Intro

I wanted to relocate this sub into the cabin, where the stock used to be located. My 8" JL sounds like crap without an enclosure. I had to make a fiberglass enclosure to take advantage of the little air space in the compartment between the cabin and trunk. This is my first time working with fiberglass. I'm already thinking of my next fiberglass project.

 

Removal of Panels

Cup Holder: Lift up th round rubber pads that the cups sit on. There's a slotted screw under each holder. Remove the screws. The cupholder will lift right up. There's a wire attached to the cupholder assembly. Just let the cupholder dangle.

Subwoofer grill: This is held on with plastic clips. There is 1 clip at the top, 1 bottom, 2 on each side. Caefully pry off the grill. Don't pry at the corners. There are no clips there. It'll only break the grill. It's easy to crack the grill. Mine cracked in several places. But when the grill is put back on, the cracks aren't visible. After you get the grill of, you'll see 4 torx screws. These need to be removed.

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Center panel: This is secured by several metal clips. Start at the bottom at the subwoofer location. Grip the panel at the subwoofer opening and pull. Work your way up, pulling the center panel towards the front of the car. Remove he screws that hold the subwoofer assembly.
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Side panels: This description is for the panel behind the passenger seat. The passenger side panel is also secured by metal clips like the center panel. Start at the lower left of the panel (left, as in when you're facing the rear of the car.), where the panel meets the door jamb. Reach under the pastic and pull towards you (towards front of the car). Continue pulling along the bottom edge until the entire bottom of the panel is loose. The top of the panel needs to be separated from the black plastic cover above it. Pull downward on the panel to separate it from this piece.
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Center plate: Disconnect the green connector plugged into the white motor at the top of the center plate. There is a ring at each base of each rollbar (2 rings per rollbar). Loosen the ring closest to the center of the car for each rollbar by turning it counter clockwise until it stops. Slide the ring up the rollbar about 3 or 4 inches. You may have to twist the ring as you're sliding it up. The center plate is connected at the top with two bolts. These bolts are located under the plastic cover that's under the rollbar. With the rings slid up the rollbar, you can lift the plastic cover to reveal the two bolts to be removed. Remove the remaining bolts holding in the center plate.

 

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MATERIALS & HARDWARE

Everything I used was either from Home Depot, Radio Shack or some dark corner in my my garage. I wasn't in the mood to drive around and source the professional stuff.

  • 1 gallon fiberglass resin & hardener (Home Depot, about $25. Comes with 2 tubes of hardener.)
  • 1 extra tube of hardener (Home Depot, about $6.00. The 2 tubes that come with the resin aren't sufficient unless you're working on a hot day.)
  • Fiberglass cloth (Home Depot, each package contains a 3' x 9' sheet. I used 5 sheets. About $6.00 per package = $30.00)
  • 1 quart Acetone for soaking brush and cleaning up (Home Depot, about $8.)
  • 1 paint brush, 2" wide or less, cut bristles to 1" length (Home Depot, about $1.50)
  • 3M spray adhesive (Home Depot, $don't remember)
  • Speaker enclosure carpet (Home Depot, $don't remember)
  • 5/8" or 3/4" MDF (I used a scrap piece I had lying around)
  • 24" wood dowel stick, 3/8" or 1/2" thickness (Home Depot, abu $3.00)
  • 1 piece of stretchy cloth (At least 14" x 10". I used an old t-shirt.)
  • Hot glue & gun (I used superglue, but hot glue would have worked better)
  • 60 grit sand paper
  • Duct tape
  • Cardboard (thickness of standard cardboard box)
  • 8 T-nuts, #10-32 (Home Depot, about $5.00)
  • 8 #10-32 screws (Home Depot, about $3.00)
  • Banana plugs (Radio Shack, about $4.00)

 

The Mold

I started by making a positive mold (also known as a "plug") out of cardboard and duct tape. You lay fiberglass inside a negative mold. You lay fiberglass on the outside of a positive mold. After the first layer of fiberglass, the object will be split across the middle so the mold can be removed. With the plug removed, the 2 pieces will be re-joined and fiberglass is applied on the outside. The enclosure is going into a very tight space. Since I'm laying fiberglass on the outside, the dimesions of the enclosure grows as I lay more layers. So, I made the mold about 1/4" smaller all around to compensate for the thickness of the fiberglass.

Here's the mold taking shape, like some architecutal structure.

After the mold was complete, I covered the whole thing with duct tape. Fiberglass resin will not stick to duct tape. This will make it easy to release the fiberglass from the mold. Some people use masking tape. The front is left uncovered because the front will be made later, once I've determined the position of the baffle.

The mold was mounted face-down on a pole so I could access all sides for laying fiberglass.

 

Laying Fiberglass

The bristles of the paint brushed were trimmed to about 1" to make them stiffer.

(I put on my respirator [not a dust mask], gloves and long sleeved shirt at this point. Cutting and sanding fiberglass releases small particles which are hazardous to breathe and itchy on the skin. Making a mess is unavoidable. Be prepared to throw those clothes away.}

Fiberglasss cloth was draped over the mold and pre-cut into pieces. When making these peices, allow about 1" of overlap.

I used 2 or 3 ounces of resin at a time. Resin was poured into a plastic cup. Hardener was added according to instructions, 14 drops of hardener per ounce of resin. Instructions were based on working temperature of 70 degrees. On a colder day, add a few more drops; fewer drops on a warmer day. I used disposable chopsticks to mix the resin and hardener. Mix very thoroughly. You'll be using the mixing stick several times before the project is done. So, don't set them down on a flat surface where they'll get stuck. After mixing, I poured the resin mixture into a larger pastic container, easier to dip the brush into.

I brushed a light coat of resin onto the mold. This helped hold the cloth in place while I brushed on more resin.

Fiberglass cloth was laid onto the mold and resin brushed onto the cloth. Use just enough resin to soak the cloth. Don't apply so much resin that it runs and drips. Keep in mind that the cloth gives fiberglass strength. Resin is the glue that holds the cloth together. Resin stays liquid in a container for 10 or 15 minutes before it suddenly turns into a thick gel. When brushed onto fiberglass cloth it stays liquid longer, giving you more time to work. Smooth out any bubbles with the brush. It helps to tap the bubbles out with the brush. Small bubbles less than 1cm are normal, but large bubbles will weaken the structure.

Soak the brush in Acetone in between applications to keep the bristles soft. Just shake off acetone before each application. Acetone can also be used to clean resin off of things like scissors. These went in the trash because Acetone melts plastics. Oh, and don't use plastic containers for acetone.
After 1 layer of fiberglass was laid, I left it to harden for 2 hours.
I only applied one layer of fiberglass before I split the object to remove the plug. It's easier to remove the mold when the fiberglass is still flexible. A seam was cut to split the object open.
The fiberglass was separated from the mold by prying them apart. The fiberglass didn't stick to the duct tape, but it still took some prying with a screwdriver to release the fiberglass from the mold.
The 2 pieces were taped back togehter to prepare for more layers of fiberglass. Since I'll be applying fiberglass on the outside, I taped inside. 3 layers were laid before I let it sit to harden. I waited about an hour. It was hard, but a little tacky. I laid 3 more layers and let it harden again, overnight this time. Once it's completely hardened, press on each surface with your thumb. If it flexes, you need to add more layers. Large flat areas need more layers than small areas, curves and angles.
Rather than laying down a hundred layers of fiberglass to eliminate flex, you can use braces. I made posts to brace large flat areas out of wood dowel. Fiberglass cloth was tacked onto the ends of the braces with superglue.
The posts were placed in position and resin was aplied to the fiberglass cloth to permanently attach them to the structure.

The surface on which the subwoofer will be mounted is called the "baffle". While I waited for the fiberglass to harden, I fabricated the baffle out of MDF. Mine was a simple ring. I made a circle cutting guide for my router using a piece of scrap acrylic (Plexiglass). You can also use a thin piece of plywood or hardboard. The guide was installed in place of the plastic pad originally mounted on the bottom of the router. To create a ring, 2 circles had to be cut.

The outer diameter of the ring was cut first. To make the cut, a screw was installed into the MDF, through the guide. The router pivoted around the screw to create a circle. After the cut was completed, I was left with a circle

A second circle was cut, leaving a ring. If you can't figure out how I made different sized cirlces using the guide, don't bother with the guide. Just use a jigsaw.


Using the subwoofer as a template, the locations of the mounting holes were marked and holes were drilled to accomodate the t-nuts. Most enclosures use wood screws to fasten the subwoofer to the baffle. Considering all the time I've spent on this thing, what's a few more minutes to drill holes and install t-nuts?

What are t-nuts? They're nuts with teeth, eek! (See the picture.) There are plenty of advantages to using t-nuts. My reason: I hate wood screws. Even if you decide to use wood screws, never use slotted (flat) screws. I once punctured the cone of a speaker when my

screwdriver slipped while installing a slotted wood screw. I swore never to use them again.

T-nuts were installed with a hammer. A good size screw to use is #10. I used hex screws because I'm hi-tech like that.

The outside surface of the baffle was covered with duct tape to avoid getting fiberglass on the holes. The outside face is the side without t-nuts.
 
The front of the enclosure is going to be an odd shape. Due to space constraints, the subwoofer had to protrude out of the enclosure at an angle. To create free-form shapes, a surface can be created by stretching fabric. I used material from a t-shirt, not mine. This is actually a picture of the t-shirt after it was glued to the baffle.
 
Fabric was superglued around the side of the baffle. Note to self: Next itme, use hot glue. Leave some area for the fiberglass to come incontact with the MDF.
The front of the enclosure was trimmed with a saw. You can use a Dremel tool, but the saw was just as quick and didn't kick up any fiberglass dust.
The exact position of the baffle was determined by test positioning the baffle with subwoofer in. Pieces of wood dowel were superglued in place as temporary braces to hold the baffle in position. Note to self: Next time, use hot glue. The baffle was then superglued in place. (After the whole project was done, I broke these two braces off and discarded them, as they didn't provide any structural support.
 

Once the fabric-covered baffle was glued in place, the fabric was stretched over the enclosure and tacked it in place with superglue. Note to self: Hot glue.

Resin was brushed onto the t-shirt material and it was allowed to harden for 2 hours.

 
Excess t-shirt material was sanded off before laying fiberglass.
 
3 layers of fiberglass were laid, allowed to dry for an hour and another 3 layers were laid. I allowed it to dry for 2 hours.
 
Excess fiberglass cloth was trimmed around the baffle and sander was used to sand the fiberglass flush with the baffle's face. Here's the end result
 
For this enclosure, I felt it was easier to use these terminals instead of the type of terminal box used in must MDF enclosures. Each one only requires a small hole for installation. Rubber washers were used on the inside and outside of each post to prevent air leaks.
 
Inside view of the terminals.

The entire enclosure was covered with carpet not for esthetics, but to prevent the hard enclosure from vibating against anything and making noises.

I sprayed adhesive on the enclosure and on the carpet, waited about 2 minutes, stuck the carpet onto the enclosure and trimmed with a blade. You can cover a couple of sides with one piece or cover one side at a time.

 
Original center bracket.
Modified bracket. Not much is left of the original bracket. I had to cut all that metal off to accomodate the enclosure. It didn't seem to compromise support of any of the panels because they snapped in just fine.
Enclosure installed.
 
Panels partially installed.
 
 Finished.