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?
there are several "cheap" alternatives for dynamat. Hi-Temp Mastic can be had from McMaster.com brown bread is supposed to be very good.
I've used quite a few different kinds. and you'll find that you get what you pay for. what the "cheaper stuff" lacks is adhesion. I've talked to several people who find all of their cheap alternative laying in a pile on the bottom of their door panel. Brown bread is supposed to be the best bang for the buck.
but I used dynamat super on every layer of the doors, and on the interior panels, and I have never had a peice of it come off. I used hi-temp mastic on the floor boards along with 3/8" carpet padding. and R-11 insulation stuffed in the rear quarter panels.
to make a long story short. the dynamat really is worth the money.
and to answer your section question, yes wood is porus. I haven't heard of many people using polyurethane to coat enclosures, but I use fiberglass resin on the inside of my enclosures to seal everything up tight.
i heard that cascade is some pretty good stuff too.. its cheaper than dynamat.. my friend put some in his 3000gt competition car.. and it works well.. its still stuck on there pretty damn tight.
