The phase switch for a sub is used for avoiding bass suck out around the sub's crossover point so that the sub can be better integrated with the main speakers. You will need to play a test CD that contains test tone. Or use the build-in tone generator of the processor if it has one. In either case, play the test tone that is closest to the crossover frequency and adjust the phase switch; whatever position sounds louder is the right setting.
The polarity switch change the phase of the input signal.
The polarity switch change the phase of the input signal.