With a crossover set at 65 the sub should be reading less than the mains by (give or take) 5dB.

Leep in mind that most SPL meters (I have no idea what you're using) are off on the low-end due to A vs. C weighting. For kicks and grins, check to make sure it's C weighted instead of A weighted.

The chart above was illustrative. Just work with 1/2s and 1/4s, 2x and 4x the crossover frequency to get an idea of what the "textbook" measurements will be, keeping in mind that the room affects measurements to some extent.

Cheers,

Surround Music Fan/Computer Geek/Curmudgeon in training.
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