Took apart my old 1518 today. It's been in storage for a few months (nearly since I got it), and I finally fired it up for a little bit at my new place. But it was getting a bit of mechanical buzzing from somewhere, and had some mold spotting here and there, so I took it apart to track down the buzzing and clean it up.
The grill wasn't the problem (which would be an easy fix). The buzzing would go away with some slight pressure in one spot of the cone, so I was worried there might be a small crack/tear in the compliance. But when I looked closer, it looked like the guy before me must have used some sort of adhesive foam to re-attach the foam gasket on the front of the speaker, and it had "oozed" before curing, leaving a messy line of the foam right at the edge of the compliance, which certainly seems like it could cause buzzing. I carefully used a utility knife to get rid of most of the oozed foam. Then I wiped off the speaker to get rid of the mold.
After that I went ahead and cleaned up the cab. I have to say, a bit of hot water really made the cab look a lot better. Looking inside the cab, these things are built pretty well. Only downside is no bracing or damping material, so I'll probably add some of both to this and the matching 2x10 when I get around to it.
Anyway, I'm hoping when I put the speaker back in tomorrow, that the buzzing will be gone (ie caused by the foam). I'm also going to mount it flipped vertically from how it was before, just in case there's a bit of "sag" from being mounted and stored the same way for 22 years.
Other than the buzzing, the thing sounded awesome, and that was with my ancient "low end" Carvin fretless (with flats) that is kind of tricky to get dialed in, unless you go for the thumpy upright kind of tone. I'm excited to get it back in action and paired up with it's sibling.