the bubbling i stated in the other, i saw first hand, and Rusty explained it to me (the owner of DC). The massive heat build up can cause gasses while the resin/glue starts to melt and evaporate on the windings, with the flatwound coils, there is no where for this gas to go, so it takes the path of least resistance, the aluminum former, which it will bubble out and create a ridge all the way down to the bottom of the former where it can escape. this ridge can touch the pole and cause a rattling sound.
your problem might be this, it might not, but a recone is probably the only thing to fix your said "rattle".
man if i have to recone 1 i might as well just recone both to upgrade them ( i have 2 woofers i had only 1 playing)
if you cut the dustcap off without hurting the cone, looking down to the pole and coil will be your best bet.
if you have the issue i stated above, you will see something like this....
which kind of dustcap do you have?
as of right now i would dare to cut the dust cap offf knowing that evrything ive done is wrong so far