Q My room is not suitable for hanging surround speakers for a 5.1-channel setup. I am considering a sound bar. How does it provide the surround effect?

A A sound bar is a long, thin speaker that is placed under or above a television. These speakers often are used with a subwoofer, because the size and shape of a sound bar doesn't allow much bass to be produced. Some sound bars are complete, self-powered systems; others are simply speakers that connect to the terminals of an audio-video receiver.

Given the poor sound quality of a typical flat-panel TV, the improvement in sound quality and clarity from adding a sound bar can be quite dramatic, even when using an inexpensive model -- more natural sound, clearer dialogue, room-filling volume.

Two-channel sound bars use electronic signal processing to create surround effects using only the left and right stereo channels. Your TV might have this signal processing available. If you turn it on, you can enjoy more spacious sound without connecting an external system. Look in the television's audio menus for settings such as SRS, VSS or Virtual Surround.

Although you might hear a more spacious sound in your room with this kind of sound bar, you won't be hearing every detail in the soundtrack because the rear surround channels contain unique audio. If this is what you want, the Vizio VSB200 is well regarded and sells for less than $100 without a subwoofer. Spending $199 gets you the Panasonic SC-HTB10, which integrates well with Panasonic TVs, and the top-rated Sony HT-CT150 sells for less than $300 including subwoofer.

The best sound bars are called surround bars because they have speaker drivers for each of the five channels. The best of these are unpowered speakers that are driven by the speaker terminals of an audio-video receiver. Circuitry in the surround bar, often in conjunction with additional drivers in the cabinet, works to create a cancellation effect similar to that used in noise-canceling headphones. It affects the sound that actually reaches your ears, creating a sound field that is enveloping and spacious while reproducing every nuance in the original program. You won't hear sound behind you, but you will hear everything the director intended you to hear, and it will sound much more satisfying than mere stereo.

A great self-powered unit is the Polk Audio Surround Bar 6000 IHT for $499 including powered wireless subwoofer. If you want the ultimate in good sound from a single speaker setup, check out the Definitive Technology Mythos SSA-42 or SSA-50 surround-bar speakers. They start at $799, and you must use them with an AV receiver and a subwoofer. This makes it expensive compared with the others mentioned, but the best rarely comes cheap.

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