Reply to S4 Connection Question - Mackie Mixer

So I've been trying a few things to get my S4 to output on my Mackie and haven't gotten that far.

I have 2 independent quarter-inch cables that I'm trying to run to one sound strip. Every time I have both plugged in at once, it only plays out of my left speaker. When just the "1" cable is in the mixer, it works in both. I just want to make sure I'm getting a stereo signal.

Suggestions? How do you hook up your S4?