Vibration Air & Roller Bearings - Thanks to Barry & Warren

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2 hours ago, Solstice380 said:

I got inexpensive concave/concave ones off Amazon to try.  I thought the plano/concave were a little small at like 35 mm diameter and a little pricey.  Unless you are supporting speakers they shouldn’t deflect under the component weight.  

 

I work in the vibration arena industrially and I’ll have some interesting measurements completed in the next week on these lenses and various cones, etc.  Both the natural resonances and through transmission will be evaluated.  I also have  steel and ceramic balls I’ll look at. 

Cool. The Silicon Nitride balls are cost effective, then there is the roundness etc.... lots & lots or variables. 

 

I settled on Barry’s reccomended aluminum (7075) with 2” diameter bowl cut and Silicon Nitride balls — tried SiC but couldn’t hear a difference. 

 

Real measurements woujd be interesting. 

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4 hours ago, Solstice380 said:

 

What size are your balls?  Hahaha, the isolator ones.  And where did you source them?

 

 

Generally 12mm or 1/2 inch.

 

The other material to check out is Tungsten Carbide

The quality that I've used is G5 and G10

 

You have to look around to get good prices -- ebay often has SiN from Hong Kong/China if you want to take a chance... not always bad if the prices are good.

 

the best place: craigballsales.com but they don't always have a wide range of product. really good site if they have what you are looking for (I assume they are reselling overstock)

 

I got access to military grade SiC -- super round  but frankly couldn't hear a difference and, well, these get expensive but if you don't mind shelling out $20/ball you can get the regular grade once (?G5/G10)

 

If you can do regular measurments, the area that really needs improvement is the vertical isolation, nonlinear springs etc. I think, you know, that super duper horizontal optimization with crazy expensive materials, is frankly not worthwhile unless a reasonable degree of vertical isolation is also done. Sort of like going crazy on voltage noise supression when youve got a ton of current noise etc.

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9 hours ago, GUTB said:

 

https://en.wikipedia.org/wiki/Constrained-layer_damping

 

Let me clarify: you called Symposium "the only game in town" which is frankly ridiculous and absurd. 

 

There are a gazillion vibration damping systems that use viscoelectric materials, including the inner tubes in Barry's design. This is all old news. What these techniques, as well as traditional springs etc. fail to do is damp low frequency vibrations ... and those have the highest amplitude in the real world (1/f phenomenon).

 

Now, Symposium looks to be a fine product and I have to criticism about what it does for horizontal, nonetheless it hasn't solved the vertical isolation issue.

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5 hours ago, Solstice380 said:

The measuements will yield the resonance frequencies, their relative amplitudes, and the Q (sharpness just like a filter....cuz that’s all a chunk of material is in reality is a band pass mechanical filter, and you can use transmission line theory to describe vibrations in objects).

 

Right. The reason that ball bearings work well is that they have a very low resistance to horizontal rolling and thus can achieve a low resonant frequency -- there's always some resistance to initial motion so the resonance can only approach zero but not achieve.

 

Vertically, a spring and mass are easy to model and understand, particularly the resonant frequency! Consider all materials somewhat spring-like! Now damping, yes damping what's that:

 

Damping is a resistance to motion that reduces the amplitude over time of the vibrating spring BUT as a resistance, it also couples the motion and hence changes the resonance (typically lowers) so while damping seems good from one perspective, really we don;t want it.

 

Consider the rollerball with a fairly violent shaking in the horizontal direction. assume the bowl is entirely flat and very large. The shaking might be entirely decoupled from the equipment, but this equipment will in time migrate horizontally. Not good if it falls off the table -- I've had this happen  

So we have a bowl which constrains the horizontal motion and keeps the equipment centered. At baseline the bowl approaches horizontal and the isolation is excellent. As the amplitude of motion increases, the resistance to roll increases and the damping increases. This is a nonlinearity.

Similarly springs tend to be linear at baseline and nonlinear as they are stretched.

 

The interesting nonlinear springs used in vertical isolation decrease resistance as they go off baseline and thus provide vertical isolation (plug the nonlinearity into the equation

 

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1 minute ago, lmitche said:

It's always about the money!

Oh right, there are professional, active anti-vibration platforms ... got to keep this all in perspective:

 

1) how much to vibrations matter

2) what equipment needs to be isolated

3) how good is "good enough" such that there is no audible or measurable difference

 

The alum bowls that I had made were cheap -- like $20-30/bowl and very high quality. Likewise you can get great balls for not a lot of $.

That allowed me to isolate everything (why not?)

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5 minutes ago, Solstice380 said:

 I use the Herbie’s to address the vertical because the ball/cup make a perfect transmitter - they have about the same acoustic impedance if using metal or ceramic and glass is not much different so there is very little reflection and high transmission.

 

Nice and cost effective to the point where I'll order some!

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3 minutes ago, Solstice380 said:

 

1)  will we ever really know?  

2)  everything with an oscillator circuit?

3)  see 1)

 

Good 1/f noise and phase noise measurements -- that's real work

 

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24 minutes ago, GUTB said:

I found out about these from Audiogon:

 

https://www.herzan.com/products/active-vibration-control/ts-series.html

 

Good stuff. Those are the kinds of specs you want to see.

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6 hours ago, Solstice380 said:

 

Sorry it wasn't clear... why below 10Hz?  Phase noise in clocks?

Well ground vibrations are one of the many phenomena that exhibit 1/f ... there is also a nonlinearity that causes 1/f noise to itself cause 1/f offset phase error ??‍♂️

 

The degree to which this actually affects our audio has not been determined.

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28 minutes ago, Solstice380 said:

 

 

It was the 1/f phase noise that you and others have discussed that I was thinking of.  

Right so 1/f phase offset noise affects audio because all frequencies vary/blur with 1/f offset (close-in).

 

The nonlinearity provides a mechanism whereby 1/f noise gets up converted into 1/f phase offset noise. 

 

The question is to what magnitude that 1/f vibrations affect components — how good does our isolation need to be?

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On 4/11/2018 at 10:29 PM, Ralf11 said:

 

I would also like to know what the audibility of  1/f phase noise is.

 

http://www.silcom.com/~aludwig/Phase_audibility.htm

 

https://www.grimmaudio.com/site/assets/files/1088/clock_jitter_spec-1.pdf

 

and especially : https://www.by-rutgers.nl/PDFiles/Audio Jitter.pdf

 

https://www.by-rutgers.nl/PDFiles/DC-receiver.pdf

 

 

 

 

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Well let's see ... thats what I got made. Tungsten Carbide Grade 10 is common. I paid significantly less than $100 but they need to make a profit. The big cost is the setup for the CNC machine -- the model is simple. and then they need to be polished. My guy would want a bunch made to do a run -- need to buy a 2" cylinder of alu 7075.

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10 hours ago, Ralf11 said:

you used solid blocks of Al, right?

 

his description makes it sound there is an acoustic foam (is there any other kind?) inside the block ("matrix")

 

could buy some and take a bandsaw to them...

 

I dunno if the cup for the balls to rest in is hardened but if it is just Al, then those are trivial to mill - even I could do it (except I no longer have access to a Bridgeport)

 

In Barry Diaments version the Alu bowls sit on 3/4” ply which itself is on inner tube — on top of the balls is a slab of “dull” marble

 

You can easily use a 2” piece of acoustic foam under the bowls. 

 

Dont get me wrong, the Symposium is a very fine product — just that I decided to put roller bowls under all my equipment and so would have been cost prohibitive. 

 

A few  years ago a bunch of folks wanted to do a group buy, but ppl spent endless time debating what to do and there was no agreement to get to a good volume. Ultimately one prototype didn’t have smooth enough polish but we found a local shop which cut a 2” dia sphere into a 2” x 3/4” disc producing a 1” dia bowl with a mirror polish.