Generally speaking, springs should be loaded according to their springs rate (stiffness). The more mass the lower the resonant frequency of the isolating system thus the better the isoalation, all things being equal. In the case of speakers it’s not really critical how you load them since speaker feedback via the floor to components cannot be less than what, 30 Hz or so anyway, whereas for electronics the seismic vibration goes down to 0 Hz. So for very low frequencies you definitely want to minimize spring rate and maximize mass. Thus, whilst stiff springs like mine or Townshend’s under speakers do prevent vibration from the floor being transmitted to the speakers, that’s a true statement, the real issue is mechanical feedback to the electronics.
The rule of thumb is to load springs until they are 2/3 of their uncompressed height. But it depends since springs have different numbers of coils, different heights, etc. But obviously you don’t want any coils to touch each other. Due to center of gravity issues for heavy objects like speakers, lateral support must often be increased by using the outrigger idea which I think Townshend does. The speakers/springs are way too unstable (top heavy) if you try to place springs directly underneath them.🏋🏻♀️
