Listening to the sellers of every room, no one was satisfied with the acoustics performance of room. Someone tried to put tube traps, other carpets and light panels with foam or wood to break waves.
Acapella room was maybe 3x4m, small, with bad shape and wooden floor. 12 chairs for people, speakers angulation was in my opinion too accentuated, maybe good only for central seats. I tried all position, it's curious that the strange mid horn sounded good in the worse place, at little more than a meter. Bass didn't impress me so much, a bit detached to double horn emission.
Ultimately, it would be nice to hear the system in a proper room, unfortunately there was no possibility

By the way, my focus was all concentrated on tweeter unit, for obvious reasons Cymbals and other highs were fantastic.
I found no noise with no signal applied, tiny idle flame, and not so much bigger in normal use. I read that starting frequency xover is 6khz, a bit high to see bigger white flame. I suspect that the trumpet is deep, with small diameter and tiny quartz cell, pretty efficient.
I hope I will fix my plasma soon, in order to discover at least the effective range and how it can sound.

I think you made the right decision, buying speaker with closed box can be really risky, unless the price is so low as to overshadow the rest