Instructables
Picture of How to Make a Fiberglass Subwoofer Box
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Fiberglass subwoofer enclosures present some real advantages for a custom car audio setup. First, they can be shaped to fit a specific vehicle or space within a vehicle, taking advantage of space that couldn't be used with a normal rectangular subwoofer enclosure. Second, if properly executed, they can present a real custom look that will make your car audio system truly "one of a kind."

This tutorial shows you how to work with fiberglass to make a sub box located in your trunk behind your wheel wells. Although this tutorial is made to go into your wheel well areas, you could use this tutorial for anything, kick panels, racks, and other speaker boxes. If you have some knowledge of working with glass, then this should be a walk in the park.

What you'll need:

-1 Gallon Polyester Fiberglass Resin
-Fiberglass Matte
-Additional Resin Hardener
-MDF (For supports, and speaker rings)
-Dremel / Rotozip / Cutter
-A GOOD Respirator
-Disposable Paintbrushes Brushes
-Masking Tape
-Tin Foil
-Glue Gun, or Adhesive Spray
-Fleece Fabric
-Wooden Dowels
-Carpeting Material
-Packing Peanuts
-Wiring Materials
-Light Sandpaper

Additional Information

This project will not be easy, it will require about 30 hours of work, drying, and adjustment time. Expect at least 8 hours of working on the first day to get your car in order, and get a good pull of your trunk space. In the end you should have a show winning sound set up that will look as good as it will sound.

 
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Step 1: 1. Remove Everything from Trunk

Picture of 1. Remove Everything from Trunk
You are now going to need to remove as much as you can from the trunk, everything you may have in there that will get in the way should be removed, even the trunk lid if it gets in your way. The carpet should remain, and you will need to get it as smooth and as perfect to the contours of your car as possible. Use a Vacuum to suck up any debris and dirt that will be in your trunk, you don't want to be dirtying up your box.
richeypaul13 years ago
This is a pretty sweet setup. I would love to have something like this in my car. Do you know anything about a sound deadener?
Go to Lowe's and get stuff called "seal & peel" it comes in a roll thats 6" by 25' and it cost less then $20, it works about as good as dynomat or better but it's way cheaper.

Peel and Seal is the aluminum liner... Seal and Peel is a caulk compound that you put around windows and doors that you aren't going to use in the winter. Very different products.

sensoh8su7 days ago

Newspaper will do next-to-nothing against resin. Go with a plastic layer just to be safe.

Excellent instructable I just finished installing my sub and box that I built entirely using these instructions and it came out amazing. I have wanted to do this for a long time and the step by step process here made it simple thank you
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SAijl5 years ago
Polyfil makes your box appear to be larger to your sub. It will help your sub if your box is too small.
Vinsu SAijl3 years ago
True. With fluffy fillings one can make the speaker "think" that the enclosure/box is bigger than it really is, virtually increasing the echoroom (not sure if proper word). In ported boxes it is more important to have a properly measured enclosure than in enclosed ones (those without ports) but it doesn't hurt to try different setups.
The sub doesn't "think" anything... It doesn't have any special electronics in it measuring the pressure behind it. The reason polyfill makes it *sound* like it's in a bigger box is because it slows the movement of air inside the box.
i was wondering, do you take out the wooden sticks after its all fyberglassed? or leave them in? :)
Vinsu3 years ago
Using fiberglass really helps to make an enclosure that isn't shaped geometric, like a box. An ideal shape for any subwoofer box would be ball-shaped, if not horribly mistaken. Even a small angleshift on a box will make the subwoofer sound better, removing "standing waves"(or something like that) using more of its possible frequency range so you can hear/feel everything that the bass is capable of producing.
Also if you need the fleece glassed into the recessed area of the speaker ring you can take a staple gun and staple the inside corner of the countersink to get it glassed in the corner.
pmartinez4 years ago
I must admit I'm not into sound systems, however; you did a very professional job and the result deserves a loud GREAT JOB!!
deltabravo24 years ago
clean install and good tutorial!
JBarker094 years ago
I am quite envious of this instructable. I didn't know about this site back when I did my own custom boxes. I have to say though, I absolutely love the job that you have done. Here is a finished picture of what mine look like.
My finished product
Instead of carpeting the subs, I went for more of a retro look and polished off the boxes and completely removed the floor of my trunk, adding an MDF floor with hinges (for easy access to the spare tire without removing subs or amp), and a plexiglas window for the amp to be mounted below for viewing pleasure.  I ran into a bit of a cooling issue with no air flow by the amp, so I installed some computer fans below the floor to circulate air across the heatsink of the amp.

I'm running an alpine MRP M1000 with two Alpine R12's and cut the cost nearly in half by doing it all my self.

I finished them about two years ago, and it was my first experience with fiberglass. I must say if you don't know what you're doing it makes things a lot harder, but you learn quick. Your instructable definitely clears a lot of things up and has great tips!

Once more, awesome instructable, keep up the good work!
are the wooden dowels ever going to be removed? will the fiberglass enclosure be strong enough to hold the woofer/speaker without them?
handy adam4 years ago
you can eliminate air bubbles with a fibre glass roller
handy adam4 years ago
by rubbing talcum powder on your hands and arms first it blocks your pores and helps prevent itching
 I like it!
I'd personally add a grill to the subs (i'm clumsy like that)


Good 'ible
almost forgot. If you know what your shape is going to be for your box, this is a good point to draw out the outer shape with a sharpie or other permanent marker. The resin will soak up the dried ink and leave you with a nice cutting line after you have removed the box from the trunk.
The foil layer is used as a mold release instead of multiple layers of wax. Polyester(fiberglass) resins don't adhear well to the coatings on foil. It also helps reflect some of the resins curing heat back into itself to aid curing.

Great write up so far.
peezy2064 years ago
I tried Building one of these but i ended up just buying one for my car from fgseonline.com... it saved me the time labor and money... Its always good to know though....
This is what my dad wanted to do with my wagon. Take out the plastic storage bins and fiberglass them.
Hycro4 years ago
I always use "Buffalo Snow" (aka polyfil) in my sub boxes, gives 'em a "warmer" sound, and don't sound so hollow, especially for ported boxes.
Hycro4 years ago
Don't forget to protect your arms from the fibres...can cause an annoying itch until you wash yourself completely off...
Hycro4 years ago
With my car, the carpet tail lights, and antenna would pose a problem, as I would have to find a way to go around the tail light wing nuts, since I have to remove the tail light buckets to change the bulbs in them, the way they're set up is kinda like dashboard lights, even with the same kind of stuff used for the contacts (that flexible plastic stuff, twist out sockets, and the bulbs clip in just like dash lights do, and the reverse lights and single filament rear park lights are even the same kind of bulb, whereas the signal & brake, and dual filament park lights use a plastic clip to hold them in) And the antenna mount just gets in the way on the passenger side, and my carpeting only follows the contours of the trunk along the floor, inside the spare tire well (well, before I removed the carpeting from there, 'cause I couldn't get it to dry out again, even though I fixed the leak in the weatherstripping) and towards the back of the fold-down seat--around the rear strut towers. Btw...I've got a '97 Plymouth Breeze that is a pretty nice car, nice, powerful engine, handles like it wants to be a sports car too. Love the mirror "struts" on it too, only they're not "break-away" mirrors, so if someone clips my mirror with theirs, mine will need to be replaced.
true poly fill (aka Pillow stuffing) does work to bring the sound out of a sub thats in to small of a box. also try filling the bottom with sand to lower a subs impact note. It makes for a much deeper thump. Great post and keep building.
lemonie5 years ago
The finish on this looks fantastic, I've done a bit of fibreglass before so I'm impressed. I guess you don't actually put anything in the boot/trunk 'cos the cones look rather vulnerable? L
MJTH lemonie5 years ago
He could put the speaker grill things over top when hes done I suppose.
lemonie MJTH5 years ago
He could, but hasn't. I wonder whether the force from the speakers blows the paper about in an impressive way? L