Phono Subsonics

try wall-mounting on something like a target wall-rack for turntables, or build yer own...

Just some sympathy here. Whenever I have the grills off and play an LP I can see the woofers pumping or oscillating out of time with the signal. It is scary looking, and varies in proportion to level, but I can't hear any trouble. It occurs regardless of the speakers or amps used. Just on LP though. Thanks for the great post! Maybe you'll get to the bottom of this phenomenom.

What is being described is a classic low frequency resonance problem. In as much as you are using a table and substructure that are both suspended (and more importantly, un-damped / under damped) you are likely experiencing the effects of a high Q system. With un-damped systems, you can experience mechanical resonance with amplification effects (Q greater than 1). Reconsider your approach, use only one suspension component that is properly damped (Q = .5 to .7). Kevin Halverson

check your pre-amp, some have a subsonic filter that is switchable.

Put the player on Nordost pulsar points or buy 3 Wheelbarrow inner tubes to put under the player,bleed them down as low as possible to lower cutoff freq.and level them without loosing the suspension effect