Turntable Causes Speaker Cones To Excessively Move Rapidly

I had the same problem years ago using a DD deck on an unstable stand on a suspended floor. Switched to a belt drive and the issue stopped.

I am currently using a lesser Technics DD deck (SLQ2) and a shimmed, for VTA, AT 440 MLA cartridge on a concrete floor. I never leave the dustcover on during play. No pumping from Velodyne sub or from 6.5” midbass drivers. Also using entry level NAD pp2e phono pre.

Remove dust cover, place the player on isoacoustics zazen 2 or equivalent. That's what I did

If you can, put the TT on the floor to test as it is most likely the stand it's on.

Hello Dman777,

I had that same experience with my Rel subwoofers cavitating rather violently when playing analog only. Most of the recommendations I received focused on isolating my turntable. After doing all the isolation options, upgrading my tonearm, changing phono cartridges, upgrading the subs, changing the turntable platter bearing it turned out to be a turntable motor issue where the screws affixing the motor to the plinth had somehow not been tightened. 

Make sure your turntable assembly is torqued down properly. Hope this helps you.

Yogiboy appropriately mentioned tonearm / cartridge mismatch as the most likely culprit. I agree. Your response assumes the vendor would not sell you a mismatched combination, but that may not be true.

Look up the effective mass of your tonearm as well as the rated compliance of your cartridge. Go to vinylengine.com, open a free account, and surf to their cartridge resonance evaluator. This will calculate your resonant frequency. The higher the compliance, the lower the resonant frequency on any given tonearm.

As an owner of a Technics TT with an aluminum arm, the arm mass can be pretty high. I had the same problem running a Shure V15-III. The problem resolved when I installed an Ortofon Concord, which has a lower compliance AND lowered the effective tonearm mass (no headshell or fastener mass).