I've been looking at the B&K 5128 measurements with great interest for some time to see what this new and supposedly much improved (compared to the previous generation) coupler has to offer for headphone measurements. So since Jude has only uploaded uncompensated graphs so far I just tried to come up with my own compensation curve. Since I am currently testing the AirPods Max and Jude's dataset is still very limited, I chose the HD800S and the APM for my target. Three tries later and my first somewhat rudimentary curve ends up producing measurements that look like this: So I think that's not that far off. I don't hear so much of a bump at 1.5kHz on the APM and I'd probably reduce the region between 200Hz and 1kHz a bit on the HD800S (but not the APM), but overall it could be indicative of what someone else hears. So I apply the same curve to the HD650 measurements: I think the results speak for themselves. I could of course make a 4th target which greatly reduces the upper midrange, but I don't hear the other headphones as that sucked out. Honestly, I wish I had done this earlier since now my interest in the 5128 is pretty much gone.