I would assume the woofer is toast before the xover is fried. Theo's advise is good, but not sufficient. If you can, remove (or just disconnect the woofer from the xover and connect it up directly to the amp (at low volume). If if sounds like a woofer, it's the xover. If it sounds like a tweeter, or nothing at all, it's the woofer.
Looking forward to continuing the diagnosis...
Looking forward to continuing the diagnosis...