Woofer motion problem.

Whenever I hook up a turntable to my rig, or play a flac file that has been recorded from an analog rig, my woofers flutter in and out dramatically more than with even the most intense digital music. I believe this is like flutter and wow that is extremely low frequencies but not sure. I notice these movements during some of the quieter passages on the LPs. Can anyone explain this and tell me whether it can be prevented?