@erik_squires
1) "Try recording your speakers and then listening that with headphones, or a friend’s voice in the room." THAT IS A BRILLIANT IDEA!!!! He has a very good headphone amplifier and headphones, so this would be a perfect exercise. I can play a couple of his favorite tracks and use my Zoom H4N stereo audio recorder: it is mostly very good at accurately recording full tonal range and area, not a specified ' directed lobed area of recording: should be very similar to the human head and sphere of hearing.
2) That is exactly why I had started by placing those absorbing panels DIRECTLY next to the speakers--to help him hear the 'opposite' extremity, before the sound even reached at least the side walls and front wall. Even then, from the sitting position if you snapped your fingers you can hear it vibrate and almost echo. I look at speakers like a semi-directed rock-being-dropped-in a-pond with square banks. The sound radiates in ALL directions, at varying intensity and phase: some frequencies cancelled, some reinforced, some refract and reflect, some gradually fade away. It makes complete logical sense for most to grip onto "first reflection points". It is insanely complex really how we try to reproduce a 3 dimensional musical performance with two speakers, who project dominantly from ONE dimension---so that first reflection is a very simple spot to lock onto "fixing" issues this audio-problem creates.
He doesn't have nearly enough to really properly make effective changes, but I think I can present enough of a positive shift that he will like what he hears more, and will follow thru with getting a nice series of absorbers/diffusers to help him really get the most the system is capable of creating. He's insanely lucky that he has NO true oddities or issues like bass booms that can be very difficult to remedy. He just needs to break up and absorb things mostly.
Happy Easter! (and thanks for continued help and idea!)
~alan