High End Isolation - HRS, SRA, Active platforms

For active isolation (ie. Halcyonics), is there a benefit to isolating each individual component to it's own platform, or could one place several stacked pieces. I'm thinking of a DAC/transport stacked onto one platform. Appreciate anyone with first-hand experience.

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.

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.