The subwoofer could be the most despised loudspeaker in America.

But why? Because it's big and fat? Because it's such a blowhard?

Well, here's some news for the anti-sub movement: The subwoofer is an indispensable part of a home theater. It does the grunt work in a surround-sound system, playing all those low-lower-lowest notes -- the explosions, the crashes and the rumble of helicopters -- that other speakers simply cannot reach.

The subwoofer injects realism, sound you can actually feel, into a home theater. Here's how important it is: I would give up both rear-channel surround speakers before I gave up the subwoofer in my home theater. I would even give up the center speaker, the critical dialogue specialist, and use a basic two-speaker setup with the subwoofer.

Powered vs. passive: A powered subwoofer means it has its own amplifier. A passive subwoofer, with no amplifier, must be connected to an audio-video receiver like an additional speaker. Avoid the passive types.

The lowdown: Look for a subwoofer that reaches down to at least 35 hertz (the lowest note produced in the musical world is the low-C of the pipe organ, 16 hertz). Check the manufacturer's ratings. The lowest rumbles of the Outlaw LFM-1, which hit 25 hertz, will seem capable of imploding your house.

Making the connection: Most subwoofers offer two methods of connection to an audio-video receiver. The "line level," which requires one or two interconnects, is preferred. If your receiver doesn't have a subwoofer output, connect the subwoofer like another loudspeaker using speaker wire.

The set-up: Remember, the subwoofer takes care of the low notes your main speakers can't reach. Treat it like a partnership. Pay special attention to controls on the subwoofer's back panel for volume and frequency adjustment.

Start by setting the subwoofer's high-frequency cutoff -- with a dial often designated "crossover" that ranges from 50 hertz to 160 hertz -- to match the lowest frequency of your main loudspeakers. (Check the speaker manual. Most smaller home-theater speakers bottom out anywhere from 70 to 120 hertz.)

When you set the subwoofer's crossover at 70 hertz, for example, it will not produce a note above that frequency.

If you hear movie dialogue from the subwoofer, you've set the frequency too high. Listen for a smooth transition from the lowest notes of the speakers to the subwoofer. Adjust the sub's volume if bass sounds too prominent or boomy. More precise settings require test tones and a sound-level meter.

The placement: Bass notes are considered non-directional -- hard for the human ear to detect where they're coming from -- so a subwoofer can be placed just about anywhere. But the front of the room is preferred, near, between or behind the home theater's front speakers. Placing it in a corner increases bass output.