Thursday, June 11, 2009

Custom Sub Box For 2006 Subaru Outback











I own a 2006 Subie Outback, which should tell you a few things:

1. I am a hippie
2. I am politically liberal
3. I care about the outdoors and having fun in it

Only one of the above is true. It's not the first two, which is shocking seeing as how I own a Subaru. To cut to the chase though, I love road tripping and I love doing outdoors stuff, namely snowboarding and camping.

My Outback 2.5i has 60/40 split fold-flat rear seats. This is awesome because it gives me a ton of cargo space. Problem is, I also love music, especially having nice crisp, punchy bass. The stock system is ok, (it's got decent front components), but the bass was lacking.

So I needed some bass, but I also needed to keep my trunk space intact, and that meant no huge box behind the rear seats.

JL Audio makes an awesome Stealthbox, which is custom-made to fit in the little storage hatch cutout on the vehicle's right rear flank just behind the wheel well. Their box is VERY nice, to the tune of $750.

So I used theirs as a guideline of sorts to create my own Stealthbox on a budget.

Because of the odd angles of the cutout, it was clear that the back of the box would have to be fiberglass, which I had never worked with before.

I read lots of great posts online about working with fiberglass. Here's the process I went through, and some pictures.

1. Mask out entire area that you'll be molding. Use masking tape or painters tape.
2. Cover the rest of the car with sheets or drop clothes. (Plastic will work OK, but fiberglass resin could eat through it if you drip enough of it).
3. Use a Sharpie to line out the area you're going to fiberglass. I used some cardboard templates to come up with a basic shape first too. I determined that the face and top and end would be made of 3/4" MDF and the rest would be fiberglass.
4. The space of the compartment area was nearly ideal for a 10" subwoofer (1.5 cubic feet). Make sure you think about math a little bit when doing any project like this because you want ideal performance when it's all done.
5. Buy some resin and fiberglass cloth at Home Depot or Lowes or some hardware store. You can get other (better quality?) stuff direct from suppliers if you live in a large city, but it's usually more expensive.
6. Do one last test fit with your cardboard template and make sure you've thought everything through because once you mix the resin with the catalyst IT'S ON! You've only got so much time before it sets up.
7. TIP: Pre-cut or pre-tear the fiberglass cloth into strips of varying sizes, because once you've got the resin all over your hands, things are going to get sticky. Having a helper might be a good idea too, but it's not completely necessary.
8. Mix the resin per the instructions. Use a plastic bucket to keep the stuff in. USE LATEX GLOVES!! You don't want this stuff on your hands. Also, you're gonna need several pairs throughout the process.
9. Start layering in the strips. There are varying methods of getting the resin on the strips, whether it's painting on or dipping the strips in the bucket then placing them in the mold area. Either way works in my opinion. I used a paintbrush and my hands to smear the resin where it needed to go.
10. PATIENCE.....you'll have to do at leat 5 layers for a decent sub box. It all depends on how powerful your sub is (i.e. how much pressure it will be putting on the walls of the box).
11. Once you're done with the layers, attach the MDF portion (the front half with the speaker cutout) to the still-wet fiberglass. This will allow the MDF to bond to the rest of the box. MDF is porous and will soak up the resin pretty well. Add layers on the inside edges as best you can to help create a bond between the wood and the fiberglass.

-Time for a 4-5 hour break- (to let it set up).

12. Pop the mold. Easier said than done. Some things I read say to grease the area with WD40 before you put the layers in. I did not do this so it was very hard to pull the mold out. Fiberglass is very strong, so don't worry about breaking it. Keep pulling and tugging from different angles until you work it loose and it will eventually pop out.
13. Sand and Fill. Use fiberglass filler (it's a grey sort of paste that you can also get at Home Depot) to fill any cracks or irregularities. Let it dry then sand away, making sure all the edges and joints are as smooth as possible.
14. Create anchor point. I cut a hole 1" in diameter in the back of the box to match up with a pre-existing screw point on the Subie's body. Using a bolt (which I had to custom cut) and some washers, you can create an airtight anchor for the box. This is important to hold the box in place when you are pounding down dirt roads, etc. I also drilled a small hole in the edge of the box for the wiring.
15. Carpet time! I found some cheap black carpet at Wal-Mart of all places. I think it was $8. Coat the contact surface of the box and the carpet with a thin layer of glue and then start fastening down edges. Carpeting is sort of an art that I haven't perfected, but I recommend starting with a large piece, layin the box face down on it, and then making incisions at the curve points. Do all the cutting and strategic thinking before you start gluing, because that stuff sets up pretty quick too.
16. Run wiring through the small hole, then to make sure box is airtight, add some caulking to the hole from the interior.
17. Hook up wires to subwoofer, install sub, and enjoy!

See pics for details. If anyone has any questions about the process, let me know!

16 comments:

  1. Hey, I just came across this and am interested in what you've done.

    Couple questions:

    What do you think the overall cost (without the sub) was?

    How much fiberglass resin and cloth did you end up buying?

    Did you have issues fitting the box in after you put carpet on the back of it?

    Any other thoughts now that it's been almost 8-9 months?

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  2. Hey Chris,

    Overall cost without the sub was around $100 if I remember right. I just bought one gallon of the resin and 5 or 6 packages of the cloth (I can't remember how many yards were in each). I ended up with too much cloth, but better that than to run out halfway through the job haha.

    No carpet on the back. I only carpeted the front and sides so it fit perfectly in its hole.

    My thoughts after having it for a while are man I wish I had enough money for higher end sub lol. I've had zero problems with the enclosure though. It stays in place and out of the way. The only thing I recommend is getting a good solid grill for the sub because when you put stuff in the trunk it can slide around and possibly run into the sub and damage it. What year is your Outback?

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  3. Hey Jake,

    Thanks for the reply! I just purchased an 05' Outback and spend a good deal of time traveling around and I'm bass head, so I'm definitely going to do this once the weather becomes stable around here in North Idaho. Where did you end up sticking the amp? In the tray under the floor of the cargo area? How did you end up running your wires from the box to wherever they went?

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  4. sure thing man. I had the amp, which is a rockford fosgate 4 channel from back in the day when RF still made good stuff, mounted underneath the passenger seat. You can do it yourself, but you'll have to actually take the passenger seat out. It was only $60 for my local shop to do it, so I just opted for that. It looks really clean though: power wire routed underneath passenger door carpeting, then hooks up to amp.

    Amp powers front component speakers (front two channels), then the rear 2 channels are bridged for the sub, and the wires just run underneath the rear carpet and behind the paneling and into the box through a small hole I drilled then pulled the speaker wire through.

    The end result is very clean - no exposed wiring or anything.

    Best way to do the wiring is just run it under panels / carpeting and kinda make it up as you go....

    I didn't put the amp in the trunk tray because of ventilation issues and also I wanted to keep easy access to the spare tire.

    north Idaho...you guys are still in deep freeze this time of year huh? It's the opposite where I live. Once it's summer it's too hot to do any sort of work unless it's in an air conditioned garage

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  5. Hi, Just spotted this and am going to do it in my 2006 also.

    Quick question, I am a nube when it comes to wiring up a car stero, I swaped the deck in a 1992 Dodge Dakota but that was just unplug and plug in. What work needs to be done behind the dash to hook the amp into the existing system in order to hook the sub in.

    Also, have you looked into Aux input at all?

    Thanks,
    ~Tom
    (Minneapolis)

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  6. Hey Tom, I'm not the best authority on wiring up amps and stuff, but long story short power wire goes from car battery to the amp, amp needs to be grounded to metal on vehicle, then output from head unit goes to amp, then speakers are hooked up to amp. It's a little more complicated than that and there are some great resources on Crutchfield (they have really good tutorials and live help too).

    yeah, as far as aux inputs go, I hooked up an aux input (1/8" stereo to stereo RCA out) and ran the cable behind the dash, out underneath the central area where the shifter is and then up through the center console hatch. I had to drill a small hole through the bottom. The result is very clean and the cool part is it can all be stored in the center hatch for security. any other questions, just ask !

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  7. Hey Jake...

    Thanks for all your info, it will be useful in a few weeks when I actually get a chance to it. Do you have the depth of your sub and how much clearance you ended up with between the back of the sub and the back of the box? Did you align it so the back would go into the compartment hole? I assume so and that's what it looks like...

    thanks man,

    Chris

    P.S. North Idaho hasn't been too bad lately and it's actually starting to warm up (60F is warming up haha)

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  8. oh also how many sqft did you design your box for?

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  9. hey Chris,

    I just looked at the spec sheet that came with my sub and kinda spec'd the enclosure to that. Your sub's user's manual will list the recommended enclosure size in cubic feet and that number will vary depending on if you're going to make a sealed or ported enclosure (has to do with air movement).

    I got lucky in that the size of the impression in that area of the car was almost exactly the right amount of cubic feet.

    as far as clearance between the back of the sub and the car, there were several inches, maybe even 6. Yeah, I centered the speaker hole over the deepest part of the that little cargo hatch area to be sure I got good sound resonation. Also, putting the sub hole in that location also looks pretty good.

    I have noticed that MOST 10" or 12" subs need a minimum of 1 cubic foot of air space (that's NOT including the volume displaced by the sub). some 12"s require more like 1.5 cubic feet

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  10. Hey! I just wanted to let you know that I am following your DIY and making myself a set of two for my '04 Subie OB (http://goo.gl/UhAyw)!
    Thanks for the great post and cheers!
    SB

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  11. @ twodeadpoets, cool man let me know how it turns out!

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  12. Purchased an 06 Outback with low miles last September. Your DIY stealthbox is insane! Thanks for posting!

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  14. Hey! Thanks for sharing! Very useful! I also had a couple of questions:

    Do you think Fiberglass Mat might work better? I was at Home Depot looking at the Fiberglass clothe and saw next to it some Fiberglass mat. Basically just thicker. I feel like that might be stronger to construct with. Thoughts?

    With that said I also want to caulk and sound proof the inside of the box. So do you think it would work to make the Fiberglass mold and not add the MDF while it's wet. Then screw them together (after drilling of course)? I figured this would make it so you can put caulking and stuff in between the pieces.

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  16. Here's a link to help choose between fiberglass cloth or mat.

    https://www.fiberglasswarehouse.com/chopped-strand-mat-choosing-fiberglass/

    Here's a link showing how to connect MDF Board to a dried fiberglass shell. (This way the face of the speaker box can be removable) (Don't know why that would be useful) I'd prefer the box to be one solid piece to avoid unwanted distortion, vibrations, etc.

    https://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/193554-diy-stealthbox-subwoofer.html#/topics/193554?page=1

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