Hi Eldartford,
Thank you for your question.
A well designed active (I assume you are describing an active pneumatic isolation mount) can do a good job by decoupling the device placed atop it from floor-borne vibration.
There are several limitations of the available commercial designs that preclude their use for audio (and video). The first is that most of the units available are made of steel and have steel top plates. Steel rings and can have negative electrical interaction with sensitive audio components (especially, but not exclusively, with cartridges and phono sections). Some models have stone options for the top plate but natural and artificial stone does not absorb vibration and has a tendency to ring. Some active pneumatic mounts have optional stainless steel top plates and they, at least, don't have the electrical interaction issues but still have ringing issues.
The overriding limitation of most commercially available active pneumatic mounts is that they cannot hold a large amount of weight. Your lab at work is a relatively quiet environment. Your listening room at home is not - it is being filled with high SPLs of music. The component on top of the active mount is being bombarded with large amounts of acoustic energy that is being absorbed into the chassis. In addition, the component is creating its own unwanted vibration internally (spinning motors, humming transformers, cooling fans, etc.). We want to restrict as much acoustic energy and as much internally generated vibration as possible from contaminating the signal flowing through the component. Adding high mass and high absorption above and below the component will accomplish this quite effectively but will also add considerable weight. Very few active pneumatic units can hold the weight required.
It is also interesting to note, as you stated "piers sunk deep into the ground with 2000 pound granite slabs on them" has not been very effective at eliminating vibration. This can illustrate that using mass and coupling only to try and control vibration is not adequate.
Please be more specific about how I can edit my post after its been submitted.
Barry Kohan
Disclaimer: I am a manufacturer of vibartion control products.
Thank you for your question.
A well designed active (I assume you are describing an active pneumatic isolation mount) can do a good job by decoupling the device placed atop it from floor-borne vibration.
There are several limitations of the available commercial designs that preclude their use for audio (and video). The first is that most of the units available are made of steel and have steel top plates. Steel rings and can have negative electrical interaction with sensitive audio components (especially, but not exclusively, with cartridges and phono sections). Some models have stone options for the top plate but natural and artificial stone does not absorb vibration and has a tendency to ring. Some active pneumatic mounts have optional stainless steel top plates and they, at least, don't have the electrical interaction issues but still have ringing issues.
The overriding limitation of most commercially available active pneumatic mounts is that they cannot hold a large amount of weight. Your lab at work is a relatively quiet environment. Your listening room at home is not - it is being filled with high SPLs of music. The component on top of the active mount is being bombarded with large amounts of acoustic energy that is being absorbed into the chassis. In addition, the component is creating its own unwanted vibration internally (spinning motors, humming transformers, cooling fans, etc.). We want to restrict as much acoustic energy and as much internally generated vibration as possible from contaminating the signal flowing through the component. Adding high mass and high absorption above and below the component will accomplish this quite effectively but will also add considerable weight. Very few active pneumatic units can hold the weight required.
It is also interesting to note, as you stated "piers sunk deep into the ground with 2000 pound granite slabs on them" has not been very effective at eliminating vibration. This can illustrate that using mass and coupling only to try and control vibration is not adequate.
Please be more specific about how I can edit my post after its been submitted.
Barry Kohan
Disclaimer: I am a manufacturer of vibartion control products.