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DIY acoustic treatment.

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DIY acoustic treatment.

Postby thefruitfarmer » Sun Sep 12, 2004 9:47 am


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.
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Re: DIY acoustic treatment.

Postby Studio Support Gnome » Sun Sep 12, 2004 8:35 pm

Hi Fruity

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

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

Best regards
Max
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Re: DIY acoustic treatment.

Postby Michael Harrison » Mon Sep 13, 2004 7:32 am

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
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Re: DIY acoustic treatment.

Postby Doublehelix » Mon Sep 13, 2004 1:51 pm

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!
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Re: DIY acoustic treatment.

Postby Guest » Mon Sep 13, 2004 1:54 pm

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
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Re: DIY acoustic treatment.

Postby thefruitfarmer » Tue Sep 14, 2004 11:17 am





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.
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Re: DIY acoustic treatment.

Postby James Perrett » Tue Sep 14, 2004 12:15 pm



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.
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Re: DIY acoustic treatment.

Postby Digipenguin » Tue Sep 14, 2004 1:38 pm



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.
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Re: DIY acoustic treatment.

Postby Doublehelix » Wed Sep 15, 2004 12:46 pm

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?
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Re: DIY acoustic treatment.

Postby Digipenguin » Wed Sep 15, 2004 1:56 pm

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
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Re: DIY acoustic treatment.

Postby Studio Support Gnome » Fri Sep 17, 2004 2:52 pm

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...
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Re: DIY acoustic treatment.

Postby Scottdru » Fri Sep 17, 2004 5:13 pm

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.

Anything for the kids, you know . . . "no child left behind" and whatnot. Hehe . . . and here we thought they were talking about education, not erradication.
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Re: DIY acoustic treatment.

Postby Digipenguin » Fri Sep 17, 2004 7:30 pm

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.
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Re: DIY acoustic treatment.

Postby leostones » Sun Sep 19, 2004 1:52 am

[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?
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Re: DIY acoustic treatment.

Postby Guest » Sun Sep 19, 2004 3:23 am

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.
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Re: DIY acoustic treatment.

Postby Studio Support Gnome » Wed Sep 22, 2004 5:55 pm

As 0VU notes, bare Panels that have been So treated, exhibit slightly lower Hf absorption figures.

HOWEVER

if you've chosen an appropriate wrapping material, this can be effectively counteracted , generally yielding results comparable to or occasionally superior to that of an untreated bare panel, but with the superior aesthetic appearance .

With relation to the health risk aspect.

ANY fibrous substance that can cause laceration to the Airways and acts as an irritant, rapidly lays you open to all sorts of secondary infection, and over prolonged exposure, this also creates scar tissue in areas where you REALLY REALLY do NOT want it.

WHY am I banging on at this???

I have absolutely NO bloody idea


I'm off to take the wife out to Dinner


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Getting worried.....

Postby thefruitfarmer » Thu Sep 23, 2004 8:34 am



With relation to the health risk aspect.

ANY fibrous substance that can cause laceration to the Airways and acts as an irritant, rapidly lays you open to all sorts of secondary infection, and over prolonged exposure, this also creates scar tissue in areas where you REALLY REALLY do NOT want it.

WHY am I banging on at this???

I have absolutely NO bloody idea



Just to add..............

If I was working with the stuff on a regular basis I would be a lot more concerned about exposing myself to the fibres. After the job I could feel a few fibres burrowing into my forearms and I expect a few are doing the same in my lungs. It is not something I would want to subject my body to again and again; ideally I would n't want to have any fibres contact me at all.
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Re: DIY acoustic treatment.

Postby Digipenguin » Fri Sep 24, 2004 4:35 pm

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Re: DIY acoustic treatment.

Postby Chris of Arabia » Thu Sep 30, 2004 9:14 am

Digipenguin wrote:Max, just for you.

http://webpages.charter.net/jdgeisen/BassTraps/BassTrap1.htm

Check out page 4.

Does no one know how to make a decent dovetail joint any more?

>;o))
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Re: DIY acoustic treatment.

Postby Studio Support Gnome » Thu Sep 30, 2004 8:35 pm

Nice one John....... they look well tasty.,...

I'll have a half dozen for Christmas yeah??

Brownie points duly awarded for the health and safety warning.

Max
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Re: DIY acoustic treatment.

Postby Digipenguin » Fri Oct 01, 2004 12:48 pm

Max The Mac wrote: I'll have a half dozen for Christmas yeah??

Max The Mac50 apiece and they're yours!

Brownie points duly awarded for the health and safety warning.

I thought you might like that. I started feeling guilty about my earlier advice. Social responsibility....what a PITA!

CYa.
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DIY acoustic treatment.

Postby thefruitfarmer » Sun Dec 12, 2004 7:10 pm

Here are the studio pictures -

I have added more panels to deaden the room further. There is now a total of ten 100mm panels and twelve 30mm panels. I have also put some packing foam on the ceiling, which reduces the flutter echo.

If I was doing this again I would maybe change the colour of the traps - the grey denim, blue denim and purple look okay but the black traps around the ceiling are a little oppressive.

The mirror type fittings on the 30mm panels work well. The fittings for the 100mm panels panels work but were tricky to put up. With two (or more) screw eyes in the wall and an eye bolt in each corner of the MDF backing of the bass trap the idea is to pull the cable tight and tension the trap into the corner. This worked easily when hanging the traps vertically across the corners behind the speakers at the floor/wall/wall tri corner because gravity pulled the trap down and “took up the slack” quite nicely. When hanging the traps at the ceiling/wall corners the job became more difficult though as the job became hindered by gravity rather than helped. Also, the heavy duty picture wire when cut to size leaves a razor sharp edge which can (and did) lacerate my hands. Still, if I ever need to move it would probably take about 4 hours to remove and pack all the panels and maybe a day to install them somewhere else.

The total cost has been about £400.

It took a bit of imagination to arrange the traps in such a limited space. The additional panels have made a considerable difference though - the music can now be played a lot louder before the room starts to resonate and exaggerate the notes at the nodal points.
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Re: DIY acoustic treatment.

Postby Scott R. Foster » Sun Dec 12, 2004 8:43 pm

Replying to various points from various folks:

1) Rockwool and fiberglass are both utterly inert materials [basically sand] - getting all worked up and pretending they are harzardous materilas is a waste of time... more fun to worry about Aluminium cookware IMO. The stuff is very scratchy, and long sleeves are definately reccomended... full hazmat suits are not a benefit to the process [unless you think they are sexy]. Paying attention to this advice may save you some discomfort, but it may also waste an absurd amount of time and trouble... use you common sense. If these materials were not safe, all construction sites would be hazardous waste zones, and all modern buildings would need to be unihabitable.

Avoided contact is a good idea but don't start pretendeing you are dealing with plutonium. Having working in the boat building trade I have more than a passing acquaintance mineral fiber [I have been covered head to toe in its dust from ginding hulls moer times than I can count]. The stuff will cover you in tiny cuts (it is like glass) and these take a couple days to heal and leave your skin and throat feeling raw and prickily. All in all it a great idea to keep it off your skin, but it aint that big a deal.. not near as bad as getting wet concrete all over yourself [now that will stuff will tear you up and leave you miserable] just because a material is abrasive doe snot mean it is hazardous.. don't confuse the two concepts. Also, once set in place the material will not bother you.. you could put a stack of 703 in the corner of your bnedroom and it would never cause irritation ['cept maybe your spouse' bitching].

2) Backing boards, fabric covers, sticky sprays, elaborate fittings and fixtures are all meaningless from an acoustic stand point... if not required to meet your aesthetics (or tin foil hat hazardoius material fantasies) then skip these parts as much as possible.. they just waste time and money.

3) In a very small room - such as the the subject room of this thread - the first logical step is an absorptive ceiling. Standard commercial grid and tile is one way to do this. The tiles can be made of thick mineral fiber - and these can be covered in cloth, or standard tiles can be topped by bulk mineral fiber panels/batts (laid above the tiles). This allows the installation of dozens and dozens of sf of treatment with zero frame building (and maybe zero cloth.. just lay them in above the standard tiles).

4 Thicker panels work much better than thin ones low in the band. In a very small room, I would suggest you need to use very thicker panels with as much air gap as is feasible [air gap enahances perfomance). The panels in the pics look fairly thin and most seem to be mounted flush to the wall.

5. Use lighter weight materials many of the descriptions and pictures linked to this thread show framework that is much heavier than required.

6. Rockwool is to fiberglass as basalt is to sand... and density variesaccordingly. The density of the two flavors of mineral wool should also vary for acoustic purposes. Corning 703 = 45 kg/m3 or 2.8/lbs/cu.ft., Rockwool board which is 60 to 65kg per m3 is pretty much acoustically equivalent to a 45kg/m3 fiberglass products like 703. See Bob Gold's site for more details. Different flavors of mineral wool have different structural properties as well as acoustic ones.. pick the right flavor to balance your acoustic needs with the least difficult means of installation and you will save a lot of time and trouble.

Good Luck!
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Re: DIY acoustic treatment.

Postby Hugh Robjohns » Mon Dec 13, 2004 9:28 am

Foz wrote:1) Rockwool and fiberglass are both utterly inert materials [basically sand] - getting all worked up and pretending they are harzardous materilas is a waste of time... more fun to worry about Aluminium cookware IMO. The stuff is very scratchy, and long sleeves are definately reccomended... full hazmat suits are not a benefit to the process [unless you think they are sexy]. Paying attention to this advice may save you some discomfort, but it may also waste an absurd amount of time and trouble... use you common sense. If these materials were not safe, all construction sites would be hazardous waste zones, and all modern buildings would need to be unihabitable.

I would agree that in itself, Rockwool (and fibreglass) is an 'inert material' that presents no long term threat if left undisturbed.

However, while handling this material there can be no doubt that very small fibres are released into the air, and if breathed in they can enter and settle in the lungs. It is the body's reaction in efforts to remove these 'alien' fibres where the problem starts -- but often not until years afterwards.

When working with any dusty material, common sense decrees that wearing a face mask is a sensible precaution. The earlier suggestion to help reduce the volatility of fibres by spraying a light glue mix on the panels may also help, and certainly can't harm.

Yes, it adds marginally to the overall time and expense, but it's not significant to the overall project of constructing panels, and the peace of mind justifies it as far as I'm concerned.

And likewise, if you find the dust irritates the skin, a disposable paper boiler suit will save many hours of discomfort and scratching for anyone susceptible, and costs only a few pence.

hugh
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Re: DIY acoustic treatment.

Postby crunchie1967 » Mon Dec 13, 2004 12:31 pm

Max The Mac wrote:
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.

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.

Firstly, thanks for the good advice for covering and sealing the nasty fibres away. I am a novice just starting on a modest home project.
Can someone clarify something for me. I have seen many postings about leaving an air gap between absorbers and walls to help the process (see quote above), but if you mount your rockwall to a board, won't that give the same effect as placing it flat against the wall? Hence, if it is board mounted there is no point in positioning it away from the wall? Or am I just missing the point here? Thanks.
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Re: DIY acoustic treatment.

Postby Scott R. Foster » Mon Dec 13, 2004 1:38 pm

Can someone clarify something for me. I have seen many postings about leaving an air gap between absorbers and walls to help the process (see quote above), but if you mount your rockwall to a board, won't that give the same effect as placing it flat against the wall? Hence, if it is board mounted there is no point in positioning it away from the wall? Or am I just missing the point here? Thanks.


Bingo!

A mineral fiber panel mounted to a board spaced off the wall aint exactly the same as flush to wall, but it aint near as good as gapped off the wall "naked". As to how to do it, there are many baths to Buddha. If we are talking about a wall unit, you can use a board wider than the panel thickness...like a 1x6, or even a 1x8 for a 4" panel, and have the gap inherent to the frame... or you could just add cleats [little feet] to the frame to gap it off the wall. If you use a French cleat this can be arranged so as to create a gap.

More to the point, all these added elements are meaningless acoustically save to the extent they serve to mount the mineral fiber where you want it. Example, suppose I took a fitted baby crib sheet [with elastic all the way around the hem] and added grommets to the backside edge... now imagine I put the sheet on a panel of 4" 703 and I threaded bungee cords through pool noodles and clipped em to the grommets.

Image
Image

Image

and then hung the whole thing on the wall. The sheet holds onto the panel, the hangers hold the sheet to the wall, and the noodles create a 2-3" air gap. Bob's your ankle.

In the corner just running across the diagonal leaves a gap.

In a drop ceiling, the gap will well neigh unavoidable as you'll have to set the grid low enough to so you have enough room to install tiles with a bulk mineral fiber topper.

This doesn't mean that a gap is better than a full thickness of mineral fiber of the proper density, rather that whatever thickness you have, a gap helps. Example, 3" of 703 gapped 3" off the wall is better than 3" flush to the wall but not as good as 6" flush to the wall.

Good Luck
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Re: DIY acoustic treatment.

Postby thefruitfarmer » Mon Dec 13, 2004 3:48 pm

Foz wrote:

4 Thicker panels work much better than thin ones low in the band. In a very small room, I would suggest you need to use very thicker panels with as much air gap as is feasible [air gap enahances perfomance). The panels in the pics look fairly thin and most seem to be mounted flush to the wall.


Hi Foz....

The twelve blue and purple panels are 30mm thick RW6 (140kg/m3) and the ten black and grey panels are 100mm thick RW6.

The 100mm panels are all across corners whilst the 30mm panels are fitted to MDF and are just hung on the wall like big heavy pictures.

How much more absorbsion do you expect I would get if I used some spacers and set the 30mm panels away from the wall?

I did consider this when planning the project and I decided that I could not lose the space in such a small room. Now everything is arranged though I possibly could set the panels slightly in from the wall. However, going with my original plan I decided to just add more panels which achieves the same result as with less panels spaced away from the wall but takes up less total space in the room.

Regards

FF
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Re: DIY acoustic treatment.

Postby olivier » Mon Dec 13, 2004 4:33 pm

Hugh Robjohns wrote:

Rockwool (and fibreglass) is an 'inert material' that presents no long term threat if left undisturbed.



I would be quite careful with such statements especially at a time where dozens of contradictory reports have been made about fiberglass and all.

may I just remind you what governments and so-called experts said about asbestos in the sixties and seventies?

they said that basically it was not hazardous as soon as you were protection to handle it. the fact is they were wrong and apart from the Quebec province in canada (with brasil, the world's biggest producer of asbestos), no one today even dare thinking about using asbestos in buildings.

after bans in the nineties, replacements for asbestos were to be found. compressed rockwool is one. the fact is rockwool and glasswool both produce tiny fibers that can potentially be carcinogenic as they ARE comparable in size and shape to asbestos. Meaning once they're in your lungs they can stay there for months if not years.

The fact is that rockwool and fiberglass are usually sitting in the "2B" class, ie "might be carcinogenic".
class 1 is tobacco, etc.
Rockwool (the company) products have been classified as "3" which puts them in the "non carcinogenic" class.

but not ALL glasswool and rockwool are , so do your homework and search around.

Besides that, official classifications like this one is not fixed once for all, and I'm sure one can find times where asbestos was classified as "non hazardous" .

asbestos has long term effects (ie 30 years horizon) on health and nobody knows about rockwool and glasswool effects on humans (yet). they've done extensive clinical (ie tests by inoculation) research on rats, not humans. The only research on humans was epidemiologic and no evidence showns yet about a link between rockwool/fiberglass exposure and cancer.

so, the message is clear :
if, like me, you smoke , drink and live in the city (gasoil exhaust fumes are carcinogenic too !) then just don't worry about handling rockwool.

if you're in the other camp, then
1/ stop using acoustic panels
2/ don't handle rockwool/fiberglass
3/ buy foam instead.
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Re: DIY acoustic treatment.

Postby Hugh Robjohns » Mon Dec 13, 2004 10:34 pm

Hugh Robjohns wrote:Rockwool (and fibreglass) is an 'inert material' that presents no long term threat if left undisturbed.

olivier wrote:I would be quite careful with such statements especially at a time where dozens of contradictory reports have been made about fiberglass and all.

I share your concern Olivier, which is why I posted my note of caution in response to Foz's rather more casual approach to the issue.

However, like Asbestos, I think it fairly safe to assume that Rockwool and Fibreglass are essntially 'inert' *provided* they are left undisturbed. It is the dust released when these products (like asbestos) are disturbed, handled or broken up that represents the hazard. And the obvious precautions against dust inhalation are thus sensible in my opinion.

Like you, I'd rather be safe than sorry when handling these kinds of materials and unlike Foz, I don't see the additional modest expense or time involved in taking such precautions to be wasted in any way.

Only time will tell whether those of us who wear face masks are over-reacting or not, but by then it will be too late, won't it!

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Re: DIY acoustic treatment.

Postby Scott R. Foster » Mon Dec 13, 2004 11:21 pm

Fruit:

I don't have any 1.25" thickness RW6 data but Bob Gold's absorption data sheet

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

shows 2" RW6 flat to the wall as dropping off a cliff between 250 Hz and 125 Hz... so I reckon 1.25" flat on the wall don't do much at all on your LF resonances.

OTOH 2" RW6 with a 12" gap aint too shabby for LF.... so I would surmise that air gap can significantly improve LF performance in this material.

Given your space constraints, I'd consider getting rid of the backer boards, and making a light weight frame that will hold the 1.25" finished panels you have and allow you to add another mineral fiber panel behind [no additional cloth covering required].

Maybe something like a 1x6 frame with one of your finished panels in front, about 3" of medium density rockwool [60 to 65kg per m3 range] behind that and then cleat the frame to wall so that between the cleats and the the extra depth at the back of the frame you get at least a couple of inches of air gap... I bet that would work noticably better low in the band than the thin panels as installed.

Also, as described previously in this thread, if you could get a full ceiling treatment system of some kind, that would really help. In a room this small, that is the first thing I would have done... getting a small room to work at high SPL aint trivial. I am given to understand from Paul [who's ears I probably trust more than my own] that Mark did it, but twern't easily done.

My $0.02
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