Equipment isolation and vibration damping.

[AnotherSpin]

Barry Diament's idea of bowls/balls makes wonders in my set. No matter if it horizontal.

[AnotherSpin]

Just want to add some facts from my own experience. I use privately machined bowls, measures are close to those from Barry. Initially I used first steel balls that I found in a store, slightly smaller than Barry suggest. After couple of months I bought on ebay chrome steel 1/2" balls (posted from US to Ukraine). Even though they are slightly bigger, and slightly better in quality, the change in sound was immediate. Enclosed is a picture with ball 1 (left) and ball 2 (right)

 

[AnotherSpin]

These are close to what Barry recommends (just use one per support instead of two) but made from coated steel instead of aluminum:Model 305 /3 (Platimum)

I was trying some variations and when I was back to following Barry advices in smallest details I was getting the best sound. So, the recipe is:

- slightly inflated bicycle tube;

- thick hard plate;

- good quality aluminum bowls made on Barry measurements, placed in correct triangles, chrome steel balls of correct diameter. No top bowls!

Thats it, guys. Of course, experiments with materials/sizes/designs would theoretically yield further improvement, but, given the costs of machinist labor + materials I stick to Barry ideas.

[AnotherSpin]

Can you give us an idea of how much your custom bowls cost per set ? And about how many sets you got to get that price ?

 

TIA

 

I am in Ukraine. Last year I paid equivalent of less than $100 for two dozen bowls for material+labour. Aluminum used was similar to 6061 (other codes here).

[AnotherSpin]

Can you give us an idea

Why did you ask?

[AnotherSpin]

Theories may sound nothing less than mind-blowing. Any comparison between practical solutions? Please no plastic egg-holders with wooden balls. Teflon? Until we are going to fry our brains.

[AnotherSpin]

Now on to the promised tome on vertical isolation.

 

Horizontal isolation is fairly easy to achieve, a pendulum or good implementation of the ball between hard surface does a good job of isolation down to low single digit Hz range.

 

But how do you do something equivalent in the vertical direction? There is this massive DC bias (weight due to gravity) that you have to somehow overcome. This is not easy.

 

Several years ago I was trying figure what a vertical isolator would do, ignoring for a moment any practical implementation details. What I came up with is a system that is stiff at DC but highly flexible at AC. This is exactly opposite to things like Sorbothane which are stiff at AC but soft at DC. All the "vibration damping" systems I could find had it all backwards.

 

So I asked this question on an internet forum, what material has a high spring constant at DC, but a low spring constant at AC? I was given the answer of a Euler spring (pronounced "Oiler"). This is not a material but a way of using common materials in an unusual way. It turns out it doesn't distinguish between DC and AC per se, but is a HIGHLY non-linear spring. As you increase the force on it the spring constant is extremely high, until you get to a specific threshold, then it transitions into a very low spring constant. This is EXACTLY what we want for vertical isolation. The system is set so the weight of what is being isolated just puts the Euler spring over the threshold into the very low spring constant range. Once you achieve this a very small force causes a large displacement, exactly the same thing as happens in the horizontal mode with the ball and shallow bowl.

 

So what IS a Euler spring? It is a rod or bar of material with the load applied right down the axis. It can be made out of many different materials, steel, brass, carbon fiber, all kinds of stuff. The trick is to arrange things so all the load is perfectly in line with the main axis, ie there is no "bending" force. In the literature this is commonly referred to as the "column". As the force on the column increases nothing happens at first, the material is basically incompressible. BUT at some point something gives, the column "buckles", it bends even though there is no "bending force" applied. This is the special zone. Now a small change in force causes a large increase in the buckling, causing a large displacement.

 

Most people will immediately think of several things wrong with this. First is "that has got to take a LOT of force to cause that to happen" maybe thousands of pounds. For a thick column, quite true. But it doesn't have to thick, take a very thin bar or rod and the buckling can start at very low forces. Then the next thought is, well it will just fall over! Yep, in order for this to work properly the column has to be constrained so the force is always applied completely axially to the column. Making a supporting structure that doesn't interfere with the basic operating principles has been one of the tough challenges with using Euler springs in actual useful situations.

 

The traditional implementation has been a pair of thin bars of metal (say an inch wide and very thin) constrained in such a way that when they start buckling they bulge out away from each other. This helps a lot with the stability, but is still pretty unstable and requires considerably more support structure. A common support is the top of each bar is connected to a long horizontal arm with a hinge at the other end. This keeps things in place and doesn't interfere too much with the operation of the spring. But it is large and cumbersome, not something you would want in your stereo system.

 

Recently (in the last couple years) a new configuration of a Euler spring has been invented which I personally think is going to revolutionize the whole concept of Euler springs and make them applicable to a much wider range of uses. This is the tetrahedral Euler spring. If you are not familiar with a tetrahedron it is essentially a three sided pyramid. The tetrahedron has four sides (a cube has 6), one as the base and three that make up the "sides" of the pyramid.

 

Think of a tetrahedron made out of very thin carbon fiber rods. Take such a structure and place one side on the ground, pointing up is a "point" of the tetrahedron. Now take three of these and place a platform on top of the three "points". It is a nice stable platform. Now start putting weight on the platform. At first nothing happens, but then as you reach the "critical force" the rods in the tetrahedrons start to buckle and the whole platform moves down an inch or so. Now a very small force applied to the platform causes it to move down. Because of the tetrahedral configuration the platform is stable, it doesn't "fall over" or wander all over the place, it just moves up and down. If you get the length and thickness of the rods right you can make the resonant frequency of the system quite low (sub hertz).

 

Now on top of the platform put the shallow bowl and ball bearing we have been talking about and you have a VERRY effective isolation system that works down to the low single digit Hertz range.

 

This generally tends to work better with longer rods, so I came up with a rack with six foot high tetrahedrons, from which are suspended strings holding up a shelf, so the system uses Euler springs for vertical and pendulum for horizontal. It would certainly be a conversation piece in your listening room! You could use these for speakers as well as equipment.

 

Note I have not built a tetrahedral Euler spring yet, my clients keep me too busy designing stuff for them.

 

I have done the traditional "leaf spring" version. These are really weird feeling things, you press down hard then it reaches the threshold and all of the sudden it is "squishy", it is a very bizarre feeling, there is nothing else in your experience that feels this way.

 

BTW the person that invented the tetrahedral Euler spring used them as a protection system for drones. A far cry from stereo systems.

 

John S.

 

John, very insightful reading. What we could try to do in a real world of cheap materials and limited budget with vertical isolation? As an alternative to bicycle tires? Would you share any pictures of your isolation solutions? Thank you.

[AnotherSpin]

 

 

So my final favourite items to place between ALU plates ... ended up being very inexpensive (the $1 Steel Sand filled Door Stops with rubber base) or pricey (the Townshend Springs or Pods).

A better photo below...

[ATTACH=CONFIG]19305[/ATTACH]

 

 

 

 

 

Hi John, what type of sand you prefer? Whiteheaven silica?

[AnotherSpin]

You just don't care, do you?

I do care. About any practical solution that might be useful for those who care. What I do not care is words about words.

[AnotherSpin]

I must add that I always find Barry Diament's posts illuminating and accurate.

+1. Very practical, simple and working ideas. No bullshit from school study-books.

[AnotherSpin]

Bear in mind that this is not an ideal implementation: we could use chrome steel instead of marbles, a smoother and stronger concave surface (even though it's metal), damp the cups better, use a smoother material than the upper platform (bamboo), better couple the speakers to it (we just laid the speaker on top), the speaker is now inches above its initial position, bringing closer to half the roof height whereas 1/3 may have been better), roof reflection effects come into play.

 

 

My initial impressions were close to yours. Space, air, better defined instruments, speakers "disappeared", etc.

I would suggest to avoid bamboo on a top of the balls. If you will go for marble plates, be very careful in choosing not only "non-ringing" plates, but go for hardest you could get. I made a mistake of ordering beautiful natural mediterranean marble plates (not cheap too) to find out they are not hard enough to avoid denting with balls under heavy speakers. Try to float DAC first. I could'n want to be without tires as well.

[AnotherSpin]

The idea isn't to avoid the vertical isolation: it's just the air-cushion under the speakers isn't very stable for speakers in the long term. The speakers are rather elevated and if the air-cushion deflates suddenly and/or non-uniformly, this could cause the upper air-bearing platform to become unstable and the speakers would undergo quite a damaging fall.

 

So, for the speaker, if I can make an alternate implementation for vertical isolation that would be interesting. For the other components, the vertical isolation by inner tube is fine.

 

Yes, I was speaking about the tubes under components. In fact, I found out, that putting the tube under my heavy tube amp gives something to the sound I do not like. So, I do not use tubes under speakers and amp, only balls/bowls. Also, it is quite critical to have tubes only slightly inflated.

[AnotherSpin]

I just rested the HDD flat on a triple cup-and-ball:

 

There definitely is a cumulative benefit: big soundstage and clarity in the mid-to-highs.

 

Choruses are huge.

 

Bass is deep, not boomy.

 

Listening to Alpha Blondy - Jah Victory - La Route de la Paix.

 

 

Yes, it works, I have HDD on alu bowls / chrome balls as well. In fact, I use it under all components.

[AnotherSpin]

It may be easier to find suitable spring-based arrangements for the vertical isolation, not unlike what Townshend does.

 

When you will find easy cheap good looking practical solution alternative to tubes, do not forget to share;)

[AnotherSpin]

Here is a simple and inexpensive implementation.

 

I founds some aluminum discs on ebay, ordered some 50mm concave mirrors and some 1/2" ball bearings. Silicone putty attaches the mirrors to the discs.

 

On the undersurface of the equipment flat mirrors can be attached with putty but it would be easier to use a flat sheet of tempered glass (or aluminum if available).

 

 

I found out by experiments that even small amount of glue would damp the sound. For example, I put a little amount of glue between hard plates and speakers bottoms because contact was not ideal and later found out it damped the sound. Removed glue and good sound was back. Also, I am avoiding glass. Even thin 2 mm alu plates above balls/bowls are good for me, although I am going to get thicker better quality alu plates and maybe go away from bamboo completely as well.

[AnotherSpin]

 

Why avoid glass ? Possibility of fracture ?

 

I was at a local non-chain, well stocked, hardware store yesterday, and noticed some small Stainless Steel sheets (4" x 8" x .018" thick) (about 10cm x 20cm x .45mm). It was next to the brass and SS tubing, so may be from K&S.

 

Barry answered about glass already. Steel - the same issues, I'd prefer to use aluminum here.

[AnotherSpin]

Already did: a large spring would do. If you opt for several springs, you would need to ensure the lowest combined natural frequency.

Can you share a picture(s)? Thank you.

[AnotherSpin]

Check this out, but also check the specs below.

I guess there are many pictures of various springs online... I decided you implemented some solutions at home already. Sorry.

[AnotherSpin]

Actually glass probably works very well. The main problem is that it need to be REALLY smooth. Because of its hardness the ball does not indent the glass very much, which means as it is rolling it will feel a lot of microscopic imperfections. The optical mirrors and lenses are probably quite good because the glass has been highly polished. But a plain ordinary sheet of window glass does not necessarily have such a good smooth surface.

 

John S.

I tried glass several times to support components, and removed fast. In theory I could imagine excellent glass surface, but I am trying affordable DIY.

[AnotherSpin]

I have no real desire to expend a bunch of time listening to different materials when you have already done the ground work -- and you undoubtedly have a much better ear for fine differences than I do that said...

 

Clearly any audio equipment with tubes would have to be a high priority for isolation. Speakers, amps sure ... A computer ... not as much. I am just suggesting that silicone putty may provide a reasonable backing material to 1) mate curved glass to flat metal 2) tone down the glass.

 

Regarding tungsten carbide vs cobalt chrome bearings ... hmmm.... when mated to a ***much*** softer aluminum bowl its really hard for me to see how this would make a difference. Wouldn't it be better to use a chrome steel bowl ... and if not, then maybe harder isn't always better in this application. If "dead" is better than live ... and hence aluminum ... then PEEK could be considered or ceramics.

 

Ideally we could do a group buy to machine say 2" 7075 alum discs with a gentle bowl (again while fascinating topic ... no time to do too much experimentation).

 

I think Barry advises regarding materials and designs would be followed safely. I did almost everywhere, except marble plates - was not able to find proper hardness. Tried other materials, including some very hard ceramics, which was not bad. But what worked best for my speakers so far is polished hard aluminum plates between bottoms and bearings.

[AnotherSpin]

I think Barry advises regarding materials and designs would be followed safely. I did almost everywhere, except marble plates - was not able to find proper hardness. Tried other materials, including some very hard ceramics, which was not bad. But what worked best for my speakers so far is polished hard aluminum plates between bottoms and bearings.

 

Update: Need to be considered as well - the choice of material may depend on preferred type of music. For example, in my system aluminum plates under speakers on a top of bearings/balls give better defined low end punch and smooth mids and works better for rock, reggae, etc. But, hard ceramic plates in the same position gives more air, transparency to more lifelike highs and works better for classic or chamber. Quite contrary to this ceramics gives less transparency and air under tube amp while alu here gives more air and better definition of high sounds.

 

Also spent today couple of hours machine-polishing already polished bowls working surface. I think it brought another slight improvement.

[AnotherSpin]

Hi AnotherSpin,

 

Something sounds amiss but I don't know exactly what.

I say this because proper isolation should not alter tonality. It simply allows us to hear the inherent character of the gear better, or put another way, it frees the gear to do what it is capable of doing.

 

Best regards,

Barry

Soundkeeper Recordings

www.soundkeeperrecordings.wordpress.com

Barry Diament Audio

 

Yes, but you do hear difference between chrome and tungsten balls?

[AnotherSpin]

Have you thought to try the ceramic plates under the aluminum ?

 

Are the ceramic and alu plates same size as bottom of your speakers, or smaller with multiple plates ?

 

I recently changed from thin steel disks between my speaker bases(wood) and the ball bearings, to 4" square, smoothly glazed, porcelain tiles. I think they sound better, but my system has been through too many uncontrolled changes to say for sure.

 

How are you polishing your alu bowls ?

 

Yes, I had a thought about combining, but didn't try yet...)

 

Alu plates are approx. the same size as speaker bottom, ceramic 10x10 cm.

 

Polishing felt head for drill with chrome oxide polishing paste.

[AnotherSpin]

I've been emailing Mike at Ingress Engineered Products and discussed modifying his current design to have a 1" wide, shallow bowl. Assuming we can get enough people together for a group buy, he could do either $75 for a set of 6 in 6061 or $150 for a set of 6 in 7075 at 10 sets or $130/set at 20 sets. Interest? I'm interested in the 7075 and would go for 6 sets, I have a friend that would go for a bunch also.

 

Barry, if you have something better, let us know now!

AnotherSpin?

 

I am interested in 7075. Still price seem to be high. I checked their site, they offer 6 pcs 6061 for $75 regular price. So, $75 for a set of 6 in 6061 or $150 for a set of 6 in 7075 at 10 sets does not seem to be a group buy price? Second, why price difference between 6061 and 7075 is double? Would they offer more attractive price?

[AnotherSpin]

what about with speakers? obviously just sitting on 3 balls or even a flat surface on top of 3 balls wouldnt be great if something were to knock it... like my 6 month old nephew!

Want to confirm Barry's words with my experience. Two points:

- My very heavy Apogee floorstanders (about 40 kg each) on very shallow bowls move freely, but everything is more stable than I was expecting before actually did it;

- 3 bottom bowls are ok, "top" bowls dampen the sound and should be avoided.