Equipment isolation and vibration damping.

[YashN]

I am in the process of building my isolation platform and devices. I am rather sure the results will be in the same vein as room diagnosis and physical acoustic room treatment, i.e. fundamental and quite a large effect, and necessary in order to properly even start to hear your gear.

 

Considering the air cushion and the cup and ball arrangements, the effects are the following:

 

1. Air cushion: predominantly deals with vibrations and isolation along the vertical axis.

 

2. Cup and Ball: only deals with vibrations and rotations in the horizontal plane. Does nothing for the vertical plane.

 

Hence, you can see people combining these to great effect. Some use Springs to reach the same total effect. The balls move in the cup surface and then, have to oscillate back to equilibrium. Thus, the vibrational energy which would otherwise affect the components or radiate outwards affecting other components and sound, is instead spent as kinetic energy and heat through friction mostly and a little through air conduction/convection.

 

The air cushion is usually done either with tire tubes or similar air-filled bags or else squash balls, raquetballs or tennis balls. These support a first platform on which the cup and ball arrangement rests, and then either the component bottom rests directly on the balls if it is smooth enough, or else another platform is used.

 

Going from the principles of both vertical and horizontal isolation, I am thinking of mounting each cup and ball arrangement on its own rubber feet. The rubber feet will then do the vertical axis damping.

 

Another thing I thought about after doing a simple fluid damping for the tonearm of my turntable is to add some oil in the cup and ball arrangement. Perhaps having a fluid filled cushion would be beneficial too.

 

Good ideas?

[YashN]

Isolation alone does nothing to deal with airborne vibration or vibration generated inside a component.

 

I think isolation works to some extent with airborne vibration. Some inherent vibrations inside a component (like crystals and capacitors) need something a little different. Some people use blu-tak or sand-bags or some other means of internal shielding or damping.

 

On the other hand, the vibrations generated internally (component A) and which could affect other components (component B), like when A is a CD or DVD reader or an HDD, are taken care of at the physical interfaces by the isolation in this thread.

 

This is not to say we couldn't investigate some additional means of internally damping too.

 

That's not to say that isolation alone won't deliver big benefits. It's just that maybe a combination of strategies might be the best approach.

 

Yes, ultimately I think this is the way to go. For the isolation in this thread we are not dealing with the inherent internal vibrations directly and this should probably be do

[YashN]

In my experience, proper isolation provides benefits in every area of sound I know how to describe.

 

No doubt about it, I have read attentively some of your previous posts on the SH forum. I have also read Thorsten Loesch (of AMR/iFi) describing similar air cushions and others saying good things about the cup and bearing arrangements as well.

 

Some folks are concerned with vibrations from the speakers reaching the rest of the gear. Some are concerned with "draining" vibrations out of individual components.

 

Certainly. I think if we tame vibrations in all directions, then the gear can do what it is supposed to be doing to the best of its ability. If it's a CD player, then it's doing A/D internally and providing that digital stream. For the speakers, taming the vibrations out of the cabinet allow the drivers to provide the fullest sound, etc...

 

My experience has been the it is the low frequencies *entering* the gear that are the ones to be concerned with... simply because blocking these is what showed me the benefits that made me isolate everything.

 

Makes sense if you think that the lower frequencies have a tendency to travel and make standing waves. Typically, there is a lot of energy around the lower frequencies.

 

As to "draining" my take is that if something is being drained, there should be less of it in the place from which it is allegedly being drained. Personally, I have not heard any audible evidence to support the idea that anything is being drained or diminished.

 

For me, the analogy and term is correct. Take the example of a bookshelf speaker cabinet resonance. The issue is that all cabinets vibrate to some extent. When the cabinet vibrates, the sound waves will interact with those of the driver thus colouring the sound. In this case, what we need to do is dampen the cabinet vibration. So, by making a stand for the bookshelf speaker we plan to make the (speaker + stand) arrangement sound better. For this, we need coupling between the cabinet surface and the stand. Additionally, we also need the stand itself to lower the vibrations. This can be achieved by using a more massive/rigid/inert structure for the stand. A way to 'drain' here would be to use sand within the stand columns: the cabinet wants to vibrate, but as it's coupled to the stand below, the vibrations transmit to the stand. In turn, this displaces the sand particles against each other, and the vibrational energy is then spent in work done to move the sand particles and as heat, i.e. kinetic energy and friction + some conduction/convection around.

 

In other words, we converted that detrimental sound from the cabinet into heat. Essentially, we drained the cabinet's energy down to the stand and sand where the loss as heat makes it sonically harmless.

 

I have had very good results making my stands for my Fostex Studio monitors initally that I re-used for my current Totem Mites. The center pole isn't within sand yet: I would need quite a thick tube to be able to do that, so this is on the roadmap and should enhance the sound even further. So currently, in my arrangement, the stand and speaker is what vibrates, and since it is more massive than just the speaker, the resonance is lowered.

 

So, it could also be a very good thing to consider that 'draining' aspect in the isolation goal of this thread. Draining is also what's happening with the cup and ball arrangement (draining vibration into other motion and heat loss).

 

On top of this, any path out is also a way in. [snip] this is pretty easily dismissed by moving the shelf on which a component on such devices sits. There is no delay in motion and in fact, the component responds directly and instantly to the motion.

 

The immediacy of response is a good thing. I am a bit more concerned about the oscillation of the arrangement at low frequencies. I have manually and visually tested the air cushion and cup+ball this morning. I am wondering whether it would be better to dampen the ball motion further. Adding oil or some similar, perhaps more viscous material like silicone could help here.

 

When there is vertical motion, the air cushion dampens it to some degree. If there's simultaneous motion of the balls, there already is some vertical component of force in the cup+ball and this then can get exacerbated by the lower platform's vertical component.

 

So, ideally, what I would like here, is that the kinetic energy in both the lower platform (air-cushion) and the upper one (cup+ball) be killed as fast as possible, i.e. I'd prefer 3 oscillations until rest rather than a 12-oscillation motion until rest of the balls in the cups.

 

Maybe a steeper curvature of the cup can help here or adding the oil or silicone.

 

As for the air-cushion, I would take the enclosure, ensure it is hermetic and try to fill it with fluid as well (perhaps just oil).

 

 

Taking the example of sand above, where ultimately, energy is dispersed at heat, this morning, I was also wondering whether I could substitute either or both of our platforms with sand or bags or sand.

 

I've seen people mention a bed of sand as support, so this is of the realm of already tested and proven tweaks.

 

For the upper platform, supposing you keep the air-cushion, 3 little bags of sand in place of the cups+balls perhaps?

 

Now, what I've learned in my own experiments is that just about anything you put under (or atop) a component will change its sound. The operative word is "change" which should not be confused with "improve." Couplers like spikes and cones *will* change the sound but what I've found is the change is somewhat random and inconsistent from component to component.

 

Quite right, and I am trying to avoid running into this rabbit hole, and that's why I am thinking through what we are trying to achieve based on the Physics principles. That can be a time-saving strategy.

 

To your question, I would advise against a rubber base for the roller bearings. An isolator needs to have a resonance in the low single digits because it doesn't begin to become effective until about 1.4x its resonance frequency. In order to block low frequencies, it needs to take effect at as low a frequency as possible. Rubber, sorbothane, squash balls and similar materials have resonances that are way too high.

 

OK, we'll avoid rubber feet because their effectiveness at damping lower frequencies isn't up to par. I can live with that and the explanation.

 

For more info see Vibration control for better performance, which I hope will be of interest.

 

Yep, already read that before starting the thread, including some long threads at the SH forums. Thanks for sharing.

 

By the way, after isolating the CD player and other electronic components, I experimented with isolating the speakers (just on rollers as I don't want to risk a tilt and fall on an air bearing, which is much easier to control with a regular component). Once I hear the changes, I described the non-isolated speakers as "bound and gagged" by comparison. Max Townshend has spoken about this stuff for years and years. Clark Johnsen too. I didn't start experimenting until about 2002. It has all been "afloat" on isolators ever since.

 

Yes, the thought of my speakers falling is scary! Maybe replacing the air cushion with an enclosure where sand can be used is better.

 

Currently, my source is mostly digital: we have as source components the external HDDs, the Computer, the DAC.

 

I think I would need a platform to isolate all these components, although I initially thought of doing the isolation for the amplifier first and then the speakers.

 

Which do you think I should start with?

[YashN]

Don't forget: A good roller bearing will also work in the rotational plane, not merely the horizontal.

 

I've seen you mention this a few times, but I cannot visualise it or translate it into normal mathematical/physical terms.

 

Let's take the horizontal plane of the upper platform, i.e. the one above the balls, and let's look at it from above. This constitutes a horizontal plane.

 

This horizontal plane can have a few types of motion which we want to dampen:

 

1. The horizontal plane can suffer translations along that plane, i.e. horizontal displacements, i.e. North-Sound, East-West, any direction and its opposite, really or outward-inward if you prefer.

 

2. The horizontal plane can suffer motion by rotating around a vertical axis, i.e. clockwise-anti-clockwise rotation. Even when rotated, it is still a horizontal plane.

 

 

Is 2. what you meant by 'rotational plane'?

[YashN]

While you may like the results of doing this, in my view, nothing was drained. What occurred by coupling the cabinet to the stand is an alteration in the resonant characteristics of the cabinet. (The cabinet is still resonating, albeit with slight changes in the frequencies because it is not part of a larger assembly.)

 

You may not like the term 'drain' as people commonly use it, but that's correct and it's exactly what is happening. The proper terms in physics are certainly lowering resonance when using a larger mass, but additionally, energy conversion and heat loss. The coupling of the cabinet and the stand does make the cabinet part of a larger assembly. The addition of sand in the column then finished the conversion from the vibration of the (cabinet + stand) into kinetic motion of the sand particles and heat loss.

 

Hence the detrimental energy at the cabinet is drained into heat, if you want a shortcut.

 

Actually, what is occurring is what I described with the speaker and stand: the roller bearing acts as a coupler in the vertical plane. The motion of the ball is due to horiztonal (or rotational) excitement and what it is doing is *converting* the motion to heat. Again, in my view, nothing at all is being drained.

 

The conversion to ball motion and heat is the draining. With the ball motion, since it has to rise along the curve of the cup, there is also a vertical component to the motion.

 

 

It is precisely the oscillation that is creating the isolation. Adding damping will work against this as it will diminish the steepness of the rolloff above resonance (that last *is* the isolation). In other words the *less* the damping on ball motion, the steeper the roll-off, i.e., the greater the degree of isolation. This is one reason why I do not recommend using a "bowl" on the top and the bottom of the ball--it adds damping, thus diminishing isolation.

 

Now this is interesting, because in my visual and manual tests today, the freer the motion, the longer my upper platform oscillates. Much like a pendulum in air vs a pendulum in water: the oscillations in air will last longer than in water. In water, the pendulum loses more energy working against water and hence the oscillations die down quicker. In other words, the freer the motion of the balls, the longer the platform and component are oscillating. Do we want our component to oscillate? Or do we want our component to oscillate the least?

 

The observation about roll-off is I believe important but are we here looking to :

(a) tame the low-frequency oscillations which are particularly detrimental at a specific resonant frequency?

(b) to isolate from vibrations effectively across a large bandwith of frequencies?

 

These two seem different to me.

 

To summarise: when the balls are rolling about and oscillating, the upper platform and hence the component is still oscillating too.

 

 

The purpose of the air bearing, as I see it, is to prevent such motion from being transferred. It should *block* it, not merely dampen it.

 

It won't prevent it, only diminish it as it is transferred with loss to the upper arrangement.

 

 

Why 3 oscillations?

 

The number is unimportant, it was only an example, together with 12, to show what I meant when I said I wanted less oscillations: if the ball + cup arrangement has to work against a viscous material there, then the kinetic motion is lost to move the material and as hear, the oscillations are damped and hence the upper platform and my component comes back to rest more rapidly instead of continuing to oscillate with the balls.

 

What I found when I did this is that the greater the number of oscillations (i.e., the less the damping) the greater the isolation.

 

By isolation here, do you mean as perceived sonically, or as vibrations as measured through equipment? (I am not going into the usual debate here at all and want to avoid it, it's just to see if I can save time building on your experience or if I must for instance just hook up a little iPhone + motion-detection app).

 

I would not want to deliberately add damping and thus waste the effort spent trying to isolate by effectively minimizing the isolation.

 

Yes, except, people mean different things when they say 'isolation'. Here, if my component is oscillating in sympathy with the balls and for too long, to me, it's not isolated. Ideally, I want the ball motion to occur but I don't want the upper platform and the component to do the same in sympathy. In the ideal case, I'd rather the energy loss occur at the ball and cup the in the smallest amount of time, so that the upper platform and component move the least.

 

A steeper curve on the "bowl" will add damping to ball motion. I recommend a shallow curve. I want the ball to move as slowly as possible (lowest resonance frequency) and for as long as possible (least damping on ball motion). In this way, isolation takes effect at the lowest possible frequency and the rolloff above resonance is as steep as possible (i.e., maximum isolation).

 

I suppoer in this viewpoint, we can consider a low frequency of oscillation below what's considered acceptable for turntable's tonearm + cartridge, e.g. something like a frequency of <10Hz to be acceptable oscillation?

 

In my experience, sand will dampen energy but it will not provide effective isolation.

 

It amounts to the same effect: I don't think we can have perfect isolation. Damping is the working principle behind normal, imperfect isolation.

 

I think I will try some arrangements if I can get my hand on some sand (doesn't seem to be easy here). If not, I may try with cat litter.

 

I'd definitely use a separate platform for each component being isolated.

While I've heard benefits with everything I've isolated, I would say the greatest benefits have been with digital gear (CD players, transports, DACs, ADCs) and with loudspeakers.

 

OK, thanks for your feedback. I think space restricts me anyway to different platforms for the sources: I have my Kurzweil K2500XS right in front of my iMac, so there's not much space on the table for a single platform to hold all three components. It's massive.

 

So between amp and speakers, I'd try the latter.

 

OK, that sounds good to me, I already have some bamboo platform for the speakers to avoid getting the cabinet in direct contact with the balls as I don't want to spoil the Totem Mites' cabinets. I just need a few more cups (coming soon).

 

If they are stand-mounted cabinets, I'd first try isolation between the speaker and stand

 

That's the plan. I won't change the isolation between the stand and the floorboard because it is working as planned: I wanted the speakers not to directly transmit vibrations to the floor (wood). That works, and also successfully prevents motion of the floor to affect the speakers.

[YashN]

Actually, there is a difference between horizontal energy (front-to-back and side-to-side) and rotational energy. You've described the difference in your post.

I suppose you could see them both as horizontal in some respects. I see them as different.

 

The motions are different: the correct terms are translations and rotations. But the plane is already defined: it is the horizontal plane and it doesn't change since it is delimited and constrained by the 3 balls.

 

This doesn't mean the horizontal plane itself cannot rotate: indeed it can because the lower platform could make it so temporarily until the motion restores it to equilibrium.

[YashN]

A cool relevant article on Wikipedia.

 

Damping is an influence within or upon an oscillatory system that has the effect of reducing, restricting or preventing its oscillations. In physical systems, damping is produced by processes that dissipate the energy stored in the oscillation. Examples include viscous drag in mechanical systems, resistance in electronic oscillators, and absorption and scattering of light in optical oscillators. Damping not based on energy loss can be important in other oscillating systems such as those that occur in biological systems.

 

 

The damping of a system can be described as being one of the following:

 

Overdamped

The system returns (exponentially decays) to equilibrium without oscillating.

 

Critically damped

The system returns to equilibrium as quickly as possible without oscillating.

 

Underdamped

The system oscillates (at reduced frequency compared to the undamped case) with the amplitude gradually decreasing to zero.

Undamped

The system oscillates at its natural resonant frequency (ω_o).

[YashN]

If something is being drained, I expect there to be less of whatever was drained in the place from which it supposedly was drained.

If you check that speaker cabinet, you'll find it is still vibrating.

 

Yes, but less, which is the whole point, hence we are draining the cabinet of its harmful resonance (nobody said we were draining perfectly).

 

More responses at length during the week

 

Thanks for the cool exchange of perspectives.

[YashN]

Hi YashN,

 

My point is that there is no less. Different, yes. But not less. In fact, I say exactly as much.

 

It would be interesting to see why you think it is so.

 

Based on Physics principles, when you couple the speaker cabinet with additional mass, it is the whole arrangement which vibrates, with a lesser resonance. The energy that the cabinet itself used to vibrate previously is now dispersed among both the cabinet and the stand.

 

It follows that the cabinet has less energy in its vibration than before. Hence, it has less deleterious effect in combination with the driver's performance.

 

I don't think anyone achieves complete vibration-less cabinets, but what we can and know how to do is reduce the extent of the cabinet's vibration at resonance.

 

Another way of proceeding is to do without the cabinet altogether: open-baffle.

 

If it is not less by your viewpoint, then it should be completely vibration-less, and then by your own standard of measure in the previous post, one should show it by measurements.

 

Now, if your speakers oscillate back and forth, what is it that happens to the soundwaves the drivers are supposed to send to you?

[YashN]

If something is being drained, I expect there to be less of whatever was drained in the place from which it supposedly was drained.

 

The energy conducted into the stand is *converted* to heat. No energy is lost.

 

I wouldn't get too stuck on the term if I were you: there is a Law of Conservation of Energy, but there is also something called 'Heat Loss'. When someone says 'drain', they do mean the conversion into heat or some other form of energy, thus less energy at the point where it is 'drained' from or converted from.

 

Thus, the cabinet vibration is diminished or drained in sand motion and heat. Yes, it is conversion and overall conservation, but the energy which would otherwise have been used for vibrating the cabinet only is now partially going elsewhere, so both are correct. It is a fact of Physics.

[YashN]

Yes, exactly: the freer the motion, the longer the item oscillates. Less damping, manifesting visually as longer oscillations, equals a steeper rolloff above resonance, manifesting as a greater degree of isolation.

 

I gather by this we are OK with oscillations that are sub-10 Hz or so, assuming these are not modulating the audible spectrum? If we are looking to maximise the oscillations for longer, then why aren't we using very large and very shallow cups?

 

The key is: At what frequency will the blocking begin? To be effective, this has to be as low as possible.

 

I've seen some commercial products managing just that for Lab equipment. Concerning our DIY arrangement, do you find that the amplitudes we are isolating for are rather small? That is, in normal use (without touching or pushing the component), do you find them oscillate visually at all?

 

I can see the upper platform move around at low frequency when testing manually (providing a large impulse by hand), so in that case, the platform moves, our component is moving as well as around, say 10Hz for several seconds. Can we live with that?

 

Taken to its logical extreme, it you damp the motion completely, there is no oscillation at all. And no isolation. Again, it is precisely those oscillations that provide the isolation. The goal is more of them, not less.

 

Depends on the nature of the damping (c.f. the Wikipedia extract above). I have seen a couple of contradictory messages about isolation/damping around the web. Perhaps someone whose Physics is less rusty than mine can chime in.

 

All I can tell you is what *I* mean by "isolation" and that is that ground borne vibrations do not impede the performance of the gear because they are effectively blocked from entering the gear. The only point of the ball motion is to impart that motion to the component being supported.

Put another way (and this is something only you can determine whether or not you want), isolation = oscillating gear. More isolation = more oscillations.

Fewer oscillations = less isolation. The relationship between the two is direct and will not change.

 

OK, that answers my questions above. So here again, assuming we have a ground wave of 10Hz which is making our speaker oscillate front and back through the cup and ball. Doesn't this modulate the drivers' sound? Can we live with that?

 

Complete different things. A cartridge/tonearm resonance needs to be ~10 Hz so that it is above the frequency of typical record warps, yet below the audible range. We're not trying to block anything there. The cartridge/tonearm (or more specifically, the cantilever/tonearm), being a compliant structure is going to have a resonance. Isolation, while also involving resonance (of the isolator, if we're using a mechanical low-pass filter like a roller bearing or an air bearing) is something else.

 

Both these cases have resonance and frequencies that we want to have at less than audible. We are indeed trying to block something in the turntable example: we do not want the tonearm/cartridge assembly's resonance to impact what we hear. So these two cases are similar, not different.

 

A good isolator will have a resonance in the low single digits. Something like 2 Hz or 3 Hz would be great. (That's why that roller ball needs to oscillate *slowly*.)

 

If this is the case, that's not what we're doing here: the cup's curvature is too steep and the cup is too small. You'd need a much shallower and larger cup and allow the ball to move as far as possible before returning.

[YashN]

But there is not a static quantity. It is constantly being replaced.

 

Nobody said it was static. Doesn't matter in the least: it is continuously being converted or 'drained' away.

 

My speakers (Magnepans) are boxless. They still benefit a great deal from blocking vibrations from entering the speaker (and crossover).

 

I think we are mostly crazy to allow our manufacturers to put the crossover circuits inside speakers Additionally, we use the crossovers after the amps (crazy as well )

 

I make no attempt to drain anything; only to block seismic vibrations from entering the gear.

 

Yes, you are draining or converting the ground energy at the interface before it reaches the component.

 

So what I hear happening with speakers that *can* oscillate due to being isolated on roller bearings, is the speaker now sounds like it has been unbound and ungagged. Performance in every area of sound I know how to describe is improved: extension (at both ends), dynamics (at both ends), low level detail, bass pitch definition, soundstaging expands (in all three dimensions, provided the recording contains the information), images are more "solid", and overall "focus" improves appreciably.

 

Thanks for that. Knowing what to listen for can help greatly when tweaking.

 

Townshends Seismic Speaker Stands accomplish the same thing. I've heard different speakers demoed on the stands vs. off the stands and found the improvements on the stands were not subtle.

 

Haven't been able to find more info yet, but I sure do know my meagre DIY stands had improvements which are not subtle at all! My first large woodworking project - I learned along the way. Never built one before. Time-consuming, but fun, and very, very worthwhile: tamed the wood-floor vibrations, and totally re-defined the attack transients and soundstage.

[YashN]

I feel terrible about injecting this very simple question into a conversation in which I really have no business being involved in, but Barry, what have you found to be the optimal "cup" for your roller bearing method?

 

Don't! The more the merrier, and it is a question I was going to ask myself. Once we know what we want to achieve, we can then see how, and then also think about how to optimise the characteristics.

 

Indeed, if it's the case that we want the slow oscillations to last longer, think we should look for very shallow cups, and it turn that means, very large ones. Probably with the smoothest and hardest surface as well.

[YashN]

I have never quite understood how the rough wood cups and imprecise marbles are able to deliver any audible performance at all, but Barry says he has heard it...

 

Certainly because even with less than ideal materials, the process of isolation is occurring to some extent. Perfect for initial experiments compared to no isolation at all.

 

All my cups are acrylic moldings made for retail display purposes. They are available in an array of sizes, shapes and colors. And they are inexpensive ! I can put together a set of 3 for $10 - $15.

 

That's very cool, Daudio. As ringing, is acrylic a good material? I gather we'd need hardest and smoothest, but also something which does not ring too much, or if it does ring, then we need to dampen that by encasing it within some other material.

 

These retail 'dimple blocks' do not have as shallow a cup as would be preferred, but a smaller size of the SS 'ball' (while still usable) can optimize the relationships of the curves to make the best of the situation.

 

I hope to learn that one day, but for now I feel have achieved almost a 'Regen' level SQ improvement, for less then even that small cost.

 

Very encouraging. How large can you make these?

[YashN]

With air bearings, I've found it is important to inflate them *only* enough to achieve air support -- to lift the load so it isn't resting on the inflation valve. One pump too many and the resonance goes up, bass bloats, and isolation diminishes.

 

Some folks use multiple small air bearings to achieve balance (so the gear doesn't tilt). This alters the function of the air bearing from isolator to level. Once that is done, it isn't such a good isolator. Better, in my view, to use an air bearing (aka inner tube) that describes a large enough circle to accommodate the component to be isolated.

 

I was going to write about just that: tilt. There are six degrees of freedom that we want to isolate from. If the air cushion deals predominantly with vertical motion, and the cup-and-ball with the horizontal plane, then we still ideally need to deal with tilt.

 

The fact that the inner tube isn't completely inflated: does that help with tilt? Would a completely inflated tube deal with tilt better? Less?

 

In other words can we consider that the inner-tube is also isolating from tilt to some extent?

 

If the air cushion's effect on tilt is not satisfactory, the separate smaller air cushions appear to be interesting, and namely why was thinking of making the air cushions part of the ball and cup assembly.

 

It is very difficult, however to synchronise the air content of three different tubes though.

 

Another question occurs if we consider tilt: if we find that the air cushion, which is in fact rubber together with air, doesn't deal with tilt efficiently, what could we do to implement tilt control?

 

For tilt control, a simple pad between two hard surfaces should suffice, something like Sorbothane.

 

3. As I noted in my article on the subject, it has been my experience that certain other things must be attended to before the benefits of isolation will be plain. Among those other things are clean AC power and proper routing of system cables (signal cables separated from power cables, etc.).

 

That's a good reminder from your article, something to be put on the checklist when testing, and generally setting up.

[YashN]

So, this is all great reading, and I just happen to be playing with my old sets of Daruma 3 mkII roller bearing isolators on a pair of Omega Super Alnico monitors

 

Checked them out at this Soundstage review. They look cool and not too expensive. Are the tops curved as well?

 

Review Summary

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[TD=width: 20%]Sound[/TD]

[TD=width: 80%]"The clarity of the music improved, the soundstage became more specific, and the bass seemed to tighten and become more authoritative."[/TD]

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[TD=width: 20%]Features[/TD]

[TD=width: 80%]Three pieces -- top, bottom and ball bearing -- that "float" components under which they are used, isolating them laterally.[/TD]

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[TD=width: 20%]Use[/TD]

[TD=width: 80%]Doug found them to work best under CD players; under solid-state electronics, "the changes range from, 'uh, maybe,' to 'yeah, perhaps.'"[/TD]

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[TD=width: 20%]Value[/TD]

[TD=width: 80%]"Is there any competition for Daruma 3-IIs in their price bracket?" "Their $99-per-set price is quite reasonable."[/TD]

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[YashN]

I agree with Barry that the Tungsten Carbide balls are 'a bridge too far'

 

But they're the most durable.

[YashN]

I wish I had a better idea of which characteristics are more important for the bowls and balls: hardness, smoothness, curvature, concentricity, or ? ??

 

From what I've read so far:

 

Hardness: as hard as possible (if it dents or marks, the motion won't be smooth anymore, and may even introduce vibrations)

 

Smoothness: as smooth as possible

 

Curvature: as shallow as possible: you want the oscillations to be as long as possible.

 

Concentricity: eh?

[YashN]

First a thought experiment. First take a large flat board that is infinitely rigid and has a top surface that is completely frictionless, then place your audio component on top, for now no wires connected to it.

 

Like Albert, I love gedankenexperiment Thanks for chiming in, John.

 

 

There are some problems with this isolator, if the board is not completely perpendicular to the local gravitational field, the gear just slides right off. Not very useful. THAT is why a shallow bowl is used in the devices mentioned, it provides a DC restoring force to prevent the gear from just sliding right off.

 

Yes, and it appears it also introduces a vertical component at this layer, as the ball rises up and down the cup's surface.

 

So for the best isolation you want the shallowest "bowl" you can get away with that still provides enough restoring force to keep your gear from sliding off.

 

I agree, so if we could get large bowls with slowly curving sides, that would be better. They would ring more though so we'd need to think of a way of damping this?

 

This is also important for cables, the stiffer your cables are they steeper your bowl will have to be so the cables don't fling the gear off the shelf. This may be a good incentive to go with very flexible cables, so you can go with shallow bowls, which work better.

 

Good point. Alternately, provide structural support for your cables.

 

The other aspect of the bowl is that it adds a resonance, in order for the isolator to be effective that resonance has to be significantly lower than the frequencies you are trying to isolate. The seismic noise in question seems to have most of its power in the single digit Hz range, so a resonant frequency below 1Hz will usually be quite effective.

 

Very interesting. I wonder what the resonant frequency of those small commercial pucks are.

 

As has been noted it can take a long time for this resonance to damp out. This is a GOOD thing, it means there is low resistance to the motion. Refer back to the original thought experiment, it is the lack of resistance that makes the isolation work, so anything you do to damp this very low frequency resonance defeats the whole purpose of the system.

 

I was having a hard time to accept this and was under the impression that we would need to damp the oscillations, but the gedankenexperiment cleared it for me.

 

Think carefully about using remote control for these functions, or using a rotary control rather than push buttons.

 

Or use devices with touch-screens (no push required).

 

That is it for the horizontal plane, the next post will cover vertical isolation, which is much harder to achieve.

 

Thanks a lot, John. Don't forget to chime in on tilt if you can!

[YashN]

Converting energy is not draining anything. It is converting it.

 

It's the same thing.

 

Law of Conservation of Energy: 100 units.

 

Case 1: A has 100 units

 

Case 2 (at moment t): A is coupled to B: Every time A has 100 units initially, B drains away 75 units =

A has 25 units, B has 75 units

 

B has drained A of 75 units. Total energy is still 100 units.

 

You can also say 75 units of A have been converted into the form of energy that B stores or expresses.

 

At time t+1, this process continues.

 

It is precisely the same thing, which is why I told you you don't like the term but the way people commonly use it is still OK.

 

I agree to disagree (already did).

[YashN]

I generally use blocks that are either 2" square, or 2" in diameter. The bowl curvature is the same. I bought some larger ones (3" dia), but they had the same curvature in a deeper bowl, which doesn't work out very well in practice. They are very pretty in a piano black finish, through !

 

I use 4 of the square ones for my 95 lb electrostatics (panel, xformers, base). A three way support is just too unstable for a 6' tall speaker, and 4 spread out the load better. Not easy to set up on carpet

 

The larger the dimension, the shallower it allows the curve to be. I think actual dimensions should vary with the components, to be able to make as large an equilateral triangle as Barry usually puts it.

 

I checked one of my amps, and for these, something with a diameter of 4" appears better.

 

I have read a lot of people hearing issues when using 4 contact points: they're hard to set in the exact same plane, and the result is that one contact point always then rattles, affecting the sound negatively.

[YashN]

Be careful here, any engineer will tell you that you can NOT optimize all variables in a system

 

I'm an engineer but I'm not telling you that

 

Concentricity - the accuracy of the surface as compared to a theoretically perfect sphere. Applicable to the ball and the curvature of the bowl, both.

 

Right. I figure high is better here, for the smoothest motion possible.

 

Yeah, but what are you going to do with them ? Launch them from a rail gun ??

 

Nope, I'd put them under my components, but with the less hard ones, if they dent or deform at any time, you'll need to buy new ones.

[YashN]

I'll speak for myself of course but I'm not seeking to isolate from anything but seismic vibrations entering the gear via its support. These tend to take the form of what are called P waves (which travel horizontally) and the lesser S waves (which travel vertically). So tilt has nothing to do with the paths by which vibration might be transmitted into the gear.

 

Interesting approach, and more things I need to read upon. S waves do not travel through liquid, so why aren't we using a liquid to deal with the vertical isolation?

[YashN]

This will eradicate any isolation. The resonance is too high. It will also cause bass bloat.

 

I don't see why having a tilt management layer is going to affect the other layers.

 

When you noticed bass bloat, what dimension of Sorbothane (or other) were you using?

[YashN]

A couple of commercial implementations for the cup-and-ball that I found: