Building enclosure for two JL10WOs?

Man, I hate to jump in here and kinda go a different direction, but Forbidden got me thinking. My son and I are building our first sub box starting this next week, right before christmas. He's got two 12" JBL GTO's, and a very inexpensive Sony Xplod amp. (He didn't want to spend a lot of money, and is just getting into this on his first car) Anyway, we are thinking of building one box, seperated in the middle to make two sealed enclosures. Forbidden's post about speakers going in different directions got me thinking. I need to know if the two sealed is okay, and if so, would I use one terminal cup, and have the neg and pos leads go to the same cup? Is there a better first time setup I should be thinking about? Like I said, this is a first for both of us, and unfortunately, I only know enough about car audio, signal flow, etc... to be dangerous. (i.e. parallel vs. series) Any help you can give me and my son would be greatly appreciated. Also, would it beveasible, or unadvisable, to build one large box, with a seperation between the speakers, but have one sealed, and the other ported? Anyway, thanks...

John

Morning guys, sorry for the delay but here is some answers...

1) the volume calculator does take into account the thickness of the materials, it ask you for the material width, remember...

(2) 1 box with 2 sealed chambers is fine as is 2 sealed boxes, actually the first is a really good idea, it actually makes the box a little stronger due to the center divider and also if you have a failure of one sub, the other will still work. For all you polar bears, up north I imagine, do not port that enclosure, only port it if the box is built to the cubic inch and the port length and width is calculated to that cubic inch. A sealed box is a much safer and usually a "better sounding" enclosure, a great first project for you. Post up the model# and make of the subs and the amp, I or someone else will get you pointed in the right direction.

Here's the info on subs and amps...

Speakers: JBL GTO Series GT120

Here's the Sony AMP: XM-2165GTX

This info is from the crutchfield site (which by the way, I'd love to know of a better place to buy stuff from).

The stuff is going in the back of a 1996 Toyota Corolla (Sedan - 4doors, his first car), and from what he's told me, the area he's trying to fit the box in is 30" wide x 17" tall, and 20 " deep. That's the trunk space we have to work with. Also, when we run audio to his AMP, we use a pre-amp output from the head unit, correct? He's got a 4x25 watt head unit, and I think there's a pre-amp out, so it's not amplified, as in the audio that's headed to his other 4 speakers. LOL, does that make sense? See I told you I was dangerous. I'm going to have to run wire from the head unit back to his amp in the trunk from the pre-amp out, if I'm thinking correctly. Also, any tips on caulk / glue I should use? We are planning on 3/4" MDF, using 1.5" drywall screws to hold it together. I was thinking of one terminal cup, with wires from the second speaker, going through the center divider (sealed off around the wires of course), and attaching to the terminal cup with the first speaker.

I don't want to get ahead of myself, so if this sounds good so far, I'd appreciate know that. LOL. Anyway, you've got the speaker / amp info. Thanks Forbidden, I really appreciate this.

Well, sorry for the delay, had to install a remote start, you have a mighty big box there, I'll do some more homework on it for you. Make sure that even though that is the space you have in the trunk, that you can actually get it into the trunk. Your best bet is to use the amp in stereo mode, it is not designed or engineered to operate in mono with the two subs you have chosen and the wiring method you are leading yourself towards. The best way for you to wire the system is as I mentioned in stereo mode, 2 channels of output, 1 for each subwoofer. You can wire the one sub into the others compartment, seal with silicone (tie the wire on each side to prevent it from pulling through in either direction). Use two terminal cups.

For wiring the amp, you are on the right track with the rca cable, you are also going to need to run a "remote on" wire from the cd player to the amplifier, this wire turns on the amp when the stereo is turned on. The common wire color for a remote on lead is either blue or blue / white depending on the manufacturer. If both wires are present on the cd player, make sure you connect to the remote on and not power antenna lead. Do not run the rca cables anywhere near the power and ground wires (or remote on), run the rca cables down one side of the car, the power, remote on down the other side. Make sure you have a nice clean ground point, a seatbelt bolt is not the best place usually. Clean the paint off and attach the ground wire at this new point. Make sure you fuse the power line no further than 18" away from the battery, this is to protect the vcehicle from an inadvertent short in the power line. Make sure the fuse is at least the same size as that of the amplifier. You should be using a minumum of 8 gauge power and ground wire, 4 gauge would actually be a little better though. This should be enough to keep you busy for now. Enjoy!

For the box volume I would recommend that you start off with a sealed box, it is easy to build, very forgiving and sounds quite good. The ported box will usually play louder and a little deeper, sometimes they work great - other times they sacrifice finesse.Build your box to a cubic volume of 2.2 cu.ft approximately.

Here is the math

l x w x h = cu.ft.

l x w x h = 1728 cu in = 1 cu.ft.

12" x 12" x 12" = 1728 = 1

Any combination of numbers that equal 1728 is going to equal 1 cu.ft

For 2.2 cu.ft. you need approx 3800 cu.inches of airspace, this is an internal volume measuement, make sure you allow for the width of your materials. If I was building this box I would build it as follows

Top and Bottom 29.75" x 115/16"

Front and Back 29.75" x 14.5"

Ends (3) 9.75" x 14.5"

This box will only assemble in one way, the ends and front back are between the top and bottom. The reason for the extra little bit on the top and bottom is to allow a little room for error when assembling the box and space for glue to expand. Use a good amount of wood glue, predrill all screw holes, do not put screw to close to the end or the mdf will split. Silicone all inside seams. Once the sicilcone has dried, spray paint the inside of the sub box, this is to seal the box, mdf is very porous. Add a small amount of dacron (pillow stuffing material) and lightly fill the enclosure. Salt to taste.

Rukuzz wrote: forbidden, I'm almost done. Next time I'll have home depot do all the cutting for me. My cuts were a little off! I got it though I just have to put the lid and cut the speaker hole. I have one question about the screws. Put the for walls and floor on my box, with liquid nails, and drilled a hole for the screws. I drove the screw in and the MDF split. I had to take off one side and replace. I have since put it back together with no screws. I think I might've used a drill bit size too small. Anyway, I'm a little gun shy, I've since stapled the wall's with 1/2" Arrow Type T50 rustproof staples. I've stapled at the corners and down the walls on the outside. Will this be enough or should I try the screws again? Thanks for all the info forbidden!

How thick was the MDF that you used?  I seem to recall that you decided on 3/4".  If that's the case, I don't think 1/2" staples are of any benefit, since they won't even penetrate the first piece of wood, much less bite into the piece underneath.  Maybe I misunderstood what you were doing with the staples?  I'd try again with the screws.  Just experiment with your scrap piece to find a pilot hole size that will give the screws a good bite without splitting the MDF.  Try to drill your screws through the face of the MDF, rather than into an edge.  MDF doesn't have a "grain" the way conventional wood sheeting does, but it will definitely split more easily if you drill into the edge of a piece, especially with an undersized pilot hole.

Scott Gardner