Hi there. First thread here on the forums. I was given a a very old speaker and I was planning on using it for and amp build. Problem is, when I went to test the ohm rating on the terminals of the amp I got nothing. So I very gently removed the dust cap (not really a cap but piece of felt or something) and very carefully scrapped off some of the black goop(?) and that very thin protective layer from the wires going to the voice coil. I measured the bare wires and got a reading that varies between high 6's and low-mid 7's. After some process of elimination, I found out that the ground wired going from the outside speaker terminal has some how disconnected/went cold to the voice coil. Question is: How can I remove the black goop safely and repair the joint without damaging the cone? My soldering skills are pretty good, but most of my experience is with PCBs, pots, jacks, etc... Thanks for any help you can provide.