Phase adjustment
The ability to shift the sound produced by the subwoofer in phase — usually by 180 °, but in some models the option is also available by 90 °.
Sound vibrations can be represented as a sinusoid. In some cases, the sinusoids from the subwoofer and from the main speakers may be out of phase — for example, with a difference in distance, inconsistency in the operation of amplifiers, etc. This degrades the sound quality. And
the phase adjustment allows you to correct the situation and coordinate the subwoofer with the rest of the components of the speaker system.
Level adjustment
The subwoofer has its own
level control, in other words, a volume control. Adjusting the bass with such a control is often easier than digging into the settings of an amplifier or other external device.
Crossover frequency
Cutoff frequency of the crossover installed in the subwoofer (or supplied with it — for passive models, see "Type").
The crossover splits the audio signal into separate frequencies so that only the bass goes to the subwoofer and only the main range goes to the speakers. Such a device is mainly equipped with home models (see above). And the crossover frequency is the upper threshold of the frequencies fed to the subwoofer. This information is important for matching with the rest of the speakers: ideally, the lower threshold of the main acoustics should correspond to the upper threshold of the subwoofer, otherwise the frequencies will either overlap or dip in them (neither of which contributes to sound quality). For the convenience of matching, the crossover can be made adjustable (see above).
