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Broadband absorbers with Homatherm FlexCL - how thick? DAW Software
Old 4 weeks ago
  #1
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midmost's Avatar
Broadband absorbers with Homatherm FlexCL - how thick?

Hi there,

I am planning to built some broadband-absorbers myself.
Right now I am using 10cm Basotect at the first reflection points but I feel I can do better with Homatherm!
Since Homatherm FlexCL has an extremely high flow resistance, it's not so suitable for building basstraps. So therefore I will use Rockwool/Sonorock in the corners.

However Homa FlexCL looks perfect for first reflection absorbers for the walls and ceiling.
What I am not sure about, is how thick those absorbers should be?!
Is 10cm Homatherm FlexCL good enough?
I read somewhere that FLexCL should not be used too thick, because it will then start to reflect again.

Maybe someone can shed some light in the dark
That would be highly appreciated

Last edited by Northward; 4 weeks ago at 10:07 AM..
Old 4 weeks ago
  #2
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Northward's Avatar
Homatherm decided a couple weeks ago to stop all production. These products are not available anymore...

We're looking for replacements.
Old 4 weeks ago
  #3
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midmost's Avatar
Quote:
Originally Posted by Northward View Post
Homatherm decided a couple weeks ago to stop all production. These products are not available anymore...

We're looking for replacements.
Holy Crap!? WHAT..??
Didn't see that comming

Wonder why they withdraw.. you seem to been their best customer haha.
So their sales couldn't be that bad.

Thanks for the heads-up, Thomas
Old 4 weeks ago
  #4
Gear Nut
 

Quote:
Originally Posted by midmost View Post
Holy Crap!? WHAT..??
Didn't see that comming

Wonder why they withdraw.. you seem to been their best customer haha.
So their sales couldn't be that bad.

Thanks for the heads-up, Thomas
Myself and others anyway don‘t understand
why using that FlexCl stuff for bass traps as its
air flow resistance is so high.
HolzFlex is better. I used instead of HolzFlex SteicoFlex because HolzFlex was not abailable anmore. it has 5kpa.
Old 4 weeks ago
  #5
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Quote:
Originally Posted by ak23 View Post
Myself and others anyway don‘t understand
why using that FlexCl stuff for bass traps as its
air flow resistance is so high.
HolzFlex is better. I used instead of HolzFlex SteicoFlex because HolzFlex was not abailable anmore. it has 5kpa.
That's because in our case Flex CL wasn't used primarily for its flow resistance but for its mechanical properties when mounted within a certain sequence. Holzflex has too big fibers to be a good flow based absorber.
Old 4 weeks ago
  #6
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Quote:
Originally Posted by ak23 View Post
Myself and others anyway don‘t understand
why using that FlexCl stuff for bass traps as its
air flow resistance is so high.
HolzFlex is better. I used instead of HolzFlex SteicoFlex because HolzFlex was not abailable anmore. it has 5kpa.
No one said I was going to make bass traps from it
Old 4 weeks ago
  #7
Gear Nut
 

Quote:
Originally Posted by Northward View Post
That's because in our case Flex CL wasn't used primarily for its flow resistance but for its mechanical properties when mounted within a certain sequence. Holzflex has too big fibers to be a good flow based absorber.
Yeah and Holzflex has also 5kpa as most other Rockwool products right ?
But 5kpa are 5kpa even if the fibers are too big! In the high/mid frequency range it reflects more but bass should be the same i guess.
Old 4 weeks ago
  #8
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Northward's Avatar
Quote:
Originally Posted by ak23 View Post
Yeah and Holzflex has also 5kpa as most other Rockwool products right ?
But 5kpa are 5kpa even if the fibers are too big! In the high/mid frequency range it reflects more but bass should be the same i guess.
Fibers size affects the absorption coefficient substantially. For a similar resistance to flow and density, there is an increase in absorption coefficient alongside a decrease in fibers diameter.

This is mainly due to thinner fibers being able to move more easily compared to thicker fibers. Thinner fibers structures also have a more tortuous path which means increased friction and viscosity.

This factor is called "Tortuosity" and is a "measure of the elongation of the passage way through the pores", basically the influence of the complex internal structure of a material on its acoustical properties.

Generally speaking, tortuosity affects the location of the 1/4th wavelength absorption peak, while porosity and resistance to flow affect the height and Q of the peaks.

Looking at the resistance to flow value and density is a good hint at what a material's properties are likely to be, but it's not the whole picture, so it must be put in perspective alongside other factors and materials properties - that are not always available which is a problem.

While Holzflex is a good thermal product and a welcomed green alternative, it is not a very good absorber due to its mechanical properties. Especially in the LF.
Old 4 weeks ago
  #9
vdH
Here for the gear
 

isover ultimate

Quote:
Originally Posted by Northward View Post
Homatherm decided a couple weeks ago to stop all production. These products are not available anymore...

We're looking for replacements.
Have you considerd Isover Ultimate?

http://www.isover-technische-isolati...9c598fe39b.pdf

It looks promising....
Attached Thumbnails
Broadband absorbers with Homatherm FlexCL - how thick?-screen-shot-2018-09-18-22.01.29.png  
Old 4 weeks ago
  #10
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avare's Avatar
 

Quote:
Originally Posted by vdH View Post
Have you considerd Isover Ultimate?

http://www.isover-technische-isolati...9c598fe39b.pdf

It looks promising....
What a great document! Pdf page 19 gives the GFR by product.

Thank you!

Andre
Old 4 weeks ago
  #11
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midmost's Avatar
Does it make any sense to make superchunks (corner absorbers) from Homa Flex CL?
Old 4 weeks ago
  #12
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Northward's Avatar
Quote:
Originally Posted by midmost View Post
Does it make any sense to make superchunks (corner absorbers) from Homa Flex CL?
Not really no.
Old 3 weeks ago
  #13
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Quote:
Originally Posted by Northward View Post
Not really no.

Okay, you'll find me getting a bit frustrated at this point ;(
I have 5 packages of Flex CL (10mm) in my garage that I would like to use.
Obviously and unfortunately I can't afford a Northward room hehe
Also I am moving cities and places often so I would like to have some mobile absorber modules that I can carry around if my studio moves again.

What would you suggest to do? My first idea was to make some nice superchunks, but apperently that's not a good idea..
I was also thinking of making some absorbers in the size of the Flex CL mats.
I was thinking of a sandwich absorber: 10cm sonorock, and then 10cm flex cl.
So a total depth of 20cm. Is that a better idea?

I know it's not the best solution.. but as I said. These are my circumstances.
Old 3 weeks ago
  #14
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Northward's Avatar
Quote:
Originally Posted by midmost View Post
Okay, you'll find me getting a bit frustrated at this point ;(
I have 5 packages of Flex CL (10mm) in my garage that I would like to use.
Obviously and unfortunately I can't afford a Northward room hehe
Also I am moving cities and places often so I would like to have some mobile absorber modules that I can carry around if my studio moves again.

What would you suggest to do? My first idea was to make some nice superchunks, but apperently that's not a good idea..
I was also thinking of making some absorbers in the size of the Flex CL mats.
I was thinking of a sandwich absorber: 10cm sonorock, and then 10cm flex cl.
So a total depth of 20cm. Is that a better idea?

I know it's not the best solution.. but as I said. These are my circumstances.
Use it as the deepest layer, soft side facing away from the wall (vacuum its surface a few times to remove all the dust in there and decrease resistance to flow a bit, place less dense layers in front of it, at least 10cm. Basically increase density as you go toward the back of the panel. 30cm deep panels would be better. Some thin airgaps would probably help a bit too.
Old 3 weeks ago
  #15
vdH
Here for the gear
 

Quote:
Originally Posted by Northward View Post
Use it as the deepest layer, soft side facing away from the wall (vacuum its surface a few times to remove all the dust in there and decrease resistance to flow a bit, place less dense layers in front of it, at least 10cm. Basically increase density as you go toward the back of the panel. 30cm deep panels would be better. Some thin airgaps would probably help a bit too.
Hi Thomas,

I have built rooms with Flex CL and I really like the product, too bad they quit production...

30cm is obviously better, would do 20cm of low density and 10cm of high density or 10cm of low density and 20cm of high density?

You also talk about airgaps. Do you create those by drilling holes (dust!) through the Flex CL or, by leaving a space between the slabs (with spacers)?

vdH
Old 3 weeks ago
  #16
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Northward's Avatar
Quote:
Originally Posted by vdH View Post
Hi Thomas,

I have built rooms with Flex CL and I really like the product, too bad they quit production...

30cm is obviously better, would do 20cm of low density and 10cm of high density or 10cm of low density and 20cm of high density?

You also talk about airgaps. Do you create those by drilling holes (dust!) through the Flex CL or, by leaving a space between the slabs (with spacers)?

vdH
20cm of low density in front of 10cm higher density.

I meant air gaps between layers / the panels of various densities.
Old 2 weeks ago
  #17
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I'll try that! Thanks Thomas.
I'll try built: Wall>Flex CL (100mm)>Thermarock 50 (100mm)>Sonorock (10mm)
So I'll go from low to high density gradually as you adviced
Old 2 weeks ago
  #18
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ReDRuMx's Avatar
Quote:
Originally Posted by Northward View Post
Fibers size affects the absorption coefficient substantially. For a similar resistance to flow and density, there is an increase in absorption coefficient alongside a decrease in fibers diameter.
Interesting! Could you define "substantially" a bit more precisely?

How "off" can the standard calculators be (acousticmodelling.com for example), considering that the only two variables they use are GFR and thickness?

Thanks!
Old 2 weeks ago
  #19
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Northward's Avatar
Quote:
Originally Posted by ReDRuMx View Post
Interesting! Could you define "substantially" a bit more precisely?

How "off" can the standard calculators be (acousticmodelling.com for example), considering that the only two variables they use are GFR and thickness?

Thanks!
I'm travelling right now - I will search in my documents for the couple graphs I have showing the differences. I remember it being in the vicinity of up to 400% more efficient (Frequency dependent data!) depending on the Denier of fibers being compared. Between 5 and 1 DPF being indeed where the "knee" of the curve is located iirc. A human hair is ca. 20 deniers.

The acoustic modelling site is great for DIY and getting a sense of what is happening when you vary the different parameters. But as soon as you're out of the fairly standard materials samples that were used to get the statistical models in the first place, take it with a grain of salt.

As a rule of thumb, the finer the fiber, the better. Sadly most of the of green materials have thicker fibers.

From the attached paper - keep in mind these studies seldom venture in the sub 100Hz region, sometimes not lower than 500hz, which is in the world of studios "where all the money goes":

"Conclusion:
The influence of various factors of a fibrous material on sound absorption is presented in this paper. Some of the important conclusions of this research are:
• sound absorption coefficient increased with a decrease in fiber diameter, micro denier fibers (less than 1 dpf) provide a dramatic increase in acoustical performance
• one of the most important qualities that influence the sound absorbing characteristics of a fibrous material is the specific flow resistance per unit thickness of the material. In general, It can be inferred that, higher airflow resistance always gives better sound absorption values but for airflow resistance higher than 1000 the sound absorption have less values because difficulty of movements sound wave through the materials
• tortuosity mainly affects the location of the quarter-wavelength peaks, whereas porosity and flow resistively affect the height and width of the peaks. It has also been said by the value of tortuosity determines the high frequency behavior of sound absorbing porous materials.
• fiber surface area and fiber size have strong influence on sound absorption properties. higher surface area and lower fiber size increases sound absorption.
• less dense and more open structure absorbs sound of low frequencies (500Hz), denser structure performs better for frequencies above than 2000 Hz.
• the creation air gap increases sound absorption coefficient values in mid and higher frequencies. At the same time, creation of airgap will have minima at various frequencies for various airgap distances.
• films such as PVC attachment increase sound absorption at low and mid frequencies at the expense of higher frequencies"


"Denier: is a unit of measurement that is used to determine the fiber thickness of individual threads or filaments used in the creation of textiles and fabrics. Fabrics with a high denier count tend to be thick, sturdy, and durable. Fabrics with a low denier count tend to be sheer, soft, and silky.

In terms of fills, in order to be considered a “microfiber” the fiber must be less than 1 denier, which is extremely fine. This gives the fill its airy weight, downy feel, and soft, silky texture. In comparison, a human hair is 20 denier, whereas Standard Fiber’s microfibers are typically 0.9 denier or less."
Attached Files
File Type: pdf 4610-4617 SEDDEQ.pdf (349.6 KB, 24 views)
Old 2 weeks ago
  #20
Gear Addict
 
ReDRuMx's Avatar
Quote:
Originally Posted by Northward View Post
I'm travelling right now - I will search in my documents for the couple graphs I have showing the differences. I remember it being in the vicinity of up to 400% more efficient (Frequency dependent data!) depending on the Denier of fibers being compared. Between 5 and 1 DPF being indeed where the "knee" of the curve is located iirc. A human hair is ca. 20 deniers.

The acoustic modelling site is great for DIY and getting a sense of what is happening when you vary the different parameters. But as soon as you're out of the fairly standard materials samples that were used to get the statistical models in the first place, take it with a grain of salt.

As a rule of thumb, the finer the fiber, the better. Sadly most of the of green materials have thicker fibers.

From the attached paper - keep in mind these studies seldom venture in the sub 100Hz region, sometimes not lower than 500hz, which is in the world of studios "where all the money goes":

"Conclusion:
The influence of various factors of a fibrous material on sound absorption is presented in this paper. Some of the important conclusions of this research are:
• sound absorption coefficient increased with a decrease in fiber diameter, micro denier fibers (less than 1 dpf) provide a dramatic increase in acoustical performance
• one of the most important qualities that influence the sound absorbing characteristics of a fibrous material is the specific flow resistance per unit thickness of the material. In general, It can be inferred that, higher airflow resistance always gives better sound absorption values but for airflow resistance higher than 1000 the sound absorption have less values because difficulty of movements sound wave through the materials
• tortuosity mainly affects the location of the quarter-wavelength peaks, whereas porosity and flow resistively affect the height and width of the peaks. It has also been said by the value of tortuosity determines the high frequency behavior of sound absorbing porous materials.
• fiber surface area and fiber size have strong influence on sound absorption properties. higher surface area and lower fiber size increases sound absorption.
• less dense and more open structure absorbs sound of low frequencies (500Hz), denser structure performs better for frequencies above than 2000 Hz.
• the creation air gap increases sound absorption coefficient values in mid and higher frequencies. At the same time, creation of airgap will have minima at various frequencies for various airgap distances.
• films such as PVC attachment increase sound absorption at low and mid frequencies at the expense of higher frequencies"


"Denier: is a unit of measurement that is used to determine the fiber thickness of individual threads or filaments used in the creation of textiles and fabrics. Fabrics with a high denier count tend to be thick, sturdy, and durable. Fabrics with a low denier count tend to be sheer, soft, and silky.

In terms of fills, in order to be considered a “microfiber” the fiber must be less than 1 denier, which is extremely fine. This gives the fill its airy weight, downy feel, and soft, silky texture. In comparison, a human hair is 20 denier, whereas Standard Fiber’s microfibers are typically 0.9 denier or less."
Awesome, I'll explore it (read the paper) ASAP.

Thank you!!
Old 6 days ago
  #21
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benoïde's Avatar
 

Quote:
Originally Posted by Northward View Post
Homatherm decided a couple weeks ago to stop all production. These products are not available anymore...

We're looking for replacements.
Hi,

Would this be a suitable material for building absorber panels (installed behind speakers for a front to back acoustic)?
Ecobati | Produit CHANVRE 100MM 1250X600

Thanx!
Old 5 days ago
  #22
Moderator
 
Northward's Avatar
Quote:
Originally Posted by benoïde View Post
Hi,

Would this be a suitable material for building absorber panels (installed behind speakers for a front to back acoustic)?
Ecobati | Produit CHANVRE 100MM 1250X600

Thanx!
Probably not the best no.

There is no clear lab data per octave or 1/3 octave anyway, so I'd skip it.
Old 5 days ago
  #23
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benoïde's Avatar
 

Quote:
Originally Posted by Northward View Post
Probably not the best no.

There is no clear lab data per octave or 1/3 octave anyway, so I'd skip it.
Thanx for the honest answer, what would you recommend then (preferably something I can easily find in Belgium)? By the way, I've recently worked at the Pro Tools studio at La Monnaie in Brussels, you did a stellar work on all accounts!
Old 5 days ago
  #24
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Quote:
Originally Posted by benoïde View Post
Thanx for the honest answer, what would you recommend then (preferably something I can easily find in Belgium)? By the way, I've recently worked at the Pro Tools studio at La Monnaie in Brussels, you did a stellar work on all accounts!
Ha! Glad you liked La Monnaie's CR.

Did you mix 2.0 or 5.1/5.0? Very few people have access to this room

Try this:

UNIVERCELL(R) PANNEAUX

- Soprema


It's a replacement for Homatherm FLEX CL I am very much considering, with a few - but significant - differences:

- less dense @ 40-45kg/m3 instead of 60-65kg/m3
- looks to have a more even density distribution within the panel (Flex CL was getting denser from one side to the other)

Some similar points:

- high tortuosity
- at first glance fairly similar mechanical properties, despite less density
- ...green

We always had to vacuum the surface of Homatherm FLEX CL a few times to suck out all the loose dust in it and reduce surface impedance a bit, with this one it is probably not necessary.

With this product we'll have to change the tuned membranes thickness in the walls and ceiling though as this constraint layer will be different from FLEX CL with such a variation in weight etc. But unlikely to be a problem. Just some numbers re-arranging, not a re-design of process.

I'm going to try it on a couple of projects and have it tested. I have a few samples at the office and I think it will be ok for the use.
Old 5 days ago
  #25
Gear Maniac
 
benoïde's Avatar
 

Quote:
Originally Posted by Northward View Post
Ha! Glad you liked La Monnaie's CR.

Did you mix 2.0 or 5.1/5.0? Very few people have access to this room

Try this:

UNIVERCELL(R) PANNEAUX

- Soprema


It's a replacement for Homatherm FLEX CL I am very much considering, with a few - but significant - differences:

- less dense @ 40-45kg/m3 instead of 60-65kg/m3
- looks to have a more even density distribution within the panel (Flex CL was getting denser from one side to the other)

Some similar points:

- high tortuosity
- at first glance fairly similar mechanical properties, despite less density
- ...green

We always had to vacuum the surface of Homatherm FLEX CL a few times to suck out all the loose dust in it and reduce surface impedance a bit, with this one it is probably not necessary.

With this product we'll have to change the tuned membranes thickness in the walls and ceiling though as this constraint layer will be different from FLEX CL with such a variation in weight etc. But unlikely to be a problem. Just some numbers re-arranging, not a re-design of process.

I'm going to try it on a couple of projects and have it tested. I have a few samples at the office and I think it will be ok for the use.
Thanx for the links!

Yes, I had to do a live 2.0 broadcast mix for the Mozart Opera opening the season (Zauberflöte), it was a real pleasure working in that room, although space was tight because we had to fit a Lawo in the control room.
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