Cause I need my thumps
I'm not looking to throw down with anyone that goes by and rattles peoples windows (like some of the lovely hoodlums around here,) but I would like Roxie to have a little more bass. As the factory subwoofer option is still going for about $800 or so, I decided to just build one myself. This will be a little write up about the building of the box and installing of the subwoofer in the back of my V70 wagon. I'm a fan of form and function, so I'm pretty pleased with the final results. Take a peek and feel free to comment.
(I'm a jack of all trades, but as it goes master of none. with that said I don't claim to be an expert system installer or subwoofer box builder or anything of that nature. These are in fact the first two boxes I've built, so it's just a noobs foray into this field)
As far as actual box materials go, I acquired the fiberglass and resin from Home Depot, the fleece and hot glue from Hobby Lobby, and the connections I just got off of Ebay.
I'd say that step one is to cut a hole in the box, but it's actually to mask off the area you're going to be working with. The masking tape fits pretty snugly to the carpet and other bits you're working around and protects the interior of the car from the fiberglass resin. I've seen other people lay down plastic or foil to put the tape on but I didn't find any need for that as the masking tape pulls off carpet with no ill effects (that I've noticed). One recommendation is that you set up a fan or something as ventilation if you're working in a wagon like I was. I've seen people use a plastic sheet to seal off the rest of their trunk area, but that's not quite as feasable in the back of a wagon. The first box I built happened to be on a windy day so there was no smell in the car. The 2nd box though was a bit larger and the wind wasn't as heavy then. It took about a week for the smell to dissipate.
I'd say that step one is to cut a hole in the box, but it's actually to mask off the area you're going to be working with. The masking tape fits pretty snugly to the carpet and other bits you're working around and protects the interior of the car from the fiberglass resin. I've seen other people lay down plastic or foil to put the tape on but I didn't find any need for that as the masking tape pulls off carpet with no ill effects (that I've noticed). One recommendation is that you set up a fan or something as ventilation if you're working in a wagon like I was. I've seen people use a plastic sheet to seal off the rest of their trunk area, but that's not quite as feasable in the back of a wagon. The first box I built happened to be on a windy day so there was no smell in the car. The 2nd box though was a bit larger and the wind wasn't as heavy then. It took about a week for the smell to dissipate.The next thing I did was to cut some fiberglass mat roughly to the size I needed. In retrospect it would have been better to start with a coat of resin on the tape directly instead of placing the mat in place, but as I've said before this is a learning experience. The mat is easy stuff to work with, just make sure you're wearing gloves. Fiberglass is no fun in your skin. The mat is better for building up like this as opposed to the woven cloth as it's a bit easier to shove into the right shape and it's easier to work out the air bubbles.You'll just brush on some resin lay down some mat, brush on more resin, lay down more mat until you've built up to a decent thickness. Make sure to get some cheapo brushes to work with and some marked plastic cups so you can tell how many ounces of resin you've used. It really helps getting the ratio right.
Once you have it built up enough, you just need to let it harden up, which only takes about 15-20 minutes. I found that by the time I was nearly finished laying down the resin it had already started to harden. Your total working time can be adjusted by how much hardener you put in the resin. From what I've read online though the more hardener the more brittle the finished product is. Of course on the inverse side of that too little and it will take forever to cure.
Once the back of the box has hardened enough you should be able to easily remove it. This may vary depending on how complex your shape is, but all in all you shouldn't have much difficulty with it. Sometimes a bit of the tape will stick to the box, but since it's going to be hidden in the end it doesn't really matter. I was able to remove this one with no tape sticking to it. The 2nd box had a few stragglers, but I sanded them down. I usually let the back cure overnight before I start doing the overall shaping. 
I forgot to take a few of the inbetween photos here, but you'll get the gist of it. Here is the overall shape, and the panel I'm using to mount the box to. You can see that I've also added the terminals. Shaping the box is easy, I just used an angle grinder with a metal cut off wheel. It took about a minute to get the shape I'd be using.Once you're at this point things will start going pretty quickly depending on what your expected results for the box are.
Skipping slightly ahead, here's the fleece stretched over the subwoofer ring and glued to the back of the box. You'll of course want to position the ring correctly using dowels of the proper length to get the angle you want. You can use hot glue to glue these to the box and the ring. Hot glue does a really good job of holding to the fiberglass and the dowels and of course the ring itself. After you've glue the ring in place you glue (or staple) your fleece to the ring. I started by gluing one spot on the ring, and then stretching the fleece across to the opposite side and gluing again. It doesn't take too much glue to hold it in place. I then went half way inbetween those glue points to the other quadrants of the ring.
Once the fleece has been secured to the ring you can start stretching and gluing it to the back side of the box. Pull it pretty taut as you'll want to minimize any sagging or wrinkles. When everything has been glued in place you can start applying the resin to the fleece. It will soak up a lot so make sure you either have plenty mixed or work quickly between batches. This small box soaked up I think 12-16 ounces on just the outside, and that was with not painting over the inside area of the ring. A helpful hint is to have a razor handy, once the resin sets up to just the right point, the fleece can 
easily be cut, with no fraying and no stretching of the fleece itself. Cut too soon and it'll tear, cut too late and well, it won't cut at all cause it will have hardened too much.
Once you have it built up enough, you just need to let it harden up, which only takes about 15-20 minutes. I found that by the time I was nearly finished laying down the resin it had already started to harden. Your total working time can be adjusted by how much hardener you put in the resin. From what I've read online though the more hardener the more brittle the finished product is. Of course on the inverse side of that too little and it will take forever to cure.
Once the back of the box has hardened enough you should be able to easily remove it. This may vary depending on how complex your shape is, but all in all you shouldn't have much difficulty with it. Sometimes a bit of the tape will stick to the box, but since it's going to be hidden in the end it doesn't really matter. I was able to remove this one with no tape sticking to it. The 2nd box had a few stragglers, but I sanded them down. I usually let the back cure overnight before I start doing the overall shaping. 
I forgot to take a few of the inbetween photos here, but you'll get the gist of it. Here is the overall shape, and the panel I'm using to mount the box to. You can see that I've also added the terminals. Shaping the box is easy, I just used an angle grinder with a metal cut off wheel. It took about a minute to get the shape I'd be using.Once you're at this point things will start going pretty quickly depending on what your expected results for the box are.
Skipping slightly ahead, here's the fleece stretched over the subwoofer ring and glued to the back of the box. You'll of course want to position the ring correctly using dowels of the proper length to get the angle you want. You can use hot glue to glue these to the box and the ring. Hot glue does a really good job of holding to the fiberglass and the dowels and of course the ring itself. After you've glue the ring in place you glue (or staple) your fleece to the ring. I started by gluing one spot on the ring, and then stretching the fleece across to the opposite side and gluing again. It doesn't take too much glue to hold it in place. I then went half way inbetween those glue points to the other quadrants of the ring.
Once the fleece has been secured to the ring you can start stretching and gluing it to the back side of the box. Pull it pretty taut as you'll want to minimize any sagging or wrinkles. When everything has been glued in place you can start applying the resin to the fleece. It will soak up a lot so make sure you either have plenty mixed or work quickly between batches. This small box soaked up I think 12-16 ounces on just the outside, and that was with not painting over the inside area of the ring. A helpful hint is to have a razor handy, once the resin sets up to just the right point, the fleece can 
easily be cut, with no fraying and no stretching of the fleece itself. Cut too soon and it'll tear, cut too late and well, it won't cut at all cause it will have hardened too much. 
Having a helper around is definitely beneficial too.Once you're at this stage you have a couple options. If your box is small enough you don't really need to add any fiberglass to the outside. I found that mixing another batch of resin and pouring it inside the box and soaking the back side of the fleece thouroughly adds a good deal of rigidity. If you're working with small boxes you don't need as much re-enforcement as you would if you were making a box several cubic feet in size. Anyway, the options lie in what you want to do with the exterior of the box. If you're going to have it painted and smooth finished it'll probably require more fiberglass and some bondo. Since I have no desire to do that I'll not go into the details.
I plan on either carpeting or doing vinyl on the exterior. So at this point I'm essentially done. I test fit the subwoofer and connect it to see how it sounds. On the downside of this first experiment, I mismatched the sub and amp. I got an amp that runs 200 watts at 4 ohm and 350 at 2. I thought I had purchased the Elemental Designs eu700 4 ohm DVC sub that I could wire to 4 ohm, but actually bought a DVC 4 ohm. The 350 watts of power is too high for the 6" sub. I did connect it briefly with the limits turned to the bare minimum. I underestimated the power of the factory speakers as a 6" was not enough to drive the low end like I wanted. I was used to the 6" factory sub in my SHO, but it turns out filling the cabin of a sedan is a lot easier than filling a wagon.
With that said I've quickly retired this box/sub to the closet pending relocation to Alyson's car. She has an Impala and the cabin is about the same size
Sorry for the lack of updates. The Vinyl has arrived and I've covered the v2 box. It didn't turn out all that great, not horrible but not as well as I'd have liked. It was a learning process though. Basically I've learned that I should just take that stuff to an upholstery shop. I'll post more pictures of the 2nd box as soon as I can.
I plan on either carpeting or doing vinyl on the exterior. So at this point I'm essentially done. I test fit the subwoofer and connect it to see how it sounds. On the downside of this first experiment, I mismatched the sub and amp. I got an amp that runs 200 watts at 4 ohm and 350 at 2. I thought I had purchased the Elemental Designs eu700 4 ohm DVC sub that I could wire to 4 ohm, but actually bought a DVC 4 ohm. The 350 watts of power is too high for the 6" sub. I did connect it briefly with the limits turned to the bare minimum. I underestimated the power of the factory speakers as a 6" was not enough to drive the low end like I wanted. I was used to the 6" factory sub in my SHO, but it turns out filling the cabin of a sedan is a lot easier than filling a wagon.With that said I've quickly retired this box/sub to the closet pending relocation to Alyson's car. She has an Impala and the cabin is about the same size
Sorry for the lack of updates. The Vinyl has arrived and I've covered the v2 box. It didn't turn out all that great, not horrible but not as well as I'd have liked. It was a learning process though. Basically I've learned that I should just take that stuff to an upholstery shop. I'll post more pictures of the 2nd box as soon as I can.
