I’ve been waiting for someone much more knowledgeable than me to jump in, but here are my quasi-neophyte opinions (worth what you pay 😉 )
The “cross over” you see I suspect is actually the linear power supply that applies the bias across the electrodes. The fact that you hear no difference in volume between the speaker plugged in or not and that the knobs don’t do anything suggests the electrodes are not getting voltage–maybe a blown fuse? I’m not sure what to make of the fact that you hear an effect of the brilliance knob–it seems it wouldn’t work either if the electrodes are not powered up?
I’d call Sound Lab and see if they can talk you through it.
I’d like to hear the Marquees–if they sound anywhere close to the big panels they would make for an awesome home theater experience.