Originally Posted by
moldyoldy
Just a side note for any that try the "manual" method. The driver in question MUST be disconnected from amps, networks, etc., or you'll likely condemn a few good speakers this way. When the coil is moved manually, it acts like a microphone and produces a signal. If the coil "sees" any load connected, you'll feel/hear what you'll swear is a coil rub. The effect may not be noticeable on cheap, inefficient speakers, but it sure is on the close-tolerance, efficient drivers we mess with. Next time you've got a loose 15" on the bench, throw a jumper across the terminals and try it. I've even checked for open coils in the field when I was without a meter or battery this way.
Typical disclaimer, don't try this at home, etc., etc. It DOES require a practiced touch.