Onkyo htx 22hdx (2.1): how to expand it to 5.1
I have the Onkyo htx 22hdx system (2.1) whith 2 speakers connected to red-black and white-black connectors and I would like to extend it to 5.1. The expansion kit (SKS-22x with 3 other speakers) is out of production, so I'm thinking to buy 3 speakers with similar characteristics (40 W - 6 ohm).
Well, before to buy, I've tried to test the other 3 output by linking my own 2 speakers to the other connectors (i.e. green-black and gray-black), but no sound occurs.
There's something I have to activate to let the 5.1 system works?
Otherwise, do you know why my 2 speakers works just if I connect them to the front-ouput (red-black, white-black) and not work if I connect them to the others output?
Thanks in advance.