So let’s forget the videos that at one point you claimed were representative of what you heard.
Yes, let's. In retrospect I think "representative" was too strong a word.
In the room, do you hear the high frequency roll off shown in your measurements
I do not hear the broad high frequency roll-off depicted in the frequency response chart. It remains a mystery to me too.
But the 4 to 5 kHz peak or edginess has objectively (measurably) been reduced. Subjectively I think it has been wholly eliminated or, at least, attenuated into insignificance.
Don, who was the most troubled by the 4 to 5 kHz peak or edginess (along with me) declared after several hours of listening on Saturday to his own tracks that he brought with him that he could no longer here it. He kept asking me "what did you change to get rid of it?"
Now that that issue has been vanquished I am now a bit nervous to push further in the smoothing/softer direction. Doing so might cause me to lose dynamics and energy and natural instrumental "bite." I'm even thinking about experimenting now with
removing a couple of the absorption panels. I'm even wondering now if I don't need to replace the Cardas Clear Beyond interconnects with a slightly smoother model of Cardas interconnects.
Don said he never really heard distractingly the 45Hz and 65Hz room modes (which puzzled me because I sure AF could hear them). But J.R.'s placement of the woofer towers inside the panels and away from the walls, combined with his placement of the AVAAs surrounding the listening position, has vanquished the unexpectedly problematic room modes.
So that leaves consideration of trying to get to an even higher indifference curve with a high power SET or PSET amplifier; experimenting with different cables; experimenting with panel toe-in to fine-tune center imaging solidity; and a bit of input tube and driver tube swapping In the JA100s.
But I am basically done. I'm loving how the system sounds right now with the 5T. I think I'll be even happier once the Grado goes on the 5T.
If I played with none of these other tweaking possibilities I think I'd now be fine for the rest of my life.