I doubt the 6 and 12 volt motors are the same. At 6 volts the current doubles. I hooked these up on a power analizer at work and they drew slightly over 2 Amps no load. The speed was about what I would consider normal. I considered adding a speed control but decided it was not worth it. You could add a 6 - 12 Vdc DC to DC inverter but not a transformer. A transformer will not work on DC.
