Originally Posted by leedesert
I would think he should run it just to get the distance of the sub dialed in. Different subs have different components and filters so that will effect the timing/distance a little. I still check everything with an SPL because I like to know I verified all my levels and many times there's room for some tweeking.
Timing, gain level, and actual filters set could all be very different with a new sub, so running Audyssey would definitely be a good idea. The only thing I was suggesting is that it isn't necessary to use an SPL meter to adjust the sub gain, as the Audyssey calibration process itself provides an easy way to do that.
Of course, there is also nothing wrong with using an SPL meter to check what Audyssey has done, and to make any preference changes desired. But, you are unlikely to be able to improve on Audyssey's accuracy with respect to making all channels, including the sub channel, play at the same volume at the MLP. The Audyssey calibrated microphone has an error factor of about +/- 2-3db, as do all but the more expensive calibrated SPL meters. So, either Audyssey, or the SPL meter, could be off a little in either direction. But, where Audyssey is not likely to be off, is with setting all of the channels in a system to the same volume. And, the Audyssey mic. will measure bass frequencies much more accurately than most SPL meters' will.
After Audyssey has set the channels to all play at equal volumes at the MLP, nearly everyone adds a sub boost, as our hearing is less sensitive in the lower bass frequencies, and we may also just want to emphasize low bass, or bass effects in movies. But, the initial trim settings for all of the channels will be very equivalent within that overall +/- error factor of the microphone. And, it will only be coincidence if an SPL meter, with it's own error factor, exactly replicates the Audyssey SPL measurements.