DDJ-200 Rekordbox headphone problem

I've got a DDJ-200, and I use Rekordbox on my laptop. I've got my speakers and headphones plugged in to my laptop with an audio splitter.

I want the master audio to come out of my speakers, and I want the channel I choose by pressing the 1 & 2 buttons to come out of my headphones. This isn't what's happening.

Both devices are behaving the exact same. They both play the master audio (what the audience should hear), and then when I press the 1 or 2 button, they both respond and play that track too.

These are some of my relevant audio settings:

What should I do to have the audio behave how I want?

Thanks in advance