Why 5.1-Channel Sound?

Why 5.1-Channel Sound?

April 23 - We all take for granted the idea of "5.1-channel" sound for home theater, but what exactly is ".1" of a channel? We all know that the ".1" in 5.1-channel sound is the low-frequency effects (LFE) channel that carries high-impact, low-bass information, usually to a subwoofer. But if you think about it, there's no such thing as a "tenth of a channel" either there's an information-carrying channel or there isn't.

In fact, the first reference to a ".1" channel was made as a joke by Tomlinson Holman, during a formal discussion with the Audio Engineering Society committee that set the standards for playback of film soundtracks in the home. You might know Holman as the creator of the THX standard when he worked for Lucasfilm; THX stands for "Tom Holman's eXperiment."

The AES committee was discussing the need for a low-frequency effects channel, and Holman whimsically proposed that it could be just "a tenth" of a channel, knowing full well that such a thing didn't exist. But the idea stuck, largely because it perfectly conveys the idea that the LFE channel has limited bandwidth compared with the other five channels.

Today we never think twice about the illogic of "5.1-channel" sound.