Digital surround sound codecs allow multiple, discrete sound channels to be recorded onto, for example, a DVD soundtrack, and, given an appropriate hardware arrangement, each individual channel to be reproduced on its own, dedicated loudspeaker, situated at various positions around the listening space. The end result is realistic, immersive sound, emanating from a full 360 degrees around the listener, as it does in the real world.
Considerations
“Dolby Digital”, a “5.1 channel” surround sound format is the industry standard for DVD, HDTV, DBS (“Direct Broadcast Satellite”) and digital cable. The “5.1” designation refers to five main sound channels that can be recorded, plus an additional sub-channel (the “.1”) for low frequency, bass effects.
Many “home theatre in a box” solutions, therefore, include an AV (“Audio Visual”) receiver, a DVD player, or recorder, and a total of six loudspeakers. The loudspeakers are intended to be arranged as front centre, front left and right, and rear left and right speakers, with an additional, specialised loudspeaker, known as a “subwoofer” – often placed in a corner of a listening space – responsible for reproducing bass effects.
“One box” solutions of this type – typically with an output power of around 50 watts per channel – may be more than adequate for rooms of average dimensions, and feature loudspeakers that have been “matched” for tonal quality, or “timbre”, by the manufacturer. This is an important consideration in any surround sound system; differences in tone between speakers will make the source of sound instantly identifiable, as sound from each individual channel is reproduced, and the overall effect will be spoilt. This type of system is also easy to connect together, and the entire system can be controlled from a single remote control unit.
Whichever type of system you choose – and do bear in mind that “6.1”, and “7.1” channel, extended surround sound formats, such as Dolby Digital EX, or DTS-ES, requiring one, or two, additional speakers, do exist – there are some basic principles of speaker configuration to which you should adhere. A centre speaker should, ideally, be placed directly above, or below, a viewing screen, as this is where dialogue, for example, is reproduced. Front left and front right speakers should be placed, equidistantly, to either side of a screen, at a distance of not more than a few feet, and rear left and right speakers should be placed at roughly ear height, of a seated listener, behind the listening position.
Conclusion
The size, and layout, of your listening space will largely determine the characteristics of the surround sound system – in terms of physical dimensions, and output power – that you can sensibly accommodate. Try to be realistic in your approach to both, and make a plan of where each component will reside, before you start shopping. This will help you to focus only on appropriate systems, and not to be coerced, by glossy sales brochures, or fancy sales patter, into purchasing a system far in excess of your needs.
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