A subwoofer is a loudspeaker designed to reproduce low-pitched audio frequencies, typically below 200 Hz for consumer subwoofers, below 100 Hz for professional subwoofers, and below 20 Hz for subwoofers used in sound reinforcement systems.
Subwoofers are used to augment the low-frequency response of loudspeakers that are unable to reproduce the entire audible frequency range on their own, such as bookshelf speakers or computer speakers. They are also used to create special effects in home theater and other applications. Subwoofers can be either passive or active, and they can be placed in a variety of locations in a room to achieve the best possible sound quality.