Last Updated: 09/27/2025 @ 07:03 am

Community Member Credit: elusive

This came about because I had to get rid of my lunker of a sub (12″ ported) and reclaim half of my trunk space. I didn’t want to spend $400 on Wicked’s box and wanted to learn to lay fiberglass. I am mounting an Alpine Type R 10″.

Difficulty: Moderate

Time: For me, it took about a week since I only worked on it here and there in between work

Cost: I spent a little over $100 on materials

Required Materials:

• Respirator!
• Masking tape
• Aluminum foil
• 1 gal. fiberglass resin (I bought mine from Home Depot but you could use your preferred brand. I went the cheap route but the box has been holding up)
• Fiberglass mat (I purchased from Tap Plastics by the yard, I purchased 5 yds but ended up having extra)
• 1 yd. fleece fabric
• Wood to build mounting ring
• Interior carpet for the finish (I used Wool from a local fabric store)
• Super 77 spray adhesive (to wrap carpet)

Instructions:

1) Wse masking tape to generously mask off the area you want to set the sub box into (commonly the nook near the trunk door). Some people remove the compartment below (see WickedCAS box) but I didn’t want to cut my trunk mat so I just did it in the corner.

Mask a lot of areas. Afterward tape the aluminum foil on top. This will allow easier removal of the first layers of fiberglass. Cover a lot of your interior and car in general, with some Kraft paper, anything that even has the remote chance of getting fiberglass resin dripped onto it.

I don’t have pictures of the aluminum foil or laying the fiberglass. See tutorials on how to lay fiberglass, that’s a whole new thread in and of itself.

2) Lay 3-5 layers of fiberglass mat (I did 4 because I was using some lighter density mat)

3) After this first layer has cured, remove it and trim the edges to your desired shape and contour, I used a jigsaw.

4) Now your mounting ring should be cut, or purchased, you’ll want to cut some pieces to act as leg supports to hold the mounting ring at the required depth (I measured the internal box volume by using packing peanuts and a cardboard box with my required internal volume [0.75 cu. ft])

5) Use the fleece fabric and stretch it over your mounting ring to the back of the shell and use the adhesive spray to hold it to the entire edge of the shell as well as to the outer edge of the mounting ring.

6) Lay resin onto the entire fleece (except for where the hole of the mounting ring is) and before it hardens, use a razor to trim the fleece from the mounting ring face.

7) After the fleece hardens, lay 3-5 layers of fiberglass over the fleece.

8) The final stretch…Once it all hardens: sand, trim, grind, fill, primer, whatever you have to do to finish it up. I had to do a lot of trimming since it was my first time using fiberglass, I made a mess with my edges so I did some grinding to make it sit flush in my trunk.

9) Unless you are painting, go ahead and wrap the box with your carpet or wool using the super 77 adhesive mounting spray.

10) Mount your sub, I drilled a hole and silicones the edges after I ran my wires through the hole. And mounted my amp in the spare tire on a wooden board cut to fit.

Enjoy the music and satisfaction of your custom box!