I really like the sound coming from the Yamaha...With the XMC-1 it always played very bright...The Yamaha reminds me of my older Rotel RSP...I had to treat my room and use REW with my Rotel, sounded very good to me. When I bought the XMC-1 it came with Dirac so I used that and spent a lot of time measuring, moving etc. In the end I simply believed that possibly this was the way it is supposed to sound. We still liked it but it lacked something
So, IOW, the REW FR graphs from Dirac looked flat, but it still lacked something that you just couldn't "see on paper"?
When it comes to various auto room corrections, there is one elusive saying that's difficult to prove - "There is more than just the frequency response curve that improves the sound
SUBJECTIVELY,
even if we can't see it".
So the Auto Room Correction isn't just making the REW FR graphs look flat. If 4 different Auto Room Corrections make 4 flat FR graphs (+/-2.5dB),they could still all sound different - one may sound good subjectively, another may sound bad subjectively.
How do we prove this intangible subjective sound quality that can't be seen?
There are opposite opinions for all these auto room corrections. Some like them subjectively, some dislike them subjectively.
And BTW, I think there is excellent reason why many audio experts believe that we shouldn't be equalizing the 200Hz-20kHz region. Just because it looks better on paper doesn't guarantee that it will sound better in real life.
Remember that Infinity P360 vs B&W 800D FR comparison years ago? How the P360 had much better on-axis and off-axis? Who's going to believe that the P360 actually sounds better?
When I had the Revel Salon2 and B&W 802D2 in my house and people listened to them (Direct Mode, Denon AVP-A1HDCI, ATI AT3002),the preference was 50/50 in "single-blind" comparisons (Adcom speaker switcher).
Whether we are talking about true anechoic or REW In-room, the FR graphs are good guidelines, but they don't guarantee better sound.