A subwoofer (or sub) is a loudspeaker designed to reproduce low-pitched audio frequencies known as bass and sub-bass, lower in frequency than those which can be (optimally) generated by woofer. The typical range for about 20–200 Hz consumer products,[1] below 100 professional live sound,[2] 80 THX-certified systems.[3] Subwoofers are never used alone, they intended augment the low-frequency of loudspeakers that cover higher bands. While term "subwoofer" technically only refers speaker driver, common parlance, often driver mounted enclosure (cabinet), with built-in amplifier. made up one or more woofers enclosure—often wood—capable withstanding air pressure while resisting deformation. Subwoofer enclosures come variety designs, including reflex (with port vent), using passive radiator speakers enclosure, acoustic suspension (sealed enclosure), infinite baffle, horn-loaded, tapped horn, transmission line, bandpass isobaric representing unique trade-offs respect efficiency, range, cabinet size cost. Passive subwoofers have powered an external Active include amplifier.[4] first home were developed 1960s add response stereo systems. came into greater popular consciousness 1970s introduction Sensurround movies such Earthquake, produced loud sounds through large subwoofers. With advent compact cassette disc 1980s, reproduction deep was no longer limited ability phonograph record stylus track groove,[5] producers could content recordings. As well, during 1990s, DVDs increasingly recorded "surround sound" processes included effects (LFE) channel, heard theater During also became systems, custom car installations, PA By 2000s, almost universal sound reinforcement systems nightclubs concert venues.