Digital Sound Processing and Home Theaters
With the coming of the DVD era of consumer video, digital sound processing is becoming the standard. Typical is the so-called 5.1 channel encoding, for which one of the names is "Dolby digital", crediting Dolby Laboratories with much of the development work. The implication of "5.1 channels" is that there are five discrete full sound signals plus a signal for the subwoofer which is limited to the low frequency range and is the ".1" in the "5.1". A popular alternative name for the low frequency speaker is a "LFE" or "Low Frequency Effects" channel.
The Dolby web site has a considerable amount of general information about setting up home theaters. Among the bits of advice given there is that the left and right surround speakers should be alongside, slightly to the rear and above the main listening position. They should be pointed so that the sound sweeps across the main listening area from both directions. This kind of arrangement is thought to be beneficial by keeping your ear from localizing the sound as coming from these speakers - they are supposed to provide a volume sound, but only rarely should be perceived as the main source of sound.
Sound reproduction concepts
Audio signal concepts