This tutorial is meant for people with small cars such as mine. I drive a MK5 VW GTI and it has very little storage space. I have always wanted a subwoofer but I have been unable to get one because of their size. In this tutorial I will explain how I was able to fit one with trunk space left over.
Step 1: Step 1: Putting Together Basic Components
The first step to creating such a small subwoofer is measuring the space in which you would like to fit it. I have a two door hatchback and I found that the best place to put it would be in the trunk behind the back seats. I would recommend this spot for most people as it will be the easiest. To create a housing that is flush with the back seats of the car I measured the angle that the seats leaned back and then out how far I wanted the box to go. I simply created the box out of plywood and carpet that matched my car's trim.
Step 2: Step 2: Wiring the Subs to the Box
Left and right positive and negative terminals have to first be wired onto the speakers and connected to the amplifier before anything else as they will be inaccessible later.
Step 3: Step 3: Wiring the Power
The first thing you're going to want to do in wiring your subwoofer is removing all of the trim down the left and right sides of your car. The first thing to wire is the power. WARNING: for safety reasons, disconnect your battery before proceeding with this step.
Step 4: Step 3b
Next you are going to wire the power from the positive terminal of your battery, down the engine bay through the firewall, and around where the trim was taken off all the way to the trunk and to the power terminal on the amplifier.
Step 5: Step 5: Wiring the Ground
The next step is wiring the ground wire. This was by far the easiest step, all that is required is attaching the black ground cable from the amplifier to the body. Any bolt on the body will work, all you have to do is attach it. I found one near my taillight.
Step 6: Step 6: Wiring the Remote Start and Line In/out
The next step is connecting the remote start cable from the amplifier to the head unit, it is easiest to do the line in and out cables at the same time. the line in and out connect down the opposite side of the trim and behind the dash and head unit. Plug them into where the head unit says "SUB". The remote start will follow the same path but will then be wired to the blue cable with the white stripe. a quick splice and tape will work just fine.
Step 7: End
After all of this, the sub woofer will be up and running. Unfortunately the amplifier I bought was fried so I was not able to experience the results of my own work. As you can see in this picture, despite the large sub box, I still have plenty of trunk space which I have used.