Originally Posted by mr_fitz
How do you correct the polarity/phase with the spl meter? What test tones do you use? And do you adjust the phase in the D2 menu until the spl meter reads the highest value?
Calibration DVDs typically include a phase adjustment test tone which sends pink noise (lower frequency range noise) simultaneously to the sub and a main speaker -- typically the LF speaker. You can adjust phase by ear by listening for the combo of Phase and Polarity settings that produce the most sound in the higher frequency range of the pink noise (i.e., near the cross-over, which is where the cancellation occurs if phase is set wrong). The worst phase setting will make the pink noise sound more like it only has lower frequencies in it. The difference is usually fairly subtle but if you listen carefully and iterate back and forth in the phase settings you will hear it. An SPL meter will indicate proper phase as having slightly higher volume because those higher frequencies in the pink noise aren't being cancelled.
Polarity inverts the phase across the entire frequency range going to the subwoofer. Phase itself operates in a manner that is more localized to the frequencies either side of the subwoofer cross over frequency. Thus inverting Polarity and swinging Phase around 180 degrees are not really the same thing, although the difference will likely be subtle (since the cancellation you are trying to eliminate also happens near the cross over). Typically you would set Polarity to normal for a sub in the front of the room and to inverted for a sub in the back of the room (i.e., just think of which way the speaker cone of the sub is moving compared to the speaker cones of the main speakers).
That means you may want to try separately measuring for best Phase with both Polarities to see which works better. A graphic frequency measuring tool, paired with a frequencey sweep test tone that goes to both the sub and LF, will help you see the variation across the range of frequencies. However, you can't use ARC for that since it doesn't send out that type of test tone, and only listens to one speaker at a time.
Note that you must get the distances and volume levels set up properly for your speaker configuration BEFORE you attempt to adjust subwoofer Polarity and Phase. It is also wise to re-check subwoofer phase if you change the crossovers (as for example by uploading ARC results), since the phase control's operation is centered on the cross over.
You can make changes to subwoofer Polarity and Phase *WITHOUT* having to re-measure or re-upload ARC results. Again, that's because ARC does what it does by listening to only one speaker at a time. So it doesn't hear correct vs. incorrect subwoofer phasing. ARC simply assumes you will set that up correctly, and the ARC results will sound better when you do so.