Tom, it really isn't very crucial and the more important point is to get all the speakers equal in level, regardless of what SPL level is used for the calibration. Be that as it may, most(all?)receiver test tones are set 30dB below the maximum level of 105dB that movies are supposed to be recorded at, so if you adjust the levels to 75dB, then the movie sound(not applicable to music discs, which have no established standard level)would be played at the designated "reference level" when the receiver volume control was at 0 or whatever number was used during calibration. Of course, few listeners find that using the "reference level" for movies is acceptable for long-term listening in the home and use a a level 10dB or more lower.
