Bret928

Ok I’ve seen a lot of posts where folks have put subwoofers in where the spare tire was and figured it was about time I looked into it too. Mind you I’m not looking for something that’ll rattle someone’s fillings out, just looking for some added depth.

Anyway like I said I’ve seen a number of homemade setups and they look pretty sweet but what I’d like to know is what’s underneath. I like the idea of having a setup that could easily be removed for access to the battery box underneath and sturdy enough that I wouldn’t be afraid to throw a duffle bag or a small suitcase on top of without worrying about any damage.

Now I figure I could just pull out the spare & cut a piece of practical board to fit. Cover it some felt or carpeting and just drop in a woofer. But I was told by a guy who worked at a local custom automotive stereo shop here in town, that it (the woofer) should be in an “enclosed” box. So if this guy is correct then that tells me that it’s a little more complicated than just lining the spare tire area with sound proofing.

Now I thought it was overkill & extremely *PRICY* – but this guy actually suggested a molded fiberglass unit that would drop in the spare tire well. Now I’ve seen some of his stuff and must admit his work is pretty amazing. Problem is this’d cost me about as much as a top tier premium sound system without the subwoofer.

So I’d really like to seem some more of my fellow Rennlist members’ setups before deciding for sure. But I figure for now if I can’t sort this out I’ll just stick with a basic sound system. Head unit, amp & speakers.

Thoughts?

Mike Frye

Bret,

What about fabbing one out of fiberglass for yourself? If the object is just to make an enclosure for underneath it, you don't have to make it picture perfect, right?

The top would be flat and the bottom just has to be clean. You were thinking of doing the particle board for mounting, just go that way and make a frame out of styrofoam or light wood and fiberglass over it. Cut away and sand whatever doesn't look like it belongs there, sand, bondo, sand, paint and you're done.

I just worked out a cool way to shape polystyrene with a heated coat hanger (shape it, heat it, then just push it through to shape). It's coming out pretty cool for my rear seat delete.


Parts would cost maybe $30 and if it doesn't work, then you make your decision.

auzivision

I'm working on a fiberglass tub myself. It's not too pricey... less than $100. Attached are a couple of write ups for your amusement.

Okay, they are too big. PM me with an email and I'll forward them to you.

auzivision

I'll try pasting the text:

Fiberglass Spare Tire Well Speaker Enclosures
This section was contributed by Big Mack who frequents the SoundIllusions.net discussion forum.

What you would basically want to do is take out anything that you don't want to get resin on. The carpet comes out easily enough, and you WILL NOT get the resin out of it if you spill it or cut through plastic or anything. I highly recommend that you take out the carpeting.

First off, SAFETY FIRST!!!! A clean, well ventilated, and spark free (no smoking) work area are vital to this. You will need good rubber gloves, a couple of mixing bowls (not wax coated), several brushes that you can throw away, some grille cloth or fleece materials, a dust mask (not a necessity if the area is well ventilated, but I recommend it just the same), some body filler, and the resin materials.

After you have the carpeting out of the trunk (as well as whatever else is in there). Clean the area that you're fiberglassing. Get the vacuum out and really get everything out of there. It will make the job easier (and look much nicer).
Now that it's clean, lay down some plastic sheeting (plastic drop cloths work good and they're cheap). Tape it up so that the odors are restricted to the trunk area (that's a little trick Fishman taught me for doing tubs in spare tire wells to keep the car from stinking for days). You can even block off the rear speaker openings if they are in the rear deck for maximum odor protection.

Once you've got this area masked and protected, you can start the process. Beware that this takes some serious time, and you have to concentrate to do it right. If you're rushing it, it will either not come out right, or it will look like garbage (and sound similar). Lay pieces of grille cloth (I prefer this for starters because it bends easily and will dry fairly quickly in air or with a heat gun) around the area that you're 'glassing. Cut it in strips that overlap and don't have too many wrinkles. Once these are laid down, you can put on your gloves and mask and mix up a small batch of resin. Follow the directions on the container for mixing the resin with the hardener (too much of this, and it will dry with the brush in it and then you're done with that mix and brush).

Once you've got that mix ready, start to spread it out with the brush. Coat the pieces well, but don't put too much on or it won't dry for a long time. They should be soaked all the way through, but not dripping. Sometimes, you can just put the strips in the resin and lay them out, but this is very tricky to do without oversaturating them, so you must be extra careful when doing this.

Once you've got the entire area covered, let it sit for at least an hour. If you have a heat gun, you can go over it LIGHTLY with that to speed the process, but don't overheat it or you'll be looking at scorched pieces and plastic.

Once the first layer is fairly dry (doesn't need to be totally, just close), start the next layer, making sure to interlace the grille cloth like you lay bricks so that there are no seams that line up. Coat this one a little thicker (very little extra) than the first layer to bond the pieces together and make them stronger.

Let this setup dry COMPLETELY. Once this is dry (will take anywhere from 2 to 6 hours without heating, but can get down to under 1 if you're careful), you can take it out of the car if you want to not work in such a constricted area, provided that it's strong enough to hold it's shape (2 layers usually are, but it depends on how large it is).

You will want to get this piece built up to 1/4-3/8 inch. After you have 3 or 4 layers of grille cloth in it, you will want to put a layer of fleece in. It will take more time to dry, but will add thickness and more strength than the grille cloth along due to the tighter weave of the fleece. Again, exercise common sense and caution and work safely. I cannot stress this enough. If you start to get dizzy or light headed, put your work down, and get some air. Open the windows of your work area and let the fumes out. Please, be careful...

Now then, once you have your piece built up, you will need to make the top. This should be made of at least 3/4 material (preferably MDF or marine particle board). You cannot make a piece from fiberglass straight enough or strong enough to merit the time it would take to try, so just cut the MDF (using your workpiece as a template). Take grille cloth and staple it around the workpiece. Make sure that this will overlap onto the MDF by at least a inch (preferably 2). Shoot a couple of screws into the edge of the MDF and the fiberglass piece you made to keep it in place. Staple it to the MDF. You won't want to cut the hole for your speaker just yet, as it will make the job more difficult than it has to be.
Continue to build up the edges around and over the MDF until it is strong enough to hold the speaker sitting on it. It will not need to be as thick as piece you made since it is screwed to it and the MDF is 3/4 thick. You're basically looking for 2 or 3 layers of grille cloth on there to ensure a good seal.

If you want the enclosure to look really trick, before you 'glass the MDF in, you can take hardboard as thick as your sub's front gasket and cut out the speaker's entire outline (including mounting area). It will allow you to flush mount the sub into the tub. Once this is cut, screw it to the MDF and fiberglass the whole thing together as described above. Once you have this all screwed together and dry, you will want to test fit the enclosure before cutting any holes for subs.

Take the plastic out of the car since it won't be there when it's actually installed. If it fits like you want, then move on. If not, then determine why it's not fitting like you want and fix that area.

Since you're happy with the fit now, look at the bottom. If you want to smooth it out by sanding it and filling it so that you can paint it, now is the time. If you don't want to paint it, then you don't need to fill the bottom, but you should fill the top to allow for the carpet or vinyl to be smooth. Put a good layer of body filler over the areas that aren't smooth to the touch and let it dry (it dries fairly quickly, so this shouldn't be too bad). Once the filler is dry, you will need to block sand it so that it is straight and smooth. The block will keep you from grooving the 'glass (but you must be careful to not groove the entire block into it by pressing too hard).

Once you're satisfied with the smoothness, cut your speaker hole and cover the enclosure as you like. I like to paint the bottom even if the top is covered with vinyl or cloth just because I figure people show them off. Takes a few extra minutes, but it's only 2 or 3 coats of paint, sooooo.....

These are the meterials that I used:

2 Gallons of Resin
Bondo
3/8 and 3/4 MDF Board
3sq meters of Fiberglass mat
2sq meters of Fleece
1 T-shirt
At least 10 pairs of gloves
5 paint brushes
50, 80, 150, 320 Grit sand paper
Vinyl covering
Tuck and masking tape
Fiberglass Sub Box

This was submitted by a Club RSX member.
For those of you who considered building a FSB but needed more guidance, this is my offering. I think I should mention right off that I'm not building a competition system. My intentions here were to build a single 10" sealed box for a more balanced sound (audiophile wanna be and to save trunk space (golf clubs). Hopefully the experiences I share will help anybody no matter what your intentions are.

I did a lotta research before I got started and I give a lot of credit to Club RSX.com Forum/website.
Thanks guys.

After I decided what size sub and what kind of enclosure I wanted to put in, I needed to figure the volume of the enclosure. Well this is a bit tricky if the shape of the box is contouring around wheel wells and the like. So here's the trick. I got a cardboard box the recommended size for the sub and filled it with styro foam popcorn. I placed the styro in a large garbage bag and conformed it to the spot in the trunk where the sub was to be. I eyeballed it and used masking tape to outline the border of the box. There is some tolerance in size & I'm no calculus buff so there it is.

I'm a pretty handy guy around the house and did carpentry for a few years so I employed the golden rule "MEASURE TWICE ,CUT ONCE". You can rush through something like this and have a disaster but you can never take too much time to do it right. So for the newbie: Take your time grasshopper, and the prize shall be yours.

Here's what I used:
-fiberglass resin w/ hardener (I used almost a gallon for mine)
-fiberglass matting/woven cloth (I used both, the fb glass cloth is a lot easier to use)
-blue painters tape (you can use the reg. tan stuff but its harder to remove from glass)
-disposable paint brushes (several)
-aluminum foil
-MDF ¾" plywood
-Liquid nails
-screws
-protective gas mask
-patience and a good sense of humor

Quickie tool list:
-table saw
-jig saw
-drill
-rotozip

I taped off the area really well. I was paranoid as hell that I would destroy the trunk of my new RSX so I went over board!! Remember, its easier to spend a little extra chump change than to replace the panels and carpet in the trunk!!

Here's a couple of pics for ya.


This is at least a couple of layers. Note that I'm going over the trunk liner. It's a personal call, what can I say. The box will be easy to remove and I can keep the trunk clean.


Another view of the same damn thing.

I then used cut pieces of foil to go over the tape. Why foil? Not really sure it's what I've seen other people use it and it may be easier to peel the form out later, just a guess. I used double stick tape to fix them in place, taped the seams between. You'll see in the next pic that I started the rows of foil at the bottom overlapping the next coarse of foils over the previous as if I were laying shingles. The point here was to avoid any seepage -again protect your investment,overkill or spill!



The below pic shows the finished tape and foil layers.



I draped plastic drop cloth over everything b/c the fbg resin is nasty stuff, very drippy and sticky. I took every precaution I could. I did the taping and foiling the day before the resin. You really want to do this on the weekend when you don't have to be any where real soon. You can't go driving around while the stuff sets up. The mix of hardener and resin I used in the first batch was conservative and took a while to set. After the first coat dries you can pop it out and do everything else outside the car.



The above pic shows the first layer of resin. You start by painting the resin on the tape layer immediately following with fiberglass material and then another layer of the resin. A note about the resin and hardener: definitely read the instructions about this. The more hardener you use the faster it sets and begins to the less you use the longer it will take. It takes a long damn time to set if you don't put enough in. There is a little trial and error involved. The colder it is the longer it takes to set up as well. I had never done this before so it was a little hit and miss. Another tip is that it seemed to work better to make stabs with the brush. Air bubbles are bad, you want to avoid them b/c they weaken the strength of the box.



Above is the hardened form and I'm about ready to pop her out. If you can do the work outdoors in reasonable temps the better. The fumes were pretty heinous in the garage. A gas mask is a must, the stuff will make you stupid if you breathe it in. I got my mask from HOMEY Depot for about 27 bucks. You shouldn't be able to smell the fumes at all with the mask on. I did the following 4 layers outside the car. After the basic form is done the other layers go really quick.

The next pic shows the form dried and in its future home. Still a little work to do yet. I trimmed the form to get the crappy edges off with a rotozip.



Another resource that I used is the following link. This guy did the whole thing out of glass. I wanted to use MDF for the facing and the sides.
http://web.njit.edu/%7Ecas1383/glassing2/

I forgot to take a few pics during the fabrication of the MDF facing- sorry. Hopefully the next couple of pics will kinda show what I did.



I used a jig saw to cut the hole, a table saw to get all the angle cuts flush where the pieces of MDF are joined. I also used liquid nails between every piece of wood and ran a bead at the seams. I screwed the MF together with 2" screws pre-drilling and counter sinking the screws. MDF is just fancy particle board that will fall apart if you rough house it too much.

I wanted the option to mount the amp just to the left of the hole for a cleaner look. As I'm writing this, I'm still undecided about the amp but still have all the options.



It's hard to see from this pic but there was quite a bit of jigsawing to get the side piece of MDF to fit the glass box. I measured quite a bit to make sure the dimensions were right before I screwed and glued this sucker together. You don't want to get done and it not fit. Here's another pic of the back.



I used a hot glue gun to tack everything and just used painters tape to hold it together before I made it permanent. I used strips of fleece inside the box with just resin to join the MDF and the glass form. I'll show more pics down the page a bit. I followed that with glass and resin on the outside seams. My plan is to use industrial Velcro tape to affix the box to the trunk carpet.

*Just a note: you can fool the sub into thinking the box is a little larger by filling the space inside with R-19 or pillow stuffing. Supposedly you can fake an increase of size by 10-13% b/c the sound will bounce off the material before it gets to the back of the box. I think it's around 1 pound of stuffing per cubic foot. Don't stuff it in there real tight either, keep it fluffy.

Here's a pic of the fleece material slathered in place with just the resin.


I tacked the fleece in place with a hot glue gun and glopped a bunch of resin on it. The object here is to make it airtight. I bought the fabric at walmart for about 4 bucks. Fleece seems to work best, it really soaks up the resin. After its dry it will be hard as rock.

Ok the next couple of pics are the dry runs in the trunk. It may be hard to tell with the low res pics but the sucker fits like a glove-SWEET!!


When I get the carpet on it should look fairly well integrated into the trunk space.

Awe Yeah! Look at that fizzle!



A dry run with the amp and speaker.......



With carpet and sub loaded...........



Final install pics............





I still have to clean up the wiring and I think I'm going to lower the amp more in line with the sub. I also installing 4 channel for the front component and rear speakers I installed. BTW it sound's frigin great!

*I'm including a couple of bonus pics of the front speaker install. I used ¾" mdf rings and attached sound deadening gaskets to absorb any rattle. While I was at it I lined the inner doors and wedged the stuff in every crevice on the door panels themselves.



Here's a close up of the rings



I screwed the rings to the door and mounted the speakers to the ring. The green material is sound deadening foam for pergo flooring. It's super cheap, like 33 bucks for 50' roll and did a great job to minimize road noise and rattle.

*everything I did to the car is reversible. Hopefully this will be of help to somebody out there. Signing off until the next project.

-- Larsito

auzivision

Here is the other one:

For over 10 years, I've been into car audio. I've always built big, rectangular subwoofer boxes that take up most, if not all, available trunk space in the vehicles I've owned. After getting married, settling down, and buying a house, it turns out that I need my trunk quite a bit more often than before. So I decided to build a custom-molded fiberglass subwoofer enclosure. After several years of researching the fiberglassing process (it's something I had been putting off for awhile), you'll notice that I've done some things a bit differently than other tutorials out on the web, and hopefully for the better.
First, some (very brief) basics on fiberglassing. Fiberglass is a cloth or netting (mat) made from glass fibers (hence the name). When resin soaks into these fibers and is cured, the result is a tremendously strong material that is very versatile for fabricating virtually anything. Subwoofer boxes are a great way to get started with fiberglassing.
DISCLAIMER: Fiberglass, polyester resin, and MEKP catalyst are all some very nasty materials. Please use caution and protective measures when working with these items. Fiberglass fabric, like Knytex, or chopped strand mat, are actually made from very small pieces of glass fibers than can get embedded in your skin. This doesn't feel good. Wear long sleeves and gloves at all times. Polyester resin and MEKP catalyst produce styrene fumes that are quite nasty on the lungs. Wear a respirator at all times, NOT a paper dust mask. A paper dust mask will do no good against resin fumes. Plus it's fun to see your neighbors drive by very slowly because some wack-job is wearing a gas mask in his driveway.
The tools I used for this project were a staple gun, a caulking gun, and a Dremel rotary tool. I purchased my fiberglass cloth, resin and catalyst, and mixing tubs from US Composites. Everything else is available at Wal-Mart and Home Depot/Lowe's. Here are the materials I used, links to some photos, and some commentary on why I chose these products:
3 yards of Knytex 1708 biaxial fiberglass cloth
2 yards of 3/4 oz chopped strand fiberglass mat
1 gallon of US Composites 440 polyester resin + MEKP catalyst
Graduated volume plastic tubs (reusable)
3/8" wooden dowels
8 Tee nuts and machine screws (I used size 8-32 with 2” screws)
Charcoal colored carpet from Parts Express (1 yard)
Bondo-Glass fiberglass-reinforced body filler (Wal-Mart)
Liquid Nails construction adhesive
1/4" nylon rope
1 roll of blue painter's masking tape
2 yards of some stretchy jersey material (Wal-Mart clearance)
Drop cloth (plastic sheet style, 1 roll)
Latex gloves (drugstore)
Paint brushes (disposable cheapo's)
3M respirator (a necessity – resin fumes are NASTY)
($6.60 per yard x 3) = $19.80
($1.95 per yard x 2) = $3.90
$25.75
($0.40 x 10 tubs) = $4.00
$0.78
$5.00
$5.00
$12.00
$2.50
$4.00
$2.00
$2.00
$3.00
$4.00
($0.50 each x 10) = $5.00
$30.00

Total = $128.73
Free items:

Cyanoacrylate (super) glue
Hot glue gun + glue sticks
Duct tape
Pam nonstick cooking spray
Paint mixing sticks
3M Super 77 spray adhesive

Everyone should have some
Stolen from wife's scrapbooking materials
it's un-American not to own
stolen from kitchen
free in the Lowe's paint department
I had some left over from another project, but it's $9.00 for a can from Lowe's

So add in shipping from US Composites, and it's roughly $150 to cover the cost of materials. Not too bad when you consider a fiberglass sub box might cost cost $500+ at a stereo shop. I also had a local guy make an MDF speaker mounting ring for me for $26, but if you have the tools and ability, then a sheet of MDF from Home Depot will run you about $18.
• Why use fancy resin and not the Bondo stuff? Many fiberglass tutorials have endorsed Bondo brand resins or similar products found at home-improvement centers and auto parts stores. After doing a lot of homework and asking several experts, these products are quite often regarded as junk. A friend who has competed in IASCA once told me that Bondo resin is the Krystal hamburger (White Castle hamburger for you Yankees) of resins – if you don't know any better, it's pretty good. The US Composites 440 is some of the best resin money can buy. It offers at least 30 minutes of working time before gelling, if instructions are followed. It also has the consistency of a thin syrup instead of thick molasses like Bondo. Due to the thin consistency, it absorbs more quickly into the fabric, and US 440 can also be painted on with brush strokes (or even rolled on for long lengths) instead of "dabbing" with Bondo brand. I don't work for US Composites, I'm just very pleased with their products. The only Bondo product I went with was their Bondo-Glass fiberglass-reinforced body filler. I used this to make my “Bondo milkshake” detailed later.
• What is Knytex, and why use it? Knytex biaxial fabric is made by Owens-Corning. It is made up of essentially two layers of fabric – one side is stranded, and the other side is woven, and both materials are stitched together. Its primary use is for structural reinforcement in boat hulls. In this project, I used it as an alternative to regular chopped strand mat that's often used in fiberglassing projects (including this one). Chopped strand mat is great for certain purposes - tight turns, tweeter pods, and smaller fiberglass projects. But for making a subwoofer box, a thicker material, like Knytex, is preferable. Why? First off, Knytex is incredibly strong. When soaked with resin, using Knytex as reinforcement results in a much faster build-up. For impatient souls like me, this is huge. Three or four layers of Knytex will be as strong or stronger than 7-10 layers of regular chopped strand mat. In addition, for as thick as it is, Knytex bends around corners fairly easily. This stuff is excellent for building up a thick layer very fast.
• Graduated plastic tubs. This is an easy one. You can tell exactly how much resin you're mixing up every time. 16 ounces of resin calls for 7 cc's of MEKP (and the MEKP bottle comes with a convenient graduated cup). I usually mixed up 8 ounces at a time, so 4 cc's usually took care of the job. However, be careful not to mix up too hot of a batch by addiing too much MEKP. Resin mixed with MEKP causes an exothermic chemical reaction – as it hardens, the mixture releases heat. It does get pretty damn warm, and these tubs will melt with a too-hot batch! I've actually heard horror stories about resin reaching its flashpoint and causing a fire. . .

Alright, on to the tutorial!
The first step is to make a mold of the area I want the box to fit into. I taped off the trunk area as shown. Blue painter's masking tape works excellent. I was sure to overlap all seams to reduce the possibility of resin seepage. Any areas I thought might be suspect I reinforced with standard duct tape. If I didn't use duct tape, it wouldn't be one of my projects. Some people use aluminum foil and/or 3 rolls of masking tape when doing this, being overly cautious about resin seepage. I just used 1 layer of masking tape. I think that if you build up too much tape and foil, you risk losing a lot of the compound curves that make up the mold. As long as your masking tape is well-seated, all areas are covered, and you use an even coating of mold release (more on that later) you don't run much risk of resin seeping through to the carpet.








I masked off the entire back end of my car with some cheap plastic painter's drop cloth. Polyester resin is nasty stuff when it gets somwhere you don't want it to be (like in your arm hair, some of you may experience).


Knytex does simple curves pretty well, but not compound curves. To help combat this, I went ahead and pre-cut several basic pieces to fit. The black Sharpie line marks where I will make my cut. BTW, Knytex cuts best on a workbench using a utility knife. Scissors are terrible at cutting Knytex.


Now, I enlist the help of my friend Pam. She is used as a mold release agent. A medium coating of Pam all over the masking tape will result in our mold easily being removed from the taped area. Skipping this step could possibly result in you breaking the form. Carnauba wax also works well. Anything greasy will work but Pam and carnauba wax seem to be the most popular.


Now on to the fun stuff – mixing up resin. As you can see, I'm working in my garage. Since the fumes from polyester resin are pretty nasty, I set up a fan to help blow them out the garage door. Then I donned my 3M respirator in preparation for the goopy fun. I mixed up a batch of about 4 oz of resin and 2 cc's of MEKP (as the directions instructed). Since too much resin can result in too long of a drying time, I went ahead and laid the first cut piece of Knytex directly onto the Pam'd masking tape. Then I brushed on the resin liberally so the Knytex was able to soak it up. I only got 2 pieces of Knytex resined before I had to mix up another batch. Here's a picture of a couple of pieces soaking in resin.


Since resin is a messy substance, and I was being very careful with my virgin glassing experience, I wasn't able to take pictures of all the buildup of the first layer. But it was a pretty straightforward process until I got around to using chopped strand mat. Since Knytex has quite a bit of mass to it, it doesn't like to stick to upside-down surfaces very well. This is where the chopped strand mat comes in. Since it's a lighter weight material, I used this on the upper corner of the box. chopped strand mat is a little trickier to work with since brushing motions don't exactly work. Here's what I did. Tear (do not cut) off a piece of chopped strand mat that's roughly the size of your hand. While holding it in your gloved hand, dab on about a tablespoon of resin, spreading it to the corners of the small piece. Then place it directly onto the masking tape. Now take your paint brush and stipple more resin onto the mat - that is, hold your paint brush like a pencil and "stab" at the chopped strand mat. This will help the chopped strand mat lay down and conform easier to your tape.
When I finished, I let it cure for about 2 hours before checking on the tackiness. While it wasn't rock hard, it was sorta floppy, but it held the shape very well. Here is a picture of the finished mold after being removed from the car. Note the area where you can tell chopped strand mat was used instead of Knytex. This area is noticeably not as stiff as the Knytex areas.


And a picture of the mold in the trunk. Fits like a glove.


With the mold out of the car, I can work on the tub more comfortably. I built up another layer of Knytex all over the box, including the flimsy chopped strand mat areas. Notice that I added additional layers on the INSIDE of the box, not the outside. We want to retain the form-fitted shape of the mold. Now, if you've made it this far, you'll notice that fiberglass, and Knytex especially, LOVES curves. That's where most of the strength is built up. However, for long flat areas, it's still pretty floppy. So, I called in the reinforcements (pun fully intended). At the suggestion of Mike Abeita from termpro.com, I used nylon rope for reinforcement on the flat areas of the box. The rope, once it soaks up resin, becomes integrated bracing for the box.


First, hot glue the rope on to the flat areas to keep it from rolling around. The nylon braid of the rope will soak up resin, so paint some more of that messy stuff on the rope. Then cut pieces of Knytex to fit over the roped areas. Since the ridges that the rope makes will make it a little tougher to lay the Knytex down evenly without air bubbles, I hot glued the Knytex directly on the rope. Then I slathered on more resin.


At this point, the Knytex seemed to work better when I cut it into various sizes. 2x6” strips, 4x4” squares, you get the picture. Continue adding pieces of Knytex and/or chopped strand mat until your mold does not flex at all after the resin is fully cured. This is crucial. If your sub enclosure flexes, you're losing acoustic energy (output). Also, try to eliminate as many air bubbles as possible. Bubbles caught between layers of fiberglass will also result in flexing.


If your resin seems to be taking too long to cure, try letting the mold sit out in the sun for an hour or so.


Here is the finished mold. Roughly 4 layers of Knytex with some chopped strand mat in there for tight corners. Notice the ragged edge that will be cut off in the next step.


I trimmed the mold back to give it a nice, even edge for mounting against the front side of the box. I used heavy-duty cutoff wheels with my trusty Dremel rotary tool. Bits and pieces of resin and fiberglass dust were flying everywhere, so covering all exposed skin was a necessity. I used safety glasses, long sleeves, gloves, and the great 3M respirator. I still managed to get some dust on my neck and it itched like crazy. Taking a garden hose to your mold is a good idea to help rinse away some of the yucky fiberglass dust.


Here's where I cheated. The next step was to make a speaker mounting ring out of MDF. This did not quite pan out as well as I had hoped. I don't own a router, and I am not in the financial situation to plunk down $150 for a good router and I refuse to buy a $50 cheapo that will break after 5 uses. I decided to try my own hand at it using a circle jig and cutting it by hand with a jigsaw. While it may have been usable, it didn't quite look as good as I wanted, so I scrapped it.





When browsing the web for some custom MDF rings, I got in contact with Triple-X from fiberglassforums.com. Turns out he lives about 5 minutes from me. In 24 hours, I had a beautifully routed, flush-mount MDF ring with a roundover edge. He only charged me $26 for the ring, and I thought this was very reasonable.







The next step was to drill speaker mounting holes into the ring and mount the T-nuts. I went with T-nuts because wood screws have a tendency to destroy MDF if used more than once. Plus, my speaker weighs around 30 lbs. I went ahead and drilled some holes large enough for the T-nuts to mount into – I used some duct tape (woohoo!) to hold the ring up against the speaker. Then I press-fitted the T-nuts into the ring just with my fingers. A little dab of super glue under the flange of the T-nuts helps keep them in place, because sometimes a screw can accidentally push the T-nut out of the hole. Then I put the sub into the MDF ring and tightened the screws down to make sure they seated properly.








With the T-nuts firmly in place, the next step was to mount the ring to the mold. Using hot glue and 3/8” dowels, I positioned the ring so that it was high enough to clear the depth of the speaker (8.5”) and still look aesthetically pleasing. This was much easier said than done! Several times, after I thought the hot glue had set well enough to be sturdy, the result was not good and the speaker ring collapsed as soon as I put the stretchy fabric over the ring (in the next step). I tried some Gorilla Glue, and it worked alright, but it foams up upon setting, causing the ring position to not be where I needed it to be. I decided to try some Liquid Nails, and after letting it set overnight, that really did the trick. What a pain! *I ended up using five dowels as support – these pics are of a preliminary setup that failed.






The next step was possibly the most exciting, in that the custom box finally started to take shape! The stretchy fabric that I bought was stapled onto all sides of the enclosure. I made sure there were no wrinkles visible on the front. Some of the staples had to be made pretty close to the edge of the box, but it turned out just fine.








Then I applied a layer of resin directly onto the fabric. I made sure to resin the area where the MDF ring meets the fabric as well as the seam where the “front half” met the mold. This creates a tight bond between the two halves.








An overnight cure resulted in a sturdy base for more layers of Knytex. The fabric has a very smooth finish after the cure that is free of bumps and ridges. So like most people who get to this step, the temptation to apply layers to the inside of the enclosure was just too great, so I had to try it. I first cut pieces of Knytex to fit and laid them down dry to see how it would work. Then I mixed up some resin and applied. The results? Not too bad. I had to snip one of the dowel supports out of the way, as you can see. But I decided that giving up additional airspace was not something I wanted to do. Plus, with how well Knytex lays around curves, a smooth finish to the outside of the enclosure wasn't too far out of reach anyway.






At this point, I decided to measure how much enclosure space I had. Some people prefer to do this earlier in the project, some later, but I luckily had a decent estimate in my head anyway. I bought 2 cubic feet of styrofoam packing peanuts and a cardboard box that measured 12x6x6 (0.25 cubic ft). I measured out exactly five boxes full of peanuts to fill the enclosure (1.25 cubic ft). Since there were some nooks and crannies in the box that the peanuts couldn't reach, there was probably 1.30 cubes in there. Speaker displacement is 0.12 cubic feet for my sub, putting me right at 1.15-1.20 cubic feet net. Perfect for the manufacturer's specs.





After that, I once again pre-cut some pieces of Knytex to fit. I did only one layer for the curved areas, and two layers for the flat areas.




A good application of resin and another overnight cure had the box feeling pretty stout. The thing was getting pretty heavy at this point.




Pleased with how sturdy the enclosure was, the next step was to file down all rough edges and trim off the excess fabric. I used my Dremel and a grinding tip to take care of the rough edges. A sharp utility knife does a great job at cutting through resined areas that you need to remove en masse like overhanging excess fabric that has been soaked in resin. After this, I was itching like hell, again.








Alright, the next thing I did is somewhat controversial in the fiberglass community. I wanted to make sure there were absolutely no leaks in the enclosure. Some people claim that a good application of resin should be totally waterproof. Maybe mine wasn't good enough, I don't know. But when I hosed off the mold earlier (rinsing off fiberglass dust), I noticed that the mold WAS leaking water. I decided to make a “Bondo milkshake”. Basically, this is a mixture of 1/3 body filler and 2/3 polyester resin, plus enough MEKP to activate both of them. I had read about body filler not being a truly strong substance, so I decided to try out my own concoction, a Bondo-Glass milkshake. Bondo-Glass is body filler with lots of fiberglass strands mixed within. As we now have discovered, what makes a resined product strong is not the resin itself, but the cloth that gives it the structure. I found this at the local Wal-Mart, but other (possibly better) brands are Duraglas and Kitty Hair.
I mixed up (in a large container) about 10 ounces of Bondo-Glass and 20 ounces of resin – the consistency was about that of pancake batter, or a milkshake (imagine that!). I added about 16 cc's of MEKP to the mix to make it a little on the hot side (temps locally had dropped into the mid 50's). The result was a sludge-like material that really defines the word “goop”. I poured this slop directly into the speaker hole and sloshed it all around the box, making sure it reached all the crevices and nooks and crannies.






I thought about adding more Knytex on the outside, but upon curing, the Bondo-Glass really looks like it brought some major strength into the mix. The box is totally flex-free. It weighs a good 10-12 lbs. It's good that I didn't add any more Knytex because at this point, I was out of resin! Also, I noticed that the milkshake mixture cured extremely quickly – it was generating heat within 20 minutes of application. While the milkshake stage wasn't as time-crucial as the initial layup stage, if I had been using Bondo resin in the other steps, I would have been pretty frustrated with how quickly it cured!
To finish the box, I layed out a reasonably-sized piece of Parts Express carpet. While it's not a perfect match for my trunk, it has some stretchy qualities that make it pretty decent for this application. First, I cut a piece of carpet to cover the box. Then, starting in the center of the flat area on the front of the box, I applied some 3M Super 77 spray adhesive (man this stuff smells so good!), making sure the carpet layed as flat as possible on the surface, without wrinkles. Again, this was easier said than done! I used a small 4” wide paint roller to smooth the carpet out in the tough areas. The hardest part was the corners, where I had to cut the carpet to fit along some of the tough edges. It's not absolutely perfect, but you can hardly tell when it's installed in the car. Also, around the speaker opening, I made sure to press the carpet down onto the MDF ring.






The finished product.






Yes, I know my trunk is dirty. And the sub doesn't look perfectly straight, but it's not very noticeable inside the car. Plus, I'm not gonna stare at it all day long, I'm gonna listen to it!
Well that is my fiberglass tutorial, from one n00b to another. I know it's not a perfect box, but it does fine for me. As I write this, I haven't gotten a chance to hear it, because I'm installing some other pieces (the sub amp, for one). But aesthetically, I'm pleased. Looking back, I probably would have used MDF for the flat areas instead of the rope. But it should do just fine as an all-fiberglass design.
Any feedback is greatly appreciated. Email me at dwicker@nospam.gmail.com (remove “nospam” from the mailto address).

Kevin in Atlanta

I also read on this forum about Kenwood self powered subs that I believe would fit in spare tire well.

Bret928

Wow thanks Kurt. Lots to digest.

Its been a long time since I worked with fiberglass (I itch just thinking about it) but I'll look into going that route. I'm thinking I'll pick out a subwoofer and go a head & mount it in the manner I described above and line the well with insulating material first.

Then if it just doesn’t sound right I’ll go ahead & build a enclosure around it with fiberglass make sure it fits properly then use packing foam to figure out how big to make the enclosure.

SteveG

The GTS came with an expensive after market system. Great sound, the sub is in a box, no bottom to it, so though a fiberglass bottom might help direct the sound out, it is not necessary. As nice as it looks, they have essentially imprisoned my spare and batt. Spare will not pass over the edge of the enclosure; I am in the process of chisling the side of the box down and maybe with some KY, I hope to get it out.

Fabio421

Do a search, Red UFO made one. He even posted a video about it on youtube or google.

anonymousagain

Brett - simple answer is yes, you can just make it with particle board.

The key is to ensure it IS a baffle, such that you seal it off from the top air space. I'd suggest a dynamat type damper for the well area, then seal and screw the baffle over the opening so it's air tight. You can also use rubber welt/weather strip as the seal and bolt it down (wing bolts or floppy-washer bolts) to allow relatively easy removal to get to the battery. [I use the ground strap for disconnect/connect while working, so access to battery is rarely req'd]

Appropriate driver to match well volume (a free air will actually work okay as well) and you're good to go. If you use a finer screen sub grill (or fabric glued to the inside of a waffle grill), you'll be nearly worry free from damage. It'll project though the carpet fairly well too, provided you remove the black foam/canvas carpet backing crap first.

btw - 100w to a single 10 is plenty and should keep $$ and space minimized. Just match the driver/amp for your intended application.

chaadster

No need to reinvent the box, guys! Dave (Ketchmi) at Motorsports SLC has some for sale that meet Brett's specs. Check this thread out:

https://rennlist.com/forums/showthre...woofer+box+amp

Bill Ball

You don't need a huge sub to provide good thump. I think I just figured out what to do with the small Subaru WRX sub I bought. It goes under the seat in the WRX but it just too thick the fit under our low seats. However, with a substitute cover for the spare tire well made out ouf mdf or plywood, it would sit above the spare and blow through a hole in the cover without requiring a raised deck, fiberglass enclosure or deleting the spare. Hmm... Out to the garage for today's project.

anonymousagain

wow Chaad - that looks like my first one !! Didn't know Dave was making them and with the piggy-back amp too. good stuff.

maroonedlandshark

Bret928,
Seeing as how you live in Poway check out a place called "Street Noyz" down by the Sports Arena. They built a fiberglass sub enclosure that fit INSIDE my spare tire and houses an 8" sub. I have 120 watts driving it and it sounds superb. Their work is of high quality and they didn't break the bank. This way, I've got killer sound.... and I still have my spare.....

JHowell37

If you don't want anything super fancy, consider a powered sub. It may not look the best, but it will provide extra bass, the wiring is simple and the price won't kill you.