High End Isolation - HRS, SRA, Active platforms

I have never used an active platform device. Having read some descriptions of such, I have a few questions. What is the bandwidth and reactance speed of the Halcyonics?
How does a platform mechanism such as this deal with self induced vibration internal to the device its trying to protect? Would not stacking more than one electromechanical device on a platform change the inneraction and transfer function of the platform. The reactance time of the platform is going to vary based on the mass and the horizontal movement as well as the center of gravity to all supported components. Tom

I hope an engineer can chime in here, but I'll take a shot at this. A rack really will only deal with vibrations that come through the floor. These are traveling through concrete or wood, and are low frequency. I personally do not see how any rack could effectively reduce air-borne vibrations which are much more brief and of higher frequency.

The active platform will automatically level the platform, and adjust for the center of gravity at the beginning. Sensors will continually monitor the motion to mathematically model the vibrations. It will then create a counter-reaction to bring the platform to rest. Based upon some graphs on the website, it appears that the system will react as soon as the first wave hits, and can settle the platform within a few tenths of a second. This is in contrast to a passive system where the vibration would continue for over a second before coming to rest. All of this depends upon very responsive sensors which are continuously modeling the behavior of the platform in all directions. The concept of halting a resonance in a single direction seems easy to grasp, but it's quite amazing that this can be integrated in 6 different directions with relative speed.

Self-induced vibrations should be effectively controlled as well. This should include spinning platters and humming transformers. Anything that alters the center of gravity or the absolute weight, such as moving the component or opening the drawer, would require the equipment to take a second to automatically relevel and compensate.

The website has some technical papers and graphs that will give an idea of the speed and frequencies involved.

Prospective buyers of vibration control products should know the basic definitions of, and the distinctions between ISOLATION and DAMPING to enable them to make informed purchases.

ISOLATION refers to the process of preventing (minimizing) externally generated vibratory energy from reaching a structure or component. Although this includes acoustic or air-borne vibration that is difficult to manage in exposed audio/video equipment, we are primarily concerned with the transfer of mechanical vibration. And, it is essential to understand that there is no significant mechanical isolation possible unless there is relative movement between the component and its supporting structure to prevent sympathetic movement with the supporting structure. Therefore, only a device or material that can compress like a spring or deform like an air-bag or a viscoelastic part, or “roll” like a bearing, can be an isolator. Exceptions to these “passive” examples include “active” systems that have electromechanical “self-leveling” capabilities. Obviously, hard “spikes” and (bare) "platforms" or "shelves" are not isolators.

DAMPING is the dissipation of energy in a vibrating structure or component. It refers to the process of removing (minimizing) internally generated vibration that is inherent in a component AND any external vibration that, for lack of adequate isolation, may enter the component, by converting the mechanical vibratory energy of solids into heat energy - a process called hysteresis. Damping is generally accomplished by the bonding of viscoelastic materials to the (vibrating) internal surfaces, mechanisms and parts of a component and by external coupling to viscoelastic materials or damping devices.

In consideration of the foregoing, it is obvious that no isolation platform or device, regardless of its sophistication, can provide effective damping. In other words, while the isolator may essentially "hold the supported component still", the component will nevertheless
be awash in self-generated and acoustically transferred vibratory energy that remains undamped.

In short, to achieve isolation AND damping there must be BOTH isolation and damping mechanisms and/or materials applied to the component!

In my opinion, both isolation and damping are essential to achieve the very best component performance. Therefore, the best solution is not a "cost no object" isolator but rather, a well engineered product that provides both isolation and damping.

Disclaimer: I manufacture vibration control devices.

Our Nimbus and Promethean isolation stands incorporate "selective frequency damping" and viscoelastic damping to "quiet" the top plate and other critical parts.

Our damping techniques address airborne and component generated vibration as well as residual structureborne vibration.

Nimbus is a 6 degree of freedom design with resonant freq. as low as 0.5 Hz.

NB - We design isolation and resonance control products.

I have no doubt on the ability of cones/spikes, elastic interfaces, and shelves of varying density to affect oscillations and change the sound for the better. I have tried some varieties of all of these things.

However, it seems the passive approach is limited by (1) the efficiency of bringing the object to rest, and (2) the selection of frequencies which are a function of the material being used.

I would think that an active system would isolate a component by damping the oscillations. Just as a swinging pendulum is brought to a stop by using your finger as a counter-force, so will an active system bring an oscillating platform to a rest by applying appropriate counter-forces. An active system would also have an advantage of operating over a wide frequency range.

It seems that the other problem with a passive approach, is that they could potentially induce their own oscillations. Placing a component on a displacable material will enhance it's ability to move at certain frequencies. Also, footers are a 2-way street, are not truly fixed, and probably resonate at their own frequencies.

Of course, nothing is perfect. I am also thinking that the only way to truly shield a component from air-borne vibrations is to literally place it in an insulated box.

It is too bad that manufacturers of racks do not routinely provide real data to aid in their design and help consumers make informed choices. Also, our rooms have very individualized frequencies being transmitted through the building structure. Hence, I agree with Jeff above that there is no one-size-fits-all. What may work well in one person's room may not work in someone else's room.

Finally, the huge advantage of passive isolation is obviously cost. Therefore, it remains a useful approach as we are all seeking to obtain the best value for our sound.