I bought a pair of Axiom made Michaura m55's on ebay that had a problem that sounds similar. I believe that during shipping the whole magnet/motor structure was jarred loose so that it was sitting at a small but discernable angle to the woofer basket. There is a flat spiral wound spring that positions the cone/voice coil with respect to the magnet structure. The spring coil is inside a paper cover so you can't see it but you can feel it. When I pushed on the woofer cone moving it back and forth I could feel the coil windings binding against each other causing the metalic rattling sound. I took the woofer out to the shop and set up a press to squeeze the magnet structure back into alignment with the woofer basket and the problem was solved.
I offer this for information purposes. I would without hesitation have axiom send a replacement driver under your warranty.
