is there a hole or other obvious damage?
if so, replace the damaged woofer.

that circular component between the woofer and it's mount is called a "surround." has it disintegrated?
if so, time for a new woofer at the repair shop.

(choose to view a larger image)

If one woofer is worn, be sure to replace the other one, too, since both woofers are the same age and will degrade at the same time.

Another casualty of manufacturing cost reduction, foam surrounds are cheap and are made to last 3 years.

Poly or accordian edge woofers (standard in AME speakers) are higher quality components and produce the best sound for years.

Treatment

	accordian edge is the best
	poly/rubber surrounds are second

Beware! woofer replacement can be expensive. check out the typical costs of speaker repair before your visit to the repair shop.

You may also find a pair of replacement speakers is the best choice! compare the cost of new to the price of repair now.

or...check with sound medic on other problems.