When I try auto-calibrating my new 990 for 7.1 set up, I get a msg. saying that since my rear speakers are large and fronts are small, I should switch the speakers and try again

So I tried manual calibration using my Avia disc, which gave poor results. Then I tried again using the 990 test tones which resulted in level differences of -4 to -5dB for the rears and backs.

Why are the levels so different? My guess is that when I calibrated using the Avia disc, I had the 990 in the wrong mode. What mode should the 990 be in for external source calibration?

Better yet, should I expect that the levels using the 990 internal calibration test tone will ever yield the same results as using an external (DVD produced) tone?