This contraption randomly spawned out of an Idea I had while staring at a broken guitar amp my friend gave me. I stuffed a new speaker, a power supply, and a Sony Xplod head unit into the carcass of the dead amp. This is what I came up with. BTW sorry for a few photo repeats. I took them at odd intervals(as you can see by the change of background).

This unit still functions as a guitar amplifier if you plug into the auxilary input on the rear. There is just no distortion or overdrive feature. I use a 1/4 inch to mono phono plug cable I bought at radioshack for ~$6. I have uploaded some photos of how I set it up....

Step 1: Gather Supplies(Or Maybe You Already Have It?)

As you can tell this was kind of thrown together with random stuff I had lying around, so the cost in my case was free. However, depending on the type of head-unit and functionality you want the price for the individual can change. I just recommend going down to a pawn shop and buying the cheapest one they have. Also if a buddy has one lying around gathering dust, ask him if he'll part with it.

Anyway back to business....

What I used:
Old guitar Amp (the one I used had the circuitry blown)
Speakers:   Visonik 6.5 in V654 Rev.02 4 way (100W RMS, 200W max)
   (Bought at Big Lots a while back for $22.00)
   The original Speaker that came with the amp.
A set of speaker terminals I bought from radioshack.
Wire (I prefer the 2 conductor from radioshack)
Powerbrick 12V (You can probably get away with 11 -15 volts, but you need at least 3 amps)
Buick Logo cut off my cars grill (Logo of your choice, or the original off the amp)

Step 2: Putting It Together 1 (Placing the Initial Components)

The pictures do most of the explaining, I replaced the old speaker with the 4-way, and mounted the old one to the back of the box so that it fires out the hole in the rear. I jammed the power brick into the space where the old metal cage sat. It just fit........ This whole project had the theme of everything coincidentally fitting together.

Nothings wired up yet

Step 3: Putting It Together 2 (Mounting the Hardware)

Next the speaker terminals were mounted to the back of the box near the power-brick so that they would not interfere with the ports on the back of the head-unit. I threw it all together to see what it would look like before I put the unit in.

Step 4: Putting It Together 3 (All Together Now!!)

Throwing in the head-unit to see how it looks. All thats left now is to wire everything up.....

Step 5: Wiring.........

I like to use solder instead of wirenuts, but hey whatever is easiest for you. You could also just twist the wires and electrical tape them. BTW thats not white electrical tape, its medical tape........ I couldn't find the electrical tape at the time.

As for the pinouts on the wiring harness........... have fun. Each company uses a different harness setup, sometimes even between different models. Installed the Sony head-unit in my car so I already knew what each wire did when I was putting this together. You can either consult you units user manual, or google for the pinouts on your harness. Most companies have the install guides for their radios on their websites, which include the wiring diagrams.

Here is the way the speakers are set up.

Front Right= Front speaker
Front Left= Rear speaker
Rear Right= Speaker Terminal
Rear Left= Speaker Terminal

When I was wiring connected the internal speakers first and then screwed on the rear hatch. After that I soldered on the external speaker terminals and remounted them. (not shown, Forgot to take a pic)

Step 6: Finished!!!..........Kinda

This is a build that is still in progress. Im planning on taking the old faceplate that was in the amp and cutting a hole for the radio so that the big hole on the left side goes away. I might also mount a 1/4 inch and 3.5 mm headphone jacks in the old holes that were used for the guitar input, and the gain adjustment knob.

Hope you guys enjoyed the instructable.