By Wilde Becker. Speaker Stands. At Monday, July 22nd 2019, 18:14:55 PM.
That’s where you need to put the sub. If your sub has a phase adjustment knob, or a polarity–invert switch, adjust this until you hear the loudest result from frequencies around the crossover point, typically 80 to 120 Hz.
The theory is that the mass and spring characteristics are chosen so that the resonant frequency of the combination is well below that of any frequency they’re likely to be asked to isolate. For example, if the lowest note a speaker can reproduce is 30Hz, then the resonant frequency of the supporting platform needs to be well below that — perhaps just a few Hertz or less.
Subwoofers can be placed directly onto solid floors, but an isolation platform of some type will help clean up the sound if that floor is made of wood or chipboard. It isn’t a good idea to position subs very far from the floor — up to about 150mm shouldn’t present a problem, but more than that and the reflections can start to cause issues.