Sounds like a good system. There are several grommet covered holes in the firewall on the drivers side that you can use to run the power wire to the amp. Since you didn't say how powerfull the amp is I'm assumming you can run a single ten gauge wire to the battery. Fuse the wire at the battery and also fuse it at the amp. Don't relay on the fuse in the amp to protect anything. Depending on where you place the amp determines where you will place the crossovers and how many wires you will run to the front speakers. Say, for example you place the amp in the trunk or behind the rear seats. Then I would place the crossovers near the kick panels under the dash or on the sides. You then run a single (for each speaker set) long run of wire to the crossover instead of two sets of wires (one for tweeter and one for mid bass woofer). If you set the amp under the passenger seat, then you can place the crossovers next to the amp and place short runs of wires to the tweeters and woofers.

So, it depends on how much wire you want to run and how long. It is better to do a long run of speaker wire (ten gauge) to the crossover from the amp and short runs of wire to each tweeter and woofer.

Ground the amp using very, very short run of ten gauge wire right next to the amp. Find a metal nut next to where you plan on placing the amp and use it to ground the amp.

Run the power wire on one side, the interconnect wire (from the head unit) down the center and the speaker wires down the other side. Cross wires only at 90 degree angles (not at all if you can help it).

Do a clean installation and you won't have any noise.

Start the engine before you put the seats and carpet back in and listen for any electrical noise from your system. You will create all new cuss words if you finish everything and didn't do this first and then you hear the electrical noise. It is 99 percent due to poor installation and not alternator noise. If you simply move a single wire or component, the noise goes away. The trick is finding which wire or component. So, do the installation clean the first time and there won't be any noise at all.

Make sure the speakers fit in the doors before you cut anything. I have seen more people buy speakers, cut the holes, mount the speakers and roll up the windows only to either have the window hit the speaker magnet or the window crank hit the speaker grill. I'm still laughing.

You can upgrade by eliminating the passive crossover, getting active crossovers and another amp. Then the sound is much much better. But, do it this way first and upgrade latter if you want. Also, the next upgrade should be a subwoofer and a sub woofer amp. I did mine your way first. Then got the active crossovers and another amp, then the subwoofers and subwoofer amp and crossover. Boy oh boy. It took a while to get there, but it is well worth it.

Have fun.

Lawren

1983 240T (287k miles, black)
1995 850 T5R (71k miles, black)
1970 Plymouth Barracuda (340 Cuda, in-violet purple)

The crossovers have little spade lug crimp screw jobbies. There's a pair od screws on the crossover for input, a pair for midrange amd 2 pairs for your highs. Attach the speaker wires coming from our amp to the input screws and then run the midrange speaker wire from the appropriote screws to the lugs on the speaker, should be labeled. Finally, you'll need to play with highs as the extra screw will allow more or less highs to the tweeter. For this reason, I would mount the crossovers under the dash near the doors so that you don't have to disassemble the doors to move the one wire. Through all of this make sure you keep the polarities the same, negative to negative, positive to positive.

As far as the RCA cables, do you have an aftermarket stereo? If not, your amp is probably equiped in such a way that you can run speaker wires to it, it doesn't sound as nice this way but it work. If your deck does have RCA outputs, how many? I could banter on and on about the 3 possible scenarios here but it's probably easier to wait for a response.

As for running wires, 10 gauge should be the smallest power wire option for you, 8 gauge would be even better. The previous suggestions should be noted and I'll sume up real quick...power wires on one side of the car and signal wires on the other to reduce the chances of introducing noise into the system.

Post back on the details of your deck, how many pairs of RCA outputs are there?
--
Portland, OR 1987 240 dl wagon (not so rusty anymore) 'rustbucket'

How I did it in my son's 81:

-front door spkrs driven by the (JVC)CD unit...17W RMS/ch is more than enough.
-rear 6.5's in the package shelf driven by two channels of the 4-ch amp.
-Rockford-Fosgate 10-in sub driven from the other two amp channels, bridged.
-sub is in a 1cu.ft. sealed box built to fit tight against the sheet metal at the front of the trunk. Ski pass-thru door is open, box front is "sealed" by dense foam rubber ring to the front of the trunk, so all the pressure impulses from the spkr cone go through the pass-thru into the car interior. Just drop the rear center armrest and BOOM! (Totally hidden, no metal cutting, removable when(if?) the car is sold, etc.)
-amp power wire is a 10ga from the battery through the firewall, and down the left side under the door sills (just pull/pry wiggle the black plastic sill covers and up they'll come), then up and over the wheel well into the trunk. 10ga is more than enough for up to a 100 (real, RMS) watt amp. Put an inline fuse in this wire as close to the battery as possible.
-run the RCA patch cord(s) down the other side of the car, again, under the sill covers. Don't run these audio signal wires parallel to 12V power wiring for any distance or they risk picking up interference.
-the amp is mounted to a piece of MDF, but plywood will do. I rigged up a set of brackets to firmly screw this to the trunk interior metal behind the seat back, over to the right side.

Crossovers? I'm guessing you mean bass-blocking capacitors. Others with more car audio knowhow may correct me, but I think the practice is to mount them inline with the speaker positive lead, close to the speaker.

Finally, if it's not too late, I'd trade the 6x9's (lots of metal cutting) for 6.5's (a little metal cutting) or 5.25's (drop in). They will have plenty of top and mid range and the sub will fill in the bottom end...you don't need the 6x9's.

--
Bob (81-244GL B21F, 83-244DL B23F, 94-940Sedan B230F)

I ran my amp power down the drivers side, drilled a hole trough the firewall near the top and put a grommit in (wiring kit came with it) to keep it water tight. I ran it all the way along the drivers side to the trunk, there is a place for it to go under the seat and there are other wires there too (for the tail lights I suspect) and there's an opening near the top at the rear seats I ran it through. I ran the RCA's and speakers wires on the opposite side (to avoid noise you can get by running the power, RCA's and speaker wires together). I had my amp against the rear seat in the trunk mounted to the wall on the passenger side. I'm not sure, mine's an '85 Turbo but I think all this stuff will be the same. I don't know much about crossovers (never used them seperate from an amp) but they should just go inline where ever before the speakers, anyone correct me if I'm wrong. HTH.

I haven't done this myself, but my buddie has the amp under the passenger seat. All wires go under the carpet and along the passenger side doors- power goes through the firewall somewhere under the glove box.