Thanks for the reply. I have used MDF quite a bit, and have found that if it is correctly sealed - and we are not talking about a very big piece - just a small box on each end of the sound bar - that it will work fine. Now pressed wood is a different story! I use the marine grade polyurethane, after sealing the ends with exterior glue, slathering it down good. Plus, on top of that, there will be a good coat of contact cement. I built my soundbar - the whole thing - out of MDF four years ago, and it has seen its "wets" and drys. No noticeable problems yet. In fact, just last week, I took off one of the 6X9's to see if a connection had come loose - stupid FM radio station had a problem with its left channel - worked fine when I changed stations! And BTW, he does love the mud and wet! Maybe I ought to put turf down on it???
2003 Rubicon, stock - but building - slowly... in Van Buren, AR