Sub box finishing question....

Hey guys,

I have built a few sub boxes over the years (im old ) and am about to do another...
But lately I have seen a number of boxes that I *think* were wood, but with some type of covering over them to allow them to be painted. From what I could make out with the speaker removed, it looks like some type of cloth over the wood, and then basic body finishing over that (bondo/filler) and then painted.
...my question is, do you know of the type of finishing that I am talking about? if so do you know a good web-site or book that explains the process in detail?
The object is to paint it black, with mystic flames to match the truck.

Thanks,
Dave-

Hmmmmm... yeah now that I think about it, it could have been glass.

Those look good!

Do you need a special type of primer for wood? Forgive the dumb Q, Ive never painted anything other than cars....

Thanks,
DD-