The key terms with regards to
vibration isolation are mass and spring-rate.. equally applicable in zero G. The other factor we've not mentioned is damping, which effects how quickly the spring-suspended-mass system is brought to rest. In terms of vibration-isolation alone (considered in isolation
), more compliant is always better. Regardless of the mass being suspended, a more compliant suspension will isolate to a lower frequency. If you want to know what effective frequency that is, you need to know the mass being suspended as well as the spring-rate. In combination with that, a more compliant suspension isolating to lower frequencies needs to move/deflect a greater distance.
In real-word situations one must find a reasonable compromise between the desired degree of isolation and an acceptable amount of deflection. Deflection in reaction to vibration or other dynamic loads is how far the suspended microphone is allowed move or oscillate when subjected to those loads. To isolate to very low frequencies the compliant suspension will need to be able to move a significant distance.
Weight is important in that it is a specific case of deflection. It effects how much the suspended system will sag due to the force of gravity acting on the mass. Deflection in reaction to weight is
sag. Sag eats up some of the available deflection which is available. If we want to keep deflection reasonable, we can't make the suspension overly compliant, or the weight of the microphone and other suspended bits will bottom out the available deflection and then there is insufficient isolation. Directly related to this is that a more compliant suspension is more wiggly in general. How wiggly is acceptable? It's a trade-off.
It may help to relate all this to the suspension system of a car, which is designed to accommodate
dynamic loads such as bumps, corners, braking, acceleration. It also counters the force of gravity, holding the car up off its lower bump-stops. When tweaking a suspension for racing, the most common things to do are to modify the spring rate and damping rate which work in relation to the mass of the vehicle. Weight matters only in regards to the
non-dynamic loading - how much the springs are compressed by the weight of the car (at rest and/or in motion) before the system reaches equilibrium, which affects ride height and suspension-travel. An old Cadillac suspension is soft and plush which isolates road noise and vibration well but feels loose and wiggly. A sports car of the same mass is typically provided with a higher spring-rate (and higher damping rate to match) which makes for a less plush ride but a less loose and wiggly "faster" reaction time. In the words of Colin Chapman, race cars are made faster by "adding lightness" (reducing weight), but its actually mass reduction, not weight reduction that maters. Weight actually helps! as it is a form of down-force that increases traction. Imagine a drag-race on the moon. One engineering trade off moon racers face would be finding the most optimal trade off between traction and inertia. Traction on the moon will be largely determined largely by the vehicle's weight (no aerodynamic down-force of any significance is available) and is necessary for transferring acceleration force to the lunar surface in order to overcome the vehicle's inertia, which is determined by its mass. A heavier vehicle with sufficient power (to overcome its increased inertia) wins the race.