The Litz cable is too thick to fit inside the screw terminal of the SpeakOn plug. To connect the cable, solder a small spiece of solid copper wire, bent in a U shape, to the end of the Litz cable. This will allow you to connect the cable properly. A single Litz cable should be connected to two internal screw terminals. The BX17 manual describes which connector pin numbers should be connected to the positive and negative BX17 power output.