Chemical Laws 1 Madmikes' Law 0

[BassAwdyO]

you can try pouring concrete on the inside of the enclosure! simply do one side at a time. Pour to the thickness desired. I'd suggest putting some screws into the wood that the concrete would surround and possibly small steel mesh? To enhance strength. But it kinda makes box calculations fun and it takes a long time! you must be very exact with the concrete

Maybe I will try this on my own sometime....

[CBFryman]

or, if doing concrete, build a box inside a box

leave the top of the outside box open and fill it, steel mesh wouldnt be needed but it would be a good idea. 3/4-1" thickness would add a lot of weight...an enclsore of any size would easily be over 100lbs...also before putting cement on MDF, coat with a few layres of fiberglass resin thined out with acetone 4:1...4 parts resin/hardener (mixed to proper porportions) and 1 part acetone, the acetone simply thins it out to make painting easier, this will keep the MDF from soaking up a **** load of water out of the concrete.

[Fixxer]

50/50 mixture of polyester resin and sandblasting sand. Works like a charm.

[Ron E]

....or the old standby of silica sand and latex paint. Probably best to seal it first through.

[boydon_lepasci]

I wish I could find the link for the design I'm talking about. An entry on a car audio site competition used a rubber ball with approximate volume of 1ft^3 in an enormous block of concrete. The ball was attached to "pucks" of appropriate size to form a baffle, and the mould was filled until the ball would sit with the pucks flush with the top. The remainder of the mould was then filled and the surface worked so the pucks were completely integrated. Once the concrete was set, some cutting took place to access the ball which was punctured and removed. The resulting enclosure, with perfect spherical chamber, weighed several hundred pounds thus succumbing to gravity while being loaded into a pickup by the builder and ONE friend. This seems to be intentional overkill, but some construction ideas could be gained. If I can track down the original writeup, I will post a link for some entertaining reading and viewing.

[Madmike2]

I found liquid rubber. Each pail of this stuff weighs about 25 pounds ...i think i found my wall liner.

[paulspencer]

One thing to watch with concrete: it shrinks as part of the curing process. If it is used inside the box, I would be concerned about it's long term adhesion to the intended surface. The box within a box idea is promising, but care is needed to ensure that they are isolated from each other by means of a damping layer.