I recently decided to amplify the door speakers in my truck. I had a pair of Alpine 10" subs, but i just wanted to do something different, so i went ahead with this project. It's not hard at all, i just felt like if there were any questions that anyone has, i maybe could address them now.
1. Start by taking off the door panel to your truck....i'll assume you know how to do this
2. THIS STEP IS OPTIONAL....with the speaker wire you will be using, make sure that you twist it tight...in that, i mean cut the wire to size, stick one end in a drill, tighten it down, have someone else hold the other end, and let 'er rip....it's to block sound distortion/noise...the idea is that the noise can't get around all the bends in the wire, only the clean, amplified sound will come thru, and trust me on this step. Just to see what would happen, i hooked them up w/o twisting, and it wasn't NEARLY as good as WITH the twist...lots better bass
3. Hook up the wire to your speakers with the + and - accordingly. Run the speaker wire thru the rubber grommet connecting the cab to the door...if you need help, you can safely pull the rubber part away from the metal, then run the wire, and pop it back in. Re-install speaker in door.
4. Run your wires according to where your amp is going to be located. I have mine under my driver's seat (see wire diagram below). Make sure to keep speaker wire away from power, rca, and ground wires, as they will add only more engine/ground noise to u're sound
This is just an example of how i ran my wires. You can improvise based on your personal needs, etc...
5. Repeat same process on opposite door.
6. Crank it up and see if everything is working properly. Did you make sure to hook the speakers up in phase? If your tweeters are positional, are they angled towards your ears? Is your amp hooked up correctly? If all the answers are yes, and you are getting a good sound, put the door panels back on and rock out!
I've noticed on some installs that there is speaker noise only evident when the car is turned on, and the whine/noise goes along with the RPM's, this can easily fixed. You will need to buy somthing called a "noise blocker" or something to that extent...$10-$12...its nothing related to the way the wires are ran, it's actually alternator noise coming thru and you can use any set of aftermarket speakers you choose...but i rock Alpine.