If you had run Audyssey when the room was quiet and you followed the instructions to the letter, then you should trust those results. The Audyssey mics were supposedly calibrated against some reference so for the specific task they should be more accurate than you spl meter. This is especially the case when checking subwoofers, that you can't trust your spl meter too much.
I have run audyssey many times (so many that I lost count long ago) and I know it is pretty accurate each time I ran REW to see the actual results.
I definitely respect your opinion Peng but, I don't agree with it in this case.
I think it totally depends on the Mic or SPL Meter he is using. The Audyssey mics are cheap, medium quality at best, and batch calibrated within a variance of 2.0db. If he is using a UMIK-1(especially if calibrated by CSA) or even a quality name brand SPL, that is accurate at the right frequency range to measure a sub, they both should be more accurate then the cheap included Audyssey mic(some peoples SPL Meters are worth half as much as their AVR's).
I am new to this and still learning but, I have read posts from several people that say you should indeed re-check levels post Audyssey and correct where necessary. Relying on a single measurement, with a cheap mic, during the Audyssey position 1 scan is not the most accurate way to do things imo. All it takes is a car driving by or any other issues and that one scan will not be fully accurate. With a quality SPL Meter/UMIK-1 & REW you can play a constant tone and recheck it until you get the level perfect. Then, you can recheck it anytime. While Audyssey does a pretty good job, I can't see how this method is not more accurate. I personally see Audyssey as a basic starting point(or finishing point for less technically inclined people)that can almost always be improved apon.
As for his question about the subs...
I believe you want the combined output of all three subs to be 75. But, that is just a starting point. Adjust the bass, post Audyssey, to the level you see fit(many find it too low after Audyssey). Just make sure to keep your AVR sub levels at about -6.0db or lower to prevent the AVR from sending a clipped signal. Use your subs gain to go higher then that while keeping them all synced.
Sent from my SM-N975W using Tapatalk