It would be VERY easy to break the switches lifting the grills off. The grills have a cross member that could easily catch the switch and whack it right off. It's a cheesy little switch.
By the way, I wouldn't recommend throwing a blanket over the speakers for any extended period while they're playing loud. Voice coils dissipate heat.
By the way, I wouldn't recommend throwing a blanket over the speakers for any extended period while they're playing loud. Voice coils dissipate heat.