I remember a while back reading a post about a cheap alternative to dynomat. I did a search but couldn't find the post. Dose anyone remember what the stuff was? Also, I'm building a custom subwoofer enclosure out of 0.75" MDF board and I have heard people say that MDF board is porous therefore the outside walls should be sealed with polyurethane. Is this true? Is this just to protect the wood or to make it air tight?
