other cases when playing back multi-channel content on a device with a mono speaker configuration all channels are downmixed into one channel. The way standard mono and stereo plugs used for common audio devices are designed ensures this as well.
(**) Stereo (2.0) is still the most common format for music, as most computers, television sets and portable audio players only feature two speakers, and the red book Audio CD standard used for retail destribution of music only allows for 2 channels. A 2.1 speaker set does generally not have a separate physical channel for the low frequency effects, as the speaker set downmixes the low frequency components of the two stereo channels into one channel for the subwoofer.
(***) This is the correct speaker placement for 5.1 sound reproduction from Dolby and DTS systems.
