Varakan, you are not alone. The speaker behavior you describe is more common than you might imagine. For years I never noticed it until I got speakers with removable grills.
The most common suggestion here seems to be better isolation of the turntable from airborne or floor vibration. Some believe this odd speaker pumping is inherent in LP playback itself. Maybe changing the turntable will help. Applying filters, clamps, and cut-in-half tennis balls may help too. Experiment and see!
Hopefully someone can say how much of a risk this untreated condition poses to your speakers.
The most common suggestion here seems to be better isolation of the turntable from airborne or floor vibration. Some believe this odd speaker pumping is inherent in LP playback itself. Maybe changing the turntable will help. Applying filters, clamps, and cut-in-half tennis balls may help too. Experiment and see!
Hopefully someone can say how much of a risk this untreated condition poses to your speakers.