I have some new sub boxes going in that I have resined and glassed the hell out of on the outside but was wondering if I am supposed to do the inside as well. I had heard in that past I was not supposed to because the density of the mdf helps with the sound but I have also heard to do the inside as well.
some times i resin both inside and out, but its not needed but its safe to.
if its a sealed box dont worry bout it, just use poly fill. if its ported it makes a better sound when smooth. plus it makes for a longer lasting box.