The 75dB datum is (I think) recommended for compliance with THX levels. I calibrate my 7.0 system to 82db because I have a DSP centre with sensitive mains/rears and powerful amps for them - I am more concerned about any loss of fidelty through attenuating the L/R signal than matching the THX standard. This is a subjective thought, not based on any hard facts.

Typical listening levels are 64/PLIIxTHX for TV, 82 for DD/DTS in THXsurEX (hate Ultra), 75 for Direct CD.

Do you notice any quality problems through calibrating to the higher level?

In the spirit of Spinaltap, I would like to confirm that I am not involved in the corrupt theft of a global sport.