John Sayers' Recording Studio Design Forum Archive

I was wondering, because I couldn't find the information I need for which kind of sylomer (or similar products) to use for what kind of purpose.
There are different standard variants of the material available with different colors, representing different properties (like compression per mm2 by weight):
http://www.sylomer.baubedarf-spezialartikel.de/
What I really don't know, is how to calculate that exactly, so that I could see which material and area to use for what kind of application. I only found the empirical example of looking for 15% compression of the material to decouple a speaker from its stand.
What would the math be behind that? I assume, I know the weight of the speaker and that tells me which color and which area to choose to put under the speaker.
The other frequent application seems to be floating floors. Is this the same behind it? I would really appreciate, if someone could explain that topic to me, both empirical and mathematical for both floating floor and speaker decoupling.

Thanks!

Also, some people seem to prefer sorbothane over sylomer, notably Stuart mentioned that many times. I am not sure, if this also might have to do with the availability in different parts of the world. Sorbothane I only found from British traders. I could buy it on ebay:
http://www.ebay.de/itm/SORBOTHANE-ISOLA ... 460feb8a96
But this version has only 3mm thickness and is made for Hifi equipment. Would that be a good choice for decoupling the monitors from the soffit boxes?
Still, I would be thrilled to get an answer about the properties of different materials and the mathematical and/or empirical determination of the right material properties for differently sized and weighing speakers ...

I only found the empirical example of looking for 15% compression of the material to decouple a speaker from its stand.

That's about right for most rubbers, yes.

What would the math be behind that?

If you get the product data sheet from the manufacturer, it will tell you how much pressure you need to apply in order to get different deflections. So, for example, if it says that you need 500 kg/m2, and your speaker weighs 5 kg, then you would need one one-hundredth of a square meter, or 100 cm2, which is a piece measuring 10cm by 10cm. So make 5 strips of 10cm long and 2cm wide, and place those evenly under the speaker.

Of course, I just chose those numbers to make the math easy! Real numbers will be very different...

Also, some people seem to prefer sorbothane over sylomer, notably Stuart mentioned that many times. I am not sure, if this also might have to do with the availability in different parts of the world. Sorbothane

Sorbathane (or "sorbothane"; two spellings) is the best stuff for speaker isolation, but probably too expensive for other things. Neoprene and EPDM are another two good ones. If you can't get Sorbothane, then get Neoprene.

- Stuart -

Thank you so much for the answer, Stuart!
Sylomer's optimum performance properties are given in N/mm2.
Adam P22A weighs 13 kg, one kg = 9.80665 N, so that is 127,5 N. Sylomer yellow properties are 0.011 N/mm2, so I have to divide the weight of the monitor in Newton by 0.011 an multiply that with 1 mm2. That makes 12748645/0.011 = 11590 mm2, so the quadratic area for the monitor t rest on would best be something like 10.7 x 10.7 cm. Does that sound about right?
Also, one question of mine could never be answered by anyone here: If I surround the monitor by a wooden box and the deflection rubber is holding it from the sides (therefore also holding it and taking some of its weight from the rubber below the speaker): Doesn't that manipulate the calculation?
The reason I ask these things is, I would like to determine the amount of material needed before I find out empirical, as sylomer or Sorbothane are all pretty expensive materials and I have no use for them besides that project I can think of right now ...

one question of mine could never be answered by anyone here: If I surround the monitor by a wooden box and the deflection rubber is holding it from the sides (therefore also holding it and taking some of its weight from the rubber below the speaker): Doesn't that manipulate the calculation?

Well, yes but no! There's an easy way of dealing with that: design the wooden box with the correct dimensions so that the rubber is compressed by the correct amount on all sides. Then when you put the speaker inside the box, adjust it manually so that the gaps are the same on all four sides. That means that the rubber on each side is compressed just right, and the speaker is fully floating in all directions.

- Stuart -

It's been a long time, but I am back and have come a long way since then. Today I have been calculating the sylomer for speaker decoupling and for a test I wanted to put the speaker on some mdf surface to see how much the vibration is still transmitted to the surface. I compared real low frequencies from 50 to 100 Hz first and compared with or without sylomer. The vibrations were nicely decoupled! Very big difference (almost no vibrations with sylomer). But when I got to the range from 100 - 160 Hz, the mdf vibrated (I could feel it with my hand) - I would say the sylomer didn't make any difference in this frequency range. Neither did increasing or decreasing the amount of sylomer under the speaker make any noticeable difference ...
So, what is this? Is it normal to still have some vibrations in this range transmitted (I would say the worst frequency was about 140 Hz)? At least those frequencies don't come very far (I could only feel it on the mdf, but not on the rigidly built framing)! Can I live with that or is it a reason to take a break and rethink something?

This is my test setup. As you can see, I just put ths speaker on top of the speaker box. Mainly, the sides of the box were vibrating. For testing I used a sine generator from logic to go through different frequencies.

This is my test setup. As you can see, I just put ths speaker on top of the speaker box.

Then you aren't testing it realistically! You should put the speaker inside the box for your tests, since that is where it will be in the end.

I've never worked with Sylomer so I can't say if what you are seeing is normal behavior or not. I normally recommend Sorbothane for speakers. It's the best stuff out there right now.

- Stuart -

Then you aren't testing it realistically! You should put the speaker inside the box for your tests, since that is where it will be in the end.

I meant test setup in regards to test the compression of the sylomer with the calculated amount in relation to the weight of the speaker. While at it I figured I might as well perform a little test how well the decoupling works. I am totally aware of the need to further test this with the speaker surrounded by the box, if that is what you are referring to.
I think I know how to find out, how much sylomer to put under and above the speaker. When the compression of the rubber is the same above and under the speaker (15 %) and the speaker is therefore vertically equally spaced in the box, the decoupling will be at an optimum (if the 15% compression are correct), right?
What I am not quite sure about is how to find out the right amount on the sides of the speaker, as there is actually no weight of the speaker involved, but rather the force of the compressed rubber presses from both sides. But how can I find out, if I chose the right amount?
When you used sorbothane in your setup, am I assuming correctly that you put a different amount of it under, above and left and right of the speaker? Logic tells me, it has to be that way, but I might be wrong ...
Also, I thought in the beginning to be able to remove the speaker (if it has to be repaired for instance). But right now it looks like it's gonna be really difficult to get it back in with the rubber staying in place. Would you recommend glueing it to the box, once the right amount and placement are found?

I've never worked with Sylomer so I can't say if what you are seeing is normal behavior or not. I normally recommend Sorbothane for speakers. It's the best stuff out there right now.

I tried to get sorbothane, but I couldn't find it on the German market. I have heard from many people here (also professional studio builder) they used sylomer for exactly the same task, so it cannot be to bad in comparison.

When the compression of the rubber is the same above and under the speaker (15 %) and the speaker is therefore vertically equally spaced in the box, the decoupling will be at an optimum (if the 15% compression are correct), right?

Right: Assuming that 15% is the optimum point for the material you are using.

What I am not quite sure about is how to find out the right amount on the sides of the speaker, as there is actually no weight of the speaker involved, but rather the force of the compressed rubber presses from both sides. But how can I find out, if I chose the right amount?

Use dimensions, not weight or pressure: You need to compress the rubber until it deflects a certain amount. For example, say you plan to use 1cm rubber and it needs to deflect 15%, so it needs to end up only 8.5mm thick. Therefore make the box 2 x 8.5mm = 17mm wider than the speaker itself. So when the box is screwed together with rubber in place, the rubber will be compressed to exactly the right extent.

When you used sorbothane in your setup, am I assuming correctly that you put a different amount of it under, above and left and right of the speaker? Logic tells me, it has to be that way, but I might be wrong ...

For the sides, use only the dimensions, since there is no weight. The same applies for the top, but for the bottom you take into account the weight mainly, plus a small allowance for the compression coming down from above by the top panel. It still works on dimensions: assuming the same rubber as above, you would also make the box 17mm taller than the speaker, but then you put in a but more rubber under the speaker and a bit less above, so that the speaker ends up centered in the box, exactly 8.5mm away from each of the four sides.

It might take a bit of nudging, trial and error...

Also, I thought in the beginning to be able to remove the speaker (if it has to be repaired for instance). But right now it looks like it's gonna be really difficult to get it back in with the rubber staying in place. Would you recommend glueing it to the box, once the right amount and placement are found?

Yes, glue it to the box, but NOT to the speaker itself! And use screws to assemble the box, not nails, as you'll likely need to take it apart and put it back together more than once...

I tried to get sorbothane, but I couldn't find it on the German market. I have heard from many people here (also professional studio builder) they used sylomer for exactly the same task, so it cannot be to bad in comparison.

Well, it's not bad, but there's no doubt that Sorbothane is the best stuff: If you can't get it locally, you can order it from eBay, Amazon and other palces:

http://www.amazon.com/Isolate-It-Sorbot ... 004LYGH3U/
http://www.amazon.com/Isolate-It-Sorbot ... 006YJ9AOS/
http://www.ebay.com/itm/Sorbothane-Vibr ... 1232246502
http://www.ebay.com/itm/Isolate-It-Sorb ... 0797069492

It's not that expensive.

- Stuart -

Hi FriFlo,

where did you buy the sylomer?
is there a webstore where it's possible to buy it?

Thanks

FriFlo wrote:I was wondering, because I couldn't find the information I need for which kind of sylomer (or similar products) to use for what kind of purpose.
There are different standard variants of the material available with different colors, representing different properties (like compression per mm2 by weight):
http://www.sylomer.baubedarf-spezialartikel.de/
What I really don't know, is how to calculate that exactly, so that I could see which material and area to use for what kind of application. I only found the empirical example of looking for 15% compression of the material to decouple a speaker from its stand.
What would the math be behind that? I assume, I know the weight of the speaker and that tells me which color and which area to choose to put under the speaker.
The other frequent application seems to be floating floors. Is this the same behind it? I would really appreciate, if someone could explain that topic to me, both empirical and mathematical for both floating floor and speaker decoupling.

Thanks!