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Most speaker boxes are either fiberglass mat, or MDF construction. MDF while easy to work with and achieve good results, lacks the custom touch. Fiberglass allows you more freedom to do what you want. In this guide we are are building a simple box to show the process of working with speaker rings and glass mat. Many of the same steps apply for a built in sub woofer box.

Start by cutting out a MDF base for your new enclosure. If you are building a built in box, this does not apply to you. Once you have your base, you need to figure out how you want to aim your speaker. How you aim them depends on the type of speaker and personal preference. Once you know how you want to aim the speaker you can start cutting and gluing dowels to hold the speaker rings in the correct alignment. These dowels only need to be strong enough to hold the rings until your first resin application dries. Make your enclosure the correct size to meet the volume needs provided by the speaker manufacturer.

Next using hot glue or stables wrap your form in either fleece or cotton. While fleece is the preferred fabric, I like to use cotton. Cotton will soak up less resin which makes for a stronger lighter box.

With the fabric stretched tight you can apply the first layer of resin. In this step you do not use glass mat. You are just trying to get the fabric to retain a shape you can work with. For resin, I recommend a cheap poly based resin. There is no need for more exotic epoxy resins as the resin will not see high stresses or UV. In any case, you should follow the resin manufactures instructions for mixing and working in only a well ventilated area. If you have experience with fiberglass you can add up to 50% more hardner to speed cure times. Any more than 50% compromises strength and creates too much heat.

Now that you have a rigid form you can begin building your mat layers. I suggest the heavy weight mat used by marinas for boat hulls. The heavy weight mat is both inexpensive and strong. Mix enough resin to lay down 3-4 pieces of mat that are 12"x12". You can cut down a large paint brush to apply resin and stab out air pocket. Another method is to use a fiberglass roller. No matter what method you use keep you tools in paint thinner between coats to prevent them from becoming un-usable. Keep applying mat and resin until the enclosure is complete and sturdy. A good gauge of when the box is strong enough is when it can support your full weight.

Once the sub-woofer box is strong enough to support your weight, completely sand it with 80grit sand paper to provide a good base for the auto-body filler you will apply.

The key to applying auto-body filler, is use thin coats and more coats than you think you need. You will need to sand between coats to prevent de-lamination. Whenever sanding use a quality dust mask.

Keep applying and sanding off the filler until all major holes and dimples are filled. Now is the time to install any speaker terminals or brackets you need to complete your install. I also take this time to remove any dowels that have become loose. For any I cannot remove, I simply mud them in place to prevent them from coming loose later.

If you plan to carpet your enclosure you can stop at this point. If you are going to paint it you need to apply a glaze coat to fill any pin holes and minor dimples left. After the finish is defect free sand from 120 to 600 grit sandpaper in preparation for primer and paint. From here you have a wide variety of choices from lacquer paint to Rhino-Liner.