ABSTRACT
A subwoofer loudspeaker is a separate enclosure from the main loudspeakers that is specifically designed to reproduce low bass. They are normally used singly rather than in stereo pairs, the assumption being that low frequencies can be regarded as non-directional. Another justification for mono subwoofers is that bass information is commonly pan-potted to the centre of the stereo stage. This is essential if the recorded material is likely to be used to cut vinyl discs, as big differences in low frequency information between left and right channels creates large up-and-down, as opposed to lateral, contours in the groove that increase the possibility of mistracking and can in bad cases throw the stylus out of the groove altogether. Another good reason for centralising the bass is that it needs large amounts of amplifier power to reproduce it, and it is therefore desirable to make full use of both channels.
In home entertainment the sub-woofer is normally of modest size, and is often installed under the television screen, in front of the listeners, though other placements are possible, exploiting the non-directional characteristics of its output. In automotive use subwoofers are installed in the boot (the trunk, to some of you) or the rear cabin space.
