How to isolate turntable from footstep shake or vibration


Even while the Oracle turnable that I use has a built-in springs suspension by design there is a low or even sub-low frequency boom every time someone walks in a room. This becomes really bad with the subwoofer’s volume set high as the low frequency footsteps make straight to subwoofer where they are amplified shaking everything around. It seems the cartridge is picking up the footsteps very efficiently as even a lightest foot down becomes audioable. What can be done to attempt to isolate the turntable from the low frequency vibrations? Interesting, that the lower the volume of the subwoofer, the less the footstep shake is evident and with the subwoofer turned off it is a barely a problem at all. 
esputnix
The resonant frequency of the system needs to be lower than the operating frequency for isolation to occur. Most isolation systems have a resonant frequency in the audio range. The only systems I know of, which are also non-powered, which the resonant frequency is below audio frequencies are all based on the "Minus K" platform. Most "Minus K" platforms are under 4hz resonant frequency.
As others have stated, adding springs under a table having a spring suspension is a very bad idea (imagine a car having two sets of springs for each wheel!)
They’re called helper springs. https://www.tarett.com/items/996-997-991-products/996-997-991-suspension/996-997-991-shocks~springs/...
One way to consider going is to install Townshend Seismic Pods under not the base of the Oracle, but in place of the stock springs, with the Pods resting on the shelf, not the Oracle’s base.

Good idea. Which is why I said:
The most cost-effective answer will be if the Oracle feet can be replaced with Townshend Pods.

At AXPONA I visited Butcher Block Acoustics. Very nice turntable platforms. But I may be incorrect here, but I am not certain there is a substantial difference between them and one of the thickest maple cutting boards you can find on eBay for a lot less. So I put my VPI Prime Signature on top of one of those thick maple cutting boards. Never an issue. Done.