This setting allows you to adjust the timing relationship between your main speakers and your subwoofer. Allows you to adjust the phase of the subwoofer from 0 – 180 degrees in increments of 1 degree and allows you to invert the polarity of the phase. Phase control is entirely dependent on numerous factors including the size and configuration of your listening environment, the placement of the unit, and seating arrangement. A good rule of thumb is to set phase at 0 if your sub is at the front of the room and 180 if it is in the rear.