James Roberts

Home Theater Audio - What's Surround Sound?

Most people understand what stereo means - two audio speakers, one left and one right. But what are all those "channels" and speakers in home theater systems about? Both 5.1 and 7.2 channel surround-sound  systems are discussed in this article.

“Hi-Fi” and stereo were the big things for music buffs many years past. Many people bought vinyl records of sound effects just to wonder at the fidelity plus stereo effects. Quadraphonic sound was tested for a while, however systems were expensive plus recording and media required 2 extra channels. In the last decade digital audio has made much more advanced systems not only feasible but also economical.

Sound Processing Formats

Stereo works by using 2 recorded sound channels to feed a left speaker and a right speaker, roughly matching to our left and right ears.

Surround sound processes additional channels to enrich the audio experience using added speakers. There's several modes of surround sound. The first uses a set listener location to get a 3-dimensional sound effect. Unfortunately this also means there exists a single “sweet spot” in which the effect is most effective. Other modes use speakers behind the audience to have an audience-wide experience. Each speaker feed is called a channel.

Audio processing from Dolby Laboratories began way back in the nineteen sixties with noise reduction. Dolby processing has evolved to multi-channel processing in many steps. Starting with noise reduction, we end up with Dolby TruHD. It provides loss-less encoding (no information lost, no noise added) of 8 or even more channels.

Many receivers mention THX. It's not really a sound processing format. It's actually a quality standard and certification system. It was first used to certify movie theater audio systems.

5.1 Surround Sound

The most common arrangement at this time takes advantage of 6 audio speakers, and is referred to as 5.1 surround sound. The “.1” channel is a sub-woofer dedicated to powerful very low frequencies. A good sub-woofer is especially important for motion picture and video game special effects. The usual left and right stereo speakers account for 2 of the remaining channels. Two more audio speakers are put right behind the listeners, effectively making the old quadraphonic setup. A speaker placed in the center of the two main front stereo audio speakers completes the system. This center speaker should preferably be installed higher.

7.2 Surround Sound

7.2 channel surround sound adds 3 more audio speakers. Most a/v systems today are 5.1.1 channel, so the majority of older receivers can only handle the 5.1 format.

The “.2" channels allow for genuine stereo bass by means of 2 sub-woofers. The remaing 2 channels can be utilized in a few alternative ways. Mounting them in the front above the primary stereo speakers commonly gives the most beneficial sound as well as effects. In that situation you may locate the middle speaker lower. An alternative could be to put this particular pair at the front and more widely spread in comparison to the principal stereo audio speakers. This pair might also be placed in an entirely different room.

Wrapping it Up

Each speaker has its  location and purpose, and even installation is normally quite straightforward. Even with so many speakers, home entertainment surround sound systems are usually not that much more complicated to setup. The only complication might be in routing cabling for those rear speakers. Wireless speakers can be purchased in cases where this is too much difficulty. It's well worth your difficulties whatever way you go. You'll get a lot more entertainment from music, films, and gaming with either type of system.

Article Tags: Theater Audio, Surround Sound, Audio Speakers

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