The subwoofer is a fairly recent entrant to the typical home entertainment system, and we see the concept popping up in even low-price desktop systems. The idea of having a separate bass speaker was first encountered in cinemas and public address systems where a lot of audio power was needed to fill the theater or stadium. Since the sound wavelengths are so long at these low frequencies (3 to 9 meters) using a single mono subwoofer will not disturb the stereo image. However, the question remains: do you need a subwoofer and what are the needs and benefits?

Subs are typically specified for systems where large full range speakers are not practical, or for large open rooms, or where very high SPLs are desired. Placing small speakers where they create the most lifelike stereo image is often at odds with the location that gives the most even and powerful bass response. The ‘sub/sat’ system is the answer for this dilemma, by allowing the sub to be placed for best bass response, and the satellite speakers to be placed for best imaging. Another great use for subwoofers is when speakers need to be hidden and must be both small and unobtrusive. To have the correct sound balance a subwoofer is called for. And probably the most common use is in the home cinema, where realistic special effects demand the power of a subwoofer. Dolby found subwoofers to be an essential element of home theater sound and even created a special ‘Low Frequency Effects’ channel specifically for a subwoofer.

The other hidden benefit of the subwoofer is that it removes the burden of bass output from the satellite speaker. This allows the speaker to play louder and with far less distortion. Since most subwoofers today are powered, they also add considerable power to the overall system performance.