Why do my bass drivers shake violently listening to vinyl

@limomangus I haven't been listening to my vinyl rig since I discovered the issue. Streaming only.

Write or call Richard Vandersteen. He is very responsive and has your answer. 

OP chat w Rutan….and as I recall RV is visiting him…today ? Jim

You won’t see the woofers dancing if they are in an enclosure that constrains motion at subsonic frequencies. You also won’t see them dancing if the preamplifier or amplifier in the upstream chain cannot pass subsonic frequencies, e.g., if you use a transformer coupled tube amplifier or if you have engaged a subsonic filter on your preamplifier. In either of those two cases, the woofers are protected from damage AND you won’t experience the audio distortion associated with the woofer dance. However, if rumble is present due to some sort of feedback (acoustic mechanical or electrical) at the source, these palliative measures do not prevent or cure it. In any system, the presence of rumble does not always cause the woofer dance. Audionoobie, if you have done the experiment of borrowing another TT to see whether the problem persists, and if the problem does persist, then I give up,... you need a rumble/subsonic filter, best inserted between your phono stage and your linestage.

I was experiencing very noticeable noise from my Technics SP-1000R table. Mostly an echo type reverberation when walking near the table etc. Tapping on the stand or plinth was like playing a drum. Ordered the Insolation feet from this shop for it and I just screwed them in. An immediately noticeable silence. Going to listen to a few records to make sure it hasn't killed the sound completely, but as far as decoupling goes they're awesome.