Here is the relevant paragraph from my original post:
I believe one reason I listen at lower than typical SPL is because at higher SPL, the reflected sound becomes more prominent and disrupts the SQ. Many of my friends like to turn up the volume when they visit. I tolerate it (they really enjoy the sound), but I don't enjoy it.
Oh, you're going to love treatments if you ever get the opportunity.
I listened to remastered recordings of both Mingus and Brubeck (both circa 1959). They were both free of hiss.
Unfortunately, I don't have the recording you mention. However, I believe you are right - I would not be able to enjoy that recording with these speakers while I might with speakers which did not have as much high frequency extension and prominence.
Who knows, eh. I've owned Mingus discs from roughly '59-'62, and they are far from being demo quality for speakers. I'm certain I didn't play them in my auditions for this reason (I think I was mostly using "Oscar Peterson and the Bassists" during this time, and while not really "demo" stuff, it was certainly of better SQ than most Mingus recordings I've heard). IOW, if Mingus works fine on them, I think most recordings will work fine on them for you.