What mixer do you have?
One option would be to run the output (a stereo headphone jack) into the mixer and then simply connect the monitors to your mixer.
To do this, use a 1/4" TRS to dual 1/4" TS cable for B2 > mixer, and then dual TS cables for mixer > monitors (or whatever they connect with).
To understand recursion, you must first understand recursion.
Colorado Club #77