hey any body know the best sealent to use to seal the mdf box, some body was telling me first use silicon sealent then let that dry then varnesh the box inside out. people were saying that mdf is not air tight. could youpost the way you buit your boxes thanks.
There is very little difference in sealants. Pretty much any kind of caulking or sealant will work. The little bead you put around the edges of the box will do little for helping rigidity. Varnish might help with that, but I've never heard it used before.
I use a glue called "Goope". It glues and seals anything. That is how I made my enclosure super air tight. Don't forget to put a seal on the speaker itself where it gets contact with the box, along with screws. To test the box, try and push the speaker. If it moves freely, then air is leaking. Mine is like a rock. Once it's sealed, it does not want to move.
I would personally do it (well I've actually done it) the way the industry have been doing it for years, just simple PVA glue aka wood glue. No more nails is also very good. I wouldn;t use silicone though, I've read somewhere that the vapours of silicone cause damage to the sub.
Also glue strips of wood along the inside edges of the wood. this would give a perfect finish.
I heard if you install the sub while the silicone is still wet and drying, the vapours could damage it. But when the silicone is dry it wont damage the sub. Someone correct me if im wrong.
Yes i use plain old elmers wood glue to bond the wood together(along with well placed drywall screws) and silicone to seal it. The cuts of the mdf have to be good, woodglue is not designed to fill gaps no bigger than 1/8 of an inch but woodglue when dry, the bond is stronger than the mdf itself. Follow the curing directions on the silicone usually its 24 hours before mounting your subwoofer. In fact if you make very good cuts and use plenty of elmers glue(and a few well placed screws), there is no need for any sealant at all.