Late last year I posted a question ,on isolating my sub to prevent
annoying the neighbours.

Well I finally got a round to testing today.

With a Platform of 2 * 18mm layers of MFD with thin silicon rubber
interlayer glued with PVA and with sorbothane feet.
I got a reading of 70 db on my rat shack meter in the downstairs flat
from a 100 db in the listening room I was playing the trance dance
scene from the matrix revisited

Then added another layer: of duck rubber non slip router-matt/
drawlinner matting and another 18mil mdf sheet : that got it down
another 6ish or so db's .
Then I put partly inflated innertubes on the platform and another MDF
sheet between them and the sub (to stop the spikes rupturing the
tubes).
Got it down to barely flicking the needle downstairs (just 50db's) it
was barely audible and that was with a spl of 110db's in the listening
room.

I would like to thank all those who provided advice made suggestions.
and to those who said I was wasting my time - yhar-sucks-boo :¬)

Chris