Speed Box S2

Pro-ject Speed Box S2 is a turntable Speed Controller and Stabilizer. 

The Speed Controller part gives you the functional benefit of having a 33/45 selector switch to change the turntable speed instead of having to take the platter off and move the belt. The 

The Stabilizer part gives you the qualitative benefit of a more uniformly spinning platter - there is less platter speed fluctuation, which in turn gives you a smoother more lifelike sound.