I used to encounter this problem in schools, mainly with JBL Control speakers, The EV ZX1s seemed harder to pop, but determined schools could still manage it. The issue was teachers/students not understanding that the knob on the front of the amplifier is an attenuator, not a volume control. There would be a complaint that the sound in the hall was too loud, so somebody would go in and turn the amps down to make it quieter. The next time the system was used, somebody would realise that it wasn't as loud as last time, and whack all the gains on the desk up to get it to the same level as before. This would result in a virtual square wave being delivered to the speakers, which eventually would take out, more often than not, the HF drivers. I spent many a training session in schools trying to make people understand that turning down an amplifier doesn't make it quieter, just makes it harder to go as loud as before.