John Sayers' Recording Studio Design Forum

Can someone tell me what kind of material this is?



It looks like some sort of compressed foam to me, but I would like to know what it's called and what to expect from it. It has a density of 120 kg/m3 and measurements 1000x1000x60 mm.

If I am not mistaken, it looks to me like carpet padding. This is just a guess.

Ok, thanks! I found out by now that I shouldn't use it as a drum raiser support, so I won't bother asking.

What you're looking at is bonded foam (agglomerated foam).
Digi and it's indeed also used for carpet padding, as for a million other things.

Making a wild guess based on the picture this one is around 60 kg/m3.
It's made from cutting rests of mainly open cell polyethers and partly polyesters.

One can give such foam very deviating densities (much higher) than the original foam it's made off.

Such foam is a lot used for floating floors even with heavy concrete topfloors.

Acoustically it certainly is not less good than the mineral wool boards one specially sells for that purpose (mostly even better).
It also has rather good absorption values.

Mostly fire properties are bad.

AK if you enter a location it always helps.

_________________
Best regards - Eric Desart
My posts are never meant to sell whatever incl. myself, neither direct, nor indirect.

Ok, Eric. So I could use this to float a platform to put drums and amps on?
My plan is to de-couple a piece of the floor from the rest of the room, because the drums and bass amp give off a lot of vibrations through the floor.
This is my main source of sound leakage and also causes frequency drops to my idea.
I'm also in the process of designing bass traps. Do you think I could use this material for basstraps or broadband panel absorbers?

AK-70 (staying a bit dignified),

With this speed this conversation lasts for the next decenium .....

Yes you can use this foam for floating floors (as said used a lot for it - better than glassfiber or rockwool for this purpose).
But the standard rules apply (material independent). Make the pieces that small that there is a deflection under load (floor + gear + person) of 10 to 15%.
Use 50 mm thick foam.
Of couse there are alternative solutions as well (neoprene, rubber, Sylomer, + a million others).

Yes you can use it for basstraps, but I shouldn't in function of bad fire properties and it's easier to work with fiberglas or rockwool (it's rather elastic stuff). And it's hard to beat the absorption properties of standard fiberglass and rockwool.
I know fiberglass/rockwool and this foam in all versions very well. I should prefer the fiberglass/rockwool.

Aglorex in Mol (Belgium) once measured the absorption of this foam in a lab for lots of densities. The absorption is very good and dependent on density.

But one can find such bonded foam all over the world, since it's a standard product made from cutting rests of all standard polyurethane foam made wherever (all/most cutting rests and production residues becomes somewhere bonded foam).
Due to the flexibility to influence its density it has enormous amounts of technical applications.
One can make it that dense that one can mill elastic profiles from it. Do the same with the original flexible foam the material is made off and you just tear it apart (plain impossible to do).

Just fun:
I know a type where one integrates grass seed and products for plant feed, during production process (mixed it with grinded polyurethane pieces before bonding). One gives this a dark black/brown earth color.
Once one spread them on a roof one's lawn starts growing ....

_________________
Best regards - Eric Desart
My posts are never meant to sell whatever incl. myself, neither direct, nor indirect.

Maybe a summary for others too.

Bonded foam

If one sees such bonded foam, what's its acoustic purpose?

Absorption is good and about comparable with mineral wool (glassfiber/rockwool).
It's better than lots of standard Polyurethane foams based on ether (this budget type foam absorption one finds in lots of studio supply sites).
The reason is that the gasflow resistance of the original ether is increased by the higher density of the bonded foam (standard such bonded foam is denser than the original foam it is made of).

However, it doesn't look nice, has standard bad fire properties, is very flexible (not-self-supporting) and isn't that cheap.
So for normal absorption purposes I should prefer mineral wool.

However for floating floors, resilient skin walls and every other application where the mass-spring system comes into the picture this foam has advantages over mineral wool.
The ratio deflection/dynamic stiffness is better than for mineral wool.

While this bonded foam isn't that common in the acoustic world (and therefore rather unknown) and more used for all kinds of technical applications, in Belgium and mainly the Netherlands, some companies specialize in designing and commercializing acoustic insulation products based on this bonded foam.
They proof to be very good in this type of applications (is also used a lot in disco type environments with lots of Low Frequent content).

Basically this bonded foam is good here because one combines the good absorption properties with the very good dynamic stifness properties in function of mass-spring-mass resonance allowing good acoustic insulation applications.

Visibly the foam is ugly and should be covered as one standard with mineral wool does as well.

As for standard foam:

If suppliers are willing to give this information, one will notice that the budget products are polyethers (cheaper to produce) and the more expensive suppliers type Auralex, Illbruck/Sonex and lots of industrial acoustic companies use polyesters (more expensive to produce).

Both polyesters AND polyethers are covered by one single name: flexible polyurethane foam.
As such one rarely will see (on the web) which type of foam their acoustic products are made of.
Certainly the polyether suppliers will not mention this, but call their polyether polyurethane (which is physically correct).

Standard polyether has much lower gasflow resistance and is, in general, less suitable for acoustic absorption purposes.
As a layman one hardly can tell the difference.

Polyether is more elastic and better resistant against moisture and humidity.
Polyester is more form-stable and easier to work with.
One should consider fire properties as well when making a choise (both exist also with fire extinguishing properties)

This are just comments related to general standards from a non-chemist and does not cover all nowadays possibilities foam factories could have.

Polyester's higher acoustic product's price is not only a matter of the more expensive basic material, but also caused by the fact that acoustic companies spending a lot in R&D, will easily use the more expensive polyester.
They also do the investigative and PR work used by other companies just bringing their own cheaper COPYCAT budget polyether versions (often without measuring) on the market.
Basically it's easy to be cheaper if one lets other pay all R&D and marketing costs and do the work, then market a cheaper, acoustic less good copycat product, knowing that laymen haven't the slightest idea about foam types but are mainly triggered by recognizable designs and sculpted profiles.
The ugliest example I know off are the "Foam by Mail" Copycat LENRDs where the used foam is Polyether rather than Polyester for the original, the density is SIGNIFICANT lower then published, resulting in an acoustic absorption curve which has no relation whatsoever with the absorption of the original.
Yet looking on the producers respective sites, the layman will notice two seemingly about similar products.

I'm not selling but explaining.
I'm a typical mineral wool guy for absorption purposes, but there are numerous people prefering foam for whatever valid or unvalid reasons.
Foam, without a doubt, has its rightfull place in the acoustic market.

_________________
Best regards - Eric Desart
My posts are never meant to sell whatever incl. myself, neither direct, nor indirect.

Last thing:

It is known here (Belgium) and the Netherlands as "Agglomerated foam" (Therefore the oldest specialized company I know is called Agglorex) but is often referred to on the web as bonded foam.
If you ask for Agglofoam, anyone knows what you're referring too (other brands will call it different but will know exactly what you mean).
It's produced in 2 x 1m (maybe larger sizes too).
It's possible that there are other sizes too now (long time i've been busy with it), and it certainly will depend on producer.
Since it's made in very thick huge blocks all other sizes are cut from that (including thickness).
Recticel also produces it (but as said there must be much more companies I don't know)

_________________
Best regards - Eric Desart
My posts are never meant to sell whatever incl. myself, neither direct, nor indirect.

I found this material on www.redux.nl .
I also prefer rigid fiberglass for basstraps, but I still have to find a supplier that will deal in small quantities. I can find the soft fiberglass, but I guess that has a much lower density and is meant for heat insulation.

What do you exactly mean by this:
>>Make the pieces that small that there is a deflection under load (floor + gear + person) of 10 to 15%. <<
If I understand this correctly.. how would you ever know this during construction? Isn't there a way to approach this by a mathematical equasion?
I mean I can make a guess as to how much weight it will have to support and then I can calculate how much surface area of agglofoam I need...
Just doing this by trial and error seems like a very tough job.

Check my explanation here

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=839

specifically the post dated Fri Oct 17, 2003- one way to "get in the ball park". Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...

Ok, thanks! Thought I read that post, but I was probably just scanning through it, looking for something else. I get the point now.

I'd very much like to nominate this for a sticky, or at least linked in a sticky referal thread (just like in the construction part of this forum)
The info on bonded foam by Eric is much appreciated.
(I lost this link and finally found it again)