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Discussion Starter · #1 ·
I recently completed a lengthy project to build my own fiberglass sub box for my 2012 V6 Premium and figured I'd share a few pictures for anyone thinking about undertaking this same project. There were a few reasons I decided to give this a shot, mostly because I couldn't justify the price of the MTX Thunderform or JL Audio StealthBox, but also because I figured it would be a interesting challenge. Overall, I'm very happy with the outcome and think it sounds and looks great. Having said that though, this was a LOT of work and occupied most of my free time over the last three weeks and not something I want to do again any time soon.

Here you can see the area taped off with about three layers of painter's tape and two layers of fiberglass. As you can see there are lots of air bubbles, most of which I did my best to sand down. I contemplated giving up at this point, but decided to keep working at at it.



After letting the second layer dry, I removed mold from the trunk since it's much easier to work on outside of the car. I trimmed it roughly to size and did my best to remove the painters tape that was stuck to the mold.


After adding a few more layers and doing more sanding and trimming I used wooden dowels to mount my speaker baffle in place with hot glue. Once the front half of the box is complete the fiberglass will support the weight of the speaker and baffle so these dowels really just need to support the baffle for the next step. There are also a few horizontal dowels that can't be seen due to the camera angle.


Next fabric was stretched tightly over the baffle and glued to the back of the mold using 3m high strength spray adhesive. I then painted the fabric with just the fiberglass resin (no matting or cloth). As you can see, the hole for the sub was not coated since that will be cut out later anyway.


Four more layers of fiberglass and a nasty splinter and this is what I have.


Lots and lots of sanding and the fiberglass box is nearly complete. Those ugly black marks on the inside are spots where I used "Bondo-Glass" around seams I was concerned there may be air leaks.


Carpet applied to the front half with 3m spray adhesive.


Sub mounted, wired, and installed and this is the finished product! I also filled the box with poly-fill since the internal volume is just barley too small for the 12" sub.



And of course, some glamour shots.




As of right now the only issue I have is that there's some noise coming through the sub. Near as I can tell, it's coming from one of the stock wiring harnesses since I can hear a slight sounds when the engine is on or when I press the door locks or windows. I also ordered an MTX Re-Q to use as a line output converter instead of the one built into my amp. The MTX Re-Q should help adjust for the bass roll-off at higher volumes that is meant to protect the stock speakers. At some point I'll move some wires around to try to correct the noise, but since it's not audible with the music on that'll be done another day.

Feel free to let me know if anyone has any questions.
 

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That looks great! I went with the MTX Thunderform because it was $200 for me, and a custom fiberglass enclosure would have cost me far more.
 

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that. is. freakin. awesome. i want one now!:kooky: are you worried about the sub eventually shattering or cracking the fiberglass?
 

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Discussion Starter · #4 ·
that. is. freakin. awesome. i want one now!:kooky: are you worried about the sub eventually shattering or cracking the fiberglass?
Thanks! At first I was a little worried that the first time I turned my music on the enclosure would just fall apart but as I kept adding layers it really got a lot of strength. I could probably stand on this thing without a problem. My only problem is getting rid of the engine and accessory noise that's coming through it...it's starting to get on my nerves.
 

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I love innovation. I think it looks great!
 

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Provided you did enough layers the fiber glass should hold up quite well. As far as engine noise, do you have the Shaker 1000 system and re-using the factory amps or did you install an aftermarket amp for the sub? 99% of engine whine is due to grounding issues. Is anything else grounded at the same point? Try another ground. Also, what are you using for RCA's and or line level inputs? Power wire and so on. I used the Audio Control LC6i. Ran my 4 gauge from the battery through the firewall and to the trunk along the passenger side. Used a grinder to get a good ground connection point behind the carpet on the passenger side of the trunk. 4 gauge ground wire. The LC6i just needs a ground and power. 12 volt remote isn't needed since it can sense power coming from your rear speakers and turns it on automatically. It also has a remote amp turn on so it eliminates the need to find a fuse and run a 12 volt remote to your trunk. Tapped the rear speakers for my low level line inputs and RCA's from the LC6i to the amp. Only reason i used the LC6i and not the LC2i was because I wanted to use a 4 channel amp for the fronts/rears and a dedicated mono amp for my sub. I get zero engine noise and no power on/off "thump" you normally get. If you are using the factory amp and wiring I would seriously consider upgrading the amp and get a good signal processor. The sound quality is 100 times better than anything the factory installed!

By the way, the fiber glass enclosure you made is fantastic, excellent work! I considered doing one myself but I was going to paint it Sterling Gray instead of carpet but figure the time involved in sanding and bondo'ing everything I had better things to spend my month on! Great work and good luck with that whine!
 

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Discussion Starter · #7 ·
Provided you did enough layers the fiber glass should hold up quite well. As far as engine noise, do you have the Shaker 1000 system and re-using the factory amps or did you install an aftermarket amp for the sub? 99% of engine whine is due to grounding issues. Is anything else grounded at the same point? Try another ground. Also, what are you using for RCA's and or line level inputs? Power wire and so on. I used the Audio Control LC6i. Ran my 4 gauge from the battery through the firewall and to the trunk along the passenger side. Used a grinder to get a good ground connection point behind the carpet on the passenger side of the trunk. 4 gauge ground wire. The LC6i just needs a ground and power. 12 volt remote isn't needed since it can sense power coming from your rear speakers and turns it on automatically. It also has a remote amp turn on so it eliminates the need to find a fuse and run a 12 volt remote to your trunk. Tapped the rear speakers for my low level line inputs and RCA's from the LC6i to the amp. Only reason i used the LC6i and not the LC2i was because I wanted to use a 4 channel amp for the fronts/rears and a dedicated mono amp for my sub. I get zero engine noise and no power on/off "thump" you normally get. If you are using the factory amp and wiring I would seriously consider upgrading the amp and get a good signal processor. The sound quality is 100 times better than anything the factory installed!

By the way, the fiber glass enclosure you made is fantastic, excellent work! I considered doing one myself but I was going to paint it Sterling Gray instead of carpet but figure the time involved in sanding and bondo'ing everything I had better things to spend my month on! Great work and good luck with that whine!
That's solid advice, thanks. I have the shaker 500 system with the new sub hooked up via a JVC DRVN Amplifier that runs 250w RMS. I tried moving my ground, sanded it down to bare metel and all, and I still seem to have some engine noise. I'm hoping that the problem is the line out converter that's built into my amp. I ordered the LC2i which is being delivered later today' so hopefully that'll fix the noise. Either way I'll update.
 

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That looks nice although I know you did it to keep out of trouble and I figure you enjoy building it yourself I bet you ended up sanding glass for about .25 per hour.....:)
 

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That's solid advice, thanks. I have the shaker 500 system with the new sub hooked up via a JVC DRVN Amplifier that runs 250w RMS. I tried moving my ground, sanded it down to bare metel and all, and I still seem to have some engine noise. I'm hoping that the problem is the line out converter that's built into my amp. I ordered the LC2i which is being delivered later today' so hopefully that'll fix the noise. Either way I'll update.
I've always heard that excessive engine whine is due to wire intereference. Are all your wires to the back of the car running together? I would try to seperate them, or at least insulate them individually better.
 

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I made my box out of partical board and then coated the inside of it with fiber glass. Mine fits up into that short section behind the seats. Doesn't look quite as fancy as yours but with minimal flex in the box the two 10" P2 Punches in there will blow your brains out if you really turn 'em up. Unfortunately it's so heavy that it's like having an extra person in trunk.
 

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That's a very nice custom built box. Plus it's in a car that's almost like mine! I like seeing stuff like this.
 

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Kudos to you brother.. thats a pretty nice project to take on & it seems as if you've executed it well.
 

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Discussion Starter · #14 ·
Thanks everyone for the compliments! I just finished installing the LC2i line output converter along with the corresponding remote level control, which I mounted under the dash near my left knee. HUGE difference in sound quality and a LOT more punch. Best of all, there is absolutely zero engine noise now and no “thump” when I start the car. Since I didn’t move my grounds at all I can only assume that the amp’s built-in LOC was in fact the culprit.
 

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Good deal, glad it all worked out for you!
 

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are the wooden dowels still in there or did you break them out once you had the outside supporting itself?
 

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Absolutely fantastic. Looks like it turned out perfect!

I've always considered a project like this since I worked a job repairing fiberglass a LONG time ago.
 

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Fiber glass is definitely a labor of love! Messy, smelly but the end results if properly done look fantastic!
 

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Glad you managed to get the sound issues corrected.
 
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