Well I recently got screwed over big time for a 12" Eclipse SW8122DVC sub I purchased off LetGo and could use some advice on buying used subs. I'm somewhat new to car audio and thought usually if you compress the cone and hear a scratching sound then it's no good. Well I was a jackass and didn't fully hook it up and test it cause I at the time I had no amp so I figured if it doesn't make noise by compressing the Cone then it's good... Well was I wrong. I hooked it up and got nothing. At first I thought maybe the amp is no good since I got it used also but I removed the quick change magnet, looked inside the aluminum former that the voicecoils wrap around and it was ripped, or cracked 75% or so around it...The guy never responded back to me so what I'm getting at is, what tests can I do to used subs to make sure this doesn't happen again? Multimeter, or what? Thanks for the help in advance.