Fiberglass Subwoofer Enclosure How-To

[Robbyho]

Hey, this is Rob from Art of Noise Audio. I build custom fiberglass enclosures for Magnums and other cars. I've seen a lot of interest from people who want to take on the project themselves, so I decided to write a how-to. I usually build my enclosures from molds that I've made of the rear pockets, but I made this one from scratch to show how you could do it. This project is not for the beginner, and if you aren't good with working with your hands, it might be best to get a local shop to do the work. I also offer enclosures for sale and you can email me at Robbyho@gmail.com for more information.

Ok, so here goes. The first thing you need is patience. Anyone can make a work of art, but you can't rush anything. Every step builds off the step before, so take your time and do each step to your best ability.

I used:

2" Blue Painters Tape (not the green, trust me)
Tin Foil
Plastic Drop Cloth
Scissors
Razor Knife
Tape Measurer
Sharpie
Respirator
Dust Mask
Vinyl Gloves
Power Drill
Hot Glue Gun
Air Compressor
Cut-off Wheel
Knurled Bit
D/A sander w/ 40 grit pad
Router w/ circle jig or Jig Saw
40 grit 9"x11" sand paper
2"x4" x11" wood block
2" Disposable Paint Brushes
Bondo Spreaders
Containers

Materials:

1.5 oz. Fiberglass Mat, approx. 38"x 2 yards
Fiberglass Resin, approx. 1 gallon
Body Filler, 1/2 gallon Z-Grip
Tee Shirt Fabric or Fleece
3/4" wood, MDF or a hard plywood
Wooden Dowels

The first thing to do is tape off the Pocket. I use tin foil for the big surfaces, and tape to cover all the seams.



When I taped the pocket, I didn't tape the the front and rear bottom corners and the top corner. Instead I used a piece of tin foil to bridge across them. If I taped tight into the corner, the enclosure would not be able to slide in and out easily when it is finished.



And then cover the floor with a drop plastic.




Now it is time to cut the fiberglass pieces. I cut them to overlap each other and to be bigger than I want the final enclosure to be. It's easier to trim more off than to add more on.

[Robbyho]

And I always keep some extra pieces that I can add to the mold after I've laid all that glass.



I get my material from Uscomposites.com. They have great material and great prices. I use 435 standard lay up resin. It is leaps and bounds better than anything from home depot or west marine.


I will spread some resin all over the pocket in order to get the f'glass to stick more easily to it.
I place the pieces on my lay-up board in the same pattern that they go in the pocket. That way I don't get confused as to what goes where.



Then I wet out the pieces one at a time and place them in the pocket. It is important to soak them completely and place them in the pocket before they get soggy and fall apart.

[Robbyho]

It's important to get the 'glass to stick when it is hanging upside down.



Notice that there are no air bubbles. I make sure to press them out with the paint brush. It also helps to use fresh, quality resin.



Fast forward an hour or two (in warm weather). The glass has to be hard in order to pull it out, if there are any soft spots, wait longer.
Pulling the enclosure out is a slight challenge b/c all the tape has to be unstuck at once.

I'll pull off as much tape and foil as I can and place the backside of the enclosure in the sun for another hour to make sure it is thoroughly cured.

[Robbyho]

And once it is cured, it is time to trim the excess 'glass off. I place it back in the pocket and draw the lines with a sharpie.



And I trim.





Now it is time for more 'glass to reinforce the enclosure. Right now there is one or two layers of 1.5 oz. matt everywhere, which is equivalent to 2-3 layers of 3/4 oz. matt that most shops use. I use 1.5 oz. b/c it makes the process quicker. When using thicker 'glass, it is important to make sure it conforms to all the curves.

When reinfocing, I use strips of 4" mat tape. I overlap each strip and put another 1-3 layers everywhere. The flat surfaces are the weak points, so I place more material there. The enclosure ends up being about 1/4" thick using this process.

[Robbyho]

And I let that cure.



I put it back in the pocket and mark with a sharpie where it needs to be trimmed.



Now I make a speaker ring. I like to recess the speaker so it will be flush with front baffle. To do this, I can a) use a jig saw to make two rings and glue them together, or b) use a router with a circle jig to make a recessed circle.

[Robbyho]

Now I place the enclosure in the pocket and set the ring up where I want it to be. If I am angling it, I will use wooden dowels to affix it in the right location. Since this sub will be pretty straight, I glue it right to the enclosure. I scuff up the 'glass where it will be glued a bit to get the hot glue to adhere.



I make sure that the sub will have enough clearance to fit. I test fit the sub (or one of equal depth) in the ring to make sure it clears. Then it is time to wrap the box in tee shirt material and soak it with resin. I use super 77 as my spray adhesive.



I use tee shirt material b/c it is thin. Fleece needs a lot of resin to soak all the way through, and to me seems wasteful. I'd rather use that resin on 'glass over the tee shirt material.



I start by spraying both the fabric and the enclosure with the super 77. Then I will wrap the enclosure, starting with the speaker ring. It is important to stretch the fabric tight.

[Robbyho]

Then I will soak the material in Resin. I make sure to soak the ring and the edges all the way through, since they have some strength in the final enclosure.



Once it cures I will trim it with a razor knife and d/a and cutting wheel where necessary. You can see the material got slightly warped when it cured, no big deal, I can smooth it with bondo easily.



And here it is trimmed.



Now it is time for some more 'glass. I place an MDF circle over the speaker hole to keep it resin free. I also place 1"x3" strips of f'glass on the inside of the speaker ring to give it strength from behind.

[Robbyho]

It cures.



And gets trimmed and test fitted.



I use a knurled bit to trim around the speaker ring.



My favorite part: Bondo. Basically I mix the bondo with some hardener on my bondo board. It is important to keep the bondo board clean. I scrape it clean after every spread and sometimes will give it a quick hit of 40 grit.

[Robbyho]

I cut the circle out witha razor knife while the bondo is still rubbery. If you've made it this far without a compressor, you can sand the bondo down by hand. I'll staple a piece of paper to an 11" block of 2"x4" to make a sanding block. That will yield a flat surface.

After sanding the first spread.



And after sanding the second spread.



At this point the enclosure is ready for vinyl. If I were painting it, I would do one more spread of bondo thinned out with resin. If you haven't thinned out your bondo with resin before, try it, it will change your life, I swear.

Now I test fit it in the pocket.



Now off to the upholsterer. I use the OEM light greystone vinyl from Jeep, not from Chrysler. The Chrysler stuff has a cloth back and is awful to stretch, the Jeep stuff is much more workable and looks a lot better. Obviously, my car is slate grey and this enclosure was for someone else.

[Robbyho]

But wait, we still need to put in binding posts. Here's the materials I use.



I drill the holes.