Phase Switch on Subwoofers

What does the phase switch ( 0 - 180 ) do for a subwoofer?
When do you want to switch phases? Please advise!

the phase adjustment pot is used to acoustically move the woofer position until it matches with the satellites. if the woofer is 3 feet behind the satellites the phase would not be correct unless adjusted properly with the pot. this is usually done by ear while playing music with low bass content.
please clicks on the following link, will directs you to previous "Phase Switch" discussion:
aggiebob98: so, i guess you must be from oklahoma, right? class of 1993? ;^] -cfb

ps: as to the phase adjustment "switch." betcha' ya' can't hear any diff, no matter how many times you engage it. don't lie to me, boy. you done be an aggie. can't get over it. much less around it. -cfb
If your main speakers are running full range, you should definitely hear a difference inverting the subwoofer phase. Of course a continuously adjustable phase pot (0 to 180 degrees) would probably be more effective in most systems than a switch that only inverts at 180 degrees. If you are running small speakers in a HT system that aren't receiving a full range signal, then flipping the phase switch won't make much, if any, audible difference in bass performance.
If I understand things correctly if something is out of phase the speaker is moving out when it should be moving in. This can also be accomplished by switching the positive and negative wires. Different manufacturers are wired differently and this switch allows the correct timing between your speakers and sub.
Perfectimage is correct. Essentially, the respective cones of your main speakers' woofers are moving either in or out in response to the music signal (provided they are connected correctly, in phase with each other). Now the cone of the subwoofer can either move in the same direction at the same time, which would result in bass reinforcement, or it can move out of sync with the main speakers, which usually results in partial cancellation/attenuation of the apparent bass level. By reversing the phase, you are attempting to put the respective motion of the sub and main speakers more in synch with each other. In reality, because of the different physical positions of the respective bass drivers, the sub could be ANYWHERE between 0 and 180 degrees out of sync with the main speakers. That's why subs having a continuously variable phase pot makes the most sense.

If you are free to move the sub around the room to find the areas of maximum bass reinforcement, that is another way to address the problem, but most folks like to put the sub in a spot where it is unobtrusive in the room. One could reverse the positive and negative speaker leads on the main speakers to put them 180 degrees different, relative to the sub, but having the main speakers out of absolute polarity might make them sound unnatural on some material. If you are using the RCA line input on the sub, then there is no way to electrically compensate for polarity, unless it has a phase pot or phase reversal switch.

I find that with multi-channel systems all these phase/polarity synchronization problems between the respective front, rear, center, and subwoofer channels are compounded. If you'd like to do an interesting experiment, just put the center channel out of phase with the mains, or connect the surrounds in opposite polarity to the fronts and see how the sound quality changes. :)
If your subwoofer is out of phase with your main speakers bass drivers, you may find that they may cancel each other out in the lower frequencies resulting in less bass.