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Acoustic treatment - DIY Rockwool.

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Acoustic treatment - DIY Rockwool.

PostPosted: Sun Jun 23, 2013 8:08 am
by thefruitfarmer
I have had four slabs of 50mm RW3 in my garage for a few years now and a mate wants to treat a corner of his room to record vocals in so I am, now my garage is not freezing, building three acoustic panels, mainly using materials I just have anyway.

First of all I need to make a pair of 50mm thick traps, so I need to build frames to go around them.

I have some 2.4 metre battens so I can saw them in half to get the 1.2 metre length required for the long edge.....(it is a lot easier to build the frame to the size of the Rockwool slab rather than the messy job of cutting the Rockwool slab itself)....

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Four of them

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Then I cut lengths of 638mm (the length of the short edge of the Rockwool slab plus the width of the battens) and fitted them to the battens cut to size for the long edges...

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Corner clamps make this part so much easier...

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Re: Acoustic treatment - DIY Rockwool.

PostPosted: Sun Jun 23, 2013 8:25 am
by thefruitfarmer
Next I am making a 100mm thick trap....

I had some 100mm wide planks, which are ideal for the job and I like to use a 3 inch holesaw, which fits on the end of a drill to "honeycomb" the plank. This is to allow more surface area of Rockwool available to absorb the sound wave in the air....

I marked the drill points at 100mm intervals and made guide holes. Then I drilled half way through with the holesaw.

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After that I flipped to plank over and finished the holesawing from the other side. This way you are less likely to splinter the wood when making the holes. If you go all the way through then you will probably splinter the wood when the round cutter exits the other side of the plank.

Then I used a couple of slats I had from a cupboard previously used as an airing cupboard which did quite nicely for the shorter edges.

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Re: Acoustic treatment - DIY Rockwool.

PostPosted: Sun Jun 23, 2013 9:00 am
by thefruitfarmer
Next I fitted the chicken wire to the front face of the frames.

This is quite fiddly and quite difficult to describe how to do. I use a staple gun and 600mm wide chicken wire, the same width as the Rockwool panel. It is nasty stuff and will cut you so you have to be a bit careful with it. Here is a photo from a previous job.

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What I do is staple the corners and then gradually staple the rest keeping it under tension. If it is a bit slack then you can stretch it a bit, pulling in the sides and using staples to hold it in place. Long nose pliers are your friend here.

This difficult bit is trimming the ends and getting the sharp wires out of harms way. What you do is tuck the cut ends over and stable them to the inside of the frame so they end up inside the frame and can only poke in the Rockwool rather than cutting curious fingers.

Whether you strictly need to use the chicken wire is debatable. I usually do because people will tend to be curious and want to touch the traps. The chicken wire gives that extra bit of protection and also keeps the slab in place, stopping it sagging over the years.

Re: Acoustic treatment - DIY Rockwool.

PostPosted: Sun Jun 23, 2013 9:22 am
by thefruitfarmer
So, after about six hours work, with a bit of time added on to go and get more staples and screws I have three traps drying in the garage.

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I sprayed them with a 1:10 solution of PVA / water, with a drop of washing up liquid added. This seals the fibres in place and stops them drifting around the room. One litre of the solution was enough for the three panels and was applied using a plant sprayer.

Rockwool is not toxic, it is made from er..... Rock so it is chemically stable and inert. However, the fibres can irritate some people with breathing issues like Asthma so you do not want them blowing around the studio. The spraying with the PVA solution drys to form a crust and reduces the efficiency of the panel slightly but not so much that it is a problem.

Furthermore, the fibres can get in your sweat glands and burrow in to your skin. Some people are less tolerant to this than others so care needs to be taken when working with the stuff. Yesterday was cool and humid so not too sweaty, hot and dry days are the worst because your sweat glands will be open. An old builders' trick is to wash your hands with cold water, which washes away the fibres and the cold keeps your pores closed. Yesterday, I moved the Rockwool slabs as little as possible and as the frames are built to their size they did not need cutting. I wore long trousers and a long sleeved shirt too so it was not a problem.

Next job is to wrap the completed framed slabs in fabric.

I have some black fabric which will need bleaching, a black studio is like a dungeon. Neutral lighter colours is the way to go. If you want it darker and moody in there it can be done with lighting.

Re: Acoustic treatment - DIY Rockwool.

PostPosted: Mon Jun 24, 2013 7:10 am
by JH Brandt
+1

Great thread with great advice.

NOTE: once the rock wool is in place, you can cover the back with a cheap fabric to hold the fibers - this can be a thin plastic sheet too!. The front can be sealed up by using automotive headliner with foam backing OR by using a thin piece of open-cell foam to cover the rock wool prior to applying your finished fabric.

If you add a thin piece of foam to the face of the 'treated' rock wool, it should off-set any detrimental effects of the 'fiber-retention treatment'.

Excellent work.

Cheers,
John

Re: Acoustic treatment - DIY Rockwool.

PostPosted: Thu Jun 27, 2013 5:34 pm
by Helmutcrab
Hi thefruitfarmer,

Great work, just as you showed me how to do it ! :)

You mention dyeing fabric. I looked into this but didn't feel confident it would work. Have you done this before on panel fabric ? ( black to white ? )
I want to dye the ceiling panel fabric from natural hessian to white or atleast a paler shade as it will be a bit oppressive having that colour above my head as well as everywhere else in the room.

Have you got any tips as it is a lot of material to dye ?
I wonder if you can use a plastic bath tub for this without damaging it ?

Cheers,

Peter

Re: Acoustic treatment - DIY Rockwool.

PostPosted: Fri Jun 28, 2013 11:02 am
by thefruitfarmer
Helmutcrab wrote:

You mention dyeing fabric. I looked into this but didn't feel confident it would work. Have you done this before on panel fabric ? ( black to white ? )

I want to dye the ceiling panel fabric from natural hessian to white or atleast a paler shade as it will be a bit oppressive having that colour above my head as well as everywhere else in the room.

Have you got any tips as it is a lot of material to dye ?

I wonder if you can use a plastic bath tub for this without damaging it ?

Cheers,

Peter


Unfortunately, my dyeing experiment was not successful....

I had some black fabric, which I put in the bath full of water with a little bleach but the bleach did not burn the colour out of the fabric. I think this is because it was a synthetic fabric and the colour is in the fibre itself rather than added as a dye.

You *can* use bleach to lighten dyed fabric, like a pair of jeans. The advice I had was to use a mild solution of bleach in the bath and leave the fabric in for a long time, rather than using a stronger solution for a shorter length of time. The bleach will eventually erode the actual fabric itself....so you want them chemical reaction to be slow enough so you can see when it is reaching the danger stage

I cannot advise about your plastic bath tub, I know some are fussy about what you clean them with and too strong a solution of bleach *could* damage it.

It looks like you can bleach hessian cloth to lighten it.

Personally, I would just test an offcut first to get an idea of how the process goes.

Re: Acoustic treatment - DIY Rockwool.

PostPosted: Fri Jun 28, 2013 2:37 pm
by Helmutcrab
Good advice. I think i will do just that.

Cheers.

Re: Acoustic treatment - DIY Rockwool.

PostPosted: Sat Jun 29, 2013 9:31 am
by thefruitfarmer
I am going to be covering the panels using some old curtains.

There should be enough material but of the 5 curtains only one is big enough and the other 4 will need to be put 2 each on the 2 panels.

They were bit musty when I got them so I ran them through the washing machine.

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It's easier if you just buy some the right size but it should be okay, I should be able to get a good finish on the front face.

Re: Acoustic treatment - DIY Rockwool.

PostPosted: Wed Jul 03, 2013 9:20 pm
by thefruitfarmer
They are all covered with a patchwork of curtains, and the front face looks okay.

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I made some spacers for the two 50mm traps...

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One on each corner, to keep an air gap behind them. It should mean they absorb to a slightly lower frequency than if attached directly to the wall. Also, they are in line with the 100mm corner trap, so it will look a bit better too.

Re: Acoustic treatment - DIY Rockwool.

PostPosted: Wed Jul 03, 2013 9:32 pm
by thefruitfarmer
We fitted the corner trap first

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Two screw eyes with two cable tie chains, each attaching to a screw eye further down the sides of the trap.

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Now there is a treated corner

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It came out okay. The cable tie allow you to gradually hoist the trap up into the corner from the inside.

How effective is it?

Well, listening to the area there seems to be a sweet spot between about 6" and 18" away from the corner trap, from top to bottom of the trap and across its entire width. It sounds fairly dead there, the colouration of the room is a lot less obvious.

It took me about eight hours to make them and three hours to fit them, not working too hard.

The cost was hardly anything because I used wood and screws I had around the house anyway, and the Rockwool slabs were left over my sound treatment in 2008.

My friend wanted it so he could record vocals at home and this should make it a bit easier.

Re: Acoustic treatment - DIY Rockwool.

PostPosted: Fri Jul 19, 2013 8:25 am
by thefruitfarmer
After a while of use I am wondering if the sweet spot can be made any bigger....

I have made a new thread but all suggestions will be appreciated.