Every now and then I recheck my levels to make sure there evertyhing is balanced to 75db. Well today I checked them and to my surprise the surround levels according to my spl meter were 4 to 5 db too low. After some trial and error I discovered that it was the THX setting that was causing the level increase. You see when I initially set up the channel levels for my receiver, it was in THX Cinema mode and everthing was balanced at 75db with the volume knob set at 0db. But when I rechecked the levels today my receiver was in THX Surr Ex mode. I noticed that when the volume knob was at 0db, the sound from the surrounds was much softer and the surround levels were reading around 71db. Does anybody know why this is? I thought that it didn't matter what mode you were in, but apparently it does. So do I need to turn off THX processing altogether and do my setup in Standard mode?