A single speaker can only output a mono signal, you need a second one to complete the stereo pair. Balanced signals are used normally with speakers because they keep the noise/interference lower when running longer distances.
The S2 balanced outs don’t send a stereo signal, they output a balanced mono signal per out. Getting that cable won’t do a thing. You need a second speaker mate, there are no workarounds.
You can change the output routing in Traktor to sum the signal into Mono, meaning that if you plug one wire into your speaker you will hear the sum of both channels. Dirty little secret a lot of newer DJ’s don’t know is that quite a few clubs and bars are only wired for Mono anyways