I personally witnessed several speaker fires back in the 70's. Crown DC300's were notorious for dumping DC into the outputs, as were Phase Linear and early BGW's I remember one speactacular event in a club (a disco) with GLI speakers powered by BGW 750's. The DJ decided to fix the system (it wasn't loud enough) by removing the crossovers from the boxes and tying the amplifier out[puts together (NOT bridged, just hardwired). The first night after his modifications I was running the lights and suddenly saw a bouncer running for the dance floor with a fire extinguisher. At that same moment we all smelled the burning stench, and I ran down to the dance floor. Speakers were 15' in the air, so the bouncer was spraying foam all over the ceiling, lights, and patrons. They got the fires out (there were 3) and continued thru the night at a greatly reduced volume. The DJ was not seen again in that club.