I use a UMIK-1 which is the recommended mic for REW and I'di got the calibration file with sensitivity data loaded.
My room is 3 tons of concrete on the floor and surrounded by sound proofing with resilient channels and behind that brick . So I guess I just get good room enforcement
Well it actually becomes a problem! My main theatre room isn't surrounded by anyone so I can play reference with no complaints. But the secondary room has neighbours hence the sound insulation. That works fine at really high levels but it's not going to do anything for all this sub 20hz bass that'll piss them off with rattling. So I'll use a mini DSP to neuter the sub to 20. Sucks but when they're on holiday I'll enjoy some ULF goodness!