How to isolate turntable from footstep shake or vibration

@cleeds , you obviously have no experience with powerful subwoofers and turntables.

Sub sonic filters are not Band-Aids. A sub sonic filter is essential if you are using a turntable with powerful subwoofers. I can play records without the filter all the way up to 85 to 90 dB before there is a noticeable degradation in sound quality. This is with the old Sota Sapphire and Syrinx PU 3 tonearm. It is not feedback, it is distortion. If I turn the filter on the distortion disappears. This is with a digital filter not an analog one. The problem is not the turntable. It could not be happier. The problem is the subwoofers trying to reproduce every little irregularity on the record causing the woofers to make long excursions. If I turn the volume up loud enough I can get the voice coils to hit their stops making a very painful sound.  
Since the signal has already been digitized creating a subsonic filter takes just a little programming. It does not add any distortion or phase shift unlike an analog filter. 

mijostyn

@cleeds , you obviously have no experience with powerful subwoofers and turntables ...

You’re half-right - I don’t use powerful subwoofers. I use a full-range speaker system that is essentially flat in-room to below 20 hZ.

The problem is not the turntable. It could not be happier. The problem is the subwoofers trying to reproduce every little irregularity on the record causing the woofers to make long excursions. If I turn the volume up loud enough I can get the voice coils to hit their stops making a very painful sound.

That sure sounds like a problem to me. I want my woofers to reproduce what’s on the LP, unfiltered. If you’re getting "irregularities" that cause "long excursions," then it sounds like you have arm/cartridge resonance problems. Those can usually be resolved without relying on rumble filter Band-Aids but - as I said - rumble filters do work. It’s fine if you like them.

After checking the suspension you should try a Wall shelf made for the TT. Like this
Pro-Ject Wallmount it 1 Turntable Shelf-Audio Advisor

This helps to eliminate foot falls since it is mounted to the wall instead of sitting on the floor. Another way with suspended tables is to hang it from the ceiling. This takes some knowhow to do but is very doable if you know how to find the ceiling joists. I used this back in the 70’s & 80’s with great success..

thecarpathian, if the bridge DID collapse, we guess you be crushed and out of a home. 😄👍