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DIY acoustic treatment.

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DIY acoustic treatment.

PostPosted: Sun Sep 12, 2004 10:47 am
by thefruitfarmer

For about £200 I made twelve acoustic panels and four bass traps.

I ordered some Rockwool Slab from the builder’s merchant. I used RW6 grade Rockwool that is the densest and therefore absorbs the most bass. The slabs eventually arrived after several weeks waiting – I had four 100mm thick slabs and twelve 30mm thick slabs. They come 1000mm long by 600mm wide.

Rockwool is nasty to work with as the fibres can work their way into your skin and cause irritation. I took the precaution apart of handling it as little as possible and wearing a long sleeved shirt. After the minimal handling I washed my hands with cold water – if you wash with warm water this opens up the pores in the skin, which allows the Rockwool fibres to burrow inside. Washing with cold water closes the skin pores and gets the fibres off the surface of your skin. If you wanted to you could use gloves and a mask to avoid any potential problems. Some people are more sensitive than others to the fibres (those with asthma for example) and I would encourage anyone with any skin or breathing conditions to take extra care.

Thanks to Max the Mac for suggesting a method to seal the Rockwool slab. Using a mix of one part PVA adhesive with ten parts water and a few drops of washing up liquid all those nasty fibres can be sealed.

I also bought some 1000mm by 600mm MDF panels, to use as backing for the 30mm Rockwool slabs and enough cloth to cover each slab. I used denim and stretch denim, opting for a close weave to keep the fibres at bay.

So, using a paintbrush I covered each 30mm slab in a daubing of Max’s mixture. A plant sprayer, that normally sprays out a mist of water could be better though as using a brush is going to release some of those fibres. I then fixed the slab to the MDF board with some duck tape and proceeded to wrap the panel in fabric. I just used one layer of fabric and a staple gun to fix the cloth to the back panel. Then I hung them on the wall like large and heavy pictures.

The 100mm thick bass traps were just wrapped in fabric like Christmas presents and stood up, two in each corner one in front of the other.

Does it work?

The room is 8’6” square and has clearly audible modes, which mean the notes B and F# are louder than they should be.

Without treatment there is a definite high frequency ring and an exaggeration of the volume of notes at the modes.

After adding the panels the high frequency ring has been reduced to an acceptable level. The bass still booms at the modes when the music is at a high volume but the traps absorb the excess bass up to a modest volume level. In general the sound has much more clarity and I can hear detail that was previously hidden.

So yes…….it works.

I have used no testing equipment as yet. I am adding more panels and judging by ear if the sound is improved.

The panels have been positioned four on the front wall, two on the back wall and one on each side wall. I used a shaving mirror to position the panels on the side and back walls. I placed the panels where the reflection of the speaker could be seen from the listening position in the mirror on the wall.

I am going to make four more panels to dampen the sound a little more and I may put some treatment on the ceiling too.

Re: DIY acoustic treatment.

PostPosted: Sun Sep 12, 2004 9:35 pm
by Studio Support Gnome
Hi Fruity :lol:

There are a few additions I'd like to make to your post.

1) The major health factor with mineral wool is not the skin irritation, (Although that in itself is bad enough) but the fact that the fibres can cause irreparable damage to your respiratory system. For this purpose I must add that it is advisable , indeed, essential that you wear a face mask during ANY work with this material. I also recommend using disposable boiler suits with elasticised limb closures and a Hood.

2) The Spray application of the liquid is far more efficient and effective, as well as safer. As I suggested, use an old plant sprayer... such as those you get for greenfly treatment of roses , but ensure they are cleaned thoroughly before use... (and After if you intend to make more ;) )

3) The Corner traps would almost certainly be more effectively used diagonally across the corners rather than directly in the corner. The air gap will lower the bottom of the effective frequency band and increase efficiency. Mount One on top of another giving 2 meters of diagonal corner trapping rather than in front of each other.

4) Tape isn't a terribly effective fixative, spray contact adhesive, applied to rear of the AMW sheet, and front of the Board is more effective, and once the material is wrapped around, is better at preventing sag over the long term.

5) Fixing the 100mm stuff to a board is also advisable, as they will sag in the long term without some support.
Also, this would enable use of these in the wall to ceiling vertices as well as wall to wall.

In general I would fit one diagonally to the centre of each wall to ceiling join, and two upright diagonally in each vertical corner.

Fitting them diagonally is actually quite easy once you have the knack of it, but is most definitely a two man job, as it's impossible to support the weight in the correct position AND fit the supports.

if you affix 4 suitably strong Eye bolts to the supporting board, and 2 to the the wall (as tight into the corner as possible) , a few inches in from the end of a panel, then you can use steel cord or chain link to suspend the panel, pulling it tight into the corner at 45 degrees diagonally across it. This basic method can be applied to both the wall to wall joins and ceiling to wall joins.


you may find you need to use a third central one if the wall construction is less than solid.... in the absence of available direct fixing to timber frame or masonry wall, proper load spreading wall inserts should be used in the case of partition walls and the typical internal room within room wall construction.

6) RW6 is NOT the densest available stuff..... AMW is available in densities up to about 120KG/m^3


7) Bearing in Mind this is part of my "day job" I hope you'll understand when I don't give away every single trick of the trade :lol:

But this should be sufficient to avoid unfunny disasters in the DIY sector !

Best regards
Max

Re: DIY acoustic treatment.

PostPosted: Mon Sep 13, 2004 8:32 am
by Michael Harrison
Great thread guys; this is particularly of interest to me, as I should shortly be commencing gutting my spare bedroom - read 'studio-to-be'. :)

Mike

Re: DIY acoustic treatment.

PostPosted: Mon Sep 13, 2004 2:51 pm
by Doublehelix
Using a mix of one part PVA adhesive with ten parts water and a few drops of washing up liquid all those nasty fibres can be sealed.


For us "language-challenged" Americans ;), what is "washing up liquid"? Is that just a liquid hand soap???

Thanks! Great post!

Re: DIY acoustic treatment.

PostPosted: Mon Sep 13, 2004 2:54 pm
by Guest
For us "language-challenged" Americans , what is "washing up liquid"? Is that just a liquid hand soap???

Nope - that's liquid hand soap ;)

Washing up liquid is the liquid soap/detergent that we brits use in the water when we're washing up the dinner plates :)

Re: DIY acoustic treatment.

PostPosted: Tue Sep 14, 2004 12:17 pm
by thefruitfarmer




For us "language-challenged" Americans ;), what is "washing up liquid"? Is that just a liquid hand soap???

Thanks! Great post!

yw

Just in case you, or anyone in America, is thinking of using a DIY method I understand that the materials available are different in that country; so, you may have a problem finding the Rockwool slab and have to use an alternative material.

Also, the DIY involves a fair amount of research, work and time which, if you factor that in with the cost of the materials, brings down the relative cost of the real traps or something similar......

I now need to rearrange the panels for greater dampening and go out again to buy more fittings.

Re: DIY acoustic treatment.

PostPosted: Tue Sep 14, 2004 1:15 pm
by James Perrett


Just in case you, or anyone in America, is thinking of using a DIY method I understand that the materials available are different in that country; so, you may have a problem finding the Rockwool slab and have to use an alternative material.



I believe that Owens Corning 703 is the US equivalent of Rockwool RW3 - but I'm not sure about RW6 - 706 maybe? Ethan would know for sure.

Cheers.

James.

Re: DIY acoustic treatment.

PostPosted: Tue Sep 14, 2004 2:38 pm
by Digipenguin


I believe that Owens Corning 703 is the US equivalent of Rockwool RW3 - but I'm not sure about RW6 - 706 maybe? Ethan would know for sure.

Cheers.

James.

RW3-60kg/m³
RW5-100kg/m³
RW6-140kg/m³

701-24kg/m³
703-48kg/m³
705-96kg/m³

We have an equivalent material here, RXL80 which is 128kg/m³, made by a company called Roxul but it is not as effective as OC 700 Series rigid fiberglass.

http://www.bobgolds.com/AbsorptionCoefficients.htm

This link is available in the sticky at the top of this acoustics forum as well.

Re: DIY acoustic treatment.

PostPosted: Wed Sep 15, 2004 1:46 pm
by Doublehelix
For us "language-challenged" Americans , what is "washing up liquid"? Is that just a liquid hand soap???

Nope - that's liquid hand soap ;)

Washing up liquid is the liquid soap/detergent that we brits use in the water when we're washing up the dinner plates :)

Hehe...thanks! Got it! Nice picture Eyan! Explains things perfectly!

So let's say that I decide to make some basic DIY panels here in the US, and use the OC 703 rigid fiberglass...should I also seal those with Max's secret formula??? ;) I am assuming that the fiberglass fibers are equally as nasty, right?

Re: DIY acoustic treatment.

PostPosted: Wed Sep 15, 2004 2:56 pm
by Digipenguin
No. As a matter of fact, as of 2001 fiberglass is not even considered a carcinogenic material based upon studies performed over the last 15 years. Here's the link to the American Lung Association's article on the matter. They don't even recommend a respirator unless you experience irritation. Personally I still use a mask but do with it what you will:

http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=35439

Re: DIY acoustic treatment.

PostPosted: Fri Sep 17, 2004 3:52 pm
by Studio Support Gnome
DP, This is unsound advice.

PLEASE NOTE

While they have , at the instigation of the industry, removed the Carcinogenic tag, it still undeniably causes physical damage to the airways and lungs, as such it should be classified as a hazardous material, and all the usual precations, INCLUDING FACEMASKS should be undertaken.

anything that causes ANY physical injury to your insides should be treated as a serious issue....

MAx.

I'll be offline for a week, so behave... ;)

Re: DIY acoustic treatment.

PostPosted: Fri Sep 17, 2004 6:13 pm
by Scottdru
No. As a matter of fact, as of 2001 fiberglass is not even considered a carcinogenic material based upon studies performed over the last 15 years. Here's the link to the American Lung Association's article on the matter. They don't even recommend a respirator unless you experience irritation. Personally I still use a mask but do with it what you will:

http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=35439
The current administration here has decided lots of things are not as bad for us as they really are, which is why they have increased the legally allowable levels of cyanide and other hazardous pollutants in our drinking water. :roll: :protest:

Anything for the kids, you know . . . "no child left behind" and whatnot. Hehe . . . and here we thought they were talking about education, not erradication. ;) :lol:

Re: DIY acoustic treatment.

PostPosted: Fri Sep 17, 2004 8:30 pm
by Digipenguin
Maybe it was. I'm not so sure. I can't find any reports of fiberglass being linked to irreparable damage except in long term high exposure incidences. Either way, note I did say I wear a mask (Momma didn't raise no fool). But I'm not going to tell anyone that they need to if I know there is evidence to the contrary. I said, "do with it what you will". Personally, I'm currently making some bass traps and I am going to seal them somehow, probably with hairspray as it is already mixed and comes in an aerosol to begin with.

Re: DIY acoustic treatment.

PostPosted: Sun Sep 19, 2004 2:52 am
by leostones
[wide.

care.

.

So, using a paintbrush I covered each 30mm slab in a daubing of Max’s mixture. A plant sprayer, that normally sprays out a mist of water could be better though as using a brush is going to release some of those fibres.


Does sealing the rockwool in this way not affect the absorption properties at all?

Re: DIY acoustic treatment.

PostPosted: Sun Sep 19, 2004 4:23 am
by Guest
Yes. Principally at higher frequencies.

If you're only using the slabs to trap bass then that's not really a problem; if you're using it as an exposed surface to trap higher frequencies in a broadband trap or HF/MF absorber then it'll affect performance. The effect increases proportionally with frequency.

However: if you're using it in a more broadband application, you'd normally be fronting it with fabric of some kind rather than leaving it bare. The fabric will restore the vast majority of the higher frequency absorption characteristics.

A couple of other points:

When I first mentioned using PVA solution to stabilise mineral wool/glass fibre slabs in this way, I deliberately suggested using a spray. Even if it's done very very carefully, brushing applies a lot (too much) of the PVA solution to the slab. A spray allows for a very thin/light and even coat of the solution and gives one the option of additional similar coats as necessary. The idea isn't to make the slab inpregnable or weatherproof, just to stabilise loose surface fibres so that they don't dislodge with the kind of vibration or airflow to which they'll be subjected in gentle handling or when installed.

Though recent research suggests that mineral wool/glass fibre products aren't carcinogenic, they are still highly irritant, particularly to the respiratory system and can cause long term damage potentially leading to very serious illness. It's important to take appropriate precautions when handling it.