Feel the Power of Subwoofers
These black boxes put the boom in your home entertainment system. Here's a look at how they work, styles and some shopping tips.
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May 13, 2008 by Dennis P. Barker

Does your home theater make the Earth move? If it doesn’t, you are not really experiencing its true power! Most enthusiasts feel that sound equates to more than fifty percent of the home theater experience. As you sit back and watch the blockbusters like “Transformers,” “Beowulf,” “Pirates of the Caribbean,” and “Ratatouille,” or all-time classics like “Close Encounters of the 3rd Kind - 30th Anniversary Ultimate Edition,” you should feel the sound viscerally as well as hear it. If you don’t, it means you either do not have a subwoofer hooked up, or you have an under powered sub. In either case, it’s time to get to step up to the next level of entertainment - namely, an earth mover.

What is a Subwoofer?
A subwoofer normally looks like a big black box. This large enclosure is a low frequency speaker specifically designed to reproduce the lowest possible bass sounds. Since bass is non-directional, it can be placed anywhere in the room. Usually, it is placed in a corner, under a coffee table, or possibly behind furniture (or the TV itself if it is shielded). Bass sounds appear to come from nowhere and everywhere at once.

A subwoofer’s main purpose is to move air. The bigger the driver size, the more air it will move. Woofers range in size from about 5-inches to 18-inches in diameter with the majority falling in 10-in. and the 12-inch categories. Some of these enclosures are ported (meaning that they have a hole on the side or the bottom) for the intake of air. The port helps add a thump to the bass response.

Virtually most A/V receivers have a subwoofer output jack on the back panel. This will attach directly to the L(eft) input of the sub. If your receiver does not have a separate subwoofer output jack, just run the speaker wire from your left and right speaker jacks of your receiver into the appropriate left and right jack inputs of the sub. In turn, you run left and right speaker wire out from the sub’s output jacks to your separate left and right speakers. It may sound complicated, but it really isn’t. In either set-up, the lowest sounds are directed to the subwoofer.

Subwoofers are either active or passive. Active subwoofers are powered by their own internal amplifier, which may be desirable for many people. Passive subwoofers, on the other hand, require power from either your receiver or a separate external amplifier. If you are in the market for either a new amplifier or A/V Receiver, you might want to consider one that has a 5-, 6-, or 7-channels of amplification built-in to it. In other words, amplifiers for each channel including a subwoofer. Passive subs are less costly than their powered siblings because they don’t come with their own internal amplification.

All have either a volume control or input level control dials. Normally, you start adjusting from the 8:00 o’clock position and move upwards depending on how much bass you like to hear. It really shouldn’t overpower the rest of the speakers though. Unless, of course, you like a lot of bass with your music and sound. It’s best, however, if the bass blends into the sound of your speaker system. Those subs that are packaged with satellite speakers may also include bass and treble controls on them as well.

Thanks to home theater, there has been a renewed interest in sound reproduction, especially low-bass sounds. All of those train crashes, explosions, and numerous background noises (doors slamming, footsteps, twigs cracking under foot, thundering hoofs, rain storms, etc.)  in many types of movies (especially action films) demand good bass response. Only a real subwoofer can provide it! In a regular home theater set-up, only one sub is normally necessary. If you have stepped up to (or are planning to add) Lucasfilm’s certified Home THX components, two subwoofers are required as part of the specification.

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Dennis P. Barker - Contributing Writer
Dennis has been involved with Consumer Electronics forever it seems. His 25+-year career includes a 12-year tour of duty at Consumer Reports magazine, as well as stints as a product reviewer, market analyst, technical editor, and consultant for the electronics industry. He lives in Ossining, NY with his two children, one demanding cat and piles of A/V equipment.

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