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Post by bodylanguage on Jan 19, 2019 2:08:57 GMT
Hi there, I'm feeling very fortunate to have stumbled across this excellent forum - what a great well of information. I'm in Australia, and about to start making some broadband absorbers and broadband bass traps for my studio. As others have mentioned, it seems difficult finding the right acoustic batts here, but I've come across a product called CSR Martini Absorb and wanted to see if anyone here has used it? The rep sent me some info which I've attached - I'd really appreciate it if someone would take a look and let me know if they think it would be suitable. Apparently the HD range is the most popular for acoustic treatment, so I was thinking of getting the 100mm stuff. Also, if there is any other information that would be useful the rep said he'd be happy to send more stuff over, so let me know if there's anything else I should ask him about. Many thanks in advance! Leo |
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Post by Hexspa on Jan 19, 2019 2:52:08 GMT
XHD100 is about the same as 4" OC705. The only caveat is that I don't know what the AS/ISO 354 – 2006 methods are. If 'on-wall', then we're comparing apples to apples.
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Post by bodylanguage on Jan 19, 2019 23:33:50 GMT
Hi Hexspa, thanks for the reply! So what's the best way to phrase the question to the rep - whether the methods for testing the performance were 'on-wall'?
Thanks again
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Post by Hexspa on Jan 20, 2019 8:22:38 GMT
Alright, take this with a grain of salt. Just because Ethan called this the Audio Expert Forum doesn't mean my advice is worthy of the implication.
For some reason I'm having trouble getting a clear answer on what AS/ISO 354 - 2006 is but, based on the picture in that section of this PDF, I'm guessing it means 'on-wall'. Don't quote me but I think it's also called 'A Mount'.
Sadly, in my experience, 'reps' are not always reliable fact fountains - I've been one myself! But, if what I've said so far is true, you can just ask to confirm.
Just say something like, "Listen buddy - I know your data sheet is all lies. Tell me the truth: Was this tested on wall or with an air gap?"
Either way, according to Bob, the difference isn't drastic.
Maybe a real expert will pop in and set us right.
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Post by bodylanguage on Jan 21, 2019 8:18:51 GMT
Thanks again Hexspa! I've sent an email to the rep so hopefully he's able to find out for me. I'll report back when he does.
Cheers
Leo
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Post by bodylanguage on Jan 22, 2019 22:09:21 GMT
Ok, I got this back from the company:
"All of our ABSORB range tests were performed direct laid to the floor without an airgap with all perimeter edges enclosed in accordance with AS/ISO 354 – 2006"
How does that strike you Hexspa?
He also asked "Is there a NRC you are looking at reaching?"
Thanks again for any advice :-)
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Post by Hexspa on Jan 23, 2019 8:56:00 GMT
That just means 'on wall'. It's the more standard way of doing things. The issue is that it doesn't account for 'gapping' which is how you get better bass response out of your panels. If you've never set up a room, don't worry about it.
AFAIK, we're not aiming for an Noise Reduction Coefficient. We compare the various bands and also real-world performance. From what I can tell, that material looks fine.
In any case, buy a lot of it.
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Post by bodylanguage on Jan 24, 2019 1:58:54 GMT
Thanks Hexspa. Now for some build related questions - given this material is polyester and doesn't break up, is there a point in covering it with material other than for aesthetic reasons - will the absorbers be more effective covered? Also wondering whether anyone can point me in the direction of a design of a membrane absorber / panel trap like the one Ethan discusses here: ethanwiner.com/acoustics.htmlAnd do you think the XHD100 is the right material to use for both the bass traps and the broadband absorption panels? Thanks again |
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Post by Hexspa on Jan 24, 2019 5:11:51 GMT
Thanks Hexspa. Now for some build related questions - given this material is polyester and doesn't break up, is there a point in covering it with material other than for aesthetic reasons - will the absorbers be more effective covered? Also wondering whether anyone can point me in the direction of a design of a membrane absorber / panel trap like the one Ethan discusses here: ethanwiner.com/acoustics.htmlAnd do you think the XHD100 is the right material to use for both the bass traps and the broadband absorption panels? Thanks again Besides adding FRK, any covering is more than likely for looks - just make sure you use fabric you can easily breathe through. The easier you can breathe through it, the easier the high frequencies will pass through.
My advice is to forget about resonant absorbers and just use FRK on frictional absorbers which will add a membrane-like quality to the panels. Remember not to use FRK on early reflection (RFZ) points.
XHD100 seems to be the way to go. Use it for all your sound-absorbing needs.
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Post by bodylanguage on Jan 26, 2019 3:27:16 GMT
So you're saying buy some FRK separately and stick it to the XHD panels? Also, what's a frictional absorber?
Thanks!
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Post by Hexspa on Jan 26, 2019 3:46:54 GMT
So you're saying buy some FRK separately and stick it to the XHD panels? Also, what's a frictional absorber? Thanks! Don't have to be real FRK: paper grocery bags work.
Frictional absorber works on a wave's velocity via... friction. The opposite is a pressure/resonant absorber like you were asking about earlier. Those work with... pressure.
Frictional absorbers, in general, are broadband. Resonant absorbers, in general, have a more narrow effective bandwidth.
We're scraping the bottom of my knowledge char here so let's proceed more practically.
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Deleted
Deleted Member
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Post by Deleted on Jan 26, 2019 9:33:00 GMT
I got a new meaning what FRK stands for, Frequency Reflecting Kratfpaper
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Post by Hexspa on Jan 26, 2019 13:16:33 GMT
I got a new meaning what FRK stands for, Frequency Reflecting Kratfpaper Something tells me you're drinking more than coffee  |
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Post by bodylanguage on Jan 28, 2019 3:48:45 GMT
Ok Hexspa, I've come across one other product by the same company (CSR Bradford). It's called Fibertex 350, it's a rockwool insulation and it seems you can either purchase it with or without an FRK type foil. Wondering what you make of it - I've attached a PDF with some info about it. I'm leaning toward the XHD stuff, mainly because it will be easier to handle, and doesn't break up so I'm not going to be breathing in particles. The thing I'm wondering about though is that the Martin Absorb XHD isn't very dense compared to say the Owens Corning stuff that Ethan recommends. Reading Ethan's articles, he definitely recommends quite a dense product. However, he also says to trust the data rather than blindly trusting the density of the product. When I asked the company about the density of the Absorb range, this is the response I got: "We don’t generally state the Kg of ABSORB as the performance comes from the bend and loft of the polyester not the mass As a guide if its really needed you can say ABSORB HD is 24kg m3 Please keep in mind our competitors with a 24kg m3 product achieve a lower aw / NCR than ABSORB" Now, I imagine the XHD range is a bit denser than the HD but probably not by much. And the Owens Corning stuff is around 90kg m3 so I'm assuming the XHD range is roughly a third of the density of the Owens Corning stuff. I guess what I'm asking is do you think it's actually possible that the Absorb range can absorb at a similar rate to the Owens Corning stuff, given the low density of the product? Perhaps Ethan could chime in here |
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Post by Hexspa on Jan 28, 2019 14:17:21 GMT
The actual density doesn't matter. It actually comes down to something known as GFR, gas flow resistivity, and even that is only weighted to the material used. In other words, focus on the published measurements for now. Later, when you get the stuff in your room, look at what's actually happening as you install it.
Take some time, if you haven't, to look over that Bob Gold's resource I posted in my second reply. There, you will find enough samples among which you can compare any absorber. Make sure to read the text at the top. By doing this, you'll gain the skill of evaluating different products for yourself. Do your best to understand that and I'll be happy to help you with any further questions.
Thanks.
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