How to Make a Fiberglass Subwoofer Box

Step 16 16. Sanding

If you made this right, making sure all the fiberglass was laid good with no bubbles and the fleece was wrinkle free you should not have to sand. But chances are there a few humps, or places where it needs to be sanded a bit. Just lightly sand the area, (wear your face mask!) until the area is filed down. If you need to have a place filed in, use more fiberglass, or use bondo. If you are carpeting the box it isn't too important to make it smooth, but vinyl or painting requires it to be smooth.