paulgardner
My subwoofer will rumble uncontrollably when playing records at a higher volume.
Your are getting "air-born feedback", and it can’t be cured with better stand mounting.
Do this.
If you just put the stylus on a record NOT spinning, turn the volume up to your normal position, one hand on the volume control, then gently tap the turntable plinth, you will see you’ll get "runaway feedback", which just gets louder and louder.
The only way to cure this is no subwoofer or the turntable goes in another room.
Cheers George