How to isolate turntable from footstep shake or vibration

user510, I have intimate experience with both the AR XA and I have owned 2 LP 12s. They are both potentially unstable and do not handle footfalls well just as ghdprentice indicates. A Sota you can rap on the surface and dance the jig on springy floor and it will not care. It is all about the self centering stability of the suspension that count.

@williewonka , Those feet do not offer isolation. Those center posts used to stabilize the magnets ruin any isolation the feet provide except in the perfectly vertical axis. 

ghdprentice509 posts07-23-2021 3:18pmI had an AR which I could rap in the the top with my knuckle and it would not skip or have the sound transmitted to the speakers. It did what it was designed to do. When I walked by it would skip every time. The solution was simple, a wall rack… that is the solution for suspended floors.

mijostyn4,747 posts07-23-2021 3:34pmuser510, I have intimate experience with both the AR XA and I have owned 2 LP 12s. They are both potentially unstable and do not handle footfalls well just as ghdprentice indicates. A Sota you can rap on the surface and dance the jig on springy floor and it will not care. It is all about the self centering stability of the suspension that count.

good feedback and I don't mind being contradicted with factual evidence.  There definitely are other suspended subchassis designs which isolate well...and I think mjostyn's suggestion that the "hungie" type of suspension proves to be more stable than is the "sprungie".  Where the hungie tends to find center while the sprungie tends to never quite find it.  Although you can get close in those adjustment sessions but those conical coil springs always point their load in one direction, which needs to be steered...and the drive belt imposes a horizontal pull which will yank the lighter subchassis in a direction we don't want it to go.
Ime with a Td126-III i can say that this design suffers far less from footfall. Even though it is a "sprungie" and needs to be adjusted in order to obtain a vertical oscillation action, it does resist the pull of the belt far better with its larger mass.  And the cast chassis does indeed not flex. 

Btw, I can prove chassis flex on the TD150/TD160.  Having checked this using a dial indicator,to see that just the addition of the platter mass alone will cause the subchassis to flex.  Now if you put this into a dynamic situation where footfall ripples the suspended floor, which causes the floor supported audio rack to teeter just a little bit and that is enough to put the turntable in motion which excites the suspension components within and then we see even greater chassis flex due to the dynamics of the compression/extension action.  And that alters the distance between platter bearing center and pivot center of the tonearm, which skips the needle out of the groove.
https://www.theanalogdept.com/subchassis_rigidity.htm

-StevePs: have we solved the issues described by the OP yet?

What user510 said. In addition, altering the distance between the platter bearing center and the tonearm pivot must necessarily create a speed anomaly, as the belt must stretch or contract to accommodate changes in the distance between the motor pulley and the platter, where the motor is not mounted on the suspension.

I am sure there are turntables less susceptible to footfalls. But, the simplest solution is to remove the tt from the trampoline.