Introduction
True surround sound is more than just playing a bunch of speakers. It is a cohesive sound field that puts the listener in the center of the recording, allowing each speaker to individually recreate part of the experience. Sure, you could set up 5, 6, or 7 speakers, put the receiver on a setting to play all channels and get the same sound from each one. However, this would lack the nuance of the separate channels recreated by a surround sound system. The process begins at the creation of your source material (DVD, television program) and ends when you hear the audio from each speaker.
Creation
Surround sound consists of three or more channels of distinct audio. Most soundtracks today use a 5.1 format, which is actually six channels: five for speakers and the ".1" for low frequency effects (LFE) produced by a subwoofer. When a movie or other program is made, the soundtrack is mixed in the studio. Technicians take individual sounds from the greater soundtrack and break them down into specific channels. In a 5.1 soundtrack there are separate channels as follows: LFE, front right, front center, front left, rear right and rear left. Other surround formats incorporate even more channels. Once the soundtrack has been properly mixed, the audio medium (DVD) is encoded with the surround format information.
Decoding
In order to play the surround sound format in your home, you need a home theater receiver or processor. Among the other functions of a receiver, it is responsible for decoding the formatting from your source, like a DVD. Surround sounds are recorded in a number of different formats and incorporate a number of channels. Dolby Digital is one standard that uses a 5.1 set-up, whereas Dolby Digital EX is 6.1. DTS is another company that produces surround formats. The receiver should be set to a program mode that is compatible with the format of your source. The receiver then separates the single input signal into the individual channels, amplifies each signal and then routes each signal to the specific speaker that it was recorded for. In order to truly experience surround sound as it was recorded, you'll need to have the correct number of speakers for the specific format being used.
Speakers
Each speaker handles the individual part of the soundtrack that it has been "assigned" to and recreates the audio for that part. The end result is that you are surrounded by the audio from the soundtrack with different parts coming at you from different directions. For instance, if there is a speeding race car, the sound may move from the front speakers to the rear to simulate a car speeding past you. The LFE channel provides deep, rumbling bass largely for special effects. If you are using more or less speakers than the format being used, sound will be mixed or split into the existing speakers.
Tags: your source, audio from, being used, Dolby Digital, each signal, each speaker