They were either responding to warps or low frequency information that was well below the point of vented resonance or your phono section was leaking DC voltage. None of those are good situations. Sean
>
>
Woofer pumping - what gives?
Some years ago I noticed that regardless of the speakers, cartridge or preamp in the circuit my woofers pump wildly out of control the more I advance the volume while playing an LP. They don't seem to be responding to the musical signal but something else. The sound is fine. My humble rig is a Dual 1219 with a NOS Shure M91ED cartridge. Tapes made from the same LP's do not exhibit this odd behavior. Who knows why woofers look like they're going nuts while playing an LP?