Dealers and exaggerated treble

No, because the treble is above the room transition frequency. Unless you are in a tiny room with no porous surfaces (the walls are made of glass or something), the difference in treble should be from whether you are listening directly on-axis or on a different angle...and if the speaker has un-even dispersion the differences in position will be exacerbated. I’ve never heard a speaker that’s bright that isn’t bright in every other room.

If you have an experience like the one you mentioned, and the angle you listened to the speakers didn't change, assuming the speaker is normally not considered a bright speaker, another possibility is the speaker has an existing peak at a frequency that was exacerbated by some reflections that grated your nerves and so it wasn't actually bright, rather you were just bothered by a high q resonant peak that was made worse. 

Erik,

I haven’t had that particular experience, though I’ve heard plenty of bad sound at dealerships.

I suppose in your cases, the harshness could have been exacerbated by the upstream components or lack of acoustic treatment.

As you well know, many speakers have HF peaks; so do many microphones; and so do MC cartridges. A bad combination could be tough to take.

Mike

When I had my shoppe(early 80’s) in Winter Park, Fl; a customer wondered how my 10", two-ways might sound, compared to the Boston Acoustics, that a local competitor carried. He wondered if he could borrow a pair to take to their location. Came back and said they were terrible. I drove over there(never had, prior) and looked around, finding a graphic EQ, far removed(on another shelf) from the system), but in the tape loop (set to BOOM and SIZZLE . He tried the comparison again, switching off the tape loop, returned and bought a pair of mine, as a kit. Knowledge = power!