I finally got around to calibrating the speakers and sub today (m60's, m2's, 150, svs box with 2 12 inch woofers) with a panasonic digital receiver.

I used avia and something very wierd happened. When I would test the right or left mains to match them to the sub, the test tone for the sub was louder so of course I turned the sub down on the receiver volume. I turned it all the way down and still the sub test tone was too loud so I started turning down the volume on the sub.

Eventually I had the sub volume all the way down so that no sound was coming from it, and the supposed subwoofer test tone was still louder than the mains. I finally realized that the sub test tone was coming out of the left or right main and the sub, and with the sub off it was still coming out of the left or right main speaker and it was 3 or 4 db louder than the test tone for the main speakers.

Next I tried the test tone for the center/sub and this time the sub test tone was much lower. So my question is, do I calibrate to match the sub to the center? I had always heard that you should match it to the mains but obviously that isn't possible.

BTW, my mains are set to small, 80 hz crossover and the sub crossover is inactive.

I've never used Avia, I have DVE. However, did you try setting your speakers to large? This should ensure that any sound sent to the sub is only coming from the LFE channel. If your speakers are set to small, then any bass lower than the assigned frequency is sent to the sub as well. If Avia is outputting bass to the fronts and LFE at the same time, then that could be what's causing the issue.

I'm not sure if your receiver will show if audio is being sent to the LFE channel or not, but check to make sure that is the case as well.

Try setting your speakers to large and do the test again and see if that makes any difference. You can always change it back when you are done. If nothing else, that will get rid of one possible issue. BTW, if you set the speakers to large and you stop getting audio from the sub, then Avia is not using the LFE channel to send the sub audio which is incorrect. (Like I said, I don't have that, I have DVE, so I'm not sure.)

Have you got the receiver in 5.1 mode?

Also, I think you should be leaving the subwoofer level alone in the receiver, and only adjusting the volume on the back.

I spent 3 hours with my brand new Avia disk yesterday, and it surprised me how much I had to turn down my EP500 to get it to match the M22s.

I disagree here. I'd do gross volume adjustment on the sub, and fine adjustment in the receiver.