[exphy]

 
which of the 2 is the ground? I think its the left one, because it was the left one on my MS1

 

[FallenAngel]

Check on the cable, they are different colors, you should be able to find out.

 

[nikongod]

It could be either. As a strange twist of fate, I had a set of headphones where the in and out of phase connections was not the same for each driver. It was very weird.
 
The vast majority of headphone drivers are wired the same way from sample to sample: Wire them both the same, and listen for them being out of phase. Its quite easy. if you want to hear what an out of phase driver sounds like wire them backwards and compare to another headphone.
 
If you are concerned with polarity you should get a polarity checker device. Lots of stuff does lots of stuff with polarity and the polarity of the headphones may not have been "correct" from the factory. One should note that the importance of the output of the system running with proper polarity is somewhere between "very low" and "not audible" but hey if people will buy cables they will buy anything.