Cap is right. The best way to set the output level (volume) is using an SPL meter and test tones, to make sure you have consistent output with your main speakers. Phase is different depending on where the sub is placed in the room in relation to the main speakers. The best way to adjust phase is to sit in your main listening chair listening to a bass heavy track while someone else adjusts between the phase settings. The setting where you have the best bass is where you want to leave it.