DIY GRP Molded Subwoofer Enclosure for My Car
Project Date: 2006 Summer holidays.
Problem Description: I wanted two 12 inch subwoofer enclosures in my small boot. I also needed enough free space for holiday purposes. I then researched viable subwoofer drivers and found some pioneers. I noted the recommended volume for each driver and made sure that i can still have enough room in the boot. These subs in my car, fit perfectly into my fibreglass enclosures. The GRP enclosures are perfectly matched in volume according to the subwoofer driver’s specifications.
I lined my boot with newspaper and used masking tape on the sides of my car to act as a mold. Car Wax was used as a releasing agent for when I applied the first gel coat.
Both sides were prepared so that I could make an enclosure for each side.
Applying the first gel coat.
Waiting for the gel coat to harden via the catalyst. More layers of fibreglass were added to give strength for use against the high sound pressure levels inside the enclosure.
MDF (Medium Density Fibre) board was used where a straight surface was needed. Fibreglass was used for any curved surface.
The MDF subwoofer rings were cut via a jigsaw and were adhered to the sides via small layers of resin and fibreglass.
The resin and fibreglass holding the woofer rings into place.
The resin and fibreglass holding the woofer rings into place.
Why not do up my side doors aswell! Make sure to use plenty of release agents for your door otherwise you’ll end up with hard to remove resin.
When the enclosure were dry, they were removed and sanded via an electric sander.
Now that we have a molded back, it is now time to mold the top. Wax coated McDonalds billboard are great to use as a mold as they already have a release agent. I however applied car wax onto the mold as extra precaution.
This is how I affixed cardboard as a mold to my enclosures.
Using a pen to help create a tight edge against the ring.
Make sure that the cardboard mold is as tight as can be to the edges. You will be applying layers of resin and fibreglass here!
Applied two layers of heavy fibreglass. I made sure they were cut perfectly for the top mold. It is also good to label the fibreglass so you don’t get mixed up between the right and left enclosures.
Applying the first gel coast on the top mold of the enclosure.
My side door fibreglassed and covered with black felt.
Forced curing the resin. The catalyst will cure faster and more efficiently when subjected to heat. Force curing is a common technique especially when building boats.
My two enclosures out in the sun sitting on top of my McDonalds McHappy Day cardboard.
Applied expandable foam to the interior of the enclosure. The suspended air pockets and randomly ridged surface diffuses and dampens the air pressure inside the enclosure.
Covered the enclosure with black felt.
Screwed the enclosure to the chasis of my boot.
My pioneer sub with its protective grate.
My two hand built enclosures with my self installed pioneer sound system with the addition of a capacitor to maintain constant electric current to my car when large transient audio signals occur.
Automotive, Personal Projects | 
December 7, 2006 7:52 pm
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By Edmond den Dekker, September 28, 2009 @ 2:59 pm
Hello, This is a project i did back in 2006. If you have any questions about this project, just leave a reply to this article! Have fun making your GRP subwoofer enclosures!