1. Set the speaker level trims for each channel to zero.
2. Press the 'test tone' button on the receiver or remote to start the test tones.
3. Turn the volume dial up to the level you want to be the 'reference' level. On receivers with relative volume displays (-inf to +something) the convention is to use 0dB. For absolute volume displays (0-max) a good rule of thumb is to set it to approximately 80% of the range.
3. Set your meter to slow response, C weighting. With the meter pointing straight up, about ear level, from your seating position, observe the SPL. Adjust the channel trims up or down so the level reads 75dB (the receiver test tones are at -30dB so calibrating to 75dB gives you Dolby reference level with peaks at 105dB).
4. Go to the next channel and repeat until all channels are roughly equal. You may not be able to get them all exactly to 75dB but they should generally be within 1dB of each other.
Note that there are alot of factors that effect the output SPL: type and sensitivity of speakers, room size and furnishings, etc. In a small room its possible that you will be way over 75dB with the volume setting up on 0dB or the channel trims may not have enough range (they are generally +/- 12dB). Just turn it down and go again.
Although 0dB is the convention for 'reference' level, it doesn't really matter what value you end up with as the reference volume setting. What matters is the SPL is 75dB and all the channels are about equal.
As an example, I used DVE to do my calibration (it uses -20dB signal so you calibrate to 85dB). My receiver, Onkyo 502, uses only the absolute volume scale. At 60 on the volume scale, I get the correct 85dB SPL (which means peaks to 105dB - Dolby reference level). That is extremely loud and like most people I normally listen below reference.
