My DIY amp went south a while ago. Not sure if it was the emitter resistor that shorted and caused the output transistor to fail, or vice versa.
Thankfully, I had installed protection boards on the outputs, so speakers were spared.
Had they not been there, the speaker would have been toast.
It’s a 30w class an amp, so there was only around 30vdc, but would have blown the speaker for sure. Rail voltages can go waaaaay high in high power amps, so should something fail, it could get dramatic.
Sorry this happened, a costly episode no doubt.
Should you buy a used amp again, one that doesn’t have DC protection, or some other kind of fuse on the output/rail, then any tech should be able to install DC protection for not very much money.