By Wilde Becker. Speaker Stands. At Monday, July 29th 2019, 19:31:33 PM.
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.
Thus, the sand provides dampening, but it also prevents the stand from ringing when it’s excited by the right frequencies – another handy little add-on.
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.