Splitting sound output on Traktor using MacBook

I couldn't find a way either, I ended up just using headphones, left master, right for cueing.

 

unfortunately macs recognise the built in speakers and the headphone output as the same device, when you plug a mini-jack into the headphone socket it will silence the speakers so it isn't possible to listen to both at the same time, let alone feeding each a separate signal.

There are some pretty cheap options though, one I like is the griffin imic. This basically gives you another stereo in and out from your mac for about £15, which you can set up as an aggregate device in your Audio/Midi setup utility.

I know this works fine with Ableton/logic/DJ-1800 and most other audio based applications but I have heard rumours that traktor has a problem recognising an aggregate device, I don't personally use traktor but I'm pretty sure there is a thread on it somewhere on macrumors.