2002 Front Door Woofers

I need to know which wires going into the head unit are for the front door woofers. I'm putting caps between the head unit and the speakers but can't find a way to get into the door panel to just put them behind the actual speakers themselves.

Okay, nevermind. I figured that out, but I do need to know one thing. I was told to put something called caps between the Head Unit and the speakers in order to reduce the lows in my front speakers.
1st: Are these going to make it sound crapy?
2nd: Does it matter if I put it on the positive or negative wire? I was told that I only needed one for each speaker but, obviously, I have to choose which wire to put it on.

No, caps will only take out the lows so you don't get distrortion or as much,4x6 speakers suck to begin with.Distrortion makes speakers sound like crap.I think caps go on the positive side.