Vortex Sound Research

I watched a tutorial on YT and setup my TR8s with 11 individual outs as audio channel in ableton. In my audio output and input I set channels 3/4 as out. All that is fine and it works fine. But when I want to add another channel for suppose synths from my Native instruments midi keyboard, I cant hear it under channel 3/4. Only 1/2. And 1/2 causes double sounds. Im so confused. Does anybody understand this? I can give further clarification if need be. Thanks!