Surround Systems and Audio Concepts.

Surround Sound Systems - Main Considerations
The concept of `surround sound` revolves around the ability to record multiple, discrete sound channels on, for example, the sound track of a DVD, or an HDTV broadcast. Each individual channel is then reproduced on its own, dedicated, loudspeaker. Loudspeakers are positioned to the front, rear and sides of a listening space, with the intention of encapsulating, or `surrounding` the listener with sound. Sound emanates from a full 360 degrees around the listener, and individual sources of sound are not immediately identifiable, leading to a lifelike, immersive listening experience.

Dolby Digital is the accepted industry standard for home theatre and home entertainment systems. Dolby Digital allows up to five main sound channels, plus a sub channel for bass effects, to be encoded, and is therefore known as a `5.1 channel` format, or `codec` (`coding/decoding`) technology.

Low frequency, bass effects are a vital part of the whole surround sound experience, and are best reproduced on their own `subwoofer`. A subwoofer is a specialised loudspeaker dedicated to the reproduction of bass audio frequencies (the `.1` in `5.1`). The problem with subwoofers is that they do tend to be quite large and obtrusive, even if placed in the corner of a room. This placement, in itself, is not a problem; indeed, in many cases, the best results can be achieved from a subwoofer by placing it in a corner. However, if space is at a real premium, very small models, nevertheless capable of 600 Watts RMS, are available.

Another important component of a surround sound system is the AV (`Audio Visual`) receiver. The AV receiver is responsible for receiving incoming audio signals, decoding them into discrete sound channels, amplifying each and directing it to the appropriate speaker. More powerful AV receivers are a little more expensive, but also often include support for more surround sound formats, and more versatile connectivity options, the some of the cheaper models.

When it comes to positioning speakers and surround sound systems, the first distance that you should take into account is the distance to the listener. Sound should arrive at the listening position from each of the loudspeakers at precisely the same moment, so ideally they should all be exactly equidistant from that position. Bear in mind, too, that each individual speaker has been designed to operate at a specific height in relation to a listener. Most speakers are designed to be positioned with their tweeters roughly at the ear height of a seated listener.