I've been fussin with Audyssey for the last week trying to get it 'right'.
My main concern was level matching of the EP800s with each other. I don't have a SPL Meter & am reluctant to spend a bunch of bucks on one for what I would think would be minimal use.
Recently my phone company gave us a cheap, free Android smart phone (Huawei) so I decided to try to download a free SPL Meter App. It was a frustrating exercise, but I finally got it installed. I then roughly calibrated it using my Denon's Test Tones. For my usage, 'absolute' accuracy isn't as important as 'relative' accuracy.
My last Audyssey run gave a -11 Db SW setting so the Subs' Gains were too high. I ran the Denon's SW Test Tones & close-miced the output of each sub individually. Output averaged 85 Db each so I tweeked each Sub's Gain down to 80 Db (Gains now at about 10 o'clock).
I ran Audyssey again & it set the Sub Level at -8.5 Db & Distance of 24' (double the actual). I ran some dynamic music through it & it is now just fine.
Interestingly, I watched the SPL Meter during the pinging of the automatic calibration process. For normal speakers, the meter bounced around 75 Dbs & the SW around 65 Dbs (understandable given the little mic in the phone). So, for my purposed this little freeware app worked wonderfully & saved me some money so that I can Trade Up more speakers, ha!