Subwoofer 101


Subwoofers present a unique chance to design arrays outside of the ruleset found for full-range speakers. Subwoofer arrays have two unique features that open the door of opportunity. The first is that subwoofers are in separate enclosures that cover only a three-octave range (approximate). The second is that large wavelengths within the subwoofer range can diffract around neighboring objects, most notably other subwoofers. It is usually not the case to place a full-range speaker facing directly into the back of another such speaker (DJ excepted). With subwoofers, this is an option, beneficial and a practical one.


Omnidirectional and Cardioid subwoofers


Individual subwoofers come in two different flavors, omnidirectional and cardioid. The omnidirectional version, like its microphone counterpart, is not truly omnidirectional, especially as frequencies rise. The cardioid version consists of front and backfiring drivers, that use phase offset to create coupling zone summation at the front and canceling zone summation ant the back. These engineered products produce substantial rear rejection over a wide frequency range. The advantages of cardioid steering are self-evident.


History of subwoofers


The first subwoofers were developed in the 1960s to add bass response to home stereo systems. Subwoofers came into higher popular consciousness in the 1970s with the introduction of Sensurround in movies such as Earthquake. These produced loud low-frequency sounds through large subwoofers. With the advent of the compact cassette and the compact disc in the 1980s, the easy reproduction of deep and loud bass was no longer limited by the ability of a phonograph record stylus to track a groove. Therefore, producers could add more low-frequency content to recordings.

Furthermore, during the 1990s, DVDs were increasingly recorded with “surround sound” processes that included a low-frequency effects (LFE) channel, which could be heard using the subwoofer in home theater systems. During the 1990s, subwoofers also became increasingly popular in home stereo systems, custom car audio installations, and in PA systems. By the 2000s, subwoofers became almost universal in sound reinforcement systems in nightclubs and concert venues.


Quality sound system


In order to achieve a quality sound system, especially for use by bands, singers and DJ`s, it is necessary to have a setup that features speakers and subwoofers, as well as tweeters, mid-ranges, and woofers. This is because they each handle a different range of notes and sounds so they cover the entire range of sound. As for a subwoofer’s structure, it is usually a wooden or plastic loudspeaker enclosure that is fitted with one or more woofers. The manner of the placement of the woofer creates room for the birth of several subwoofer variants. Subwoofer variants vary depending upon the efficiency, size, cost, power handling, and distortion characteristics that they display. The designs created thus include bass reflex, horn-loaded, bandpass and infinite baffle subwoofers.


Frequency range


The frequency range that a subwoofer delivers depends on its use. So a subwoofer for home-use would have a frequency that would typically range from 20-200Hz; while that used for professional sound would be below 100 Hz. There are subwoofers with a frequency below 80 Hz as well.


Active and Passive subwoofers


Active subwoofers and passive subwoofers are the two options that you need to choose from in case you wish to buy them. The active subwoofer boasts a built-in amplifier, while the latter needs an external amplifier, and comprises of just the subwoofer driver and enclosure.


Source texts


Sound Systems: Design and Optimization: Bob Mcarthy

Subwoofer: Wikipedia