By Wilde Becker. Speaker Stands. At Monday, July 22nd 2019, 20:28:26 PM.
An isolation platform works in a similar way to a car’s suspension, and comprises three mechanical components: a spring, a mass supported by the spring, and some form of damping to prevent the sprung mass from continuing to bounce around. In a car you have the springs between the axles and the car body: the car body provides the mass and the shock absorbers provide the damping, to stop you having a bouncy ride.
One way to improve the situation is to add mass by means of a platform fixed to the top surface of the foam. Primacoustic do this in their Recoil Stabilizer by using a very thick steel slab with rubber matting on top, while Auralex and other companies use MDF topped with dense rubber on their more up–market platforms. IsoAcoustics take yet a different approach, by using a frame made from rigid components joined by resilient isolators.
The theory is that the mass and spring characteristics are chosen so that the resonant frequency of the combination is well below that of any frequency they’re likely to be asked to isolate. For example, if the lowest note a speaker can reproduce is 30Hz, then the resonant frequency of the supporting platform needs to be well below that — perhaps just a few Hertz or less.