About Home Theater Subwoofers

Subwoofers, a component of home theater systems, replicate the lowest bass frequencies on a soundtrack. Although subwoofers are add-ons and a home theater system will function without them, a subwoofer helps provide accurate reproduction of movie soundtracks. If you want ground rumbling special effects, a subwoofer is a must.

Function

Subwoofers are basically speakers dedicated solely to the lowest frequency sound. They are particularly useful in home theater applications because many soundtracks include low frequency effects, such as explosions, that a regular set of speakers cannot accurately reproduce. Many soundtracks actually have a dedicated LFE (low frequency effects) channel recorded in, so you will not get the full effect of the soundtrack without a subwoofer. The .1 in home theater soundtracks like 5.1 represents the LFE channel.

Types

There are two basic types of subwoofers: powered and passive. A powered subwoofer relies on a built-in amp to provide the increased power necessary to produce low frequency sound waves. These subwoofers require their own separate electrical power supply to operate.
Passive subwoofers function more like traditional speakers, using power and amplification from the amplifier or receiver.
For most common home theater applications a powered subwoofer is preferable because most receivers do not have the power output to effectively drive a passive sub.

Effects

Like most audio equipment, subwoofers come in a variety of sizes and price ranges. They are classified largely by power output, an indicator of how loud and effective they are. The power necessary depends on the size of the room that your home theater is located in and how much bass you want. Audition subwoofers at local shops and get a feel for what you're looking for.

Significance

Subwoofers are particularly important in home theater systems that rely on a series of small surround speakers. Smaller speakers are incapable of producing deep, quality bass and therefore rely on the use of a subwoofer. An example is the cube speaker systems designed by Bose that uses an array of tiny cube speakers and a subwoofer.

Geography

Low frequency sound is not directional the way higher frequencies are. Therefore, subwoofers are very versatile as far as placement. While it is common to place the subwoofer in front of the system next to one of the speakers, you could also place it on the side or in the rear and get largely the same effect. Experiment with different positions to find the one that is most favorable to you.

Considerations

Most receivers allow you to make adjustments to the crossover (frequency where the subwoofer takes over bass reproduction from the speakers). This is particularly useful when using small speakers with limited woofers. You may need to turn the subwoofer "On" using your receiver. Many receivers utilize a simple adjustment that allows you to designate your surround speakers as "large" or "small." When you choose "small," the receiver diverts all low frequency directly to the sub. Experiment with settings to find the best balance.