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Is MDF airtight? (Long-ish)

Posted by Dyak (A) on June 25, 2007 at 10:05:39

Hi Everyone,

I'm looking for suggestions as I'm building my first kit/DIY speaker using MDF. It is meant to be a sealed enclosure (a pair of 10"s, a dome mid, and ribbon tweet) and I found this little tid-bit about a vacuum lifting 5-stacked pieces of 3/8" MDF (below). Is this possible?

I quote:
"Most people choose MDF for their enclosures. Believe it or not, MDF is not airtight. All the hours you have spent sealing your seams with Silicone, Latex Caulking, and the like, while important, are only half the problem. During a recent visit by Dave Gumienny of Kicker Car Audio, he reminded me about the breathability of MDF. He told a story of one of the training courses they did years ago when he worked for PPI, where 5 small pieces of MDF, 3/8 thick, were stacked, and all where lifted by a vacuum into the air."

"If you choose to use MDF, you have two readily available solutions to seal the cabinet. Paint the interior or exterior with a gloss or semi-gloss paint, or even a varnish. Anything that sinks into the wood, and will seal it. Your second option is to coat the interior of the enclosure with fiberglass resin. This is very rigid as well."
:End quote

Has anyone used fiberglass resin to coat the interior of their MDF speaker cabs? Any drawbacks or thoughts on alternatives (other than what's listed)? I do not want to coat the exterior of the cab as I'm using a paper backed cherry veneer and I know that the contact cement I have works well on both the paper back of the veneer and on the MDF (Tested: made another cabinet w/it).

I want to do this as best as possible the first time, and figured an appeal to the inmates may be the best way to move forward in an informed manner. If I had the time and $$ I would be happy to build 2 pair and report back on the differences, but alas, since I have neither I am at your mercy.


Thank you and best regards to all,


Doug

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