Cant you use a DMM to see if there is a change in resistance of the coils.


SHY

 

The "push down on the cone and listen for grinding" isn't 100%. Perfectly good speakers can do that if you don't push them carefully. When you push you might place a bit more pressure on one side of the cone then on the other - making the piston travel on a slight angle, giving you grinding noises. While if you push with all even pressure, it could sound nice and clean.

 

^ Werd