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Loudspeaker isolation!

Purité Audio

Purité Audio

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AMC MECANOCAUCHO, manufacturer isolation devices for, well everything from heavy industrial equipment downwards.
I posed the question of loudspeaker isolation, their engineers couldn’t have been more helpful.
I have invited Egoitz Rivera (the engineer who has been so helpful ) to the forum, I asked for loudspeaker isolation for nominally a 28 kilo loudspeaker, D&D8C AsciLabs new C8C for example.
His recommendation backed by calculation was four blocks of Sylomer ( registered trademark) SR-11 with dimensions of 100x100x25mm each having a natural frequency of 22.5Hz.
Below the calculation he submitted.
2026-02-04 - Purite Audio - 28kg Loudspeaker Suspension - 4x Sylomer® SR-11 100x100x25mm-4.png
 
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We also discussed the need for isolation at all, his reply.
Quote,
‘Regarding the isolation of loudspeakers, it depends on the case. If they are already in enclosures that are well isolated, elastically suspending them might not be necessary, since the enclosure itself might keep the loudspeaker elastically suspended. However, if this is not enough and structure-borne noise is transmitted to the nearby rooms, elastically suspending them will normally improve this.



The springs are very effective isolating low and mid frequencies, but at high frequencies the system does not behave as a mass-spring system, and the composition of the materials plays a big role. Moreover, the coil springs have their own structural natural frequencies (which usually lie in the order of magnitude of few hundred Hz), so they can resonate at some high frequencies.



The Sylomer® is a polyurethane with a microcellular structure with many air-filled cells, which break the continuity of the material. This lack of continuity makes that the sound waves encounter interruptions, which scatter, reflect and attenuate them. At each discontinuity, part of the noise and vibration energy is converted into heat and damped and part is reflected. Moreover, each discontinuity also creates a difference in mechanical impedance (the material’s resistance to motion under vibrational force), which also reflects part of the energy towards the source, preventing it from traveling through the material. In a continuous material, the waves travel in a relatively direct path. Breaking the continuity of the material randomizes the pathways, dispersing the energy rather than allowing it to travel directly.



Your assumption is right that the Sylomer® is available in different thicknesses and densities, and we can select the right density, thickness and shape depending on the weight and shape of the speakers.’

I have asked to the Sylomer SR-11 blocks which appears to offer an effective and inexpensive isolation solution.
Keith
 
Purité Audio said:
AMC MECANOCAUCHO, manufacturer isolation devices for, well everything from heavy industrial equipment downwards.
I posed the question of loudspeaker isolation, their engineers couldn’t have been more helpful.
I have invited Egoitz Rivera (the engineer who has been so helpful ) to the forum, I asked for loudspeaker isolation for nominally a 28 kilo loudspeaker, D&D8C AsciLabs new C8C for example.
His recommendation backed by calculation was four blocks of Sylomer ( registered trademark) SR-11 with dimensions of 100x100x25mm each having a natural frequency of 22.5Hz.
Below
Click to expand...
 
Purité Audio said:
His recommendation backed by calculation was four blocks of Sylomer ( registered trademark) SR-11 with dimensions of 100x100x25mm each having a natural frequency of 22.5Hz.
Click to expand...
Very interesting information. Sylomer seems like a very good solution to the problem.
The "natural frequency" is more a characteristic of the speaker-sylomer system than the pads alone, though.
I wonder why he opted for such large and thick (and expensive) pads instead of using a stiffer version of sylomer and maybe thinner pads as the vibrations we have to deal with are sub mm.

Purité Audio said:
If they are already in enclosures that are well isolated, elastically suspending them might not be necessary, since the enclosure itself might keep the loudspeaker elastically suspended.
Click to expand...
Hmm, elastical suspension of drivers in the enclosure is quite rare, typically the baskets are bolted down.
Purité Audio said:
The springs are very effective isolating low and mid frequencies, but at high frequencies the system does not behave as a mass-spring system, and the composition of the materials plays a big role.
Click to expand...
What springs?

I wonder whether he considered the direction of vibrations. The typical speaker vibration (from which we want the floor to isolate) is from woofer diaphragm movement and will mainly push the enclosure back and forth and not up and down (depends on the position of diaphragm and center of mass of the speaker).
I would expect a significantly different "natural" (resonant) frequency in this case (shearing motion).

EDIT: As I was interested in the isolation with Sylomer but could not really understand the second graph and the table with it, I searched a bit.
Here is a page where data sheets can be downloaded
rrg.de

Sylomer (PUR) - RRG INDUSTRIETECHNIK GMBH

Sylomer® ist ein spezielles PUR Elastomer und findet Einsatz in Bautechnik und Maschinenbau. Er wird als druckbelastete, anpassbare, Feder verwendet.
rrg.de rrg.de
and the data sheet for SR11. All in German as I could not find English versions.
To understand this better and for general technical explanations about Sylomer there is another document (again in German).
In the data sheet there is a graph for the resonant frequency of a SR11 bearing of given load and thickness.
I marked the case from the OP in blue.

1770317277931.png

The form factor=3 relates to a different geometry (strips of Sylomer). For a block 100x100x25mm the form factor=1 and this will decrease the Eigenfrequency by about 7%. This will give more or less the 22.5Hz result from the OP.
A load of 0.007N/mm^2 is about 64% of the maximum specified load. Increasing the load (by decreasing the block size/area) would significantly lower the Eigenfrequency to about 15Hz when approaching the maximum load. Marked in red.

Another diagram gives the isolation of the bearing for different vibration frequencies.
The blue line for the variation of 22.5Hz and the red one for the higher load version with 15Hz.
Isolation.png

This is all for a movement of the vibration that is vertical. But as mentioned this is not the principal movement of the speaker enclosure. At the corners the cabinet is very rigid and the movement mainly is a reaction (Newton) to the movement of the woofer diaphragm.
This results in a vibration back and forth in a shearing motion of the foam bearing.
In the technical file from above there is mentioning of the behaviour for shearing motion.
1770314906123.png

Translation: For shearing motion the bearing is softer and the relation of the respective stiffnesses is between 4 and 10, depending on the geometry of the bearing.

In the data sheet the shearing modulus is given as about 50% of the elastic modulus for SR11.
So, as a result I would expect the eigenfrequency of the horizontal motion to be about half (to a third) of the vertical one. The isolation will accordingly be greater for horizontal vibration.

Lastly, I was interested in using smaller blocks from stiffer material like Sylomer SR42 or SR55.
One could further decrease the support surface of the blocks by a factor 4 (35x50x25) and use SR42 which has four times the load limit.
From the data sheets this would result in another reduction of the resonant frequencies and thereby better isolation. (And it would be cheaper, too.)
 

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We were discussing the use of springs which have an internal rubber gasket, if you check out the AMC you can see their extensive range.
Keith
 
frankenschaum.de

SYLO - Schwingungsdämpfer

Die Sylo Schwingungsdämpfer sorgen für eine vom Boden entkoppelte Akustik. Die fast vollständige Isolation sorgen für guten Sound und gefallen auch deinem N
frankenschaum.de frankenschaum.de

Hello
I used SR110 for 29kg speakers
  • Sylo gelb für Lautsprecher von 2-6 kg
  • Sylo orange für Lautsprecher von 5-10 kg
  • Sylo blau für Lautsprecher von 7-15 kg
  • Sylo rosa für Lautsprecher von 11-22 kg
  • Sylo grün für Lautsprecher von 15-30 kg
  • Sylo braun für Lautsprecher von 23-60 kg
geluidsisolatiedokter.be

op maat gesneden Sylomer pads en strips

Door pads en strips op maat van een specifieke toepassing te versnijden kunnen we flexibele oplossingen aanbieden.
geluidsisolatiedokter.be geluidsisolatiedokter.be

No measurements done but no audible difference
Enjoy...
 
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I have ordered some SR-11 to try, each 25mm x 50mm x 50mm pad sells for the princely sum of £2.50.
I will report but they look a viable alternative to sorbathane.
I have suggested to AMC it is a market they might consider investigating.
Keith
 
Purité Audio said:
I have ordered some SR-11 to try, each 25mm x 50mm x 50mm pad sells for the princely sum of £2.50.
I will report but they look a viable alternative to sorbathane.
I have suggested to AMC it is a market they might consider investigating.
Keith
Click to expand...
Maybe ask them if a combination of the two might cancel out each others deficiencies?
 
Egoitz of AMC explained how Sylomer works, and I have added the explanation to my ‘News’ page.
www.puriteaudio.co.uk

Purité Audio's NEWS

Purité Audio London, Dutch&Dutch 8C, GGNTKT, KEF ,Eversolo,Ascilab, Mesanovic, Sigberg Audio 'Manta', RME, EVERSOLO , the finest measuring and thus sounding equipment and no bullshit.
www.puriteaudio.co.uk www.puriteaudio.co.uk

Keith
 
If you've got some particular problem (like maybe vibration feedback between the speaker and a turntable), or maybe a poorly designed speaker with a thin or resonant cabinet that vibrates excessively, there may be no benefit. I believe that in most situations wall/ceiling/floor vibrations come from sound waves.

This is one of the few careful "scientific" experiments I've seen. Testing Speaker Isolation Products (No significant difference.)
 
I agree and so did the engineer from AMC, see the first post, but for those rare case scenarios, a resonant desktop perhaps..
Keith
 
Mnyb said:
Yes the sonic design feet’s , used them in the past, not costly at all .

Are they also made of this material ‘ sylomer ‘ ?
Click to expand...
Yes. Released 40 years ago?
One case of isolation from a bench/desk. Case audible? Yes.
www.audiosciencereview.com

Springs Under My Speakers: What's Happening?

Regarding the audibility I gave an example with a speaker placed on my hifi equipment rack with hard and soft speaker feet (sonic design). First two sweeps are hard coupling, last two with soft coupling. Perhaps an extreme example, but it shows the principle that applies...
www.audiosciencereview.com www.audiosciencereview.com
 
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Mnyb said:
Yes the sonic design feet’s , used them in the past, not costly at all .

Are they also made of this material ‘ sylomer ‘ ?
Click to expand...

That's correct, the old classic Sonic Design loudspeakers' feet are made of Sylomer. These are probably the most commonly used soft-material feet for loudspeakers here in Sweden. They come in many different sizes and types of Sylomer compositions to suit loudspeakers and electronics of various weights. The price is under €30 for an 8-pack. :)
 
I've used Sonic design's feet for at least 20 years, they're in fact built in on the bottom of my Guru 28 speakers
 
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