OP. I did the same thing with my new Audio Research REF 6SE and my then new Sonus Faber Amati Traditional. I think I got it turned off in closer to two seconds… and hopefully no hearing damage. It did not damage the speakers fortunately.
I was actually rather upset that ARC would cluster the three output pairs together and not, at least, put some caps on the pass through outputs. Wiring your system up against the wall… with you head upside down is asking to have this happen. My dealer puts tape across the outputs so his folks don’t accidentally do this in the show room. I think this is a real stupid oversight by manufacturer not put in some safety mechanism.