I have a NAD t-753 receiver and I've being using it's test tone to level match my 5.1 system. I use an SVS pci 20-39 sub. Today I set up using a digital video essentials DVD and it showed the bass volume to be 20dbs higher than what the other speakers were set at. If I use the DVE settings the sub is 20dbs too low according the test tone. Does any one have an explanation for the different readings and which one is accurate?