Why do turntables sound different?

 I agree it is all about vibration and speed stability. I am puzzled when I see a high priced turntable sitting on a rack between two speakers. The positioning of the turntable to avoid vibration is critical.

 I have my turntable in the corner on the opposite side of the room from my speakers. It sits on a 3" maple block which sits on a  VPI turntable stand filled with sand. I have all my front end equipment in that corner as far from the speakers as possible. I run a pair of 9 meter interconnects from the preamp to the amp which sits between the speakers.

 rsf507, What about airborne vibration?

The corner is the strongest part of a suspended wood floor.  The corner of my room is approx 22 feet away from my speakers. You cannot feel any vibration when standing in front of the turntable stand. You can feel the floor vibrate a bit when standing behind my speakers. I rather have my turntable and all my front end gear (which is tube) as far from my speakers as possible.