From: New BTL not very loud...

[Handcrafted Car Audio 42]

bump test it with a 9v battery.... if it moves out, then polarity of the terminals is correct, if it moves in... well one got missed as Nick said.

No chit man, good info

Not really. Think about what is being stated here and how a speaker works. When you connect positive to one side of the coil and negative to the other, you complete the circuit and current flows through the coil creating a magnetic field which reacts to the stationary magnet. When the signal swings positive the cone moves outward, it swings negative and the cone moves inward. If each voice coil were wired in opposite of eachother and connected to a mono amp, the end result would be no movement. Or atleast very little. They would be fighting eachother.