Springs are useless and actually make transmitted vibrations worse. Rigidity is the answer, and that has been my approach for over half a century. I can assure you that it is a total solution and the correct solution. I have had total freedom from transmitted vibrations for years. You can skip and jump all you want round my turntables and there are zero problems.
Springs don't make vibrations worse - depending on the type and materials they can convert some frequency ranges to heat - dissipating it, other vibrations will tend to be converted to energy at the springs resonant frequency (which can be calculated from springs constants and mass etc...) - with a turntable, if the resonant frequency of the spring/mass combination is outside the critical zones - you effectively remove the undesired vibrations and shift them to where they do less harm.
Solid materials will reflect and refract frequencies (just like light, prisms and lenses) - that means with judicious use of materials that reflect or refract at specific frequencies, combined with materials that damp (convert vibration to heat) - you can trap and dissipate specific frequencies.
The trouble with all this is, that in most cases the user has no idea which frequencies are being reflected, which ones refracted and which ones damped - so the end result becomes completely random!
If you use your TT as a measurement instrument (place the needle on the platter with the motor turned off - it becomes a VERY sensitive measuring tool for the frequencies we want!!!) - then you can see what comes through from environmental vibrations/noise, or from feedback, footfall, etc...
And then you can experimentally work through options to reduce those vibrations and improve performance.
Almost invariably, springs are part of the answer.... (in my case Sorbothane pucks acting as combined spings/dampers)
