A high-quality multi-channel audio system surrounds the listener with realistically lifelike sounds from all directions. These systems are used to:
The same fundamental principles of a stereo system also apply to a surround sound system, except that you need five or six channels of audio, rather than just two. Obviously a surround system can be quite a bit more expensive than a 2-channel stereo system of equivalent quality.
In addition to the usual front left and right speakers, a surround system adds a center front (or "dialog") speaker, rear left and right speakers, and usually a subwoofer. Space and budget considerations aside, you would have five identical speakers optimally positioned equidistant from the preferred listening position.
When cost precludes five identical best-quality speakers, our recommendation depends upon your priorities:
You may have heard recommendations to use special-purpose "bipole" speakers positioned at the sides of the room, rather than regular speakers positioned in the rear. With the advances in surround technology brought by Dolby Digital and DTS, we no longer favor bipole side/rear speakers.
In addition to 5.1 there are also 4.0, 4.1, 6.1, and 7.1 systems. A 4.0 system is two front and two rear speakers; a 4.1 system just adds a subwoofer to a 4.0 system. A 6.1 system adds a rear center speaker to a 5.1 array, whereas a 7.1 system adds 2 more side-rear surround speakers. You can even do an 8.4 system if you wish which would mean 8 full range audio channels and 4 subwoofer channels! Generally speaking most people are doing 5.1 systems these days, although some people are doing 7.1 systems instead. All things being equal 5.1 systems are of course less expensive than 7.1 systems.
2009 Update: Some BluRay discs now come with 7.1 soundtracks, so now there is more of a reason for installing 7.1 surround systems than before. Having said that, the percentage of discs being released today in 7.1 surround is still relatively small.
The acoustics of the room will also greatly affect the performance of the surround system. If you are custom building a room, we suggest that you consider acoustics when you choose the size of the room and the listening position. The primary listening position should usually not be located halfway back into the room as this position has anomalies that will interfere with the sound from the speakers.
As in a 2-channel stereo system, the electronics and cabling that you use with the speakers will greatly affect the system's overall performance. If you are listening to movies, the dynamic contrasts in the loud passages may dictate a somewhat larger amplifier than usual.
Instead of a preamplifier, a multi-channel audio system employs a surround-sound processor which:
Surround sound processors vary considerably in sound quality and capabilities. In addition to the sonic merits of the equipment, you may wish to consider ergonomics, as some processors are considerably easier to use than others.
If 2-channel stereo listening is very important to you, then you may wish to consider a separate high-performance stereo preamplifier. With the surround processor's left and right front channels connected to the preamplifier, the system reuses the front amplifiers and speakers for multi-channel use. With a high-performance CD player, turntable, music server or other source connected directly to the preamplifier, this type of system design bypasses all the surround equipment during stereo use. We have found that this configuration usually provides the highest possible quality stereo listening.
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