What's phase 0 degree - 180 degree?

when the audio signal goes through an electronic crossover in either in the sub or processor, the phase of the signal is changed. The phase contol on the sub allows you to readjust the phase of the sub so that it is in phase with your main speakers. When the two are in phase, the bass will be louder. Ideally, the phase contol should be adjustable from 0 to 180 degrees not just 0 and 180.

I know this thread is close to 2 decades old, however I felt the need to share. To answer your question, the switch is simply an easy way to set speakers up for an Isobaric loudspeaker enclosure with a cone to cone configuration without having to hard wire one speaker to be approximately 180° out of phase. One woofer pushes as the other pulls is the best I can describe how it works, without going all "M.I.T.". The long story made short is that you end up with the same thump in half the space. Four 18's in the same sized enclosure as a typical two 18's enclosure. Pretty awesome right? Below is a link to the Vue website, which is a great M.I.T.-Light explanation of this design. Have fun!!

http://www.vueaudio.com/isobaric-subwoofer-design/

I dont know what everyone else is talking about, but just cause I don’t know what they mean doesnt infer they are wrong. just that I have a different understanding of phase, which may just be one concept of many. But I have my degree in audio engineering, so I think this applies here particularly. Phase is a term that describes the relationship between two Sine waves. All sound is made up of waves, and a sine wave is simply a smooth curved symmetrical wave. And all frequencies have shorter or longer waves which means the time it takes low-end bass to reach your ears at its peak point of wave. Keep in mind phase on will do something in a stereo format, because phase shifting on occurs when the sound of audio does not all match up exact. Mono signals dont have any competing sound fighting for the air next to your ears. Not even headphones will correctly reproduce a phase issue cause each ear has a dedicated speaker which the sounds never cross from each speaker. So, when sound is considered "in phase" that means you double your amplitude of whatever sound which comes out to be a 3db sound gain. it gets louder. Sounds cool, however, if you were to have the same exact sound coming from left and right speker and were in phase, you’d essentially just get a 3db boost in mono. Now, phase-only is in phase for one listener in one position. if you were to move from the spot you hear in-phase audio, then the difference in time of the sound wave will no longer match up 100% which is called phasing. go all the way until your sound wave peaks at the complete opposite and mirror of each other, that is called "out of phase" which means, no sound. Sound is still math and when you take a phase of +1 and add out of phase of -1, they cancel each other out. So as you probably guess it, any variation of phase between 1 and -1 will have differing degrees of sound elimination, which as an audio engineer is an invaluable tool to have because when using multiple mics to record singe instruments, like drum overheads, or top/bottom snare, the sound can be crappy because of phasing issues. we just call a 180 degree phase "flipping the phase" which essentially kills the sound you were getting and brings back everything else you could hear. Works for room noise. If I have a track with room noise thats hard to solo out with eq, I simply can record a sample of my room, then flip the phase on a parallel track which willl eliminate the room sound within the track i want to restore. When it comes to bass phase, trust me, there is no 1 is better than the other. Cause all music is produced and mixed differently. Some song may sound better at 0 and other at 180. It also depends on what you want. If you have a very thick bass that kinda bottoms out, flipping phase often will tighten up that bass and make it more staccato.