Speaker Problems

[Digital_Soul]

Hey guys, I got my car a few months back now and the previous owner has had a sub in the back, so I have just been using the front speakers as the rear standards were not wired up.
I finally managed to get the wires necessery to get the standard rear speakers to work, but now that they are the front comps have stopped working, at first I thought it might just be something to do with the fader but theres just nothing at all coming from the front, anyone able to shed any light on what the problem might be?

thanks