Bunnings Insulation - Suitable Broadband Panel Absorber?

[DwaneHollands]

If you compress it too much between your inner-leaf and outer-leaf, you run the risk of creating a flanking path, and therefore bypassing your isolation completely... I'd just leave it lying loosely in the gap. Fill as much as you can, but don't compress it.

Hi Soundman2020,

Thanks for your response!

I'm building broadband panel absorber, would it still be a problem?

[Soundman2020]

Ahhhh!!!! That's what I get for having several threads open at once, and confusing things... Sorry!

I'm not sure if compressing it would help or hurt in an absorber application. Maybe Andre, Ro, John, Rod or someone like that can throw more light on the subject. My best guess is that compressing too much will always be bad, but I may be wrong...

- Stuart -

[najsion]

Dwane, the more you compress insulation the more it's values decrease. I know this for certain in it's R value, I presume the same for RW values. Saying this, 25mm compression should not make a huge difference.

Paul

[DwaneHollands]

Thanks Stuart and Paul!

Sorry I didn't get an email notification of your replies, hence the long wait! Ok, so a gentle compression shouldn't be too much of a problem. I may even avoid all compression.

This is the idea for my mixing area. I realise I don't have an bass traps there, but I'm working on the broadband panel absorbers first. I'd like to do it progressively for two reasons. one budget and two to be able to see the difference each modification makes. This image is as if you sitting at the desk with the two speakers facing straight back at you.

The frames are going to be wooden, about 15mm thick by 75mm deep. I'll staple gun the canvas to the inside of the frame. Wrap the rockwool in some other cotton material and put in the back, and staple gun the cotton material to the back, to hold it in.

BroadBandPanels.jpg

Just thinking I might get a bit of diffusion between those wooden panels. Is that going to be a problem? Artistically, I'm probably going to use different images. The goal is to have one composite image over the 9 panels. I'm a sucker for appearances.

[DwaneHollands]

OK,

I finally got a prototype put together. I used 42mm deep frames as I couldn't find any 50mm. However I may have to go to the 68mm, since that's the closet the thickness of the 75mm insulation I've purchased.

The 42mm version 'bulges' as a result of stuffing the 75mm thick insulation in the 42mm deep frame.

I think I'm going to get a pneumatic staple gun too. The manual one, won't penetrate all the way through. Getting the canvas taught enough was a bit of an exercise. Once I worked out exactly how to cut the corners properly, it will make things easier and more precise. I may be able to get better tightening of the canvas.

Thoughts/Comments?

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[Soundman2020]

I'm wondering about the material that the graphic is printed on: it looks to be shiny, and I'm wondering if that means it is plastic? Can you breathe through that material easily, with no resistance? If not, then it will probably be reflecting high-mids and highs back into the room, not absorbing them, Is that what you wanted?

- Stuart -

[DwaneHollands]

Hi Stuart,

The material is canvas with an emulsion on it to make printing consistent. It would be similar to a painted canvas.

I'm looking to absorb lower mids to mids. If I get a bit of diffusion higher than that (with a 3 x 3 grid of panels) I'd be happy I think.

[elenahusky]

Hey there..!! Nice stuff..!! Thank you for sharing this with us.


[SPAM SIGNATURE DELETED BY MODERATOR]

[Lawsy]

I'm from Australia and for a long time I've been looking for the best sound absorbing material; I just got so fed up that I gave up for quite some time.
Recently my wife and I just purchased a house and now I've rekindled my interest in sound absorbing.
I've come back to find that, well, nothing has changed.

We still pay stupidly out the ass for products the rest of the world seems to enjoy at half the price. As an engineer who deals internationally every single day, this is just unacceptable and enrages me greatly...

Anyway, on to my question.

I cannot find any reference to a Fletcher product called "Mineral Wool Slab" being used as an acoustic absorber, specifically bass traps, when according to the ASTM testing, used for the rest of their range, it utterly annihilates everything else I've thus far seen.

No, I haven't priced it, nor do I know what it is like to handle, but take a look at this for a purely technical analysis and tell me what you think.
NRC Data: Coefficients at Frequencies per ASTM C 423
For standard whole octave NC values, starting at 125hz as per usual..
Here's three comparisons
Mineral Wool Slab
192kg/m3 50.8mm 0.40 0.79 0.78 0.94 0.94 0.87 0.85
96kg/m3 50.8mm 0.36 0.79 1.15 1.04 1.01 1.04 1.00
96kg/m3 101.6mm 1.15 1.17 1.18 1.03 1.06 1.08 1.10

vs.

OC703/5
703, plain 2" (51mm) on wall 3.0 pcf (48 kg/m3) 0.17 0.86 1.14 1.07 1.02 0.98 1.00
705, plain 2" (51mm) on wall 6.0 pcf (96 kg/m3) 0.16 0.71 1.02 1.01 0.99 0.99 0.95
703, plain 4" (102mm) on wall 3.0 pcf (48 kg/m3) 0.84 1.24 1.24 1.08 1.00 0.97 1.15


As far as I can tell, assuming the testing is legit (which I assume it would be considering Fletcher represent OC), then this stuff utterly destroys anything else as a wideband absorber.

What am I missing? Is it priced like gold? Is it going to kill me the second I touch it? Will it turn thermonuclear if I put it in the sun?

I'm in the middle of designing a 150mm thick panel, 100mm of absorber (maybe 75) with 50 - 75mm of air gap, in a common frame. I've been using a calculator from http://www.whealy.com/acoustics/Porous.html to test various combinations and a half half split of 150mm, of most flow resistivity values, seems to do a good job. This changes when you go thicker, which I can't do, otherwise I'd use something fluffier.

But this still begs the question, is this "mineral wool slab" a hidden gem for us Aussies? Or does it have so many objectionable qualities that no one wants to touch it?
A note about me: I'm a mechanical engineer, have always liked sound gear and acoustics, and I've read probably (just today) over 20 web-pages and/or entire forum threads on bass traps today alone... I've not read anything similar to this elsewhere so I figure I'll ask on a forum that seems to have a legitimately knowledgeable community. Cheers..

[Soundman2020]

Hi "Lawsy". You seem to be hijacking Dwanes thread: Please start your own thread, and also check the other forum rules for posting.

Thanks!


- Stuart -

[Lawsy]

Hi "Lawsy". You seem to be hijacking Dwanes thread: Please start your own thread, and also check the other forum rules for posting.

Thanks!


- Stuart -

My apologies, new thread now started.
I just didn't want to start yet another thread about how we don't get OC705 here for a reasonable price, or several of the other products sold in the US. At four times the price, many products available, might as well not be....

I also didn't think it deviated enough from the topic at hand to warrant a new thread, but after even further investigation I cannot find anyone else who has made mention of this particular Fletcher product, let alone for its use in Bass traps... Thus I've started a new thread in the hope that I'm not rehashing something that people have known about for years...