single active speaker (PA) with stereo source


2010-12-15 10:05 am
hi everybody, i have one question:
i have a FBT jolly 12ra active speaker (200W), only one. it has XLR-TRS neutrik combo input on retro.
i want to drive the stereo signal out of my pc soundcard (AC 97 realtek) to this speaker: so i have to convert stereo signal into mono (right?).
i know that i have to build a 3.5mm TRS jack (soundcard output)-XLR (PA input) cable with two resistor for each line (left and right) before connect them together (to have mono audio).
my question is: how much kOhm (or Ohm...) should be the resistors?

additional info:
i know that Input Impedance of FBT speaker is 22 kOhm.
i don't know impedance of a basic soundcard (i guess 32Ohm...?)

Thank you very much!