Many audio products use foam, particularly speaker surrounds. As those who own such drivers know, they are prone to deterioration.
While working for another store which sold Boston Acoustic speakers which used a lot of foam in their designs, many would never even make it through the warranty period before failing. Boston was alarmed at the failure rate and requested the defective drivers to be returned for analysis. Their analysis revealed that the culprit was mildew.
Apparently , here in Hawaii, the warm climate coupled with the high humidity, allows moisture to condense inside the foam pores where mildew can breed and proliferate. The mildew eats away at the foam cell walls and causes the foam to collapse. This effect is not confined to speaker surrounds. The foam lining used in many cars for the headliners, likewise, will collapse, as will even certain running shoes.
A good friend who taught electronics at Nanakuli ( now retired) was dusting his running shoes one day and stopped to read the label. It was advertised as being anti fungal and anti mildew. He then realized that perhaps dusting his speakers with the foot powder could stop the deterioration. He reported that his Bostons had lasted for over 5 years, whereas the first set (original) lasted only a couple of years. I believe his set went well past 15 years.
The key is to dust the foam portions liberally with an anti fungal foot powder about four times a year. This incidentally also works for foam ear cups for headphones. You can use a fine brush to spread the powder, or in the case of the ear cups simply place them in a bag, add powder, and toss them inside the bag. For speakers be sure to play something with loud bass before replacing the grills to avoid the white powder from creating rings in the grill cloth.
Incidentally many Martin Logan Speakers also fail because for the same reason. ML uses that 3M white foam double stick tape to glue the diaphragm to the stator panels, Over time that foam also deteriorates and the foam collapses and shorts the the panels out.