Two shots of mine //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
MDF sandwiched with a top layer of butyl rubber...and lots of clay.
The big door holes were covered with 1/8" Lexan panels, that were held in place with cyanoacrylate and Liquid Nails then covered with yet more deadener.