Why headphone ground cable does nothing?

[yoreei]

Hi!
I tried to fix my headphones following this guide
https://www.youtube.com/watch?v=OhnXUQRQ4u4&list=PL380B15A8B48AAFF3
Just out of curiosity, I tried connecting only the red and the green wire. The headphones worked properly. Connecting or disconnecting the ground did nothing. Why is this so?

 

[justcallmetom13]

It's probably because the red and green cancel out because they are positive and negative. Ground probably just stabilizes it, making it safer.