This was my first attempt at building a car sub, so I decided on a simple sealed sub. It turned out okay but the cool part was hacking together a PSU for in-home use. Read on...
NOTE: This build has since been redone with as a ported box, using better tools (table saw!) resulting in a cleaner look and smaller tolerances. See this post.
I only used a half sheet of MDF for the box. I measured and cut the panels to achieve a specific internal volume of around 1.25 Cubic ft.
Since I was going more for sound and not looks, I wanted to make sure that my box eliminated vibrations and resonance, creating a flat response and quality sound. In order for this to happen, I tried to avoid parallel walls and I placed small MDF cubes in the corners to keep the sound from collecting in the corners of the box.
This meant that the panels would NOT be equal and my box would be slightly off square... (This is up to the builder)
Next step was to glue the 4 body panels together. These are the panels that will make up the top, bottom, left, and right panels on the box, and not the front or back panels.
Applying the glue was easy. I had quite a bit of runs as I made sure to use ENOUGH glue to make a good seal. To hold the box firmly together, as wood glue does tend to expand, I taped up the box so it would not shift durring the drying process.
After these panels were dry, I glued the bottom panel on.
At this point, I glued the cubes in the corners and caulked all the seals.
Next, I needed a way to make connections from inside the box to the outside. I had some spare wall terminals lying around so I stripped them from their plastic casing, drilled holes in the box, and epoxied the ports into the box, with 8 AWG wire soldered to their terminals. Later, I would just solder the male connectors to the amplifier outputs.
Before closing up the box and moving onto the final steps, I autographed the insides and added stencil paint to personalize my project. This step, of course, is completely optional. (As you can see, my stenciling skills still need some work!)
The last thing to do was to take care of the front panel, which required a 9 1/4in diameter circle to be cut from the panel. Since I did not have a router and a circle jig, I simply drew the circle with a compass and used a jigsaw. Then, I sanded the edges and applied some sealing tape to the edges so that the the sub would create and airtight seal. Then, the panel was caulked, glued, and screwed to the rest of the box, parallel to the back panel.
I lined up the subwoofer and marked and drilled the holes for screwing the sub in. Then, I wired the two voice coils in parallel, and connected the wires from the audio ports. I used some electrical tape to insulate the connections. Then, I screwed the subwoofer in tightly for a good seal:
The amplifier needed small modifications to work, as it is normally for use inside of a car. First of, I needed a source to simulate a car battery/alternator (12v - 15v), but this will be covered later.
I soldered some easy-connect power connectors, and attached 8 AWG wire to all the connections. Then, I bridged the "remote" terminal with the "+12v" terminal with a flip-switch in between, so I could turn on the amplifier manually. Next, I wired in a 3.5mm -> RCA converter in, so I could get input from my phone or computer.
Because I wanted to use this subwoofer in my house I needed some sort of PSU to simulate a car battery, which would normally be powering this amplifier. Now, the draw on this 12v source will be enormous so I needed something very heavy-duty. At first, I was convinced that I needed a car battery and a charger in my room but thankfully someone pointed out that server power supplies are capable of up to 1000 watts at 12 volts! I chose the Dell PowerEgde 2800 which delivers 930 watts.
In order to make it work, I had to add switches to simulate the power and fan controls on the server, as well as make the power readily accessible with enough wires to carry all the current.
Now, the only thing left was to install the inline fuse, solder remaining connections, and plug everything in properly.
And, you are done. Adjust the gain and subsonic filters on your sub to your liking, and have fun. Try not to disturb the neighbors, however!