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This project will cover the creation of a custom subwoofer enclosure for a 12" MB Quart Subwoofer.  If you have any questions regarding the procedure, etc, please email us and we will be glad to help you on your project.

[click for larger image]

  • fiberglass roller tool (to remove air bubbles)
  • scroll saw
  • sanding block
  • good dust filtering air-mask
  • basic hand tools
  • polyester resin (standard fiberglass resin)
  • polyester resin catalyst
  • mixing vessel
  • one yard of lycra
  • MDFB

Always wanted to know how the pros make these fiberglass enclosures?  Read on ..

The following mini-project will cover the basics of how to create your own custom-subwoofer enclosure.  In this project, we made use of dead-space in the spare-tire well - this is a particularly good source of air volume for installing a 15" subwoofer without sacrificing trunk space.

  • exact enclosure volume
  • odd mounting locations achieved
  • show quality finish
  • custom work (always a bonus)

Before you start the project, read ALL manufacturer's labels for warnings, directions, etc.  Chemicals are dangerous - especially ones found in fiberglass resin + catalysts like methyl-ethyl keytone (the most flammable liquid on earth).  Having said this, should you decide that drinking fiberglass resin is a good idea - you're on your own.

For beginners, you should make sure you mask off anything that you don't want ruined by fiberglass resin.  Also be sure to throw on some garbage clothing - it will be ruined no matter what.

Once the area is masked off, coat the area you plan to make a fiberglass mold from with a generous helping of Vaseline or release wax.  This allows you to pull the finished mold out of the original spot without too much trouble.

Once you are ready, review your fiber glassing technique and proceed to make the initial "layup".

If you do not understand the basics of fiber glassing, have a look at our techtips section for more information.

figure 1

figure 2

If you decide to place your subwoofer in the space where your spare tire once occupied, you will have a workspace which looks similar to that of figure 2.

Once the fiberglass has had a chance to set, you are then ready to remove the mold from its form.  This is a great deal of fun! 

Tip:  If you have access to an air compressor, use an air blower nozzle to help you get the fiberglass form out of the car.

Once the initial form is free from the car, continue to add more layers of fiberglass to the inside to strengthen the walls - this is absolutely critical.

Once reinforcing is completed, move on to the more complicated portion of the custom enclosure: the baffle.

figure 3

figure 4

This step is the most involved portion of this fabrication.

As I was too busy making the form you see to your left, I did not take the time to snap any photos of the process.  I will however re-create this project come spring to better illustrate the process.

Essentially, you create a "baffle ring" which will be the ring you mount your subwoofer "into".  This ring is then held at an angle by a series of stilts which you will cut and measure to fit.  Once the baffle ring and its stilts are joined, join the baffle ring assembly onto a flat piece of MDFB.

In the next step, you will stretch the lycra (or similar stretchable material) over the entire project - sort of like a tent.  This part is critical - too much tension and your project will not have the soft curves, too little tension and you have an alien looking enclosure.

Once you have stretched the lycra over your project, you then bathe the lycra in fiberglass resin.  To do this, I recommend you use a disposable paint brush and liberally apply the resin.

The result will cause the lycra to loosen up slightly and droop a little more than when it was stapled taught.  This is a good thing.  Your initial form is complete!  Congrats.  this is the most difficult stage.

The next few steps will be to reinforce (heavily) the currently thin walls of your new form.  Do do from the outside, gradually making the wall _extremely_ strong. 

figure 5

figure 6

If you do not reinforce the walls enough, your enclosure will flex too much and you will both loose power and sound quality.

Once you are content with the structure's strength, proceed to finish the fiberglass process by sanding and laying down a gel-coat for final finish.

The gel-coat layer is only required if you will be painting the enclosure as opposed to carpeting it.

PS: Carpeting something like this requires a great deal of skill and is thusly not reccomended

Once you have finished the exterior surface of the enclosure, install the subwoofer in the mounting baffle ring and gawk.

Then remove the subwoofer and measure the volume of air inside the enclosure.

Tip:  Fill the enclosure with water, then in measured portions, remove all the water and note the number of liters (L) you removed - this is the enclosure's air volume minus the subwoofer's displacement.

figure 7

figure 8

The next part will include you measuring the bottom portion of the enclosure as well.  The idea is to match your air space as closely as possible to the "Q factor" of your subs.  In my case, the ideal "Q factor" was 0.75 square feet.  I managed to hit 0.74 square feet by simply filling the dead-space in the bottom compartment with fiberglass.

Once your volumes match up, mate the two pieces ensuring an extremely strong joint and you are done!  Simply install the terminal block for your wiring and install this bad boy in your ride!  Congrats!

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