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Installer Institute: Custom Sub Box
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For a few years now it has been a trend for subwoofer manufactures to create huge monster subwoofer that require a crazy amount of power and can take up your entire trunk. I guess those of us that don’t have trunks are out of luck that is unless we remove one of our rear seats and drop in a square MDF box. Well I don’t know about you guys but that is not an option for me so I was glad that manufactures heard our cries and recreated a quality shallow mount woofer. In this article we will be taking you though a step by step of building an enclosure for a 2007 Nissan Frontier 4 door truck. This enclosure will be constructed completely out of fiberglass not wood was used in the final product. This build took a total of 10 hours to build and have a material cost of $65.00.

Step 1 The storage bin was removed from underneath that rear passenger seat and the Pioneer TS-SW251 was set into place to check the clearance between the sub and the bottom of the seat.


Step 2 2” masking tape was applied to the entire area to help protect the carpet. We applied some red electrical tape so the reader came see the outline of what the base of the enclosure will be. Once we had the outline we cut 5 layers of 1 ½ oz fiberglass mat.


Step 3 Aluminum foil was then applied over the tape, it was attached with 3M super 77 spray glue. When using this technique you should apply 2 layers of foil, this will make it much easier to separate from the floor when you are ready to remove it. Fiberglass resin was mixed up and applied to one layer at a time. After each layer you should roll any air bubbles out with a fiberglass roller.


Step 4 With the glass dry we popped the base out and begin to shape it. First, remove all the foil and retrace our line, then a jig saw was used to trim edges smooth. Next a speaker ring was made and the base and ring were set back into the vehicle to check the available height. Wooden supports were set into place and the seat was dropped again for a final check.


Step 5 With the supports made the next step was to tape up the top of the base and create a wall of tape around the edges of the part. Once completed the ring was super glued into place on top of the tape. 2 part expanding foam was mixed up and poured into the taped area. Special note: using a cheap blender to mix up the 2 part foam will give the foam even consistency throughout the entire project. Once the foam dried it was cut and roughly shaped with a hacksaw blade and a grinder.


Step 6 With the shape rough the project was sanded flat by hand and then set back into the vehicle for another test fit. When everything checked out we started to reshape the panel to give it some unique contours. With the final shape decided on the panel was covered with aluminum foil, then mold release wax and prepped for fiberglass.




Step 7 Again, five layers of 1 ½ oz fiberglass mat was cut and applied one layer at a time over the entire panel. Special note: While the fiberglass is drying you have about a 2 minute window that the glass is strong enough to trim with a razor blade this will help prevent you from having to grind a lot of fiberglass. With the glass dry the base of the project was separated from the top and all the foam was removed from the inside of the project.


Step 8 Because the panels were built together they will almost snap back into place. To help hold the two parts together extra thick super glue was used around the entire seam. We don’t want to permanently attach them together yet incase we run into a problem when we do our final test fit. Next two rings were cut one to surround the speaker and one to be used as an accent piece for the project.


Step 9 The speaker use set into place and taped up to protect it form filler. The speakers wood ring was also taped with 4 layers to compensate for the thickness of the suede and paint that would be applied later. Dura-glass was mixed up and used to fill in all the areas above and below the accent ring. Once dry it was popped out and trimmed.


Step 10 With the accent ring done it was time to form the ring to the box. To do this it had to be taped with a layer of 2” masking tape, then a layer of double sided tape (compensate for material thickness) and a last layer of masking tape to hold the double sided tape in place. Then body filler was mixed up and applied to the entire panel including accent ring. Once dry the box was sanded smooth.


Step 11 The accent ring was removed from the panel and taken to our spray booth where high build primer and color match base and clear were applied to the accent ring.


Step 12 It was decided to cover the panel with black suede, contact adhesive was used and sprayed on both the box and the back of the cover material. Special note: It is always a good idea to use a new pair of latex gloves to protect the new material. The speaker ring was next to get covered.


If you would like to build your skills as a mobile electronics installer and learn from the best fabricators in the industry log onto our web-site and see what the Installer Institute can do for you.

Installer Institute
1524 Ridgewood Ave.,
Holly Hill, FL, 32117
(800) 354-6782

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