i vote tinsel lead slap, allthough i havent seen an ARRR in awile, take that thing out, play it just loud enough so it makes the ratttle, and the stick your finger in there and try and stop the rattling if you can find it, ive done this with really old crappy subs and its usually tinsel slap, or the spider could be lose where it meets the coil? and if it is, just glue it, and p.s. subwoofer break in is nothing to worry about its just the softparts of your woofer loosening up i havent nor heard of anyone blowing a sub hooked up correctly just becuase it wasnt "broken in"