When I built an absorber for the first time and simply used some rock wool at the time, I would not have thought that I would build such an emotional connection to an absorption material! :)

I probably had to endure the sometimes unpleasant experiences with rock wool in order to finally really appreciate the alternative to mineral wool in the form of Caruso Iso Bond.

But seriously, there are simply several points that I noticed in the direct comparison between the two substances during my experiments in the past few weeks. And I am sure that if you deal with the topic of room acoustics, sooner or later you will also have to choose which material you would like to acoustically improve your recording studio or living room or home cinema with.

And since I couldn't find much about Caruso Iso Bond vs Rockwool in my research, I would like to shed some light on the subject and share my personal experience and assessment with you.

No Health Risk

I can't name any studies that scientifically list the risks that could be associated with mineral wool. But I can tell you from my own experience that after a day of building the absorber I was able to see a clear reddening of my forearms. And if you occasionally touch your face with your hands during the day, there is a certain itching sensation there as well.

Everything is not a doom of the world and somehow predictable (and reckless on my part to deal with rock wool without protective equipment), but the point is: there remains a certain health risk associated with mineral wool. And even if we naively assume that there is no risk, every contact is unpleasant in any case. At least that is my previous experience.

Caruso Iso Bond, on the other hand, I have been using daily for almost two weeks, move the plates from here to there, rearrange them, and have absolutely no skin irritation. On the contrary, while I always think three times about touching the rock wool absorbers again, the Caruso Iso Bond feels absolutely fluffy and cozy.

The manufacturer even confirmed to me that these absorbers are made from the same material as their allergy-free pillows.

At this point, of course, you would need to contact the manufacturer yourself if you worry about allergies and need a safety certificate. In my personal experience though, I think Caruso Iso Bond is absolutely suitable for the living room.

Hygienic

I only became aware of this point when I had several weeks of experience with rock wool. It should be clear to everyone that it gets dirty while processing rock wool during absorber construction. But even if you later rearrange your absorbers to experiment a little with the positioning, small flakes loosen from the mineral wool every now and then. With glass wool this should be similar. So when building an absorber, you have to be very careful to pack the rock wool well in fabric or foil.

At Caruso Iso Bond I didn't even notice that material residues would come off somewhere, no matter how often I move the absorbers and set them up again. And since the whole thing works so cleanly and hygienically, I have been using this material so far without any housing or fabric covering. No dirt when building absorbers, no dirt when using.

Stiffness

Most of us have less than 20 years of experience in the construction of absorbers, neither do I. And it is correspondingly advantageous if you have the freedom to experiment at the beginning. Will 10cm be enough, or will it be better if I use a depth of 20 or even 30cm? Is a 120cm high corner absorber sufficient or would you prefer to use the entire room height?

For hygienic reasons, experimenting with rock wool in small steps is difficult. Because you would have to wrap your rock wool in appropriate packages beforehand so that you do not come into contact with your rock (and your lungs) all the time.

In addition, rock wool (at least the one I used) is quite unstable and cannot be stacked. The only possibility: you use the complete package from the hardware store unpacked in original film. That may work for corner absorbers in the dimensions 60x60cm, but unfortunately this way is not useful for wall cladding.

In most cases, you have to build a suitable construction immediately after unpacking in order to be able to use the rock wool upright at all. Either in the form of a slatted construction on the wall or ceiling, or as in my case in the form of mobile absorbers. But of course this requires a decision in advance as to how big and deep the absorber should be. You can only experiment by placing two absorbers in front of each other. But if you find that you really want to use twice the depth, you actually start again from scratch and build a new absorber.

And - how could it be otherwise - with Caruso Iso Bond this is all more practical! The absorbers can be stacked as desired. Freestanding in the middle of the room doesn't work. To do this, the packages would have to be tied together so that they do not collapse.

But leaning against a wall, I have so far been able to try out any combination that came to my mind. With a room height of over 2.40 m (8’), for example, two absorbers can be placed on top of each other (1.20 m, 4’). And this works at any depth. Due to the plate thickness of 10cm / 4’ (sometimes also available in 5cm / 2’), you can try out almost continuously how the whole thing behaves acoustically. And you also get a visual impression of how the new situation feels - before you touch a single piece of wood!

Only when you are satisfied with the arrangement can you think about which fabric or curtain to stretch in front of it so that it is not only acoustically but also visually a pleasure.

Available flow resistivity

Almost every hardware store offers mineral wool in its range. Very few are related to acoustics. And so you occasionally either find no information about the flow resistivity, or there is only one material with this one flow resistance. Accordingly, it is sometimes a matter of luck whether you can get the right material for your purposes from the “hardware store next door”.

Caruso Iso Bond is available in three versions:

• WLG 045: flow resistivity 3000 Pa * s / m², density 15kg / m³

• WLG 040: flow resistivity 5000 Pa * s / m², density 20kg / m³

• WLG 035: flow resistivity 10000 Pa * s / m², density 40kg / m³

And so it actually covers all areas of application that you want to treat acoustically. For thin absorbers (10-15cm) you use the heavy WLG035, for 20-30cm the medium WLG 040, and above that the WLG 045 is light enough that you can also build absorbers with 40cm and more. [More about flow resistance in this article.]

I have already experimented with plates in WLG040 and WLG045. And so far I am satisfied with the measurements in that they meet my expectations and also offer results similar to what I would have expected from the flow resistivity.

Since my Rockwool is 14400 Pa * s / m², I cannot compare both products 1: 1 in terms of measurement technology. At the moment, however, I have no concerns that the flow resistivity specified by the manufacturer fits and the acoustic properties correspond to those of rock wool.

Delivery service

Stone wool has almost every hardware store in stock. If you decide to build an absorber today, chances are good that you can start today. However, you need a large car for this and probably have to drive several times. On the one hand, you will make a first visit to note down the different materials and then do your own research at home, which flow resistances are to be expected and which one is ultimately the best for you. And if you don't have a large van, you will probably only get one or two packages in your car and may have to drive several times.

I ordered Caruso Iso Bond online from Don Audio. Except in this (German) online shop, I have so far found no way to get the material. This means that most people no longer have the opportunity to pick up material for a spontaneous acoustic treatment.

However, this also has its advantages: the goods are usually sent via DHL and thus come to your front door. The standard dimensions of Caruso Iso Bond (120 x 60 x 62cm) including the packaging are however oversized and a bulky goods fee will be charged at DHL.

Incidentally, there is also the option of having mineral wool sent to you if necessary. Both Amazon and some hardware stores have rock wool products in their online catalog.

Price

Ok, let's face it, the many advantages mentioned also have a slight disadvantage: the price of Caruso Iso Bond is higher than that of rock wool. Since the dimensions differ depending on the product, I convert the prices into cubic meters (1m³ = 35 ft³) :

• Rock wool: 50-100 EUR / m³

• Caruso Iso Bond WLG 045: 210 EUR / m³

• Caruso Iso Bond WLG 040: 400 EUR / m³

• Caruso Iso Bond WLG 035: 650 EUR / m³

While, according to my research, rock wool only differs slightly in price between the different densities, the price structure at Caruso Iso Bond is very clear: you pay not by volume, but by weight.

It costs almost the same whether you use 10cm WLG 035 or 20cm WLG 040 or 40cm WLG 045.

For thick absorbers, Caruso Iso Bond in the light version WLG 045 is about 2-3 times more expensive per cubic meter than ordinary rock wool. If, on the other hand, you want to use a small absorber depth and want to use the heavy Caruso Iso Bond WLG 035, the price difference is more likely to be 8-10x.

Alternatives

There is another competitor product to Caruso Iso Bond that offers similar advantages: Basotect. I have not tried it myself and therefore cannot give details on handling.

Technically, with a flow resistivity of 14000 Pa * s / m², it is close to Caruso Iso Bond in the WLG 035 version. Basically, according to my research, Basotect is even more expensive than Caruso Iso Bond.

Basotect also has an advantage: at 9kg / m³, it is extremely light and therefore particularly suitable for mounting on the ceiling. However, since Basotect is only available in a single version with a very high flow resistivity, it is only suitable (also in terms of price) for rather thin absorbers.

Conclusion

Everyone has their own situation.

One is currently studying, does not yet have his own income and has a correspondingly low budget and is happy to accept the dirt at home when he can finally improve his acoustics.

Someone else is already in the middle of a professional life, accordingly has a larger budget, and maybe also a partner and children in the household and attaches great importance to hygiene and health.

And one wants to set it up in one day, dress it up well and then never touch it again in the next 10 years. And the other wants to experiment and learn a lot and may already be planning to move to a new apartment next year.

Accordingly, I cannot make a recommendation as to which product is right for your situation. It is clear, of course, that with a factor of 2-10 of the acquisition costs you get far more cubic meters of rock wool for the same money than Caruso Iso Bond. And I have never heard from anyone or myself that the acoustic absorption quality differs between the fabrics - as long as you choose a material with the right flow resistivity for its purpose.

In my case, I take a middle course. I have already done the dirty work with rock wool, I have already built the appropriate wooden housing and also the fabric cladding. And acoustically, I'm happy that I can use my rock wool absorbers. So they can and should stay! The rock wool in my ceiling cloud is also well wrapped in foil and I have no plans to touch it more often in the future. Thus, the health and cleanliness risk is minimal.

For all further purchases and attempts, I have clearly arrived at Caruso Iso Bond. The joy and motivation when trying out and measuring has just been so much greater since I've been carefree working with Caruso Iso Bond than was the case with rock wool. And since I primarily work with medium-thick absorber depths and am currently not planning to purchase the expensive WLG 035, the additional costs for me are “only” a factor of 2-4. And it is worth it to me, my health and my joy of experimenting!

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