Buyers Guide.

When listening to music or watching a movie, surround sound 'immerses' the listener in sound by playing individual sound channels through dedicated loudspeakers, so a different sound channel is supplied to the front, sides and rear of the listening position, making the sound seem to come from a full 360 degrees around the listener, giving a much closer approximation of how sound is naturally experience in real life.

There are currently two main formats for surround sound. Dolby Digital, or Dolby 5.1, is the industry standard for both DVD and HDTV broadcasts, and consists of five independent sound channels to carry the main sound, plus a LFE (Low Frequency Effect) channel to carry low-frequency bass, which the listener more 'feels' than hears, as one would feel the bass in a rock concert, for example. The other format is also '5.1' and is called DTS (Digital Theatre Systems), but this is mainly found in commercial applications like cinemas and is unlikely to turn up in your living room any time soon. There are also extended formats, Dolby Digital EX, that provide even more channels, but these are only for the serious enthusiast at present.

Although you'll find surround sound speakers in all sorts of different configurations, by far the most popular is a 5.1 channel set up, with a front centre speaker, left and right speakers to the front, another set of left and right to the rear and a subwoofer for low-frequency effects. When TV manufacturers go on about 'home theatre', 5.1 is generally what they're talking about. Although larger speakers tend to have better sound quality, produce deeper bass and can handle higher volumes, if you've got a 15 foot living room, you probably don't want five 3 foot speakers taking up the space where the coach used to be, so try to choose the largest size you can without being intrusive.

'Tonal balance' is very important with surround sound, and basically means that you have to have a system where the characteristics of the sound, like its treble and bass, will be reproduced in the same way across all five speakers, otherwise the sound will seem to 'jump' from one speaker to another, completely ruining the surround sound effect. So, unless you really know your stuff, try to buy all your surround sound speakers as a set from the same manufacturer, as they should all have been balanced against each other before they left the factory.

And don't skip on the cabling that connects it all together - the wires that come with the system will be pretty much the cheapest that the manufacturer thinks they can get away with. They'll work OK, but try replacing them with proper cables with gold-plated connectors and you'll be amazed at the difference.

Although most of us will just plug our speakers into an LCD TV or a hi-fi that claims to support surround sound, spending a little extra on a dedicated digital A/V receiver to decode the incoming video signal, and amplify and direct each channel to the right loudspeaker, is well worth the expense. You'll get much better sound quality, better amplification, support for different surround sound formats and more connections for different types of players.

Questions and Answers.