The trend toward small, easily concealed main speakers has fueled an increase in the use of subwoofers. Compact main speakers, and in-wall or in-ceiling speakers, are often bass-shy. Large, costly floor-standing speakers often have plenty of bass, but they may be cosmetically unacceptable. Also, the speaker room placement that results in the best stereo imaging is almost never the best placement area for reproducing deep bass.

A subwoofer is a dedicated low-frequency speaker cabinet, usually self-amplified, that fills in the deep, rich bass that is missing from most main speakers. Subwoofers are specialized, and don't reproduce midrange or high frequencies. They are designed to reproduce the deepest notes in the musical spectrum, and low frequency energy provided by home theater soundtracks. Most main speakers are passive (unamplified). But most subwoofers include a power amplifier, creating the raw power needed to cleanly generate deep bass, without robbing excessive amplifier power from your receiver. Subwoofers usually handle frequencies below 150 Hz or so.

A quality subwoofer not only reproduces the thrilling deep bass notes with authority. Its presence in the system also allows the receiver / amplifier to reproduce mid-bass and mid-range notes more cleanly. The burden of reproducing deep bass, the most difficult frequencies to reproduce, is lifted. Your amplifier and main speakers work more efficiently, with less distortion. All kinds of instruments, including voices, can be heard more clearly. Why should you add at least one great subwoofer to your system?

1. Deep bass adds the emotion, the physical feeling of presence and excitement, to a good music or movie performance! One reason that inexpensive speakers sound "just OK" is that they cannot reproduce deep bass very well.

2. Subwoofers help solve problems in speaker set-up and placement. It's difficult to set the main speakers where they are able to provide realistic imaging, and set them in the best place for bass. A separate subwoofer can be placed where the bass sounds best, with the main speakers set up to provide the best image. In-wall and in-ceiling speakers can be placed where they work best cosmetically, without concern for their bass reproducing ability, when the system has at least one great subwoofer.

3. High-quality subwoofers are engineered to generate the massive cone movement required by low bass reproduction. Main speaker drivers are often taxed to their limits, and beyond, by the demands of deep bass, and audible distortion results. A good subwoofer is specifically designed to generate deep bass. Whether you like jazz, classical, pop or rock, a good system can be made better with a good subwoofer.

Regardless of your musical preference or taste in movies, a good subwoofer can make a good listening experience great. There are two main types of subwoofers:

In-room subwoofers are still the most popular choice. If a consumer doesn't need to conceal the subwoofer by hiding it in the wall, ceiling or floor, in-room subwoofers work well. The cost vs. performance ratio is very high.

Built in subwoofers are preferred by many design-conscious consumers. These subs cost a little more to build and engineer properly. But hidden subwoofers are very popular in homes where space and the look of the interior are primary concerns.