first of all....how can a speaker coil have a + and - side?? and what is that thing that stereo shops use to test polarity of speaker coils and how does it work?

 

A 9 volt battery. If the speaker pops out, you're good. You got the + and - right. If it pops in, you got it backwards.

 

the coil magnetizes the cone and moves it.....ofcourse it has a + and - side....but is it really strait from a 9 volt? that seems like it would destroy some smaller speakers.

 

I generally use that for subs. i guess you're right on the smaller speakers. Usually, my smaller speakers are marked. i only had to do that battery trick w/ my subs. don't hold the battery to the posts long. just to check it move and that's it. it'll pop in or out

 

I've tested the polarity on hundreds of small speakers, as small as 3.5" with a whizzer cone, and I haven't blown any yet. A 9 volt battery has very little current capacity, plus if you figure 9 volts through a 4 ohm speaker, that's about 20 watts, but that requires 2.25 amps of current, which that 9 volt can't get anywhere near.