Go to JL's website and download the owners manual. It will tell you how much airspace you need for different boxes...sealed, ported, etc. Then do the packing peanut trick. Either go to a box shop and buy enough peanuts to fill that amount of space, or do what I did when I built my boxes for my 12, 10 and 8.

For the 8 I cut up cardboard boxes and made a box which matched the sealed enclosure inner dimensions per the Boston manual. I then filled the box with packing peanuts and set them aside. I then had a measurable amount of airspace and could mess around with different dimensions for my box that was different than a simple square enclosure. One important thing that is easy to overlook is that your peanuts measure the inner dimensions of your box. When you build the box you have to calculate in how thick your MDF board is to account for how large the outer dimensions of the box is going to end up being...how much overlap you need on each side in order to have enough material to screw the thing together. I created a top for my mock box with the opening for my sub cut so that I could use that as a template for the top of whatever box I was going to end up with. I measured the depth of one of the wells to make sure I had enough depth behind the magnet of the sub. I then cut 2 more pieces of cardboard to act as sides of the box. I had a 3rd piece to act as the top and the 3 remaining sides of the well(bottom, front and back) to create an enclosure. I poured the already measured peanuts into my virtual box with my cardboard sides keeping them contained. Then I could move the sides around with the peanuts contained to get proper width, depth, length and I'd always know that as long as the peanuts came to the top of the box that I had the proper airspace. I had already measured it with my mock box.

With everything measured I laid a plastic tarp in the well. I ducktaped the cut sides in place so that I could measure and created a frame to not only build the fiberglass resin around, but also so that I'd have something to screw the top down to. With the cardboard sides in place and taped to the tarp I'd measure off liquid fiberglass resin, add the hardening agent and with some precut fiberglass mat cut into strips I'd paint the tarp and cardboard in fiberglass. Let one coat harden before adding another. After a few coats had been layered you put the constructed frame on top. You layer on some more coats to enclose the frame within the fiberglass. After you've gotten a hardened framework done you can then pull the enclosure out of the well and continue to add layers without fear of spilling liquid fiberglass in your car. You can sand the plastic tarp off the enclosure, you can sand, grind and cut the cardboard sides off also. After that you simply add layers to the either the inside or outside until you have all the sides thick enough and without any holes. You cut the top cover out of MDF board, cut an opening for the speaker. At some point you're going to want to buy a terminal for the speaker wires from radio shack and cut that into one of the sides. Screw that into place and caulk all around it so that an air-tight seal is created. For the top, first sand down the framed top of your box. Inevitably you'll end up with fiberglass hardened on the top of the frame. That will make it hard to create an airtight seal when you screw down the top. Sanding down the top of the frame so that it's as level as possible will make an air-tight seal that much easier. A good idea is to pre-drill the screws that will hold the top down...it makes it that much easier to screw down the top. Before you screw down the MDF board you will also want to put a healthy amount of caulk on the frame so that when you screw down the top you have another air tight seal. I personally go completely over the the top with how much I put on. I figure that you can always remove the excess after it's hardened, that way you are sure you got all the nooks and crannies. I put so much on that it comes oozing out like marshmellow fluff as I'm putting the screws in place.

After that the rest is all cosmetic. Get some carpet to match your interior if you'd like.

I haven't bothered to carpet the top of mine for a couple reasons. With a vert reardeck it's hidden and no one ever sees it. Matter of fact it's a PITA to remove the reardeck to show people. That and I wasn't and still aren't sure if I'm going to keep that box. I'd really prefer to have the 8 firing directly into the cockpit of the car from between the two seats. Boston Pro line is known for it's tight, accurate bass and I don't like muffling it by having it firing up and into the reardeck cover. For now I have a bridged 150 watt Zapco amp pushing the Boston and a JL slash amp pushing my components. When I have the time I'm going to rewire my amps so that the JL is bridged to 300 watts and pushing the Boston and the Zapco is 75x2 and pushing the components. Doubling the power into the Boston might also create that dreaded rattle that I hate so much. That would be one more reason to create a different box.

So anyway, that's my write-up on building a custom fiberglass enclosure.

I forget what kind of enclosure that is called? I haven't messed with anything but sealed enclosures so I may be wrong. Don't you need some air pressure created behind the cone of the speaker in order to create proper soundwaves coming off the cone? The way I've always seen those boxes being designed is that you have two seperate enclosures within the larger box. One enclosure is behind the cone and the other in front with the front one ported. But again, I've never paid those types of enclosure much attention because they never suited my needs.

You are thinking of a bandpass (multiple enclosures in one unit).

There is no benefit to mounting a subwoofer backwards (other than being able to make a slightly about 25% smaller enclosure). It is primarily a cosmetic install and has nothing to do with performance or where/what the sub is firing into.

Most of the time you see a sub mounted in this way it is part of an ISOBARIC setup. That is the combination of TWO subs mounted in a push/pull configuration.

If you absolutely have to mount it backwards make sure you understand phase principles and be sure to contact your subwoofer manufacturer to determine if any damage can result from such an install.


-- FWIW I'm not just making this stuff up. I earned my MECP AIT cert in the mid90s and have built USAC and IASCA champion systems. I admit I no longer hold a certification as I have been out of the business about 10 years.

Yes, that's it...thx

Isobaric was the setup I didn't bring up and couldn't remember the name of if I had. I've never paid much attention to anything more than single sealed enclosures. All the cars I've owned have been small hatchbacks or RX7 verts. I've never needed more than a 10" sub and really prefer the tight accurate bass of a quality 8". I didn't like my JL 10 cause it wasn't accurate and tight enough in most cases, or simply wasn't large enough to create quality low end frequencies. But then again that could have been the product of a poorly built box. I picked up a Boston Pro 12 a few years back and bought it simply cause the deal was too good to pass up. It was my first sub in a trunk and I truly, truly hated the muffled bass that setup created. I guess I was spoiled by always having my subs in the cockpit of the car.

But each to their own. I've just never been one for asphalt peeling SPL...in fact it annoys me most often. I don't much like unbalanced systems which mutilate the music by overpowering the bass compared to mids and highs. Too often the bass sounds good to them, but everyone else in public hears their license plate and other areas of the car rattle.

BTW doesn't Kicker make a square shaped sub that plays off the isobaric name?

Yeah Solobaric. They haven't always been square. They used to be round just like the normal C-series. They were a different color however and had a much different motor assembly as well as much different power handling capacities I still have two Solobaric 8s that are being powered by over 800w of power each. They are excellent subwoofers (at least they used to be, however I have heard mixed reviews in the last 3-4 years since they went square.)

I blew a JL 12w7 thanks to isobaric design. I've heard of measuring volume using packing popcorn, but I'm a math nut, so I went and drew out all the schematics. From my experience, I'm never going to do an isobaric design again. I only really did it because I had both 12's in a sealed box, but I needed the space so I went iso. I personally like the way ported boxes hit, but they just take up too much space.

Did you reverse the phase on one of the subs.

9 times out of 10 people don't do that and end up tearing 1 or 2 of the subs to shreds.

those 10's will be plenty loud enough...if you want them to go into the storage bins.. its really not the best location for the best sounding setup, but if its just for convenience then go ahead and make some sealed boxes...

each sub comes with the proper measurements for sealed boxes, but typically the bigger the box the lower the bass, smaller is more punchy...

just make sure you're supplying them with more than enough wattage..RMS wattage.. because for one the amps aren't 100% efficient, and you always want to give your amps some head room. Also dont cheap out on a cd player...that's your tuning source...

amps i would recommend either JL if you want to keep it all the same, or Crossfire VR or BMF series amps


i kept it rather vague because you seem to have some previous experience..but IMO those bins arent the place to put subs.

Kinda sounds like what I've been hearing about Boston Acoustics products. The company was apparently bought by another company...just aren't what they used to be.

Oh...and to correct myself Boston Pros need less space than I remembered.

8 = .3 cu
10 = .5 cu
12 = 1.0 cu

DrKillJoy, I did reverse the phase. At the time the isobaric design didn't "hit as hard" as it did in sealed boxes, so I turned up the power and boom, lost a sub. It sucked, but it was a lesson learned.

l3eltinck, where would you say is an ideal location for 2 10s in a coupe?

DrKillJoy, will be able to correct me, or better explain this one. If you are using two subs, don't you ideally want them contained in the same enclosure? If you are bridging an amp to one channel and power two seperate enclosures I believe there can be problems if one box is smaller than the other.

I wasn't asked and I'm not familiar with the storage bins, as verts don't have them. So take what I have to say for what it's worth. Things I would want to know are:

1: how many cubic feet of airspace does each bin have?
You could do the math and get a more exact number. Or buy packing nuts and get a rough idea.

2: what is the bin constructed of?
I'm guessing that it's simply molded plastic. That doesn't make the best enclosure material. If it is plastic, I'd want to reinforce and sound deaden the bin.

I'm going to be rewiring my amps so the JL 300/2 is bridged and pushing my Boston Pro 8 and the Zapco Studio150 is seperate channels and pushing my Boston Pro 6.5 components. To finish off my setup, I've got an Alpine V12 amp that pushes Boston Pro 5 mids under the dash. While I have the headunit out (Eclipse...not sure the model) Moving RCAs around, I might as well wire in my headrest speakers off the headunit. I keep the gains way down on the Alpine so those speakers are more fill than anything else. I rarely even turn on the headrest speakers, but use the headunit fader to do that.

While I"ve got the reardeck off, I'll get some pics of the enclosure and I think I saved a couple from when I was making it. I'll post what I can.

DoH.. that sucks. I've cooked a few in my day too.

I'm a fan of sealed enclosures. Tight, punchy bass is something I have typically always been a fan of. In that case I wouldn't consider it preferable that's for sure. Each sub has X amount of airspace needed to perform properly. A sealed enclosure relies on that specific volume of air to produce the desired sound at X amount of power. Power can be much more important in a sealed box than it is in a ported box.

In a ported (vented) enclosure it is much less of an issue as long as there is sufficient and proper airflow/waveflow in the system. Some ported boxes with multiple subs work just fine, however the dynamics of building a proper ported box can be much more complex. Two subs in a big chamber will sounds like crap, however with proper wave guides and properly placed ports you can make some tremendous noise. If you want to build a box for deep boom, this is your path.

Surely, of course this can be dependent on all of the hardware involved. Assuming you are talking about a high powered system the problems can increase parametrically as the power increases. Bridging amplifiers can presents all sorts of fun problems as the power increases, even with "perfect" setups.

1 - I'm really not sure, I've never tried to build an enclosure in the stock bin. Eyeballing it I would guess around 1 - 1.5 cu ft, maybe more if you built the box with odd angles.

2 - Actually it's pretty much a plastic lid and ring, with a carpeted bag hanging from it. The bag hangs above the same/similar metal area you have in the vert, behind the bulkhead.

I just made a box out of wood and mounted it to the lid.

http://i444.photobucket.com/albums/q...7/subbox03.jpg

All glued and silicone sealed.

I like the way that box looks actually. Nice work

Obie

Nice job smoothing those edges.

Any reason you went with standard plywood instead of MDF?

Because its a little bit lighter, mostly.

Did the plywood ruin your sound quality?

No. Should it?

Here's my frankenbox, still not sure if I'm keeping it and finishing it. I switched the amps around today. Of course doubling the power and turning down the gains makes for better sound. I still need to mess with gains and crossover settings, but so far I'm really surprised how much I like the 8 under the reardeck. The 8 seems much more suited to the cars limitations and my preferences. I haven't spent enough time testing it with different types of music. I was running errands today listening to jam bands, but I also like good ol' electronic from the 80's and 90's (NIN, the Prodigy, Underworld, Nitzer Eb, etc) which will be more of a test for rattling and all that.

Oh yeah....here is where I originally wanted to put the 8. With my experience with the JL10 under the reardeck, I wasn't expecting much satisfaction from the 8 under the deck. BUT it was also much, much easier to build than the same speaker mounted in the cockpit of the car.

90FC that is nice, much more pretty than mine

Thanks! As long as it sounds good, right? It won't be seen.

Excuse my ignorance, but is the green stuff fiberglass?

I'm definitely function over form. Yeah the green stuff is fiberglass resin hardened. Read my post a little ways up, there is a quick write-up on how I made it.

I've got a couple pics of the opposite side of the box I can post if you'd like.