DIY *Completed* How to build a custom fiberglass subwoofer/ speaker enclosure

xXCiviXx

Well-Known Member
890
657
Calgary, AB, Canada
Vehicle Model
Si
Body Style
Coupe
Alright, so here's a little background for all of you. Music is probably my favourite thing in the whole world. I either have headphones in or have the stereo on while I'm doing anything around the house or driving. I have always have an FM transmitter, AUX cable, phone cord or bluetooth adapter wherever I go so I can listen to music. In all three cars I have owned, I have completely redone the head units and speakers because stock is NEVER good enough. My 2013 Si is a little different, but not by much. I love the Nav and will stick with it for the foreseeable future but the 8" stock mid-woofer is absolutely atrocious and needs to be replaced. Only reason I haven't upgraded it yet, was because I haven't had the time to undertake THIS project. This is the second car I have built a custom Fiberglass enclosure for, and both for similar reasons:
#1 They look incredible if done right
#2 They sound great if you know what you're doing
#3 They can be crafted to suit any and all of your special needs
#4 They are incredibly strong and lightweight
#5 Significantly cheaper than paying someone to make it
and most important of all #6 If you love working with your hands and making something amazing on your own, the satisfaction is incredible when you see the finished product. Even if you drop more :unicorn: than "The Wolf of Wall Street" it's an incredibly experience.


Alright let's start this baby up

This is a complete list of what I used for the build (In somewhat order of use):
1 roll of masking tape
some tin foil
Nitrile gloves (use whatever kind you want, just be sure to have LOTS. You can go through a whole box)
N95 or other type of mask
Scissors/ knives
Jig saw
Power drill with drill bits
Work/ saw benches
MDF/ HDF (Amount depends on size and number of speakers being installed)
Paint brushes or sponge brushes
4 bottles of Fiberglass resin (Lots i know)
3 packages of Fiberglass mat
Fleece to wrap the front and part of the back of the enclosure
Staple gun w/ staples
Glue
Body Filler and spreaders
Sandpaper
Primer and Paint (or carpet if that's the look you want)
Screws to secure speaker
Wire terminal (Not required but nice to have)
Subwoofer or other speakers (JL Audio 10W3v3)
Amplifier (JL Audio JX500/1D)
Amplifier kit
Vinyl

Step 1

OBLIGATORY DISCLAIMER STATING YOU ARE RESPONSIBLE FOR EVERYTHING YOU DO. 9TH CIVIC AND MYSELF ARE NOT IN ANY WAY LIABLE FOR ANY DAMAGE TO VEHICLES, PROPERTY OR PERSONS. I HOPE ANY OF YOU THAT ARE WILLING TO ATTEMPT THIS WILL PUT SAFETY FIRST AND FOLLOW PRODUCT AND TOOL INSTRUCTIONS AND SAFETY WARNINGS. BASICALLY DON'T DO ANYTHING STUPID.

Figure out what you want to make and where you want to put it. I wanted to utilize the rear wheel wells so i still had access to my spare tire and maintain a fair amount of trunk space.

Once you know where you will be building your enclosure, you must tape off the entire area you wish to use (and then some for spillage and what not). Make sure to overlap the tape so no resin seeps through and sticks to your carpet or its :unicorn:. Also, if it sticks to the carpet, it will make removing the back shell a :unicorn:.

Here's what mine looks like:

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NOTE: Your back and neck may start to get sore. But you better suck it up cuz there is more to come.

Also included in this step (but not pictured) I covered the area with tin/ aluminum foil and taped them all together on top of the masked area to ease the removal of the mould once dry.

Step 2
Gather your fiberglass supplies:
Resin
Mat
Gloves
Mask
Brushes
and a bucket or container to mix your resin

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NOTE: Mix a small amount of resin for your first go... 1/4 of a liter should be a good amount until you know what you're working with and how quickly your resin will dry. Follow instructions for mixing. Use more or less hardener with the resin to get more or less time to work.

Also...
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This :unicorn: is toxic and will :unicorn: you up if you breathe too much of it in. Safety glasses is also a plus. You don't want this :unicorn: in your eyes and the fumes may make your eyes burn. DO THIS IN A WELL VENTILATED AREA SINCE THE TRUNK MAY HOLD FUMES AND YOU WILL BE WORKING IN IT.

TEAR up the mat into workable sizes and place the first layer OVERLAPPING EACH OTHER on the floor of the trunk. Apply resin mixture with brush until all mat is completely saturated and entire surface is covered with both mat and resin. DABBING is better means of saturating mat than brushing as brushing will pull mat and fibers across your work surface, ruining you overlap of mat.

Repeat this process for the walls of the work area but only lay 1 row of mat HORIZONTALLY up the wall at a time for ease of application and to avoid having the fiberglass wall collapse on you while it is still wet. I say this, because once you have resin on you or your clothes, you will have a :unicorn: of a time removing it once it dries.

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I forgot to snap a pic before I pulled it out and removed the masking but you get the idea.

And here it is out of the trunk:

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Step 3

Trim any excess fiberglass. As you can see in the image above i already started marking where I will cut to get the fit I want. It will look something like this when you have your base ready for step 4:

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I used trauma sheers to cut the fiberglass because I always have them handy while at work, though not usually used for this application. I also made some adjustments to the depth and edges after this picture to get my desired fit.

Step 4

I was too eager to get this project rolling and forgot to take pics of cutting speaker rings and mounting them inside the box and accidentally jumped to Step 5 but I will do my best to walk you through this process. This step requires you to trace the entire mounting diameter onto a piece of .625" to .75" MDF or HDF. Once this is done you will need to measure the inside mounting diameter and apply this inside the initial circle. Test it out on your speaker once you cut it out with a jig saw to make sure the speaker fits through the hole and is flush with the wood. This is also a good time to make sure you don't have any excess MDF beyond the outer diameter of the speaker. Sand as required to fit.

Step 5
Also did a poor job documenting this step with photos but its fairly straight forward. Cut 0.5'' x 0.5" rectangle supports out of MDF that will be used to mount the speaker ring. I used 3 supports to mount my ring. Find the desired angle and height that you want to mount the ring and cut your supports to the desired length. At this point, you can glue the supports to the speaker ring and secure everything in place with tape until it dries, or mark on the fiberglass base where each support will go. From here you will need to make more of your resin mixture, but significantly less than when you laid the base. Get more mat and resin and attach the supports to the base. For the 3 mounts I used, I placed them at 10 O Clock, 2 O Clock and 6 O Clock. Once the supports were in place with some mat and resin, I placed the ring on the mounts and taped the supports to the ring so the supports would dry where I needed them to. This is where the heat gun comes in. To get the resin to dry and cure faster apply heat to the wet resin from a safe distance. avoid heating the resin too quickly as this could cause it to dry too fast and crack or could cause the dry resin/ mat of the base to crack.

Here is a shot of my "6 O Clock" support from the next step as I forgot to take pictures once again:

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Step 6

This is where you get the first glimpse of your hard work paying off... Wrapping the base and mounts with fleece. You're probably thinking "Why the :unicorn: am I using a blanket on a :unicorn:ing bad *** custom subwoofer box?" Well the answer is simple: It's a means to get the desired shape of the finished product, eases in the application of more resin and mat, and will soak up extra resin and increase the strength of the enclosure.

Now you can wrap the fleece around the enclosure and glue it around the back edges of the base. Make sure to get a nice tight fit so you have a better surface to apply mat/ resin to and to avoid sagging of the fleece when it becomes wet (I know... phrasing lol http://www.bite.ca/wp-content/uploads/2013/06/archer-point.gif)

Once the glue and fleece is applied, you can start stapling the fleece to the speaker ring and in my case, to my special enclosure port. I will leave this step out as some may want a sealed enclosure or will buy a circular port and attach this once the enclosure is completed.

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I will mention here that the "bite" out of the "pizza dough" on the top is from where i removed a portion of the base because it wasn't flush with the trunk and I would touch this up with the next layer of mat/ resin.
Here is what it looks like in the trunk:

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Step 7

Prepare your resin materials again because we're going to apply more mat and resin to strengthen the :unicorn: out of this enclosure. Apply mat to fleece in an overlapping fashion like before and have enough excess to wrap around the edges and secure to the base, essentially fusing one solid piece out of the fiberglass and creating a seal.

With mat applied:

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From pizza dough to Chewbacca in minutes.

Continue to next post for moar...
 
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Step 7 continued...

Here it is once the resin is applied:

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You can kind of see where the "bite" is fixed but the colour of the fiberglass matches the dry wall so it's hard to see.

Here it is in the trunk again:
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Step 8

Cut the speaker hole open and prepare for filler.
Follow instructions on your container of filler and again, use a small amount at first until you know what you're working with and how long it takes for the filler to start to dry. Cover the :unicorn: out of the front of the enclosure while trying to create as flat lines/ curves as possible. There will be many "bumps" in the fiberglass finish as you can sort of see above. This step tries to make a flush surface (once sanded) to prep for the very final stages of priming and painting!!!

After close to 8 hours of applying fillers then sanding and repeating. OH! and did I mention :unicorn:ing cursing and swearing and hating :unicorn:ing life cuz you're sanding the whole :unicorn: :unicorn: :unicorn: by hand and your whole body is sore and tired. But I digress, after all that, you should have a pretty slick looking enclosure. It looks a little weird in the pictures due to fiberglass and layers of filler but it is much much more flush than when I started. And even though sanding was a :unicorn:, it was extremely rewarding seeing how it looked at the end of this step:

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Step 9

I jumped to this step as I am in the process of moving and on my last day of work before two weeks off, so I wanted to transport everything to continue working on the enclosure at my parents house. This step was drilling screw holes into the enclosure to mount the sub and see what it looks like before priming and painting.

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As you may have guessed, the Honda emblem I grabbed from a Pick Your Part will be the face plate over the port. Just something I thought would look pretty :unicorn:ing neato.

Step 10

Use a softer filler material to remove any knicks or scratches in the filler and sand down to get a completely smooth surface for paint. I went from 60 or 80 grit sand paper to 320 grit to get rid of as many scratches as I could. Spent another 8 or so hours applying filler and sanding to get a fairly smooth finish.

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Step 11

Prime then paint. Simple enough. Sand after first coat of primer and before first coat of paint with 1000 grit sand paper and wipe clean with isopropyl alcohol/ water mixture (about 50/50) after each time sanding. I did 3 coats primer, two paint and 3 coats clear coat. For the paint I used the Dupli-color Color Match automotive spray paint, but since there was no Dyno Pearl Blue, I used Intense Blue Pearl. It ended up pretty close, and I know someone that may love this color match as much as I do... *Ahem* @Pauly99to17 .

After 2 coats of Intense Blue Pearl and 3 coats of Clear coat
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Step 12

This step involve cutting a square in the back of the enclosure to secure a wire terminal. Not mandatory, but nice and convenient for amp install or for removing the enclosure.
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Step 13

For this step you can secure your enclosure to the trunk liner with some velcro that you attach to the back of the enclosure or you can bolt it to the trunk frame. Which ever suits your needs better.

Step 14

Install amplifier and connect sub to amp.

There are other DIY's for this step so I will skip this part of my install. Or you could just take it to some professionals to do it for you. But where's the fun in that? Why pay someone when you can DIY in an hour or two and save yourself a hundred bucks?

TIP: I spent most of my free time in the past week trying to figure out why the sub sounded terrible and really distorted. I believe it was because I tapped into the L and R rear speakers to use as my high level input. From there I disconnected the high level and decided to splice RCAs into the preamp sub out so I could maintain factory subwoofer control levels. This was a cleaner sound but still very quiet for a 500W amp, even with the input sensitivity cranked up. From here I decided to tap the subwoofer post amp signal in the trunk for another go at subwoofer specific control from the factory deck. Since high level inputs are usually combined L and R signal I spliced one positive and negative speaker wire to the sub wires then ran that to the high level and and combined L and R positive high level to sub positive and L and R negative high level to sub negative. Even with my input sensitivity set to minimum I finally have a 100% improvement in sound quality and especially volume! Hopefully this will save some of you a LOT of time if you plan on hooking up your amp yourself.

Here is a shot of the amp behind the drivers brake light assembly. Secured to a black vinyl wrapped plank, with velcro 3M'D to the back so it sticks to the trunk liner, and then twist tied to the trunk frame for increased support. All wiring was brought through the trunk liner with small incisions made to retain OEM look if I disconnect the system.

Prior to securing the amp, I tuned it to manufacturers specifications. 31.6V at 2 ohms for 500W output.
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Step 15

This step isnt necessary either, but it is something I wanted to include to make the enclosure look cleaner upon install. I have a length of Black vinyl upholstery that will go all the way to the trunk seal and cover the edges of the enclosure all the way around to make it look like it is a perfect smooth fit in the trunk.
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Step 16

Here I went back and refinished the enclosure because I scratched the top by accidentally closing the trunk while it wasn't in place. There were also a few sandpaper scratches I wanted to get rid of. This is what it looked like after sanding areas down and reapplying bondo and sanding smooth. The surface is so smooth and the lines flow much better. Tedious and time consuming but definitely worth it!
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Step 17
Enjoy the :unicorn: out of your enclosure.

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