The 411 on 7.1 Surround

A home theater is nothing without a first-rate surround setup, and a 7.1-channel system can give you the most compelling sound experience that today's technology can offer. But having the right receiver and the right number of speakers doesn't mean you'll magically get the most out of your system. The best speakers in the world can sound bad if you don't take the time to set them up correctly.

Positioning your speakers for 7.1 channels - or 5.1 or 6.1 - isn't rocket science, but it does require some time and thought. Whether you're simply upgrading from a home-theater-in-a-box 5.1-channel setup or starting from scratch, here are the rules, tips, and tricks you need to know to get your surround speaker system arranged properly. (We're assuming, by the way, that you're using basic freestanding speakers and not in-wall or ceiling models, which are best handled by a custom installer.)

Work the Room

For a 7.1-channel setup, you'll need to decide between the different recommendations of Dolby and THX on where the two rear speakers should go. THX advises having them no more than 3 feet apart, while Dolby recommends spacing them the same distance apart as your front left and right speakers.
FRONT SPEAKERS
The front left and right speakers should be placed at an equal distance from the side walls and from the wall behind them. Since the front left, center, and right speakers should all be the same distance from the listener, you can use the settings in your receiver's speaker-setup menu to compensate for any differences.
SUBWOOFER
Begin by placing the subwoofer in a corner of the room, since this position can help to reinforce the bass. But if the sound is boomy, experiment with different locations, keeping notes on how the sub sounds in each place you try.
SURROUND SPEAKERS
Since the surround speakers are supposed to have a diffuse sound that heightens the sense of space, they can be placed higher on the wall than the front speakers, which should be positioned so that the tweeters are at ear level.

Unless you're able to design a room from the ground up, you'll have to work with the dimensions that you're dealt and make your system fit the space. If possible, avoid using a room that's perfectly square or with one dimension that's twice the other, since spaces like these tend to accentuate resonances that can have a negative impact on the sound. Bare surfaces can also cause reflections and make the speakers sound harsh, particularly if the room has a lot of glass, such as windows and mirrors. Adding some dampening materials like curtains, drapes, rugs, and upholstered furniture can help take the edge off the sound. (Just don't overdo it, since having too much of the sound absorbed is as bad as having too much reflected.)

Remember that the closer you place speakers to intersecting surfaces like corners and other areas where the ceiling and wall or the floor and wall meet, the more the bass will be reinforced. While this can help boost bass-deficient speakers, it can also make your system sound boomy. Don't be afraid to experiment with placement, since moving a speaker only a few inches can make a big difference in how it sounds. Have pen and paper handy to keep notes on how your speakers sound in different locations, and use masking tape to mark the various positions in case you want to go back to one you prefer.

Front and Center

Your front left, center, and right speakers reproduce up to 90% of the sound of a movie in surround and all of 2-channel music, so getting them set up right is essential. How you position your front speakers will depend not only on the size and shape of the room, but also on the type of TV you're using and how far away from it you'll be sitting. For HDTV sets, the general rule is to sit at a distance twice the screen's diagonal measurement. (Displays with 1080p resolution let you sit closer than 720p and 1080i sets do - about 1 and 1/2 times the distance - but the guidelines here will give you a basic idea of where your listening position should be.)

For the best sound, the front left and right speakers and your seating position should form the points of an equilateral triangle, and the speakers' tweeters should be at ear level. Also make sure that the speakers are at an equal distance from the side walls and an equal distance from the wall behind them, using a tape measure for accuracy.

The position of your center speaker is critical because it carries 60% or more of a movie's sound and almost all of the dialogue. Placing it in line with your front L/R speakers will position it closer to you than the other two speakers, but you can compensate for this by using the distance settings in your receiver's speaker-setup menu. If, like most people, you're using a flat-panel or rear-projection TV, you'll probably place the center speaker just below your set. (Again, use your receiver's setup menu to compensate for any differences in distance between the front left, center, and right speakers and your listening position.) If the center speaker's tweeter can't be at ear height - a likely result if the speaker is below your TV - slightly angle the speaker upward to compensate.

It will also help your system's sound if you "toe in" the front L/R speakers slightly so that they're aimed toward the listening position. Start with the speakers placed parallel to the wall and then, using music you're familiar with, experiment with the toe-in angle to find the best sound.

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