How to isolate turntable from footstep shake or vibration

There is also another condition that might be the cause of the Sub Woofers exuberance.
The Condition if present will be quite easy to resolve, as it simply means checking the Earth Connections are at the correct termination points and ensuring they are clamped effectively.
I refer to this as it has happened to myself on occasion over many years, and very recently as well, when I working with a Selection of Phon's SUT's and Head Amp's 

An Incorrectly Earthed Vinyl chain can produce effects that manifest through the Bass of the Speakers.
When I am trialling with Phon's and Ancillaries, I have at times got the Earth connections incorrect at the time of exchanging.
An incorrect Earth even though not being a Audible Hum, can react to activity around it and produce noticeable Bass Cone Movement.   

Being a perfectionist does not mean you are paralyzed.

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It is my biggest obstacle, GETTING started. I think and think and think.

Then pull the trigger. A guy taught me 50% of getting the job done is just starting.. He was right..

The older I get it's closer to 100%. :-)

Townshends, yes. I have a Seismic Isolation platform and it is quite effective.

Being a perfectionist does not mean you are paralyzed.

<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>

It is my biggest obstacle, GETTING started. I think and think and think.

If you can get started then you are not a perfectionist :)

.....and of the transmission of the sound waves that impact against the arm and the cartridge and everything is amplified we want to discuss?
This also impacts the negativity of the rumble.