Wood blocks underneath components?? snake oil?

Newbee, by rigidly coupling the CVDP to and appropriate damping shelf and stand the vibrations would never be there to begin with. Quoting the "Bad Vibes" article:

This, then, is the most practical solution for a good supporting platform: Employ specific materials and geometry that increase the platform's stiffness:weight ratio so that the improved rigidity raises the resonant frequency

Hence my "infinitely stiff / infinitely light" pumice material.

2) By rigid coupling you are reducing the number of vibration modes in the entire stero component system. This makes it easier to tune the system tahn if each component is singing at it's own frequency. Soft rubber dampers have the oposite effect.

Again quoting the article:

Elastomer Supports
A rudimentary version of the traditional damped suspension is formed when elastomer materials such as Navcom or Sorbothane are used to support a heavy preamp or amplifier, either directly or with an intervening platform. These elastomer pucks can be quite effective at isolating moderate amplitudes of vibration ranging from the upper bass and above, and will generally have a fairly predictable performance throughout this range of frequencies when used with a wide range of gear. Also, a broad band of vibrations generated within the component is partially damped by these compliant materials. Unfortunately, their damping and isolation ability is not only ineffective at very low-level vibrations of any frequency, but is essentially transparent to all amplitudes of very low frequencies, acting basically like rigid coupling rather than an isolator in response to vibrations lower than the natural resonance of the suspension.

For many systems using rubberlike pucks, the resonant frequency ranges from approximately 10Hz to 20Hz or higher depending on the actual compliant material, how it is shaped, and the load it bears. So even though the peak displacement at resonance will be reduced, vibrations below resonance will either pass right on through or be amplified. In practice, many such suspensions have relatively high resonant points, so this amplification will often extend into the lower audio band. For example, a system formed by typical rubber pads or pucks supporting a moderately heavy steel plate will have a vertical resonance of around 15Hz or so. Its related resonant displacement is fairly well controlled, yet the zone of amplification actually extends from approximately 3Hz up to around 25Hz---above which isolation finally begins. This scenario can contribute to the subjective impression of a "mushy," "soft," or "boomy" bass response, even as the suspension reduces the amount of transmitted vibrations from the midbass on up, and partially damps the component-generated vibrations.

Unfortunately, this limitation of certain elastomer supports is often misconstrued as "over-damping," even when describing its effect with amps and preamps, and has led to the unfortunate condemnation by some of any sort of damping at all. Actually, this negative subjective effect, reported when elastomer supports are used in some systems, stems from the amplification of the suspension's relatively high resonant frequency intruding into the lower audio band (the opposite of damping).

Paradoxically, systems that emphasize the bass can sometimes sound rolled-off in the treble as well, although this is usually a psychoacoustic effect rather than a genuine rolloff. In any event, this example highlights the danger in drawing cause-and-effect conclusions about subjective experiences in audio without trying to tie them back to real physical principles. The positive sonic effects of elastomers are almost entirely due to their damping and isolating qualities; when properly applied, elastomers can result in a significant reduction of vibrations from the upper bass on up.

Incidentally, several equipment supports or footers now on the market combine a degree of rigidity with a measured amount of damping, without being overly compliant. These devices seem particularly well suited for connecting components to a platform already isolated by a suspension. (See my Townshend/Vibraplane review elsewhere in this issue for some examples.)

The ideal stand as I gather would be:
1) completely rigid and operate as a single unit. Bad vibes article "Minimize the relative motion between different elements that comprise a system"
2) resonant frequencies would be pushed as HIGH as possible so vibration's amplitudes are as LOW as possible. Bad Vibes article:
"lowest natural frequency will be the most dominant". Minimum resonant frequency = maximum amplitude".
"Reduction in frequency leads to an increase in dispalcement...resulting in a "noisier" less stable
platform".
"The lower the resonant frequency of a platform, the less desirable-the associated increase in amplitude will cause more serious ringing that damping can only partially reduce." So using sorbothane actually INCREASES ringing which damping can only partially reduce.
"Enough damping should be applied" BUT ITS PURPOSE IS TO "further lower the displacement of resonances" not increase it.

As I understand it, sorbothane has
1)high amplitude as in actual dimensional dispalcement
2) soft material with numerous, complex. vibration modes.

So maybe we just disagree on everything.

Rotarius:

Why not try to minimize the problem by first isolating the chassis from the rack and then dampen the chassis?

Because isolating will 1) increase the number of vibrational modes in the system since each component will be vibrating at its own frequency 2) Do nothing to reduce the amplitude of those vibrations - you need to raise the resonant frequency to do that. Then you dissipate the HF / low amplitude resonances by, perhaps and composite shelf of differing materials laminated together.

IMHO you need to DRAIN the component's vibrations and rack's vibrations into a suitable shelf material (there are other threads at A-gon on suitable shelves which do this). Sorbothane isn't going to do this, rigid material will.

cdc,
1) Even if you rigidly couple all components in your rack, each component will still have a different resonant frequency due to differing mass, volume, materials which result in different natural frequencies. This based on scientific fact. A spring or an elastomer is typically used to reduce the amplitude of the wave that produces vibration in a medium btw. Rubber is used to isolate a jet engine from an aircraft frame. For the record, unless the component is bolted down to the shelf, it is not a "rigidly coupled" system to which you can apply the formulae from rigid body mechanics. A component on brass cones can very easily be disturbed compared to the rack it sits on.
2) Please read my earlier post on this subject. The only way to reduce magnitude of the vibrational force transferred from the shelf to the component is to have an isolator and damper in between. Increasing the mass of the platform helps in theory but for practical reasons can't be the only way to dissipate vibration. If the offending force can make it's way through concrete slabs of your floor, you will need a lot of mass to dissipate it if you do not want to use a real "isolator". BTW, what makes you so sure that by rigid coupling everything you have raised the natural frequency of all the components beyond the audible range? Glass ringing/resonance occurs at higher frequencies, why are glass shelves frowned upon by audiophiles in that case? Lastly, anyone in the isolation business ought to have measuring devices (that are readily available) and back up their claims with numbers. How many of them do?

Rotarius I agree with the Vibes article that:
"The goal of vibration control is to minimize the relative motion between different elements that comprise a system"

"Rubber is used to isolate a jet engine from an aircraft frame"

Sure but the engine will still be vibrating. It's a different objective - don't shake the plane apart vs. audio get the vibrations out of the CDP. Isolation won't do this.

" The only way to reduce magnitude of the vibrational force transferred from the shelf to the component is to have an isolator and damper in between"

No as in the Vibes article you can do this by raising the resonant frequency. Then you reduce these small amplitudes will good shelving or maybe some thin, relatively hard rubber like neoprene. As the Vibes article says, putting cones 22% in from the edges of a shelf will minimize amplitude as this is the first node of near zero displacement. Would you agree this would be a good thing?
Again, these values have to be calculated, I'm just giving the theory as I understand it.

"Increasing the mass of the platform helps in theory but for practical reasons can't be the only way to dissipate vibration"

I agree, a better goal is to inprove the stiffness to mass ratio as even granite will ring.

"what makes you so sure that by rigid coupling everything you have raised the natural frequency of all the components beyond the audible range"

That what engineering is for and why we pay all those audiophile companies big bucks.

"Glass ringing/resonance occurs at higher frequencies, why are glass shelves frowned upon by audiophiles in that case"

Nope, the Sound Organisation racks use glass shelves and were praised by What HiFi? for fooling them into thinking it was a wood rack. Manna used 1/4" thick tempered glass with outstanding results. Glass alone will ring but glass is not used alone. It's all in the design. It's complex and requires soem serious engineering expertise. These things are not always intuitively logical.

"Lastly, anyone in the isolation business ought to have measuring devices (that are readily available) and back up their claims with numbers. How many of them do?
"

And thats why audiophile industry has the reputation that it does. Of course you could always buy a Vibraplane for $5,000.

Cdc, FWIW, You are probably correct. I doubt that we will agree on anything when it comes to this subject.

But, FWIW, I would pose a question which no one has ever answered for me. Assuming, for the sake of discussion, that you are correct regarding the "drain" theory, and assuming that you have a component, or part with-in which is more likely because each component part will have its own individual resonance point, which resonates at, say 5000hz, exactly what amplitude must this resonance reach before it actually affects the SOUND of the component.

IMHO, it's only an esoteric theory unless one can establish that it not only actually exists in the minds of our scientists, but as pratical matter for audiophiles that advertised methods actually work to solve a real problem experienced in audio components and their use in the home.

It seems to me that if we have a problem based on something as well explored by the scientific community as resonances/vibrations that there must also exist a method of quantifying the amplitudes necessary to cause a deterioration in sound quality. IMHO this is not an area where 'subjective' observations have much meaning (to me at least).

IMHO, the 'drain theory' is on the same level as someone saying that we aught to provide for compensation in out TT set ups for the effect of the moon. I mean it (the moon) sure effects our invironment - no arguement can be made there - so it must effect our TT's operation which are infinitely suseptible to all sorts of things, and we should be able to make adjustments to compensate, shouldn't we?

FWIW, I get a real kick out of someone saying that a 'component' has a resonance point which can be moved by choice of isolation/coupling. As I suggested above, if a component has 100 parts, it has one hundred resonances within, one for each uncommon part. Do these somehow combine to make just one resonance for the whole component? Perhaps I'm just speaking from ignorance - I guess I'll have to take some physics course so I can understand this

As indicated before, I think the drain theory offers more commercial opportunities than it actually solves real world problems. IHMO of course.