So much rockwool...




It was free!!! I asked the right guy if he knew where I could track it down. He's a manager of an enormous construction site, and just snapped his fingers and it was delivered the same day (today in fact).

They are 100cm x 100cm x 5cm, and 200kg per cubic meter. That's 12 pounds per cubic foot; I realize it will reflect more high frequencies and be a pain to mount, but it's not so high as to be less efficient at trapping bass than say 100 or 150kg/m3, is it???

It's going in this tiny little space...

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http://ryanmead.net

Associated questions:

1) is it TOO dense for effective bass trapping?

I'd like to layer it 3-ply to get 15cm depth. I've read here that people use diluted carpenter's glue (white glue) to do that.

2) How strong is the bond? Is white glue strong enough to hold a piece of this stuff?

3) If I apply the diluted glue mixture too thickly, could it not create some kind of membrane and negatively affect the bass trapping efficiency?

4) Can I glue the fabric to the front of the rockwool, or would it be better to just stretch it over the front? (I want it to look half decent.)

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http://ryanmead.net

1)No it should be fine.

2)No sure what you mean here.

3)I am sure you could come up with something but I would pass on it. If you want to reflect some of the highs use something like FRK to the front.

4)Once again I would not do that. Build some frames with wood and put the fabric around it. That is going to be the best bet to making it right.

Glenn

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www.GIKAcoustics.com
Now with offices in the USA and Europe

Hi Glenn,

Thanks for the patient answers over the last couple of months.

I guess I wasn't too clear on questions #2 and #3. The rockwool I have is only 5cm thick, so I'm hoping to laminate it to achieve a greater thickness. I've gleaned from other threads and articles that the thing to do is to apply a dilute white glue (aka carpenter's glue, pva adhesive) mixture to the rockwool to bond two pieces together.

So #2 means: can I expect to hold one piece of this heavy stuff to another simply by spraying some dilute pva adhesive on them and pressing them together? I'm guessing it won't be strong enough.

I've since read in another online tutorial that the goal of using the dilute glue mixture was merely to prevent rockwool fibres from going airborne, not to hold slabs together, so I might be totally out to lunch here.

And #3 means: Far from having the goal of reflecting high frequencies, I was worried about creating an air-impassable layer and impeding the bass-trapping efficiency by putting a thick white glue mixture in between layers of rockwool, or coating it on the outer layer.

Still tossing over designs in my mind. Good to know anyways that the rockwool isn't too dense!

Thanks again.
rd

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http://ryanmead.net

Yes, the dilute PVA is to prevent loose fibres escaping at the surface, and won't be strong enough to hold multiple slabs together. As you've surmised, a thick enough layer of glue to do this will impede air flow and thus significantly reduce the absorption.

I'd follow Glenn's advice and build a wooden frame and then stretch fabric over the top - as long as the fabric is taut this should hold all your individual slabs together. If you're still unsure, why not try chicken wire to hold them together and then add the fabric over the top again.


Martin

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YewTreeMagic

As Martin was saying there is no problem stacking them together..

Quote:

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And #3 means: Far from having the goal of reflecting high frequencies, I was worried about creating an air-impassable layer and impeding the bass-trapping efficiency by putting a thick white glue mixture in between layers of rockwool, or coating it on the outer layer.

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No way of knowing unless you take it to a lab and have it tested. I would NOT invest in the idea.

Glenn

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www.GIKAcoustics.com
Now with offices in the USA and Europe

you cannot laminate the rockwool with pva.

build frames and use chicken wire on front and back to hold the stuff in


see Zukan's website for a tutorial with images on how to do that.


www.samplecraze.com

Quote idris y draig:

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you cannot laminate the rockwool with pva.

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not sure where I got that idea from...