silly concrete question

[hacknet]

i've got a 90 liter sealed box for my fullranger at the moment but the box rings like a church bell...

i was thinking of lining the inside of the box with a layer of concrete, say about an inch thick...

would it help to stop the box from ringing..?

thanks a million!!

[rcavictim]

If that box is MDF or particle board pouring wet cement on it will ruin the wood with the moisture. Even if plywood you might end up with buzzing between the wood and the cured cement. I would first look at installing internal bracing. After that you could look at gluing pieces of cement board in the open areas between the braces with a heavy duty industrial adhesive that remains flexible.

[mikelm]

You can do the concrete thing and in my experience nothing else except marble cabinets in come close to reduce colouration.

I just made MDF / concrete open baffles and it turned out very nice

This is what you have to do:

Use a weak solution of PVA wood glue ( about 6 : 1 ) and seal all of the surfaces that will come into contact with the conrete. Any small cracks need to be sealed up with some kind of filler. leave to dry for about 24 hrs

now mix up the cement 1 : sand 2 : stones 2 in that ratio with a generous dollop of PVA for good measure.

once the concrete is looking well mixed & right consistancy...

paint neat PVA all over the previously sealed surfaces.

then put in the concrete mix and pat it down nice and thoroughly untill a little hint of water comes to surface - you will see what I mean when you do it.

then wait for several days ( at least 4 ) before moving the panels to vertical position. ( and for me it was 4 days drying indoors may be longer in a garage )

If you can dis-assemble your boxes into flat panels it will be a lot quicker ! but you will have to plan quite carefully to get all the shuttering in the right places.

Before you do all this you have to make sure that your drivers will be happy in a slighly smaller volume cabinet.

I was very very pleased with the sonic results of my OB speakers.
rock was rockier and clasical more refined.

good luck

any questions - just ask

cheers

mike

[hacknet]

hey! thats cool!

what about putting concrete on the outside...? does that simpify things?i dont mind having to putty it down later or something like that..

thanks man!

[mikelm]

this how it look

front:

[mikelm]

and back:

[mikelm]

closer view:

[mikelm]

The wooden baton was just a precaution and is now removed

So, on the outside - sure but not very pretty ...

mike

[johninCR]

I've used concrete inside several wooden enclosures. My concern, in addition to the initial moisture, has been eventual separation of the concrete and wood resulting in rattles. I put screws partially into the wood, so the heads would be imbedded in the concrete. I also used an epoxy mixture made for concrete, which is used to bind new concrete to existing concrete. I slather the epoxy, which is about the consistency of latex paint, on the wood and put the concrete in.

A 1" layer of concrete will likely crack though. Proper wood or mdf bracing is definitely the best option in your case.

[Colin]

FWIW, I recently tiled a plywood bathroom partition prior to assembly and was surprised how much stiffer and less resonant the 6 foot high board became. I thought this had potential and had the added bonus of giving me future speaker plans to think about whilst doing some boring household DIY.