Bad bad thing happened after church today, help?

OK after prayer, I installed the first $600 pair split speaker in the front penger door of my 2006 M5, anyway i had to construct supports, blah blah and when I bolted the speaker in I had to shorten the bolt at the back with the grinder so the door trim would go back on, so i put a rag around the back of the speaker and cut it off but noticed a few sparks beyond the rag. Will this hurt my precious speaker, I inspected it after, seem ok, no marks but theres some wooly fabric stuff back there, OMG.