How do I set subwoofer phase?

Depending on the absolute phase of your main speakers and amplifier and the distances of the subwoofer and the main speakers from the listening position, the bass in the crossover region may be smoother if you reverse the subwoofer's phase. Typically, though, phase is left at 0/180 for most applications.

While seated in your listening sweet spot, play music with bass content that is familiar to you and then have someone switch the 0/180 phase switch on the sub to 180-degrees. This will let you determine if the bass sounds louder in your seating position. The more bass-heavy setting is where the output of the subwoofer and the main speakers are most in phase. Use whatever position (0/180) is louder at your seating location. (Note: some subwoofers may contain a "variable" phase control, which provides variable control between 0 and 180 for even more precise phase control of your subwoofer.) However, if you do not notice any difference when changing the 0-180 setting, it only means there are no issues in your room and all is fine.