It's a subject I don't totally understand -to say the least, since it can be very technical. But I want to learn to do it right.

First, here are 2 great threads about the subject, covered mainly by Thomas JJ/Northward. All quotes from this message are from these threads.

Does speaker stand quality matter?

Testing Loudspeaker Isolation Products

If there are other threads I missed that could enlighten me please, post them.


Let's resume the most basic thing here (please correct me if I'm wrong):

• The first thing is to have the heaviest stand we can get (to get some MASS)?

Is it to reduce mechanical transmission of vibrations?
More mass = less transmission?


Thomas said

1. "Low budget: go for Blu-tack and DIY damping!"
   [...]
2. A key to having all this work well is to also make sure the surface the speakers decouplers are resting on is as stiff as possible"
   [...]
3. "Sylomer and springs + dampers remain by far the best products to use but need fairly heavy loads. With properly implemented systems, you can have a natural frequency as low as 8Hz with Sylomer and 4Hz with springs + dampers, decoupling effectively way below 20Hz"

1.What is Blu-Tack exactly?
By damping, does Thomas mean "adding mass"?
Since "Blu-Tack: no decoupling, only some limited surface damping in the higher midrange." Thomas JJ.
I presume adding some Blu-tack to a very heavy stand (like full of sand?) is not enough.


3.What kinda of Sylomer? When I google Sylomer, I get ton of results.
Is spring necessary? Or is it depends on the weight of speaker?
Mine are 15kg (Adam S3X-V). Are springs necessary/useful in that case or even counter productive?


Here is a freestanding speaker from Northward (not sold yet...I think!)


*Real* freestanding speaker decoupling system designed by Northward Acoustics (Northward Systems) tested and built like a tank for us by our friends at AMC in Spain. Variable Push-pull system with Springs+damper and Sylomer used for full bandwidth efficiency. Unit will be placed on top of a dedicated speaker stand. Range from 30kg with f(n) 8.00Hz (e.g. ATC SCM20 ASL) to 75kg with f(n) 5.16Hz (e.g. ATC SCM110 ASL). Some further testing needed, but ETA of final product should be late September.
More about it here


All these principles can be applied to sub?

Sorry, lot of questions, I don't ask for long answers. It's a very interesting subject, but like other topics in acoustics, we can read anything on the Internet...

AMC | Vibration Isolator Pro

Ah yes I saw you mentioning it! Thanks for the reminder!
I just get a new phone! couldn't download the app with my older one... will test it!


Another related question:

Let's say my door is vibrating (at a specific frequency) when speakers play loud.

Is it because of bad decoupling? Or just the acoustic pressure (not sure if it's the right term, probably not)? both?

Could be both yes (pressure variation at boundary and/or structural transmitted vibration from elsewhere).

Sorbothane hemispheres are the best thing for this. Get a set that are rated for your speaker weight. They cost about $30 USD for a set. They’ll stop 99% of the vibration that is being lost through whatever surface your speakers are sitting on and make them sound a lot better!

Thanks, can you recommand some?

When I google I get ton of results. Hard to say from me, since I don't know anything about it.

From Northward, regarding Sorbothane:

Sorbothane: can be very efficient if the right type for the load is used. Best is to add a dummy load (heavy blue stone) under the speaker to add mass to the system that needs decoupling and to be able to use stiffer Sorbothane pads to avoid unwanted cabinet movements at higher SPL. You also must pay attention to loading of the Sorbothane since speakers are usually front heavy. Calculating load spreading is a must, unless the weight of the added dummy load is many times fold the one of the speakers at which point the difference becomes negligible.


Even after reading it, I still don't know where to look for the right Sorbothane.

What speakers are you using? How heavy are they?

Adam S3X-V : 15kg (33lbs)

Adam SUB 12 : 26kg (57,3lbs)

So for each 33 lbs speaker you want 4 hemispheres that are rated for about 8.25 lbs each. Same for the sub, divide it’s weight by 4.
Here is the guide:
https://www.sorbothane.com/Data/Site...othane-SPG.pdf

Find the appropriate hemispheres here and then order them from isolateit.com or amazon.

You will likely dampen, not decouple with sorbothane. Although crossover frequency will play a role.

DIY Cinder block monitor stands

^ Good thread link!


I have been asked about energy transmission in the past as it is assumed that Sorbothane is merely converting physical vibration energy into heat and therefore not providing as much benefit as they claim but in my experience, this is simply not the case. Conversion to heat my be occurring but a before/after frequency response test will confirm that the efficiency is negligible.

As a cinema designer/installer I use Sorbothane in every project I do, 5-10 theaters a year, around the world. It really is great stuff!

I've given some to friends in the past, especially when they have floor standing hifi speakers. Often they claim that they sound like totally new speakers due to suddenly hearing all of the low end they were transmitting through the floor previously.

I can't recommend it enough for this application.

Another thread, Jh Brandt and Thomas have interesting posts

Floating Floor Rubber


I'm getting even more lost.

Will try the app Jens post tomorrow.


Anyone has tried it? What are your results?

I have the app on my phone. It takes a LOT of mass to get a spring with a natural frequency low enough to decouple @20hz.

But, since youre using a sub, if you set the crossover high enough, you dont have to get so low

How lot is a lot?

Idk, for example, i just punched in 100kg load on one isolator with 100% decoupling at 20hz and it returned zero results. Its a free app. Play with it. I installed it and quickly realised it was not going to be practical to shoot for decoupling in my room with my budget.

Hmmm, maybe im just dumb.

50kg at 95%@5hz returns results.

Perhaps 100%@20 is impossible, i tested up to 400kg with no results

For the record, it is possible to use Sorbothane to decouple most speakers down to well below the cutoff frequency. I have used a technique for doing that in many of the soffits that I have designed, and it works. I won't say it is easy to do (it isn't... lots of math), careful construction, etc.), and I won't be going into the details of how I do it, but for those willing to try, you can probably figure it out. As Jens mentioned, you do need to get the natural frequency below about 15 Hz for most speakers, and that can be done. Just one word of warning: Sorbothane has put out two different calculators for figuring all of this out, and they do not agree with each other, nor with reality, unfortunately. The original V1 calculator was way off, so if you are using that, forget it. The newer V2 calculator is a bit better, but still not accurate in predicting deflection from load and the characteristics of the Sorbothane... so don't trust what the calculator tells you. It's best to use the published equations for figuring it out. Yes, you do need a lot of deflection to get down to low natural frequencies. Yes that can make the speaker unstable if you put four thick feet under it. Yes there are ways of getting around that... but that's all I'm prepared to say...

Yes Soundman, I understand you can't publish it on public forum.

The goal is to DIMyself with low budget.

Getting the better result I can get based on cheap materials needed. Avoiding making mistakes. Will keep on read it! Thanks!

?!!!

Does that mean when Thomas uses it, he adds mass to the speakers in order to get the right weight/pressure on springs?
Thought the deflection is used for it?

400kg is A LOT!

Will keep reading.

That's why we use hefty dummy push/pull loads on the Z axis. And custom designed & built high pressure pre-constraint dampers for the X & Y axis since you can't dummy load on these axis. At least not in a practical way.

I'm afraid the more I read, the less this spring+damping solution can't be applied to DIY guys like me. Specially with these lightweight speakers.

Let's go for the basic, is a solid and heavy stand full of sand a good start?

Yes, this is getting deep!

I'd go for some solid stands with heavy fill and Sorbothane feet for the speakers.
I think you'll get great results going that route and save some cash and sanity in the process.

Most of this is for flush mounting. Bracing for xyz isnt practical for stands.. If youre going on stands, either put the light weight monitors on massive stands and decouple the stands from the floor. Or, dampen the speakers on top of massive stands. You can also hang the speakers from springs on a massive base. Personally, i went with sorbothane hemispheres under the speakers, and then adjustable sorbothane bumpers to stabilize them along the other axis inside my enclosure. Since I'll be using subs with a crossover around 100-180hz i only need to decouple to around 50hz.

I might go for this solution:



Cinder block stand, filled with sand + AMC sylomer Pad 110 (25mm) (3 or 4) between stand and speaker.

Sub will be on the floor with 4 Pads.

You can check AMC Sylomer pad here:
sylomer pad | AMC Mecanocaucho

Main date here:



My question is: Do these pads work with such light weight (15kg in my case)?

Seems to good to be true.

Don't do it - that won't work. You will get substantial rocking mode issues (hence HF distorsion) due to the pads being too soft and unevenly loaded... And with a way too high f(n). You'll trade a given set of problems for another set of problems. This problem very much exists with Sorbothane too. It's hard to measure unless you have special equipment.

Check further data about Sylomer in their tech data PDF, the form factor bit and the elasticity modulus etc. That will explain why very clearly.

Filling stands with sand seldom helps with anything: it's not because you make something heavy that it helps with decoupling on its own. If you want to dampen the stands (which is different from decoupling) there are easier ways to do that than with sand.

All a stand needs to be is like a good structural column/beam. You need it strong, non-resonant and very rigid so the loads are properly transmitted to the 3 or 4 feet and then the structural floor with minimal elasticity in the system. The only reason you'd want added weight on top of rigidity is for decoupling interface loading so you optimize the static to dynamic loads. That is, if you decouple between the floor and the stand (which in your case is what needs to happen so you can reach much lower f(n) while using much stiffer springs which will eradicate the rocking mode issues). If you decouple between the stand and the speaker added weight won't do much - all you need is rigidity so the decoupling interface is the compliant element, not the stand.

Basically you want the dynamic load (speakers) comparatively low to the static load (rest of the assembly) and be as close as possible to critical damping factor of the system. Then you will achieve much less residual modes.

Damping ratio - Wikipedia

Without an all axis decoupling system (X/Y/Z) it's not because you filter your mains so they dont play e.g. under 80Hz that the rocking mode won't happen. The rocking mode in this case is triggered by the f(n) of the spring itself as it stores energy and releases it, not by the speakers necessarily playing that specific frequency. The answer to that is mentioned higher up: Static vs dynamic. See what I mean?

OK. Many many thanks Thomas. Been reading a lot.

Lot of terms to digest:

-Rocking mode
-Dynamic load
-Static load (and the relation between the two)
-Form factor

First, I mixed up damping and decoupling. Difference is still not very clear. But I'm on it!

Some shorts definitions found here on GS (might help others as well!) (copy paste on google to found the original post if needed):

Added mass has to be substantial, many times the weight of your speakers: you want the ratio of static load to be high. And load repartition fairly even.

Damping is in short reducing the ability of a given material to store and release mechanical energy elastically. Sturdier stands won't do that. Although it won't hurt.

Damping is usually done by layering structural parts with materials having particular properties (viscosity for example) that will reduce mechanical transmission with the structure. Like a layer of EPDM on steel.

Damping is reducing the ability of waves to travel within a given materiel/unit. But it does not stop vibrations. It just reduces the amplitude (and hence, risks of re-emission further down the line).

f(n), f(n)x√2 ) : transmission factor = or >1 (amplifying or inefficient)
> f(n)x√2 : transmission <1 (decoupling).

It is not decoupling.

Decoupling is preventing vibrations from travelling from one unit to the other altogether.



About form factor:
"It is the ratio between the area of circumference x thickness and loaded area (one side). A circular disc of Ø 4 cm has an area of 12,57 cm², a square piece with the same area has a side of 3,55 cm. The total circumference x thickness areas are different though, larger for the square one. (If I remember correctly, the circular disc behaves "softer", compresses /deflects more easily with the same load applied. This is explained a bit if one digs deep down into Getzner's technical diagrams.)"


I read more about tech data on AMC website.
I understand the dynamic load to reach lowest f(n).

I'm still confused about the dynamic/static ratio.

Thomas, why did you chose to mount several individual springs (like V-SH series) on your speaker stand, rather than using 1 single 'spring system' using 3 or 4 springs (3V-SH series or 4V-SH series)?

The system is custom built for Northward. So it's optimized parts wise.

It's a push/pull, so it's a different design than what you're trying to achieve and requires to be strong structurally due to the high pressure within the system.

Thomas, you exclusively do flush mounted mains though, don't you? I believe JayPee wants to use stands. What is the best option in his case? Decoupling seems like its next to impossible using stands.

The best option is the freestanding speaker decoupling system by Northward heh

I'm eyeing AMC products but I have no idea how much would they cost.

Even if at the end I can't make it because of lack of $$ and knowledge, it's great reading and learning

Heh, i see. So you're using another hanging type decoupler upside down to pull down on the other springs to acheive appropriate compression? Pretty dang smart.