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Home Theater Engineering 101

by Clare Kaufman

Repair-Home Columnist

The movie buff's ultimate home improvement project is home theater design. Home theaters bring Hollywood indoors, with sophisticated surround sound systems and of course, the big screen. Many homeowners focus on the appearance of the room--but to truly capture the magic of Hollywood, acoustics are king. Here are some engineering basics to keep in mind as you design your home theater.

Home theater acoustics depend on sound reflection. Too little reflection and the sound dulls. Too much reflection and the sound echoes or gets distorted.

Dimensions of Room. A theater home improvement project often means constructing an extra 'room within a room' to optimize sound. For more consistent, true acoustics throughout the room, the 'inner' room should have varied length, width, and height. A room with equal dimensions (or dimensions that are evenly divisible by each other--10x 20, for example) won't distribute the resonant frequencies. The peaks and dips in the sound waves coincide with each other, intensifying some sounds and canceling others. A room with variable dimensions distributes resonances, resulting in smoother, more consistent sound quality.

Seating and Speaker Position. Sound waves travel between low and high sound pressure (called nulls and peaks). The optimal seating is midway between these two extremes. Acoustic engineers point out that the supposed 'best seat in the house,' in the exact middle of the theater, is likely to fall in the null zone, producing a low frequency response. The best position typically falls between 1/3 and 1/6 of a room's width away from the wall. To design your seating and speaker position for optimal sound quality, use a sound pressure level (SPL) meter to map the sound waves.

Sound Absorption. Another important factor in sound quality is absorption. By adding absorbent materials to walls and ceiling, you can prevent sound waves from bouncing, canceling, or echoing. Drapes and carpet can help, but home theater designs often include special wall treatments and 'bass traps' to diffuse these waves.

Designing a home theater is a home improvement project worthy of an engineer and a contractor can help you find a trained acoustics professional. But if you're working with a shoestring budget for this home improvement project, these tips should point you (and your sound waves) in the right direction.


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About the Author

Clare Kaufman works as a writer and editor for an online media company. She has completed a graduate degree in English.