I know, I've said -- and I believe -- that Directors, Producers, even many Musical Directors are unreachable not because they can't understand the underlying acoustics and psychoacoustics, and not even because they haven't realized that there are such underlying principles with very real (and dramatic) effects on the sound of a show, but because they are unable to make the cognitive leap to accepting that this matters; that acoustic realities don't go away just because you are ignorant about them.
If I believed differently, I think I would start by presenting one simple question:
"Have you heard of the Haas Effect?" (More commonly known these days as the Precedence Effect.) "More importantly, have you had the Haas Effect personally demonstrated to you in a controlled listening environment?"
IF for some reason the paradigm shifted and they were mentally open to noticing the cognitive gap, this question would provide the wedge.
Alas, that moment never happens. Conversations are always in the moment, about a specific issue, and framed and phrased in a top-down form. "The actors are complaining the side fill speakers aren't on. You need to turn them on."
Any attempt to explain that the issue is actually one of perception of sound sources; that if you modify the relative volumes or delays in order to bring those speakers into perceptual range, a different set of speakers will perceptually vanish and thus become potential target for the same complaint (as well as, of course, delivering less of what the actors actually need in an attempt to fix what they think is broken), it can only be seen in the frame of those discussions as a lame attempt to escape responsibility.
No matter what you say, what is heard will be, "I can't or won't fix the speakers because reversing the polarity of the transporter buffers or something...um, actually, because I'm lazy."
(Not an actual example, and the real ones are often less clear-cut. The way bass frequencies approach omnidirectional, meaning the rear of a full-range speaker is not "a place where no sound comes out," but, rather, a dangerous space full of extremely loud, muffled, time-delayed, low-end sound. As a for-instance. So, no, I don't care if your 500-watt keyboard monitor is pointed at the rest of the band. The audience is listening to it as well, and what they hear isn't good.)