With gas prices rising and the economy tanking, maybe we all (that includes car audio enthusiasts) need to take some cost-cutting measures. I decided to take a car that had an install in it for years and update it. There's a lot of carbon fiber in the rest of the car, and I wanted to use carbon fiber in the sub box to match the theme. I also wanted this box to be as light as possible. I took a piece of 12-inch PVC left over from another project and decided to use that for the box shape. This enclosure is made from 6061 aluminum, carbon fiber, and a little epoxy to hold it all together.
Since I knew the radius of the PVC, the outer size was easy to figure out. I then drew up a few braces using a square, adjustable angle finder, and some Mobile Solutions templates. Once the final MDF brace template is done it can be transferred to aluminum on the router table. I'm lucky enough to work with someone who could transfer my design and CNC it, so they were all perfectly symmetrical.
For the face of the enclosure I used 1/4-inch 6061 and cut it on the table saw. I cut an angle on each side, as close as possible to the angle the carbon meets it. Two holes were rough-cut with a jigsaw for our Polk Audio MM1040 woofer. I then used an MDF template to cut perfect holes on the router table. A small landing arch (slightly smaller in diameter than the end cap) was glued to the end cap. This provides a spot for the carbon fiber to be glued to the aluminum.
Squares and clamps were used to ensure the end caps were straight. More clamps and pieces of MDF were used to attach the braces. A 1/2-inch square aluminum rod was glued to the back of the face for a spot to glue the carbon fiber. Duramix panel bonding epoxy was used for all aluminum/aluminum attachments.
Nineteen-ounce dry carbon fiber weave was taped to the PVC then wet-out with surfboard resin. A second and a third layer of 19-ounce carbon weave were added and wet-out as well. Multiple coats of resin were added on top of the third layer of carbon fiber to ensure a flat surface after sanding. A dual-action sander and a long board were used to sand the resin as flat as possible.

|[pic] |[pic] |[pic] |
|1 and 2. Since I knew the radius of the PVC, the |3. For the face of the enclosure I used |4. Two holes were rough-cut with a jigsaw |
|outer size was easy to figure out. I then drew up a |1/4-inch 6061 and cut it on the table saw. I|for our Polk Audio MM1040 woofer. I then |
|few braces using a square, adjustable angle finder, |cut an angle on each side, as close as |used an MDF template to cut perfect holes |
|and some Mobile Solutions templates. Once the final |possible to the angle the carbon meets it. |on the router table. |
|MDF brace template is done it can be transferred to | | |
|aluminum on the router table. I'm lucky enough to | | |
|work with someone who could transfer my design and | | |
|CNC it, so they were all perfectly symmetrical. | | |
|[pic] |[pic] |[pic] |
|5. A small landing arch (slightly smaller in diameter|6. Squares and clamps were used to ensure |7. More clamps and pieces of MDF were used|
|than the end cap) was glued to the end cap. This |the end caps were straight. |to attach the braces. |
|provides a spot for the carbon fiber to be glued to | | |
|the aluminum. | | |
|[pic] |[pic] |[pic] |
|8. A 1/2-inch square aluminum rod was glued to the |9. Nineteen-ounce dry carbon fiber weave was|10. Multiple coats of resin were added on |
|back of the face for a spot to glue the carbon fiber.|taped to the PVC then wet-out with surfboard|top of the third layer of carbon fiber to |
|Duramix panel bonding epoxy was used for all |resin. A second and a third layer of |ensure a flat surface after sanding. |
|aluminum/aluminum attachments. |19-ounce carbon weave were added and wet-out| |
| |as well. | |
|[pic] | | |
|11. A dual-action sander and a long board were used | | |
|to sand the resin as flat as possible. | | |

The carbon fiber popped off the PVC very easily since I waxed the PVC before taping the first layer of weave to it. I rough-cut the carbon fiber with a reciprocating saw, using MDF as a template. After rough cutting, I fine-tuned the cuts with a dual-action sander using MDF as a template once again. With the carbon fiber cut to size, I used Duramix universal adhesive to bond the carbon fiber to the aluminum. Ratchet straps were used at all brace points until the epoxy cured.
The end caps were marked for the mounting braces. I taped two holes in the aluminum for bolting pieces of the old strut tower bar, which then bolts to custom steel plates on the floor of the car. To finish the aluminum, I started by sanding out all the deep scratches, then progressively moved up to 3,000-grit before using a polish compound. Spraying water helps to keep the aluminum cool while sanding. The aluminum was masked off to protect it from being scratched, and automotive clearcoat was sprayed over the carbon fiber.
Once cured, the edges of the clearcoat were sanded smooth. The clearcoat was then buffed and the edges of the aluminum were polished. The MM1040 10-inch woofers fire toward the rear deck of the car. Both the woofers and the box weigh in at less than 50 pounds total. The carbon fiber and polished aluminum match the carbon throughout the car and aluminum rear triangle brace in the trunk.

|[pic] |[pic] |[pic] |
|12. The carbon fiber popped off the PVC very |13. I rough-cut the carbon fiber with a |14. After rough cutting, I fine-tuned the cuts |
|easily since I waxed the PVC before taping |reciprocating saw, using MDF as a template. |with a dual-action sander using MDF as a |
|the first layer of weave to it. | |template once again. |
|[pic] |[pic] |[pic] |
|15. With the carbon fiber cut to size, I used|16. The end caps were marked for the mounting |17. To finish the aluminum, I started by |
|Duramix universal adhesive to bond the carbon|braces. I taped two holes in the aluminum for |sanding out all the deep scratches, then |
|fiber to the aluminum. Ratchet straps were |bolting pieces of the old strut tower bar, |progressively moved up to 3,000-grit before |
|used at all brace points until the epoxy |which then bolts to custom steel plates on the|using a polish compound. Spraying water helps |
|cured. |floor of the car. |to keep the aluminum cool while sanding. |
|[pic] |[pic] |[pic] |
|18. The aluminum was masked off to protect it|19. Once cured, the edges of the clearcoat |20. The MM1040 10-inch woofers fire toward the |
|from being scratched, and automotive |were sanded smooth. The clearcoat was then |rear deck of the car. Both the woofers and the |
|clearcoat was sprayed over the carbon fiber. |buffed and the edges of the aluminum were |box weigh in at less than 50 pounds total. |
| |polished. | |
|[pic] | | |
|21. The carbon fiber and polished aluminum | | |
|match the carbon throughout the car and | | |
|aluminum rear triangle brace in the trunk. | | |