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Apebot 18th August 2019 12:11 PM

Cork under speakers
 
Needing a cheap alternative to bought speaker dampeners I sliced a cork into 9 rounds and placed 3 rounds under each of my front speakers (L,C,R).

It's raised them from the wood cabinet they were on, and I've read that cork is a good vibration absorber.

Any thoughts on the efficacy of this welcome.

Starlight 18th August 2019 05:35 PM

Ideally you would dampen the speaker so that vibrations are not transferred to the cabinet. This means finding a material that would be partially (but not fully) compressed by the weight of the speakers. I do not know how you can tell whether the cork is partially compressed.

It gets difficult to know what to recommend when the budget does not stretch to £15. I would suggest saving up for a pack of sorbothane hemispheres of the correct size and durometer that will suit the weight of your speakers.

PJAcoustics 18th August 2019 11:48 PM

Cork is quite common in products marketed as vibration isolators. Typically a compressible medium density cork. If you were to use say, a cork drinks coaster, this would probably be too rigid.

You've already bought the cork... does it seem to work to you?

Otherwise, a rubber material, or neoprene is a good option.

I reckon cutting up a decent mousemat would do the trick, try it (before cutting!) if you've got one lying around.

All the best
Chris from ParkerJones Acoustics

Soundman2020 19th August 2019 06:38 AM

As Starlight said, the material has to be compressed by the right amount in order to isolate the speaker properly.

Think of it this way: the cork (or any other isolator) is acting as a spring, and you want it to be just "bouncy" enough that it really does isolate. In terms of cars: if you look at the suspension of any car, truck, bus or whatever, you will find springs. That's what makes the ride pleasant, so that the vibrations bumps and dips in the road don't make it into the car. But you can't just use any old spring you feel like! If you take the spring out of a Smart-car suspension and try to use in on a 20 ton truck, obviously the weight of the truck will squash the spring totally flat: it won't isolate that truck from the road at all. And if you do it the other way: take the spring out of the truck and put it in the Smart-car suspension, and it won't be springy at all! It's way too solid for that, and the tiny weight of the Smart Car does not compress it at all. So once again, no isolation. If you don't use the right spring for the right job, then either the spring is overloaded with too much weight and "bottoms out", or it is under-loaded with not enough weight, and "tops out". Either way, it does not isolate.

The same with speaker isolators: You have to get the right amount of spring compression (technically, it is called "static deflection", not "compression", but it's basically the same thing) for the weight of the speaker. If your speaker is too heavy for the isolation pads, then you over-compress them, they bottom out, and they don't work. And the other way too: If your speakers are not heavy enough for the pads, then you under-compress them, they "top out", and they don't work.

So how much compression do you need? That depends on the type of spring, but as a general rule an isolation mount needs to be compressed about 10% to about 25% to be in the range for good "springiness" and good isolation. In other words, if your cork pads are 10mm thick, then when you have the speaker siting on top, they need to be compressed down to about 8mm thickness or so (2mm compression over 10mm is 20%). You can measure that with a ruler if your pads are thick enough. If not, then you'll need a micrometer.

But that's not all! There's more to it than that. Just because you got the right compression does not mean that you'll get good isolation: With the wrong compression it is guaranteed that you won't get any isolation, but even when you have the right compression, there's other factors to be considered as well, that are inherent to the nature of the "spring" that you are using: cork is not the same as rubber, is not the same as a a coiled steel spring. Factors such as internal damping, compressive stiffness, dynamic sheer, and other things can change the way it works in practice. One key factor in all of this, is frequency: your pads need to isolate properly down to at least an octave lower than that the so-called "cut-off" frequency for the speaker.

So MAYBE your cork pads are working... but likely they are not. They same would be true from chopped-up mouse pads, unknown bits of rubber, packing foam, or any other material that does not have the right characteristics for decoupling speakers. Beware of such silly advice not based on facts, science, or reality. And ignore all other advice from the same sources, too! Caveat emptor...

Personally, I pretty much always use Sorbothane pads for the speakers in rooms I design, as it's a rather amazing material. It has high damping, and very good isolation. There's nothing better that I have found for decoupling speakers. You can buy sell self-adhesive Sorbothane "hemisphere" pads that you can stick to the bottom of your speaker, but you have to get the right type! They have different types of Sorbothane with different properties ("durometer rating"), depending on the weight of your speaker, so first weigh your speakers, then buy the correct pads for that weight.

- Stuart -

Apebot 19th August 2019 09:21 AM

So much good advice, thanks all!

My speakers are 7.98kgs (Dynaudio LYD7s)

These Sorbothane hemispheres: https://www.amazon.co.uk/Fonotek-Sor...6&sr=8-10&th=1

have a 50 durometer rating and claims to be great for 'audiophiles'. Any thoughts?


This product is a lot cheaper than many other alternatives out there. I'm guessing the more expensive you go, the law of diminishing returns starts to creep in?

bert stoltenborg 19th August 2019 09:28 AM

Quote:

Originally Posted by Apebot (Post 14156857)

This product is a lot cheaper than many other alternatives out there. I'm guessing the more expensive you go, the law of diminishing returns starts to creep in?

Yes, and sometimes the law of snakeoil & bullsh*t. :)

These things are 3,76 to 7 kg each.
Your speakers are 8 kg, so you could put something with a weigth of 20 kg (a tile?) under the speaker

Adhoc 19th August 2019 06:07 PM

Those in the ad aren't the best for your light weight speakers, -as Stuart wrote the isolator foot needs a certain deflection to work well. Also, not mentioned above: Most speakers are "front heavy" which if you are really nerdy and picky about it, means the feet at the speaker front should have a larger contact area and / or a harder rubber than the ones at the back. With your small speakers it will not matter much but for those with large and heavy speakers it can be essentiai to find out centre of gravity for the speaker so it stands horizontal and doesn't lean forwards if all feet are identical and placed symmetrical versus the speaker's foot print.

Starlight 19th August 2019 10:40 PM

Apebot, these would be suitable as they will support from 4 to 8kg per set of four.

yewtreemagic 20th August 2019 12:42 PM

Quote:

Originally Posted by Adhoc (Post 14157717)
Those in the ad aren't the best for your light weight speakers, -as Stuart wrote the isolator foot needs a certain deflection to work well. Also, not mentioned above: Most speakers are "front heavy" which if you are really nerdy and picky about it, means the feet at the speaker front should have a larger contact area and / or a harder rubber than the ones at the back.

Regarding 'front heavy' loudspeakers - I've always used three feet for mine (two at the front, and one at the back forming a triangle), which should hopefully resolve this issue in most cases kfhkh


Martin

Apebot 20th August 2019 04:42 PM

Quote:

Originally Posted by Soundman2020 (Post 14156741)
As Starlight said, the material has to be compressed by the right amount in order to isolate the speaker properly.

Think of it this way: the cork (or any other isolator) is acting as a spring, and you want it to be just "bouncy" enough that it really does isolate. In terms of cars: if you look at the suspension of any car, truck, bus or whatever, you will find springs. That's what makes the ride pleasant, so that the vibrations bumps and dips in the road don't make it into the car. But you can't just use any old spring you feel like! If you take the spring out of a Smart-car suspension and try to use in on a 20 ton truck, obviously the weight of the truck will squash the spring totally flat: it won't isolate that truck from the road at all. And if you do it the other way: take the spring out of the truck and put it in the Smart-car suspension, and it won't be springy at all! It's way too solid for that, and the tiny weight of the Smart Car does not compress it at all. So once again, no isolation. If you don't use the right spring for the right job, then either the spring is overloaded with too much weight and "bottoms out", or it is under-loaded with not enough weight, and "tops out". Either way, it does not isolate.

The same with speaker isolators: You have to get the right amount of spring compression (technically, it is called "static deflection", not "compression", but it's basically the same thing) for the weight of the speaker. If your speaker is too heavy for the isolation pads, then you over-compress them, they bottom out, and they don't work. And the other way too: If your speakers are not heavy enough for the pads, then you under-compress them, they "top out", and they don't work.

So how much compression do you need? That depends on the type of spring, but as a general rule an isolation mount needs to be compressed about 10% to about 25% to be in the range for good "springiness" and good isolation. In other words, if your cork pads are 10mm thick, then when you have the speaker siting on top, they need to be compressed down to about 8mm thickness or so (2mm compression over 10mm is 20%). You can measure that with a ruler if your pads are thick enough. If not, then you'll need a micrometer.

But that's not all! There's more to it than that. Just because you got the right compression does not mean that you'll get good isolation: With the wrong compression it is guaranteed that you won't get any isolation, but even when you have the right compression, there's other factors to be considered as well, that are inherent to the nature of the "spring" that you are using: cork is not the same as rubber, is not the same as a a coiled steel spring. Factors such as internal damping, compressive stiffness, dynamic sheer, and other things can change the way it works in practice. One key factor in all of this, is frequency: your pads need to isolate properly down to at least an octave lower than that the so-called "cut-off" frequency for the speaker.

So MAYBE your cork pads are working... but likely they are not. They same would be true from chopped-up mouse pads, unknown bits of rubber, packing foam, or any other material that does not have the right characteristics for decoupling speakers. Beware of such silly advice not based on facts, science, or reality. And ignore all other advice from the same sources, too! Caveat emptor...

Personally, I pretty much always use Sorbothane pads for the speakers in rooms I design, as it's a rather amazing material. It has high damping, and very good isolation. There's nothing better that I have found for decoupling speakers. You can buy sell self-adhesive Sorbothane "hemisphere" pads that you can stick to the bottom of your speaker, but you have to get the right type! They have different types of Sorbothane with different properties ("durometer rating"), depending on the weight of your speaker, so first weigh your speakers, then buy the correct pads for that weight.

- Stuart -



The spring analogy has been fantastic for me to help wrap my head around what it actually happening when you put a speaker on a thing.

Plus I used to have Smart car, the suspension on those things is horrendous - I would imagine now it's 'bottoming out' - thanks!

dinococcus 20th August 2019 04:55 PM

Quote:

Originally Posted by Apebot (Post 14155562)
Needing a cheap alternative to bought speaker dampeners I sliced a cork into 9 rounds and placed 3 rounds under each of my front speakers (L,C,R).

It's raised them from the wood cabinet they were on, and I've read that cork is a good vibration absorber.

Any thoughts on the efficacy of this welcome.

As explain by Northward, this is more complex. The better is to do nothing if you can't do following the state of the art.
You could search the Northward's post.

Apebot 20th August 2019 05:09 PM

Quote:

Originally Posted by Starlight (Post 14158217)
Apebot, these would be suitable as they will support from 4 to 8kg per set of four.

Got it, very useful - thanks!

Soundman2020 20th August 2019 05:33 PM

Quote:

Originally Posted by Apebot (Post 14159365)
The spring analogy has been fantastic for me to help wrap my head around what it actually happening when you put a speaker on a thing.

Plus I used to have Smart car, the suspension on those things is horrendous - I would imagine now it's 'bottoming out' - thanks!

Great! Glad it was helpful. I think simple analogies to every-day situations often help to understand complicated principles in acoustics. A LOT of things in acoustics are not intuitive, but simple analogies (even if imperfect!) can help to get your head around what is actually happening.

- Stuart -