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CSR Bradford Fibretex 350 or 650?
Old 2nd September 2008
  #1
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Question CSR Bradford Fibretex 350 or 650?

In Oz we don't seem to have OC 703/705 available, but after searching around for a while, I have come across Bradford Fibretex 350 and 650.

FIBRETEX 350 rockwool
Sound Absorption
When tested in a reverberation chamber in accordance with AS 1045-1988

Density 60 kg/m3

Product Thickness Frequency (Hz)
(mm) 125 250 500 1000 2000 4000 5000 NRC
Plain 25 0.18 0.29 0.69 0.86 1.05 1.2 1.16 0.71
50 0.21 0.69 1.13 1.15 1.16 1.18 1.14 1.05
Faced 25 0.14 0.38 0.87 1.07 1.06 0.9 0.79 0.85
50 0.31 0.83 1.16 0.99 0.9 0.78 0.73 0.97

FIBRETEX 650 rockwool

Sound Absorption
When tested in a reverberation chamber in accordance with AS 1045-1988

Density 100 kg/m3

Product Thickness Frequency (Hz)
(mm) 125 250 500 1000 2000 4000 5000 NRC
Plain 25 0.21 0.29 0.52 1.14 1.02 0.97 1.06 0.74
50 0.59 0.97 1.18 1.00 1.04 1.02 1.03 1.05
My question is which would be more suitable for bass traps and creating a RFZ?

Regards,

Harry
Old 2nd September 2008
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Fibretex 350

Andre
Old 3rd September 2008
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I was under the impression that the higher density of the 650 would be more suitable for broadband bass traps and the 350 for the RFZ, but that is why I posted before making this decision on my own.

Harry
Old 5th September 2008
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Does anyone else want to chime in?

Harry
Old 6th September 2008
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Hey im having the same problem finding as we dont have 703 in aus. In bradford i found a product called Quietel it says it is for specialist accoustic treatments. It is 130kg/m3 and here is the absorbsion levels at 50mm
125 250 500 1000 2000 4000 5000 NRC
0.36 0.81 1.12 1.18 1.11 1.12 1.22 1.05

CSR bring it in im yet to find out a price ill post this in a diff forum topic too and see if we can get reply's
Old 6th September 2008
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The fibretex seems to have better absorption ratings at 125hz but I haven't found out the pricing yet. I can imagine the Quietel stuff being more expensive because of having 'Quiet' in it's name.
I'll post the prices for fibretex when I get a reply from my local supplier.

Harry
Old 6th September 2008
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yeah i see what u mean with the 650 ill ask andre why he recomends the 350 for bass traps i though the more it dampened it the better it would be. the only other thing i found about the quietel is apparently it is alot longer lasting than rock wool have you heard the it breaks down at the edges too?
Old 6th September 2008
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Quote:
Originally Posted by rushton View Post
ill ask andre why he recomends the 350 for bass traps i though the more it dampened it the better it would be.
As absorbers get denser, they tend to start to reflect sound internally. It is a non-intuitive (what part of acoustics is?) part of acoustics. It gets technical, but this thread and post 29 with the pretty drawings is about as clear I can think of to describe what is going on with the materials.

Andre
Old 6th September 2008
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Would someone be able to explain why the less dense 350 fibertex is better recomended then the quietel or 650.
Just interested in how and why
Thanks guys
Old 6th September 2008
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Quote:
Originally Posted by rushton View Post
Would someone be able to explain why the less dense 350 fibertex is better recomended then the quietel or 650.
Just interested in how and why
Thanks guys
Read the thread I linked in the post right before yours. Look at post 29 at a minimum. The answer is in there.

To give a condensed version, which I am certain is terrible, here goes.

Porous absorbers work on producing resistance to sound waves. For a given amount of material, it has to located where the sound wave velocity is high. If you have a limited space, you try to get as much material (within reason) into the area. High density material. As high density material is used thicker and thicker, sound waves reflect internally in the material. So as you use thicker material, you use less dense material to get the absorption.

Andre
Old 6th September 2008
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Ah so if i am correct the less space you have to put the material in the denser you would use, but if u have a fair amount of room use less dense material. This is because with dense material it will only get so far then it will reflect back out of the material as if it had say hit a wall. Where a less dense material will let it travel all the way through and use all of the material to better absorb the sound and stop the reflections coming back out. If so is there a way to calculate what density is most effective according to the aloud thickness of the trap? But then i guess its also coming down to how the materials work and various other factors which are probably too advanced for a little home studio hahaha.

In saying this what would the quietel (that i asked about in an earlier post) be good for? Just as a sound proofing to stop sound transfering all together? And if so what is the little frequency index that is on the facts sheet with the absorbtion details actually tell us?
Old 6th September 2008
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Your density analogy is good. Yes there is a way to calculate it. It involves (surprise) the gas flow resistivity of the materials. What the linked thread is about. Trying to keep it simple, the goal is to have the acoustic impedance at the surface of the absorber fairly close to the characteristic impedance of air.

Home studio building guidelines, hmm generalizations are fraught with inaccuracies. For absorbers up to 100 mm thickness use 48 kg/m^3 glass wool or mineral wool. For thicker use lighter. If over 300 mm, use regular wall insulation. All of those guidelines have exceptions a kilometer wide in them.

Quietel is designed for in wall specific applications. It is good fro that.

Andre
Old 6th September 2008
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doodlebug andre is absolutely right go tohttp://www.bradfordinsulation.com.au/Bradford/UploadedFiles/2e/2e40873c-ed41-4863-9dbf-64d7cc172722.pdf then go to page 67 and they have recommendations for different applications and a recording studio is there and it recommends the fibertex 350 there is a little bit of reading in there which is useful on a few of the other pages just look and the contents and have a browse
Old 7th September 2008
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Quote:
Originally Posted by rushton View Post
yeah i see what u mean with the 650 ill ask andre why he recomends the 350 for bass traps i though the more it dampened it the better it would be. the only other thing i found about the quietel is apparently it is alot longer lasting than rock wool have you heard the it breaks down at the edges too?
I was thinking that the 650 would be good for 100mm corner traps and the 350 for the 50mm and 100mm RFZ absorbers.
As far as breaking down at the edges, I didn't know that but I wouldn't think that would be of concern if mounted in frames.

Harry
Old 7th September 2008
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Quote:
Originally Posted by avare View Post
For absorbers up to 100 mm thickness use 48 kg/m^3 glass wool or mineral wool. For thicker use lighter. If over 300 mm, use regular wall insulation. All of those guidelines have exceptions a kilometer wide in them.
Andre
Fibretex 350 is 60 kg/m3. Should I look at a less dense product?
100mm corner traps is what I'm planning on building and probably a mix of 50mm and 100mm for RFZ absorbtion.

Harry
Old 7th September 2008
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Quote:
Originally Posted by rushton View Post
doodlebug andre is absolutely right go tohttp://www.bradfordinsulation.com.au/Bradford/UploadedFiles/2e/2e40873c-ed41-4863-9dbf-64d7cc172722.pdf then go to page 67 and they have recommendations for different applications and a recording studio is there and it recommends the fibertex 350 there is a little bit of reading in there which is useful on a few of the other pages just look and the contents and have a browse
Ah yes, one of the many files I have downloaded and read. Looks like the decision is coming down to BMF or no BMF...although Andre stating "For absorbers up to 100 mm thickness use 48 kg/m^3" confuses me more when Fibretex is 60 kg/m3....

Harry
Old 7th September 2008
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Quote:
Originally Posted by doodlebug View Post
Ah yes, one of the many files I have downloaded and read. Looks like the decision is coming down to BMF or no BMF...although Andre stating "For absorbers up to 100 mm thickness use 48 kg/m^3" confuses me more when Fibretex is 60 kg/m3.
When I wrote the generalizations I included something like "full of exceptions a kilometer wide." congratulations, you found one of them. Fibertex at 60 or 64 kg/m^3 is acceptable.

If you read the gas flow resistivity thread, you will recall several times the acoustic performance between 48 and 64 material being described as something like "not much."

Andre
Old 7th September 2008
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Hey Harry there is actually a glass wool that is recomended on that page i mentioned earlier in the bradford guide that is 48kg/m^3. Im unsure now whether that would be better then the rockwool at 60kg/m^3. They recommend one or the other for studio applications so would either one be better? they both have roughly the same acoustic values.
And for the bass traps it would actually be better to use the less dense product, then a slightly more dense product for the thiner absorbers. Go have a look at the forum post 69 from andre's link above its got pics to go with the theory which made it alot easier to understand.
Im about to do a post in the building section with a layout of my room my rough plans and the materials im going to use to get some advice so that might make it easier too.
Old 7th September 2008
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Quote:
Originally Posted by avare View Post
When I wrote the generalizations I included something like "full of exceptions a kilometer wide." congratulations, you found one of them. Fibertex at 60 or 64 kg/m^3 is acceptable.

If you read the gas flow resistivity thread, you will recall several times the acoustic performance between 48 and 64 material being described as something like "not much."

Andre
So should I look for a material with lower density than Fibretex 350 for 100mm corner traps?

Insulco make a semi-rigid product http://www.insulation.com.au/INSULCO...Semi-Rigid.pdf that is only 32 kg/m3 but seems to have good bass absorption. I can't seem to find any other info on this product. What do you think?

Harry
Old 7th September 2008
  #20
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Quote:
Originally Posted by rushton View Post
Hey Harry there is actually a glass wool that is recomended on that page i mentioned earlier in the bradford guide that is 48kg/m^3. Im unsure now whether that would be better then the rockwool at 60kg/m^3. They recommend one or the other for studio applications so would either one be better? they both have roughly the same acoustic values.
Would that be the Ultratel? It seems to have a higher "Air Flow Resistivity" than Fibertex 350.

Quote:
Originally Posted by rushton View Post
And for the bass traps it would actually be better to use the less dense product, then a slightly more dense product for the thiner absorbers. Go have a look at the forum post 69 from andre's link above its got pics to go with the theory which made it alot easier to understand.
Im about to do a post in the building section with a layout of my room my rough plans and the materials im going to use to get some advice so that might make it easier too.
I read that thread quite a few times and I think I'm beginning to understand...or not.

Have you looked at the Insulco products?

http://www.insulation.com.au/INSULCO...Semi-Rigid.pdf

http://www.insulation.com.au/INSULCO...ustic-Data.pdf


Harry
Old 7th September 2008
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For 100 mm thick, of all the products discussed IN THIS Thread, the original Fibertex 350 identified asked about in the first post is most appropriate. The difference to the other stuff is "not much", but unless there is a significant price advantage to another product, use the 350.

Andre
Old 8th September 2008
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yeah the ultratel is the glasswool. haha yeah took me a lil bit to get my head round just think of it as u want the sound to travel all the way through reflect off the wall then try and come back through the other way so it gets absorbed. if it reflects off the denser material half way through it wont absorb as much sound
Old 9th September 2008
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Quote:
Originally Posted by avare View Post
For 100 mm thick, of all the products discussed IN THIS Thread, the original Fibertex 350 identified asked about in the first post is most appropriate. The difference to the other stuff is "not much", but unless there is a significant price advantage to another product, use the 350.

Andre
Thanks very much for your help, Andre. Now I just have to figure out how many sheets I need. Should I get the faced 350 for the front layer of the bass traps?

Harry
Old 9th September 2008
  #24
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Quote:
Originally Posted by rushton View Post
yeah the ultratel is the glasswool. haha yeah took me a lil bit to get my head round just think of it as u want the sound to travel all the way through reflect off the wall then try and come back through the other way so it gets absorbed. if it reflects off the denser material half way through it wont absorb as much sound
Yep, that's what I made of it.

Harry
Old 18th September 2008
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I have a similar situation.


I am building a fake wall/broadband trap
If you look at my plan I am going to build these Walls (?) in the 1 meter gaps
either side of the vocal booth.

I have 3 choices now


Choice 1

FIBERTEX 350 - 60kgm^3

1500x900x50 x6 sheets/pack (8.1m/sq) AU$170
(I need 8.7m/sq - bummer 1'll be 0.6m short, i'll have to make up 0.15m with wood each side)

That's AU$21 m/sq

I plan to make the walls with 2 50mm layers with a 50mm gap.




Choice 2

Other stuff from AGI - 32kgm^3

AU$34.56 each i'll need 4 sheets AU$138.24

2400x1200x50 can purchase 1 sheet at a time 2.4x1.2 50mm 32kgm^3
That's AU$12 m/sq

I will use 2 layers with more of a gap ie 100mm



BONUS I'll have 2400x200 X4 left over for more smaller traps/clouds.




Choice 3

R6 - 12.3kgm^3 1300x430x 260 mm thick 6 per pack AU$61.60

I'll get 2 packs at $123.20

That's AU$18 m/sq

I'll only use 1 layer to make the walls seeing the R6 is 260mm thick.

construction might be trickier due to the floppy nature of the R6.


Bonus I'll have 4 x 1300x430x260 left over for traps/clouds




Andre.... Ethan...Glenn What would you do ???

I'm chasing assorted standing waves from 80- 140 htz

I have a massive Helmholtz slat resonator over the mix area which tamed down a triple standing wave around 138hz due to the room dimensions
4.2 x 5.5 x 2.4
Attached Thumbnails
CSR Bradford Fibretex 350 or 650?-new-traps.jpg  
Old 18th September 2008
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Gurubuzz:

Choice 3. It is the thickest.

Andre
Old 19th September 2008
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Thanks Andre,

So in a generalised way we could say that the 260mm thick stuff even though the density is around 12kgm^3 will catch the lower freqs.

and if the denser stuff was that thick the lows would bounce out like a catchers mit which is too slow to grab the ball
Old 19th September 2008
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Quote:
Originally Posted by gurubuzz View Post
Thanks Andre,

So in a generalised way we could say that the 260mm thick stuff even though the density is around 12kgm^3 will catch the lower freqs.

and if the denser stuff was that thick the lows would bounce out like a catchers mit which is too slow to grab the ball
Thank for starting with the "in a generalized way." Your summary is correct.

Andre
Old 22nd September 2008
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Quote:
Originally Posted by doodlebug View Post
So should I look for a material with lower density than Fibretex 350 for 100mm corner traps?

Insulco make a semi-rigid product http://www.insulation.com.au/INSULCO...Semi-Rigid.pdf that is only 32 kg/m3 but seems to have good bass absorption. I can't seem to find any other info on this product. What do you think?

Harry
This stuff has the very best figures I can find out of any insulation product here in Oz. My concern with it is that at only 32kg/m3 it could be overly floppy and flakey (like my current insulation is) and as a result be difficult to make traps out of.

Anyone have any extra info to illuminate the finer points of Insulco Semi-Rigid and how it relates to our purposes?
Old 22nd September 2008
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Quote:
Originally Posted by Ermz View Post
This stuff has the very best figures I can find out of any insulation product here in Oz. My concern with it is that at only 32kg/m3 it could be overly floppy and flakey (like my current insulation is) and as a result be difficult to make traps out of.

Anyone have any extra info to illuminate the finer points of Insulco Semi-Rigid and how it relates to our purposes?
the 32kg stuff is fairly rigid.. I will be using the 260mm thick R6 as space is not a problem for me... I will need to do the chicken wire thing to hold it in place
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