I found a huge difference when I moved my system from an upstairs bedroom to a big rec room in the basement. The big room just seems to suck up the sound, had to turn the volume control up a lot higher for the same perceived volume.

I didn't have the sound level meter at the time or would have measured the difference... and NO I'm not going to haul it all upstairs and measure now.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8