Springs under turntable

millercarbon, please recall what I said about substrate, the more unyielding the substrate, the higher percentage of the energy will deform the springs.

Did you ever bolster the floor, specifically directly under the places where you have springs isolating your speakers?

One suggestion is to use the granite laminated to MDF, I haven't tried it, however I suspect laminating MDF (or some pretty hard wood?)  to it top and bottom, will change it's tone from ringing significantly. Use the granite under the TT, atop a shelf on your rack with appropriate springs to isolate? Sharing the kenetic energy between multiple absorbers, are you sure you want to do that?

@noromance
I did keep the old springs I had under the 401 for weeks just to see if any change but it really never did, the return to solidity for want of a better word once they were removed was palpable.
Some members have rightly said I do not give changes enough of a chance, so this one got a more than adequate trial at the time.
Now I do agree with Mahgister that they were likely not compressed enough.
With the Nobsound I will be able to adjust that compression rate and should give a better idea of what might work.

What about the Triton Audio Neolev magnetic isolators?

@uberwaltz 

Now I do agree with Mahgister that they were likely not compressed enough.

That is an issue I have been working through by trial and error.  I am new to using springs under my gear/speakers and have been trying to achieve a combination of stability and appropriate compression and stiffness for the best sound, while maintaining as low a profile as possible.  The Nobsound devices are nice because they can be easily adjusted to change the stiffness but I am instead using individual larger springs.  I had a couple of instances where the springs were slightly over compressed (i.e., hardly any travel remaining) due to the weight of my speakers and I was able to solve the problem by placing an additional adjacent spring.  I previously asked this question in a different decoupling thread but did not receive any responses (I believe the same issue likely applies to speakers or turntables):

For those of you supporting heavy speakers on springs, do you recommend stiffer or more moderate spring support? In other words, how does the supported combined speaker/stand weight compare to the total available spring loading capacity....something moderate like 50% or something less (i.e., stiffer springs)?

 In addition to stiffness, I believe the issue may also include a component of compression/travel, which is related to the number of winds. 
Any experts here? 
Where is Geoff when you need him?

Uberwaltz, the 401 is a heavy turntable. To do this even close to right you have to find the center of mass of the table and place three or four springs equidistant from that point. Then you have to get the spring rate low enough to get you under the 3 Hz limit. At best the situation will be wobbly. You could put the springs in cylinders and add heavy oil for damping and the engineering continues. The more stable way to do this is to hang a solid platform with springs. Look carefully at the SME 30/12 turntable. You could replicate this situation without too much difficulty. 
If you are not into this degree of experimentation you probably should leave things as they are. The MinusK platform although expensive really is the best solution for unsuspended turntables. You just weigh your table and they will send you a platform with the right spring rate.