Building a complete car audio system is expensive. When deciding on installing a subwoofer, you must decide whether you would want to be able to carry groceries or have better sound. I like my groceries so I decided to build a custom enclosure to maximize the space I have available in my car. Using the layout of the hatch area, I found a suitable space for the subwoofer and cut out the shape on cardboard. I liked the use of this space as it wouldn’t impede in any lights and there is ample space for a nicely sized subwoofer there as well. The only thing it would block would be the emergency jack but the sub-box shouldn’t be too heavy to move it.

After identifying where to place the subwoofer, I needed to mock up some patterns on cardboard to later transfer onto our MDF board. I liked having the cardboards like this as it allowed for a simpler assembly while retaining a good use of space. 

Together with the top and bottom panel, the idea was coming to light and I liked the direction where it was going. I hadn’t decided on the side depth permanently at this point however.

Ready with the patterns, I began with the side pieces. I used the table saw to trim up a 2’x2′ sheet to fit.

Cutting the sheet in half made it easier to use with the saw. However, in my amazement, I failed to take into consideration the non-zero thickness of the blade and made imperfect cuts. Additionally, I forgot to take into account the thickness of the MDF when dealing with non-perpendicular joints. Thus, the work with the table saw was almost all in vain, except for the top piece, the round piece on the previous picture. 

Using a combination of a miter saw and a jig saw, I cut the pieces and assembled them using wood glue first, then wood screws to provide a strong hold.

At this point, I had the box mostly assembled except for the side piece. Here I should have waterproofed the seams from the inside but I did so in a later step. 

My workstation had become quite a mess after a full day of work on building the box. I had test-fit the piece several times and with each piece on the car before assembling it all together.

After fully assembling and waterproofing the box with silicone from the inside. I sanded the piece using 80 grit sandpaper to remove all the sharp edges and corners. I also used this to flush the pieces. I wasn’t too worried about the surface finish of the piece as it was to be wrapped with a carpet fabric. I began to wrap the box with carpet to blend in with the natural environment of the car. I used wood glue as I didn’t have 3m 77 spray adhesive handy, but this worked well enough. I stapled the fabric on the bottom and cut it around the main shape of it with scissors. I carefully cut gussets so that the fabric could fold over itself without bunching together.

Putting glue on the piece itself served to be an easier way of installing the fabric. I first wrapped the three main sides, similar to a baseball. 

After wrapping the main three pieces, I noticed there could be some rigidity added with a few additional screws and added some final touches before wrapping the back side.

After a few test fits, I proceeded with wrapping the back side.

I enjoyed how flush the piece looked from the top and how it didn’t stick out far in front as well.

After verifying that the fitment was adequate, I wrapped the backside and installed the subwoofer and amplifier. I used Alpine’s S-w10d4 subwoofer, a 600w 10″ 2-ohm subwoofer. For the amplifier, I used Alpine’s S-A60M, a 600w mono class D amplifier at 2 ohms. They were a perfect match for each other and they fit nicely with these specifications of internal air volume. I screwed the amplifier to the top side to be able to route cables around the back side. I screwed the subwoofer to the enclosure as well and placed the grill and the gasket on top of it as well.

Here is the back view of the subwoofer enclosure, not the prettiest, but when installed, it’ll never be seen.

The other backside of the box, the staples are quite noticeable but I do plan on removing them later when the glue dries more fully.

From this angle, the subwoofer looks quite thin.

And after so many hours and second-guesses, the custom-powered subwoofer is finished and fits very nicely in the corner.

Semi-fully installed in the car, the fit is nice and all that’s left is running wires from the battery, from ground, and from the headunit.

And after all that work, you have built a subwoofer that fits nicely in your car and still allows you to buy groceries.

Costs (excluding subwoofer and amplifier)

Tools used:

• Table saw
• Miter saw
• Ridgid impact driver
• Ridgid drill
• C-Clamps
• utility knife
• Sharpie
• Wire stripper
• Jigsaw
• Sanding pads
• Stapler

Available at TX/RX with a membership of $50

Materials:

• 3/4″ MDF sheets 2ft x 2ft (3) = $30
• 3′ x 4′ carpet fabric = $ 10
• 25 wood screws = $5
• 16 oz Wood glue = $10
• scrap cardboard = free
• Waterproof silicone = $5

Total material cost = $30 + $10 + $5 + $10 + $5= $60

Labor:

• 11 hours @ $10/hr = $110

Total cost of tools + materials + labor = $50 + $110 + $60 = $230

Total cost (including subwoofer, amplifier, 3 feet of speaker wire) = Enclosure ($230) + Subwoofer ($160) + Amplifier ($240) + Speaker wire ($3) = $633