Originally a concept developed for use in cinemas, and the like, the availability of high quality audio sources, such as DVD and HD “High Definition” TV, and more affordable receivers and amplifiers, has meant that surround sound has become, and is likely to stay, very much a part of the “home theatre” experience.
How Does Surround Sound Work?
The most common surround sound formats are Dolby Digital and DTS (“Digital Theatre Systems”), which both facilitate the recording of five discrete main channels, plus a separate channel for low frequency effects. Correspondingly, these formats require five individual speakers, plus a “subwoofer” for bass effects – what is known as a “5.1” channel system.
Unlike more traditional methods, in which, for example, sound may emanate from speakers at either side of, say, a TV screen, surround sound speakers are positioned strategically around the listening space – so that sound is heard not only from in front, but also from behind and from the sides.
Correctly configured, high quality surround sound systems create a large number of so-called “sweet spots” throughout the listening space, where the audio signals from the various speakers combine to produce a totally immersive, lifelike, listening experience. The listener can enjoy not only flawless dialogue, music and main effects, but also more subtle ambient sounds, like the rustling of leaves, or the patter of raindrops.
The number, quality and positioning of surround sound speakers obviously has an effect on the number of sweet spots produced.
Surround Sound Speakers
A standard surround sound configuration usually comprises five main speakers: a centre speaker, which reproduces the dialogue, left and right front speakers which reproduce the main sounds, and left and right rear speakers, which reproduce the ambient effects. In addition, a subwoofer reproduces the low frequency, bass effects.
The centre speaker, which is normally placed above or below the TV screen, should, if used with a traditional, CRT (“Cathode Ray Tube”) TV, be magnetically shielded, to prevent interference with picture quality. This applies equally to any other speakers which are placed in close proximity to TV screen of this type. Mission M34I speakers, for example, are floor standing models, with magnetic shielding.
All speakers in a surround sound system should be “voice matched”, so that, as sound switches between the speakers, there is no discernible difference in quality. There is a strong case for “in a box” surround sound systems, where matching is performed by the manufacturer. The JBL CS460 BK 5.1 Speaker Pack is an example of this type.
Conclusion
Trying to evaluate a surround sound system from specifications and other literature is like trying to learn to drive from a book – it’s all very well, but no substitute for your own experience. You really need to listen to any system, with your own ears, before committing to it.