Cars & Vehicles Car Audio

How to Build a Custom Fiberglass Subwoofer Box

    • 1). Determine the size of the enclosure. The specific speakers/drivers you use will have their own requirements and recommended enclosure volumes. Determine the inside air volume necessary to produce an adequate amount of pressure. Determine the enclosure's type.

      Sealed enclosures are best for tighter bass and driver response, but do not offer the same amount of bass resonance as other types.
      Ported enclosures produce additional, deeper bass, but at the cost of of mid-range bass and tight responses.
      Band-pass enclosures are a special design that provide exceptional response at a specific frequency range. They are not suitable for all drivers or all types of music.
      Make your pattern. Use cardboard, tape, and glue to form the shape.
      Apply fiberglass resin and mat to the surfaces.
      Cut the box in half, then in half again. The fiberglass box is now larger than the pattern.

    • 2). Remove cardboard from the inside. Lap joints 3/4" (all equal).
      Use pop rivets or other fasteners to assemble the box.
      Apply additional fiberglass resin and mat again while maintaining a flat and uniform thickness. Two coats of resin and mat will be extremely strong. Use an automotive body filler, such as Bondo, to further strengthen and seal the box.
      Sand as needed. Start with a 40 or 60-grit sandpaper to even out uneven or rough areas. Move up to a 200-grit or higher sandpaper to finalize the finish.
      Coat the inside and outside with resin.
      Use polyfill inside the enclosure if additional air volume is desired. Polyfill will dampen the pressure inside the enclosure to simulate a greater overall air volume.

    • 3). Finish with auto paint, auto carpet, or leather

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