I received an E145 woofer off craigslist. It looks in great condition, but the voice coil won't move easily when I push the dust cap. It seems the woofer was buried in sand for some time, there are many fine magnetic sands got inside the rear port of the magnet. I believe the sands block the movement of the voice coil.

What the best way to clean up the inside of the magnet? Do I have to recone it? the original cone looks in excellent condition.