A speaker that reproduces the lower end of the audio spectrum. A subwoofer system typically includes a crossover circuit that filters frequencies around 100Hz and under to the driver. In a home theater, the placement of front, center and surround speakers is critical to the listener, but subwoofers are non-directional and can be located in a convenient spot, although corners are not recommended.

Passive and Active Subwoofers
Passive subwoofers contain only the speaker (the driver) and crossover. Active subwoofers are self powered and include their own amplifier. See woofer.