Channels in an audio system -- a clarification

Rory Buszka

Partition Master
In an audio system, when a number of individual signal paths are provided for differing or unique audio signals, those signal paths are referred to as channels. A Monoaural ("mono") audio system has only one channel. A Stereophonic ("stereo") audio system has two channels, which provide an aural "image" which allows sound sources to be located by your brain at varying positions between the two speakers. Usually, this is what you see referred to as a 2.0 system, which is meant to indicate that there are two audio channels and no separate low frequency reproduction. Surround sound systems use five, six, or seven loudspeakers which are placed around the room and fed signals which correspond to their position in the room, to create a continuous surround sound field. Generally, there is a "center channel" speaker which is placed directly above or below (or even behind) the screen, to center the dialogue on the screen. Then there is a front left and front right speaker, much like in a 2-channel audio system. Then, there are two, three, or four speakers which are placed beside and behind the listener to complete the sound field. These would be referred to as a 5-channel, 6-channel, or 7-channel surround sound system, respectively. Yamaha makes a 9-channel receiver, though I know of no surround sound format that carries nine discrete channels of information.

If any of the above systems contain a separate, specialized loudspeaker ("subwoofer") to accomplish low frequency reproduction below the frequency range of the satellite speakers, then ".1" is added to the number of channels. (e.g. 5.1, 7.1) The ".1" comes from the fact that the subwoofer only reproduces about one-tenth of the total audible spectrum (the frequency band from 20Hz to 20,000Hz, of which subwoofers generally cover from 20-200 Hz). Therefore, if a system uses two subwoofers, or a subwoofer with two drivers, it does not become a 2.2, 5.2, 6.2, or 7.2 system, because the subwoofers are still fed with the same signal, which covers only 1/10 of the audible spectrum. If you have four subwoofers and five main speakers, you still do not have a 5.4-channel system. This is a silly mistake that I've been seeing a lot recently, and it's a shame that people keep making it.

So now you know, and moreover, you can tell when somebody else doesn't know.
Last edited:



Coming from an audio professional environment, I totally agree with Taterworks.
The post was very well explained, and specific. I work as a general manager in the audio field for Orange County Speaker in Southern CA, and I hear this mistake from customers everyday. We repair, test and spec about 150-200 speakers everyday from simple home audio to high end pro-sound for places like Dodger Stadium and Disneyland. It still surprises me to hear this misnomer from even the most experienced people in the industry.
Very well done Tator. Spread the knowledge.