The subwoofer is a subtype of an active marine speaker designed to reproduce approximately the first two octaves (the most serious, usually between 20 and 80 Hz) of all 10 that make up the full spectrum of audio frequencies.
The subwoofer intended, therefore, complement the conventional two-way speakers that are never covered the first octave (20 to 40 Hz) and often only manage to reproduce the sharp components of the second (40 to 80 Hz).
Typically, home subwoofer integrated into its most simple powerful power supply (usually between 100 VA and 1 kVA sometimes because currents can flow over the coil 10 ARMStransducer), an active low pass filter, protection overload, a dedicated amplifier and a single large diameter transducer.
Design and mechanical properties of the enclosure in which the transducer is another factor in the performance of a subwoofer, in any case, much more decisive for the reproduction of the higher octaves.
Although the most common are analog type, there are already on the market digital versions (the digital input signal is to be applied to the digital low pass filtering, matching and processing DSP room correction and digital-analog conversion later).
Among the advantages of digital models is the fact that they allow adjustments in the frequency and phase response for the correct alignment with the playback environment (Digital Room Correction) and better integration of the subwoofer with other speakers.
Since the wavelengths in air (at normal room temperature) of the frequencies of sounds that typically plays a subwoofer are at least several tens of times the diameter of the transducer that reproduces the sounds and directividad5 of these is reproduced completely negligible (see Huygens’ Principle and Diffraction). It is not possible for the observer; therefore, to locate the source of these sounds so that the stereo in the reproduction of the bass octaves is useless. Is unnecessary to record / play these songs in more than one channel (and, therefore, speaker) for both stereo and multichannel systems.