Cheers I will look at that if I have chance before I go to work would fronts be causing interferance on 6x9 then?
I don't think so. Might be worth checking the wiring that's going into the 6x9s too. Also check the wiring going into the headunit.
Here's a few causes & solutions for you;
• Speaker Cables or Wiring - Your next step in diagnosing the problem that is causing crackling in your speakers is to check the wiring or speaker cable. Look for areas that are worn or frayed. Move the wiring around a little; if you notice any change at all, even if moving the wiring helps the sound quality of the speakers, it means that your wiring or cable has some problems. To fix this you will either have to replace the speaker wiring, or if the wiring is built into the speaker, you will have to replace your speakers.
• Your Speakers are Bad - If you have checked all of these potential problems and are still hearing the crackling in the speakers, the problem is likely within the speakers and you will need to replace them.
• Speaker Connections - It is always possible that the connections are dirty; to determine if this is the cause you can unplug your speakers and clean the connectors. When you plug them back in, listen to see if the crackling is still present; if it is, this was not your problem.