Isoacoustics Stands VS Primacoustics Recoil Stabilizers

[iasomph]

I recentrly upgraded my Auralex Mopads with Primacoustics Recoil RX-5 in order to further reduce resonancies of my Adam A5x monitors with my large (and not really heavy) desktop. I'm 50% satisfied, because it improvved transients and decouple monitors a bit better, but I still feel some vibrations (especially bass and kickdrum) on the desk .

My question is: are the Isoacoustic Stands (ISO-L8R155) better in this regards? Would they improove the isolation from the desk, compared with Primacoustics?

I know Primacoustics are regarded as one of the best desktop monitor stands (and this is why I bought them, the RX-5 model to be precise) but these Isoacoustics are pretty new on the market, and didn't find any trustable A/B test between them.
Would be nice if someone tried them both and can tell me which one is better, especially regarding decoupling / vibrations.

I really like to understand if some vibrations are inevitable on the table, or if I can improove my sound buying the Isoacoustics

Thanks for your advice!

[Dynamic Mike]

I really like to understand if some vibrations are inevitable on the table, or if I can improove my sound buying the Isoacoustics

Even if you could persuade your speakers to float, your desk would still have a resonant frequency. I've experienced my desk vibrating even with completely decoupled wall mounted speakers.

[iasomph]

Thanks for the reply Mike.

Even if some vibrations still have to pass (even if the speakers would float in the air), it would be great to find which of the 2 solutions offer the best results on this problem

Anyone tried both Isoacoustics and Primacoustics?

[Guy Johnson]

Put rubbery carpet underlay on your desktop, then a layer of plywood the same size, maybe 18mm thick.

[Hugh Robjohns]

I suspect your A5x's are too too light to compress the foam in the recoil sufficiently to maximise it's damping. After all, the Recoil RX5 is designed to cope with speakers up to 15kg, and your A5Xs are less than half that.

Adding some extra mass will probably help -- a heavy floor tile or another slab of metal, for example -- with something like a sheet of kitchen surface protector to grip the speaker to the additional mass.

Provided the loading is sensible, I've not found anything better than the REcoil Stabilisers for this kind of application.

H

[iasomph]

Hi Hugh,

thanks for your points. But this arises some doubts in me, because this statement is in contrast with the explanation given on Primacoustic website. Reading Primacoustic website, they say:

"After extensive listening tests, we have found that a 4:1 ratio is the minimum mass required to properly stabilize a monitor. So if you have a near field monitor that weighs 20lbs (8kg), you would select a Recoil that has a mass that is no less than 1/4 the weight or 5lbs (2kg). To make selection as easy as possible, we have also provided a cross reference that is sorted by manufacturer and model". (http://www.primacoustic.com/recoil-use.htm )

So, considering that the Adam A5x weight is 6.5kg, and the RX-5 is 2.5 kg, the weight ratio should work perfectly (mass ratio is 2,6:1 , a big margin compared to the limit of 4:1). The problem would be if the monitor would weight more than 10 kg...in that case, the recoil would be too light to work effectively.

The other consideration I'm doing is: Primacoustic made different sizes for different monitors, so it would sound strange to me that after spending 160 euro for a couple of Primacoustic targeted for my Adams A5x, I still have to make some work, cut the steel and add weight. At this point...why spending 160 euro if I still have to make some work on them? And why Primacoustic targeted the RX-5 model(2,5kg) for my Adams A5x?

Am I missing something?

[Hugh Robjohns]

Just offering a suggestion based on my experience of using them...

At the end of the day you're trying to make the best of a bad situation. Speakers work best if mounted securely and rigidly in such a way that they can't move, and cant pass any vibration into anything else -- which typically means good floor stands.

If you're mounting speakers on a desk or shelf you usually need to prevent the passage of vibration into the desk or shelf, and that's where the idea of a 'damped isolation mount' comes in.

Devices like the mo-pad and Recoil work as a mass-spring-mass system, with the foam providing the spring... except that it really only becomes 'springy' when it has been compressed... hence the suggestion to add more mass to the speaker side -- which is why the sheet steel is there already, and why the recoil design generally works better than the straight mo-pad!

hugh

[iasomph]

Hi Hugh,

don't get me wrong, I'm really happy that you give me your advice. I'm here to ask for receiving precious advices from people that know more than me

I just found not so nice that a desktop stand that cost 150 euro needs further work to work at its best. Would not be better if they already use heavier steel plate? Or advised for a different mass Speaker/stand mass ratio (maybe 2:1 instead of 4:1) ?

I find pretty bad that they have different size for different monitors, if at the end the smaller ones don't work as expected... if they say that a ratio of 4:1 works, a ratio of 2,5:1 should work even better...but it seems it's not my case.

Maybe some vibrations are normal and cannot be completely avoided. It's possible that I am too exigent too, but I expected an almost complete vibration dumping in the moment I spent 150 euro for a couple of foam with heavy steel on them. just this.

[Hugh Robjohns]

I just found not so nice that a desktop stand that cost 150 euro needs further work to work at its best.

Everything in audio needs further work to get the bet! Speakers wont give their best unless you invest in appropriate acoustic treatment for your room. A mic won't give it's bet unless you buy a good shock mount and pop shield. Isolation mounts need to be optimised carefully to the speaker... It's just he way it is.

Would not be better if they already use heavier steel plate?

Maybe, Yes... But that would also add significantly to the cost, both in materials and shipping costs.

Or advised for a different mass Speaker/stand mass ratio (maybe 2:1 instead of 4:1) ?

They obviously advise on what they think is a good, cost effective, solution. I'm just suggesting how you might make a cheap and simple alteration to address the particular situation you described specifically because you aren't happy with the way the recoils work as supplied.

Maybe some vibrations are normal and cannot be completely avoided.

This is true -- just as a car's suspension doesn't isolate and remove all vibrations as you drive down the road. All mass-sping-mass systems work over a finite frequency bandwidth, and with finite efficiency. None are perfect and none remove all vibrations at all frequencies completely.

H

[alexis]

I suspect your A5x's are too too light to compress the foam in the recoil sufficiently to maximise it's damping. After all, the Recoil RX5 is designed to cope with speakers up to 15kg, and your A5Xs are less than half that.

Adding some extra mass will probably help -- a heavy floor tile or another slab of metal, for example -- with something like a sheet of kitchen surface protector to grip the speaker to the additional mass.

...

I realized that when I read this the first time a few days ago there was something that didn't seem to add up in my mind …
If these tools are meant to decouple the speakers from everything else, it just seems counterintuitive to me to be trying to **increase** the degree of coupling by putting weight on top of the speakers, just so the Recoil Stabilizers can be given a chance to **decrease** the coupling. As pointed out in the thread, even the best design is less than ideal, so some of that increased coupling is going to sneak through the system, where it wouldn't if the weight hadn't been added in the 1st place. Whether that would affect what we hear depends on how ideal the system is, but I can't help thinking adding weights is going in the wrong direction Awaiting the for when it's pointed out where the fallacy in my thinking is - thanks!

[sambrox]

The extra weight goes on top of the Stabilizer or acoustic pad, and under the monitor. Then you need, as has been suggested, something like Blu Tac to stop the monitor moving about on the tile or whatever you've used as the extra weight. The theory (correct me if I'm wrong, Hugh) is to compress the foam of the pad, making it denser and harder for the bass vibrations to travel through.

Cheers,
Sam

[Hugh Robjohns]

The foam is intended to work as a spring, but it can only do that if it is placed into a spring-like state. The nature of the foam block is that it has a natural rest state where it is 'relaxed' -- just like an unloaded spring -- and in such a state it doesn't follow the properties associated with Hooke's Law.

Just like the springs in the shock absorbers in your car, they need to be compressed into their working range before they work as intended.

If you imagine a light car sitting on very stiff springs, any vibration from the road will just be passed straight into the car and its occupants, and you'll get shaken to bits as you drive along. The springs have insufficient compliance to absorb the vibration energy, so they just pass it on.

In contrast, if the car is heavily loaded, the springs go into compression, and now they absorb a lot of the bumps and dips in the road, giving the occupants a much smoother ride because the vibration energy is absorbed in the spring as it compresses and relaxes.

Foam-based speaker dampers work the same way -- and if they are insufficiently loaded it's like an empty lorry bouncing along the road where the vibration is passed straight through from the road to the lorry cab -- or from the speaker into the shelf or desk.

Load the foam properly, so it starts out partially compressed and spring-like, and it works like a properly loaded lorry, where the springs absorb the energy, giving the load a much smoother ride... and stopping any speaker vibrations from reaching the shelf or desk.

It ain't rocket science... but it is science!

H

[sambrox]

Ah yes. This!

Cheers, Hugh.
Sam

[alexis]

The foam is intended to work as a spring, but it can only do that if it is placed into a spring-like state. The nature of the foam block is that it has a natural rest state where it is 'relaxed' -- just like an unloaded spring -- and in such a state it doesn't follow the properties associated with Hooke's Law.

Just like the springs in the shock absorbers in your car, they need to be compressed into their working range before they work as intended.

If you imagine a light car sitting on very stiff springs, any vibration from the road will just be passed straight into the car and its occupants, and you'll get shaken to bits as you drive along. The springs have insufficient compliance to absorb the vibration energy, so they just pass it on.

In contrast, if the car is heavily loaded, the springs go into compression, and now they absorb a lot of the bumps and dips in the road, giving the occupants a much smoother ride because the vibration energy is absorbed in the spring as it compresses and relaxes.

Foam-based speaker dampers work the same way -- and if they are insufficiently loaded it's like an empty lorry bouncing along the road where the vibration is passed straight through from the road to the lorry cab -- or from the speaker into the shelf or desk.

Load the foam properly, so it starts out partially compressed and spring-like, and it works like a properly loaded lorry, where the springs absorb the energy, giving the load a much smoother ride... and stopping any speaker vibrations from reaching the shelf or desk.

It ain't rocket science... but it is science!

H

Thank you, Professor!

[forumuser837953]

FWIW, there would seem to be many interpretations of that 4:1 recommendation getting about across various fora. The following is a response from Jay Porter at Primacoustics to my question about this:

There has been some discussion on web fora about the need to suitably ‘compress’ the recoil stabilizers with enough weight for them to work efficiently. On the other hand, your site recommends the 4:1 ratio where the minimum mass of the stabiliser is no less than 1/4 the weight of the monitor. The two views seem slightly at odds. In any case, I have read all of your material and the FAQ and don’t really see the following question answered and wondered if you might advise?

I’m considering RX12s primarily because these neatly fit the entire dimension of my meter bridge(s). Three speaker systems live there: SE Munro Eggs, some small Genelecs and the L&R of a Logitech 5.1 system. All of which doesn’t weigh that much, perhaps 12kg or so in total.

Would the RX12 be suitable for this application, where the weight bearing capacity of the Stabilizer is far greater than the weight of the monitors combined. I would have thought the extra weight and steel would have helped, but can’t really see a scenario where this is mentioned.

Hello Paul,

Thank you for your interest in the Recoil Stabilizer. We have found that in testing, the less you compress the foam the better the performance. The most important part of the Recoil is the ability of the steel plate to stabilize the speaker, whereas the foam is there to decouple the entire platform. If you compress the foam too much, it will no longer isolate the platform as well as it should. This is why we do not recommend exceeding the 4:1 ratio for optimal performance. Using an RX12 for your 3 speakers is perfectly reasonable, and I am sure you will love the result.

Let me know if you have any other questions, otherwise have fun!
Jay
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Jay Porter
Radial Engineering/Primacoustic
1588 Kebet Way, Port Coquitlam, BC V3C 5M5, Canada
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