Superchunks - keep my RS60 or change to pink fluffy? Please vote/advise!

[Max Dread]

Hi all

When I treated a room a few years back, nearly everything I read suggested using something like RS60, RW3 or OC703 for superchunks (as I remember that is!). So that's what I did.

I've recently moved and I've done the same in my new room. But as I read on I notice more and more suggestions that the lower density products are more effective for LFs - especially the "pink fluffy" stuff.

My superchunks are 60cmx60cmx83cm and are in three of the room's corners.

So - should I count my loses and change out all the RS60 for some pink fluffy? Or would the difference not be worth the effort and cost?

On a related note and for info, all reflection points and some other areas of bare wall are covered with absorbers also made from RS60 (100mm with a 50mm air gap). It's my understanding that RS60 IS a good choice in this application - although I'd be interested to hear otherwise if it is not the case.

Any votes/opinions would be fantastic!

And cheers to everyone here at GS for such invaluable knowledge and great help.

Max

PS - I used the newer Ecose Rocksilk RS60....... thought it was worth mentioning.

[Hannes_F]

Hi there,

what you should do is to research the gas flow resistivity of both materials. If you can not find that in the data sheet then phone up your dealer or the manufacturer. Also we would need the mode frequency that you have most problems with and the area coverage ratio. Then we could tell you better what to expect with which option.

This is less a question of polls, more one of mathematics and physics . Thick absorption with low density material is only 10 % of the arsenal and does not apply always. But if we decide to have it we can use science to our advanteage.

[neuro]

Isn't there a "more or less defined" relationship between the density of a material and its flow resistivity ?
like for example, if i have an insulation material that is 10kg/m3, can't i roughly deduce its flow resistivity ?
doesn't the density give a precise enough indication of the flow resistivity ?
if not, then why do people recommend using any attic insulation material ("fluffy stuff") for building superchunks ?

[Max Dread]

Thanks Hanns.

I will email Knauf today and try to find that out. Whilst I'm at it should I ask them for any other relevant data?

However, with regard the pink fluffy stuff, I'm not even entirely sure what product to look for........ Seems most people who recommend it are on the other side of the "big pond" where pink fluffy insulation is very commonplace. So perhaps someone here already knows the gas flow resistivity for pink fluffly! And hopefully someone from the UK can tell me what's the most similar product in these parts.


Incidentally, when I first moved house we only had a small amount of loft insulation so I went out and bought some top up. It was on a great offer! A large roll (200mm thick) for £3. This was before I read about "pink fluffy". But because the price was so good I posted on the SOS forum about it, suggesting that if loft insulation has its place in a studio, then what a great time to buy it at such a cheap price. The answer was that loft insulation has no place in a studio......

[Hannes_F]

Originally Posted by neuro

Isn't there a "more or less defined" relationship between the density of a material and its flow resistivity ?
like for example, if i have an insulation material that is 10kg/m3, can't i roughly deduce its flow resistivity ?

No, not really.

For example the material that I use sometimes is Isover Acustic TP1. It is very light but has a gas flow resistivity of 5 krayls/m. Another product is Sonorock Acustic which is quite heavy and has 6 krayls/m.

Isover Acoustic TP1 is bonded at the surfaces with some sort of a glue. I don't know exactly what it is but it makes the surface harder and sort of compressed. That way the gas flow resistivity is quite high in regards to the weight/m³.

Bottom line: there is no linear relationship between density and gas flow resistivity.

if not, then why do people recommend using any attic insulation material ("fluffy stuff") for building superchunks ?

Ask them.
I have never blindly/wildly built superchunks nor have I used material with unknown properties. That is not my working style.

[Hannes_F]

Originally Posted by Max Dread

Thanks Hanns.

I will email Knauf today and try to find that out. Whilst I'm at it should I ask them for any other relevant data?

If you have both the density and the gas flow resistivity we can feed that into more sophisticated calculation models than the Whealy calculator if necessary.

[neuro]

thanks once again Hannes.
your example is somewhat specific. as you say, Isover Acustic TP1 has a different surface than more homogeneous materials.
hypothetically, assuming a somewhat homogeneous material, wouldn't flow resistivity increase linearly with density (compression) ?
(i seem to remember seeing a graph that showed exactly that but i can't remember where i saw it..)

Originally Posted by Hannes_F

I have never blindly/wildly built superchunks nor have I used material with unknown properties. That is not my working style.

i'm not surprised

Ask them.

well then, SAC, Avare : why do you recommend using any attic insulation material ("fluffy stuff") for building superchunks ?

[Hannes_F]

Originally Posted by neuro

thanks once again Hannes.
your example is somewhat specific. as you say, Isover Acustic TP1 has a different surface than more homogeneous materials.
hypothetically, assuming a somewhat homogeneous material, wouldn't flow resistivity increase linearly with density (compression) ?
(i seem to remember seeing a graph that showed exactly that but i can't remember where i saw it..)

Hi neuro,
I know which graph you mean but can not re-find it either at the moment.

The basic idea is of course that if you press the same amount of fibre into a panel of lower width then not only the density increases but also the holes for the air get smaller. Therefore there will be more resistance.

However the relation is not linear. Well, if you set your variation small enough you can fit a straight line to any curve :-) but what you remember as lines are double logarithmic graphs that make any exponential curve look like a straight line.

These are persons that are referred to in this field: Fridolin Mechel, David Bies, Colin Hansen, M. E. Delany, E. N. Bazley, J. F. Allard, Y. Champoux, Y. Miki. There are a number of models and equations that work for different frequency ranges. Some are refinements of the others which does not mean the others were wrong but still give slightly better results.
The porous absorber calculator uses only one of them (see attachment). For more info you can see the Cox/D'Antonio book and/or google some of the names above.

Studio acoustics is only one (very small in terms of money) field for which porous absorbers are used. Industry, architecture and military need much more sound absorption, hence the scientific investigations.

P.S.: I found this link
http://apmr.matelys.com/PropagationM...MikiModel.html
and maybe we can make an updated version of the porous absorption calculator with it. Sounds like a good idea.

[Max Dread]

OK - I spoke to someone at Knauf but they said they have not tested and do not have figures for gas flow resistivity. Damn!

However, he did say that there should be very little difference (if any) between their products and Rockwool slabs of the same type. So I'm going to see if I can get the spec for Rockwool RW3 100mm - which is the equivalent product. I'm sure I've seen the gas flow resistivity for figure for this in the last few days. Unless of course anyone has it to hand.....

[Hannes_F]

Knauf? I have some data for Knauf Germany materials. Which especially do you use / want to use?

[Max Dread]

Hi

I'm already using it and it is the Rocksilk RS60 slabs - the newer browner (rather than yellow) ones which are made with Ecose technology (different binder, etc.).

Thanks a trillion for the help.

Max

[neuro]

Originally Posted by Hannes_F

Hi neuro,
I know which graph you mean but can not re-find it either at the moment.

The basic idea is of course that if you press the same amount of fibre into a panel of lower width then not only the density increases but also the holes for the air get smaller. Therefore there will be more resistance.

However the relation is not linear. Well, if you set your variation small enough you can fit a straight line to any curve :-) but what you remember as lines are double logarithmic graphs that make any exponential curve look like a straight line.

These are persons that are referred to in this field: Fridolin Mechel, David Bies, Colin Hansen, M. E. Delany, E. N. Bazley, J. F. Allard, Y. Champoux, Y. Miki. There are a number of models and equations that work for different frequency ranges. Some are refinements of the others which does not mean the others were wrong but still give slightly better results.
The porous absorber calculator uses only one of them (see attachment). For more info you can see the Cox/D'Antonio book and/or google some of the names above.

Studio acoustics is only one (very small in terms of money) field for which porous absorbers are used. Industry, architecture and military need much more sound absorption, hence the scientific investigations.

P.S.: I found this link
Delany-Bazley-Miki model - APMR
and maybe we can make an updated version of the porous absorption calculator with it. Sounds like a good idea.

ok then, as many things related to audio, the relation is not linear but logarithmic/exponantial. there's still a relation though, which should eventually mean that compressing a material more or less would vary the results one can get with a given material (no ?). interesting IMO.
i doubt i have the scientific knowledge to read the Cox/D'Antonio book (yet ?) - i'm reading some simpler books at the moment - but thanks for the suggestions.

[DanDan]

Seems like a popular topic at the moment in several threads.

Various calculations and tests indicate that lighter material is more absorbent at LF when the layer is thick.
However the behaviour in corners can be different to the typical flat test conditions.

So, I don't think we can say with any level of certainty that light fluffy is better in SuperChunks. Neither can we say that denser is better.
bwo has tested SuperChunks using different densities of fibre. There was no discernible difference. It was clear however that both worked well.
It seems unlikely that the physics is completely off or unknown regarding the corner situation. Personally I would be quite confident building SuperChunks over a wide range of densities. For the larger 34 inch wide ones, I would definitely consider the fluffy, perhaps for financial or availability reasons. When it comes to 24 inch, I am inclined towards 48KG (703), because it is tested.
I would not ignore the predictions and the tests and go for higher densities.

Confusion can arise because sometimes 705 panels can outperform lighter materials at LF. This is due to resonance effects, particularly in corners.
The Corner Straddling panel is a remarkable performer, particularly when one considers the small amount of fibre compared to a SSC.

DD

[Glenn Kuras]

Originally Posted by DanDan

Seems like a popular topic at the moment in several threads.

Various calculations and tests indicate that lighter material is more absorbent at LF when the layer is thick.
However the behaviour in corners can be different to the typical flat test conditions.

So, I don't think we can say with any level of certainty that light fluffy is better in SuperChunks. Neither can we say that denser is better.
bwo has tested SuperChunks using different densities of fibre. There was no discernible difference. It was clear however that both worked well.
It seems unlikely that the physics is completely off or unknown regarding the corner situation. Personally I would be quite confident building SuperChunks over a wide range of densities. For the larger 34 inch wide ones, I would definitely consider the fluffy, perhaps for financial or availability reasons. When it comes to 24 inch, I am inclined towards 48KG (703), because it is tested.
I would not ignore the predictions and the tests and go for higher densities.

Confusion can arise because sometimes 705 panels can outperform lighter materials at LF. This is due to resonance effects, particularly in corners.
The Corner Straddling panel is a remarkable performer, particularly when one considers the small amount of fibre compared to a SSC.

DD

Not to mention that Ethan tested different densities with and without FRK. I am with you on this one.

[Youn]

My guts tell me it's not worth the swap-out, so I say keep what you have already done and use the fluffy stuff in the future, as it's cheaper and easier to get.

On the other hand, if you want to be a super hero (ie: well-liked around here) do a test using your existing stuff, then swap them out for pinkfluffy and let's see what difference there is... I'd understand if you don't wish to do this, but it's make me very

[Hannes_F]

Originally Posted by neuro

which should eventually mean that compressing a material more or less would vary the results one can get with a given material

Absolutely.

[Max Dread]

Originally Posted by Youn

My guts tell me it's not worth the swap-out, so I say keep what you have already done and use the fluffy stuff in the future, as it's cheaper and easier to get.

On the other hand, if you want to be a super hero (ie: well-liked around here) do a test using your existing stuff, then swap them out for pinkfluffy and let's see what difference there is... I'd understand if you don't wish to do this, but it's make me very

At the time I made this thread (a month ago) i was a bit scared by the whole taking measurements side of things. I was debating whether to learn REW or not. Well, I've almost learnt it and have started taking measurements. I have three SSCs in my room - all with RS60/RW3. I might try swapping one of them for fluffy and see what happens to measurements. I'd love to say that I will try swapping all three but I cannot promise anything! Then again, if the one swap shows any improvements I'll be more likely to TRY swapping the other two as well!

bwo and Hannes mentioned earlier about a linear graph showing a (questionable) relationship between density and resistivity. Well, here they are for future reference:





Hannes - you said you might have some data for some Knauf products. Any luck by any chance?

Cheers

Max

[localhost127]

Originally Posted by Max Dread

At the time I made this thread (a month ago) i was a bit scared by the whole taking measurements side of things. I was debating whether to learn REW or not. Well, I've almost learnt it and have started taking measurements. I have three SSCs in my room - all with RS60/RW3. I might try swapping one of them for fluffy and see what happens to measurements. I'd love to say that I will try swapping all three but I cannot promise anything! Then again, if the one swap shows any improvements I'll be more likely to TRY swapping the other two as well!

what specific (measured) room problems are you looking to cure?
if you're going to swap out w/ pink fluffy and you have the space, why not go on and make the corner traps much bigger (deeper) than you had before? or is real estate a constraint?

[Max Dread]

Hi localhost127

Details are here:

My first room measurements - initial thoughts on the results...

Main issues at the moment in the low end are:

- Huge decay/ringing at 40Hz

- Huge dip/null, the lowest point of which is at 120Hz, but which has a wide "Q" ..... Starts to drop at around 80Hz and comes back up at around 155Hz.

Here's a more up to date graph (from a few days ago) than the one in Post 1. Various slight tweakage, but the main one was moving the speakers back closer to the FW (thanks Jens) as well as closer together.





Still a lot of work to do and a lot of measuring!

If you are interested, my last post in that thread outlines where things are at for me at the moment.

Cheers

Max

[PaulRain]

I just did 2 new superchunks made of 6000 rayls/m fluffy glasswool....they do are effective...but I don't think it will make so much of a huge difference if you have the SC already even if it is a denser material....
I think you should invest money on more traps, maybe in this case, if you can go thick, you should buy fluffy because it's cheaper
I suggest you also to measure the noise floor of your room maybe some peaks on the WF are coming from somewhere else....under 35/40dB, if you don't have a very silent room, it could really be noise.

[Max Dread]

For the better of anyone reading this in the future, I thought I'd add a link to another post I made asking whether there's a difference in gas flow resistivity when using a absorbant product frontwise or edgewise. There was no conclusive answer, but it is something to bear in mind. Here's the link:

Another Gas Flow Resistivity Question - difference between "facewise" and "edgewise"?


I think it is fair to say there is A CHANCE that the superchunks I have made using RS60 are actually a little closer to the fluffy ones than I originally thought (IF the resistivity is actaully lower than [the unknown] spec on account of edgewise orientation). Don't get me wrong, I think I would have used a lower density/resistivity "fluffy" type product if I knew then what I do now, but never mind.....

I'm still half tempted to try out a swap just to measure the difference..... will have to see if I get the time....

[Audioactive]

i was actually going to open a thread to ask a similar question since i was gonna order rockwool panels 40kg/m3 to build my basstraps, but i wasnt sure it would be the right choice to create superchunk corners as well..

if i have a 1200x600x100mm mineral wool panel and i use the 100mm side of the panel to "fight" the sound, i guess changes the scenario, cos the specs regarding density, rayls etc...are calculated on the larger side of the panel ..(?)

so, my question is, in your experience, when building bass traps for the corners, do you get better results with superchunk or with panels??

thanks