I have two jl audio 12 w3s in my 97 supercab. I had to raise the seat to fit my boxes under it and now I want to do a dual box and set it on top of my back seat. I need dimensions for a box that will fit the subs perfectly. Im doing this to see if there will be a huge difference from my boxes my seat. Thanks guys!

 

Ported or sealed?

 

I was thinking more of a ported one. But sealed is fine too.

 

If you can get some max dimensions of what you'd like I can probably come up with a simple ported box for you.

 

And sorry, their the Jl wx-4's not the w3s. Im not sure in your 98 but in my 97 my back bench seat is two different parts. The right and middle are together and the seat behind the driver is bolted alone by its self. I was thinking about taking that seat out and putt the box standing up on its side right in its spot. Or should I just set it on the seat?

These are the dimensions of the JL website
Nominal Diameter 12.0 in / 300 mm
Overall Diameter (A) 12.52 in / 318 mm
Mounting Hole Diameter (B) 11.0625 in / 281 mm
Bolt Hole Circle (C) 11.7 in / 297 mm
Magnet Diameter (D) 4.13 in / 105 mm
Mounting Depth (E) 5.30 in / 135 mm

Do you need anymore info about the sub?

 

Yea mine are the same way, but you'll run into a problem doing it that way because even though you can pull the cushion off there's still the actual metal frame that runs underneath the whole rear seat. When I did that I had to custom mount just the top portion of the long section of the seat, it wasn't fun getting it to work right and it always felt flimsy without the main metal piece underneath. But I'll see if I can come up with something for both ways.

 

According to jl's website those subs love room in a box, like a lot for such a low power sub. It came out to be about 1.35cf sealed and almost 1.75cf ported. While doing research on them, I found they prefer sealed a little more than ported, but they worked good either way. On a side note though I doubt the box you had under the rear seat was nearly big enough for what the subs wanted even sealed.

But here's some dimensions of boxes that would work better, and they're gonna have to sit across the seat.

Ported:
External Dimensions are 39x15.5x13.5. Internal airspace is right at about 3.5cf after sub and port displacement. You'll need 2 4" round ports at 17 3/4" long each to tune the box to 30hz at jl's specs. Mount the ports towards the back of the box on one of the sides so they run along the back wall on the inside and the subs will have to mount on the front thats 15.5" tall.

Sealed:
External dimensions are 30.5x15.5x13.5. Again mount the subs on the 15.5" front. This box is right around 2.75cf after sub displacement.

Note, these dimensions are for building it out of 3/4" mdf which I'd recommend for a box this big.