So I was measuring the in-room response of my speakers (Paradigm 85f) with REW and a u-mik1 for shits and grins as part of testing a couple integrated amps to figure out which one I wanted to keep. I threw in my AVR as well for a baseline. I was expecting them to measure more-or-less the same, but was really surprised when I measured them. The amps were an Arcam SA20, my Denon x3500h, and a Schiit Ragnarok 2. The Denon and Schiit measured pretty much the same, although I was really surprised at exactly how close they were. Then on to the Arcam. It was wildly different: Here it is zoomed out a bit to 1/3 octave. Should amp affect measurements that much? It's funny because the Arcam's response squares with my understanding of the Paradigms (less energy between 2-4k), but thats not the Schiit and Denon's response at all. I'm weirded out in general that two amps would measure lock-step the same, and a third amp pretty vastly different (that room mode at 45hz is boosted by almost a full 10 dB)!