I struggled also with the right ear fatigue during the listening sessions and had to make my sidewall treatment more absorbing.
My room is not large (13.5Wx14.5Lx10H) but it's heavily treated with the room's acoustic elements. Sometimes, my ear will ring for a few seconds later on in the day. I'm not sure how much KEF R500 is responsible for it but the FR is only a few dB down at 20Khz in my MLP.
I sit 8.1 feet from the tweeters and speakers are toed in so I can see some inner sidewall of the pannels. They sound very bright if they are aimed straight at my ears. Not sure if this ear fatigue has any correlation with tinnitus.
Below is the smooth-out (psychoacoustic filter) FR of KEF R500 in my listening room without any EQ or DSP corrections.
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