Woofer is the term for a loudspeaker driver that is designed to produce low frequency sounds. Typically from around 40 Hertz up to a few hundred Hertz. Some woofers produce frequencies up to around 1000-2000 Hertz and are usually called Mid-woofers.
Nearly all woofers dynamic cone speakers and typically have a nominal diameter of 5 to 18 inches.
A low Resonance frequency, obtained by loose suspension (more compliance) and heavy cone, makes the speaker capable of producing low frequency sounds.
The term woofer can also refer to a speaker driver and cabinet combination that produces low frequencies.
See also