I recently just purchased another set of 12" subs to go with the set I already have. The problem with this is that my original subs seem to be worn out, the suspension is very sloppy. Can someone tell my what part of the sub determines the stiffness of the suspension and if it is cost wrothy to get them fixed?

Thanks

 

Obviously, the spider & surround make up the mechanical compliance of the sub itself. However, electrical compliance makes up most of the QTC in the real world.

If you are really concearned, you may want to measure the sub's T/S parameters... (you will need a frequency counter and a few other things)