 :this article is about a loudspeaker driver. for other uses, see woofer (disambiguation) thumb|600px|a pair of woofers woofer is the term commonly used for a loudspeaker driver designed to produce low frequency sounds, typically from around 40 hertz up to about a kilohertz or higher. the name is from the onomatopoeic english word for a dog's bark, "woof" (in contrast to the name used for speakers designed to reproduce high-frequency sounds, tweeter). the most common design for a woofer is the electrodynamic driver, which typically uses a stiff paper cone, driven by a voice coil which is surrounded by a magnetic field. the voice coil is attached by adhesives to the back of the speaker cone. the voice coil and magnet form a linear electric motor. when current flows through the voice coil, the coil moves in relation to the frame according to fleming's left hand rule, causing the coil to push or pull on the driver cone in a piston-like way. the resulting motion of the cone creates sound waves as it moves in and out. at ordinary sound pressure levels (spl), most humans can hear down to about 20&nbsp;hz. woofers are generally used to cover the lowest octaves of a loudspeaker's frequency range. in two-way loudspeaker systems, the drivers handling the lower frequencies are also obliged to cover a substantial part of the midrange, often as high as 2000 to 5000&nbsp;hz; such drivers are commonly termed mid woofers. since the 1990s, a type of woofer (termed subwoofer), which is designed for very low frequencies only, has come to be commonly used in home theater systems and pa systems to augment the bass response; they usually handle the very lowest two or three octaves (i.e., from as low as 20 to perhaps 80 or 120&nbsp;hz). == woofer design == thumb|right|400px|cross section of a standard loudspeaker, not to scale good woofer design requires effectively converting a low frequency amplifier signal to mechanical air movement with high fidelity and acceptable efficiency, and is both assisted and complicated by the necessity of using a loudspeaker enclosure to couple the cone motion to the air. if done well, many of the other problems of woofer design (for instance, linear excursion requirements) are reduced. in most cases the woofer and its enclosure must be designed to work together. usually the enclosure is designed to suit the characteristics of the speaker or speakers used. the size of the enclosure is a function of the longest wavelengths (lowest frequencies) to be reproduced, and the woofer enclosure is much larger than required for [[midr
Loudspeakers