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imhoffg 03-11-2013 10:22 AM

07 Grand Cherokee Custom 'Stealthbox' project
5 Attachment(s)
Just for kicks, I'm posting a before and after series for my first spring project on the WK; a stealth box style fiberglass subwoofer enclosure and hidden amp setup. I used to be in to the window shaking sound, but this time around I'm just going for an inconspicuous system upgrade with the equipment i pulled out of my old GC. After this I'm going to custom form a fiberglass enclosure to fit along the left side of the trunk and be carpeted to match.

So far it's been a cakewalk thanks to the designers of the 07 Grand Cherokee interior... After completing a similar setup in my 97 Grand Cherokee I've really learned to appreciate the easy trim removal in the 07. The Radio Bezel makes radio changes a snap, and the trim is super easy to remove to route wiring. The storage compartment is an awesome place for an amp too.

So far it's just a 1400 watt duel channel amp wired with 0G wire straight from the stock battery, bridged for a 12" pioneer champion series sub in a MDF plain box. I made the box to be ugly and boring/downfiring so it wouldn't get stolen like my last awesome fiberglass one, but perfectly dimensional and ported for great sound. Problem is, it's HUGE. That's why I'm going for a less sound-perfect fiberglass box that you'll hardly notice. It wont sound as nice, but it will be inconspicuous.

imhoffg 03-11-2013 10:28 AM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
I also utilized the C2A-CHY aftermarket amplifier adapter put out by PAC-audio. It works well as far as I can tell so far. The equalizer settings still work and it still sounds just as good. Made installation a snap as far as wiring goes; plug and play with no cheap trick installs like splicing speaker wire or anything. Glad I didn't have to go cheap and compromise the integrity of the original system. The only thing that is unfortunate is the lack of sub output equalization with the stock deck, so I have to fiddle with the sub equalization from the trunk and can't do it on the fly like when my wife complains about the boom :)

macmac 03-11-2013 08:50 PM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
Please make one, and send (or sell) me one as well. Have looked into the stealthbox for a while, but way to much cash from the factory oem. Progress pics would be great.

imhoffg 03-24-2013 07:18 PM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
1 Attachment(s)
Start of Part 2: Building the Sub Box

Yesterday I started building the fiberglass "stealthbox" style enclosure for my 12" subwoofer. I had a pretty hard time deciding where to put it but ended up deciding i would do on the left side of the trunk over the wheel well.

Step 1: Shopped around town over the last month to find the best prices on materials. Surprisingly, it varied quite a bit here in the Twin Cities. I found the best prices were at Menards, however, they only sold the smaller 29oz cans of resin. I figured that was ok because a gallon would leave me with a lot of left overs for this project and I would have over spent on that.

This is what I ended up with:
-Fiberglass clothe (i use woven because it seems to be more moldable and easier to cut than mat)
-rubber gloves (a pair for each layer of fiberglass. they are cheap)
-masking tape (i bought the cheapest all purpose kind and it worked ok. It doesnt adhear well to the textured plastic in the jeep interior, but it sticks well to itself, so if you layer it well and are gentle with it you can get it to mold pretty well. I haven't tried any of the other types of tape like blue or frog, but the list of uses for this kind was longer so i'd assume it sticks to more stuff)
-fiberglass resin (a gallon will do medium to big jobs. this is a small job so i bought two of the smaller ones hoping I could save a buck.)
-extra resin hardener (comes in a small tube. it's five bucks you might not need to spend because each jug comes with it's own hardener, but ive found that you always run short on it so you might want more. You can always return it if you dont open it)
-paint brushes (get almost as many as you plan on doing layers. Once the resin hardens they will be spatulas, which still works if you are just globbing on resin for final coats but sucks if you are trying to daintily lay new sections of clothe)
-a stir stick (i literally used a stick because we didn't have any and I forgot to ask for some. The ones in the paint dept. will probably be too big for this job anyways)
-scissors (from home)
-a tin can (the directions say mix in a plastic cup, but the heat from the chemical resin/hardener reaction and the fact that its a sort of corrosive chemical melts the cups eventually.... I've found a tin can works just fine and can be reused a ton)
-some plastic drop clothe (they were selling it for like 2 bucks at menards, too easy to be careful and not regret mistakes later...)

Suggestion #1: shop around and find the best prices. If you can go bulk on paintbrushes, rubber gloves, hardener, and fiberglass clothe. You will use a lot of this stuff (for this small project I've used 3 sheets of 8' sq fiberglass clothe, a couple pairs of gloves, and the never give you enough hardener to mix the whole can).

Suggestion #2: Don't try to get by with the least amount of supplies. It all comes in small packages so what you don't use you can always return. It will save you trips to the hardware store later.

imhoffg 03-24-2013 07:31 PM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
3 Attachment(s)
Step 2: Decide where you want it/start the masking

I finally decided I wanted it somewhere on the left side over the wheel well. Couldn't decide if I wanted it by the back near the tailgate or near the seat, however. I taped up the whole area in question to start glassing and decided to play it by ear. I also taped the drop clothe into the edges and ran it throughout the back (a little overkill but the sheet was huge). Note, there is an air vent, a couple grocery bag hooks, a 12v outlet, and a net hook there that I covered up. I just taped over it all with no problems. The grocery bag hooks do come out with a 90 degree twist and pull though.

Like I said, the tape worked out ok. Not too sticky as to damage, but not quite sticky enough that I was afraid it wouldn't hold. Needless to say, I layered it enough that it wasn't going anywhere....

Suggestion #3: pick the place you want the speaker first. I wasted a lot of time and some materials by changing my mind half way through the job.... glassed parts I didnt need.

Suggestion #4: I can't claim responsibility for this idea, but layer the tape from the bottom going up, using a positive lap. Any good roofer or guy that's done siding can understand why this is a good plan.

imhoffg 03-25-2013 12:24 PM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
3 Attachment(s)
Step 3: Start laying resin and clothe

The first thing I do is get everything ready to go. This is crucial because if you're not completely ready to work you will waste a lot of resin that cures before you can get it applied. I try to get everything set; clothe cut, brush out, even where i want to sit while I'm working on it. The more planning I do, the smoother it usually goes.

I cut the clothe into squares of varying shape for the first layer. The smaller the squares on the curvy spots the easier it seems to work with. You will also experience less bubbles. I make them into all sorts of rectangle sizes too to fit almost any need. However, after the first two layers that I'd like to be more accurate are laid, I usually cut the squares larger. It makes it go faster and it doesn't have to be as precise. This all depends on your finishing plan though. If you plan to paint the box, be as clean as possible because sanding and filling is a pain.... but I'm carpeting the box and this is going to be the interior so I'm not super concerned about bubbles and things for this part.

For this project I mixed a little extra hardener in because it's so cold (about 35 degrees the past couple days) which slows dry time quite a bit. Unfortunately the time that it takes to make the resin turn into a jelly seems to be about the same as in moderate temps but the the cure to solid time is much slower; it stays sticky and goopy for about an hour and a half to two hours. I did use a small space heater on it to help it cure. It doesn't put out much heat so I felt it would be safe. The directions on the can say you can help cure time by using an industrial blow dryer as long as you don't overheat it for risk of cracking.

Other than that it's a pretty self explanatory step. I laid 3 layers of fiberglass while it was in the car so it would be solid enough to pull out. I let it sit overnight so it would cure completely after the 3rd layer.

imhoffg 03-25-2013 12:37 PM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
2 Attachment(s)
Step 4: peel the form out of the trunk

This was a lot easier than I expected. I first peeled all the drop clothe away around the edge just by ripping it. Then i peeled all the exposed tape off the trim. It didn't leave any residue, which made me happy. I was worried about how long the tape had sat on it, but it was fine.

Then with a plastic puddy spatula I lightly pried the tape off the carpet and pulled with my fingers at the top part (i wanted to avoid using the spatula on the trim for fear of scratches). I was worried for a second because the edges just flexed and it didn't budge, but a little bit more tugging and it just popped out. Piece of cake.

Then once I had it free i played around with the sub orientation in the car to decide how i wanted it. Once I had a plan set (trying to get a little bit of curve and a little bit of angle (upper right support) like the jeep interior has) I stenciled it in with sharpie so I would know where I needed to keep glassing to make it stronger. This is where step 1 planning should have been better. As you can see, I wasted a lot of resin and clothe in glassing areas I'm just going to cut off anyways.

Guenther 04-27-2013 06:41 PM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
Do you have any further information, pictures, etc on this set up?

imhoffg 04-28-2013 10:13 AM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
2 Attachment(s)
Hey guys, sorry it's taken me so long to finish this thread. I finished the box a couple weeks ago but I've been so busy with school... anyways.

Step 5: Continue layering to make it stronger.

I kept adding layer on layer till i felt the base was strong enough. Pretty self explanatory. I glassed just over the sharpie line, and the sharpie was pretty visible through the layers so I had a good reference point and stopped wasting materials.

Step 6: Cut the form.

Once I felt I had it thick enough (probably not thick enough for professional car audio enthusiasts, but thick enough for me, my budget, and how much materials I had) I cut out the form along the sharpie line I'd already drawn. I think it ended up being 7 layers? This was also a pretty self explanatory step, cutting along the line with a band saw.

*the attached photos show the base form with the support ring I built attached, however, I didn't attach this until the form was fully layered and cut. I guess I forgot to take pics of the form without the support frame.

Step 7: Build and attach the support frame.

I knew the fiberglass wasn't going to be as strong as it should have so I wanted to use some wood supports to help it hold the weight of the speaker that would be sturdy and permanent. The last sub box I did had supports only to keep the rings up during glassing, and the fiberglass itself was the main weight supporting structure. Now the wood you see is the main support. This cut down drastically on my need for layers of glass. Once again, not exactly auto pro standards though...

I just cut a ring of the dimensions needed from the wood I had left over from my old MDF sub box. Its not pretty, but you wont see it anyways. The right side support also gave the box a little angled edge for artistic design. I was going for something like the jeep interior with all it's angles.

To attach it i just used 3/4" drywall screws. It was the shortest screw I had handy

imhoffg 04-28-2013 10:30 AM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
3 Attachment(s)
Step 8: Set up the clothe for making the rest of the form.

To go with the cheap set-up and not have to go driving around town looking for materials I just used an old white Tshirt to stretch over the frame and give it shape. It worked fine, however it was pretty stretchy and as soon as the weight of the resin soaked it, it began to sag. You'll notice that the final product has a bit of a sag in the sides where the clothe drooped under the weight. I didn't mind, but it wasn't exactly planned to do that.

I also had a hard time getting the clothe to stay. It stapled fine into the wood, but the had stapler I had was too weak to punch through the fiberglass. For this reason, a hot glue gun would have made it easier. I ended up using pin nails to hold it down. It looked like when you pin the skin of a frog down during a dissection lol, but it worked. I would highly recommend the glue gun though, because I ended up with lot of ripples in the clothe on the backside that the nails wouldn't hold down, and I had to sand them all off in the end.

One important point that goes along with step 7... If you plan to wrap the fiberglass all the way around the inner edge of the ring where the speaker will fit into, you need to cut the support ring inner diameter a hair larger to fit the extra material. I wrapped the tshirt into the ring thinking it would make it stronger, crossing my fingers that the speaker would still fit... It didn't, so i had to sand and sand and cut and chip and sand to get all the fiberglass I had put on the inside of the ring off. It was just as strong anyways because when it tried it must have schrank just a hair, which squeezes down tight on the wood, and also soaks into the wood, making the tshirt and the wood almost one piece in itself. I wish I would have taken a better pic of this. I was just so eager to finish it...

Bottom line, a little extra time in glassing to plan ahead and avoid mess ups will save you a TON of time in the sanding process.

Step 9: Fiberglass the clothe

The first layer of fiberglass will take a lot of resin, because the cloth material soaks it up like a sponge. This is really nice because it will make it rigid after just one coat. After the first coat of resin and glass on the cloth it felt as hard as 3 coats of just resin and glass over the tape when it was in the car. I layered this about 6 times I think, once again, not quite as thick as it probably should be, but it was enough to not flex or be a risk for cracking under the vibrations.

imhoffg 04-28-2013 10:42 AM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
2 Attachment(s)
Step 10: Sand sand sand

Once the box was dry and solid and exactly the way I wanted, I began sanding. First I took a utilitiy knife and cut off all the strings and pointy pieces of fiberglass. This will help save on your paper, because those sharp points will tear it.

I used an osculating palm sander for the job. This is almost a must, because using a block or just your hand would take forever...... I sanded till it was smooth enough to get the carpet to adhere to. The last box I did I painted, so i had to use body filler and get all the bubbles and uneven spots, and sand for days and days till it was flawless..... this time I was going for the factory look so i bought carpet from the local car audio shop for $6 a sq yard and some 3M spray adhesive for $7. Once most of the bumps were out and it was smooth enough to glue the cloth down, i cleaned it up. This is very important because the fiberglass dust is super fine, and just blowing it off isn't enough. You need to take a rag and a bucket of water and wash it down. Even taking it under a hose or the sink isnt a bad plan. This will clean off all the dust and give the glue a good surface to stick to.

Like all fiberglass jobs, you will get itchy! I'm terrible about safety equipment, so i just pulled the collar of my sweatshirt over my nose and mouth to sand but you should really wear a mask. At a minimum, wear safety glasses during any cutting, sanding or drilling. I at least do that. Also, you should wear a respirator when you glass, and do it in a well ventilated area. God knows what those fumes did to my insides.....

imhoffg 04-28-2013 10:56 AM

Re: 07 Grand Cherokee Custom 'Stealthbox' project
5 Attachment(s)
Step 11: Wiring

After it was all sanded down and exactly the way I wanted it I started prepping it to be carpeted. I had a nice wire terminal part that I got from our local car audio shop a long time ago for my old sub box that I just reused. I used a big holesaw bit to cut the hole and fitted it right in, too easy. Before I fully attached it though, I pulled it out and laid the carpet. I let some carpet overhang the hole to give it some seal so no air could escape. I also ran about a foot of speaker wire from the terminal and had it ready to attach to the speaker, the same high quality Rockford Fosgate wire I used to go from the amp to the box.

Step 12: Carpeting

Now that all the sanding, cutting, and fitting was done, and it was cleaned as best as I could get it, I started planning the carpet. My goal was to get at least the front and sides covered with no seams. I basicly started with the base on one side, and wrapped it around, over the top to the other side, then folded it over in the front and back. The car carpet is pretty stretchy and flexible. It's easy to work with. Like i said, I used some medium tack 3M spray adhesive and it worked just fine.

I did end up carpeting the back side, which I'm glad I did. At first I thought it would hurt the way it fit, but it really didn't because the carpet accepts the contours of the fiberglass perfectly. I think it helps because now it doesn't rattle against the plastic of the interior when the sub is playing.

Then I put the terminal in, and screwed it down. After that I cut all the excess off and put the speaker in, wiring it to the terminal. put her in the car, wired it to the amp, and voila... a custom made, matching, and discreet subwoofer enclosure that cost about $60 (less if I hadn't made mistakes along the way....) So far she sounds great!

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