Jeep TJ unlimited box design
 

Ive got a 2005 Jeep TJ unlimited Rubicon. I know its not the greatest vehicle to design a sound setup for, but i love it for more reasons than that.

Im looking to design a ported subwoofer box for 2 12" subs, firing to the floor. it will be placed behind the rear seats.

My jeep is an Unlimited, it has a 15 inch longer wheelbase, which gives me these dimensions to work with behind the rear seat:
33.5" wide, 23" to the top of the seat and 21" deep

Im hoping for the box to be around 3 cubic feet.

does anybody have any design insight?
anyone else with subs in their jeep?

I have been thinking of designing something for my Jeep as well. I imagine one very well powered 12 would rock our jeeps... speaking of which, do you have the factory sub in the back as well?

i dont have a factory sub in the rear, rather i have the factor 6.5 inch in the center console. Ill disable it when i hook up some better bass

You can easily get 3cuft into that space. I would vent the box and fire it all down at the floor. Should return decent sound even with the top off and be fairly stealth too.

Thanks Dukk, Im gonna try and build a 3D model on my computer when i have some time, then ill post the renders up here when i get that finished. This is the first major enclosure Ive built. Now i just have to pick out some subs and and amp! any recommendations? (Looking to get some bang for my buck)

jeep subs
 

i have installed the stereo intergy flat piston sub work amazing,1/2 cu ft of air space is a must no more.please go to the web site and check it out,he builds them and ships them.nick

i googled the subs you're talking about, and couldn't find the site. you got a link for me?

sorry about the spelling stereo integrity.com try this lmk

Okay, here it is. Ive chosen to use 2 Cerwin Vega VMAX 124 subwoofers, powered by a Rockford Fosgate 1000W RMS amp im going to build the box with both the subs and the vent pointing downwards. Id like to tune it to 33Hz.

Cerwin Vega recommends a 1.75 cubic foot box for each subwoofer with a 4 inch diameter X 7.5 inch length port. although on this design i'd like to use a slot port.

I have a couple of Questions. I have tried to use winISD to design this, but it doesn't make a ton of sense. Its hard to make sense of what the relationship of port length and diameter is according to winISD. Is there any insight that i can get on designing ports? am I just looking for a target volume or a specific air speed as it comes out of the port?

Also, for building a two-sub box, can I just multiply the target volume for 1 sub by 2? or is there any other recommendations? Would you recommend 3.5 cubic feet in my situation, or would you recommend more or less? ive got some room to work with

another question, I cannot build the box to the dimensions that are considered optimum by winISD. how do i keep my frequency tuned to the 33Hz that I want?

Also, is there any other ideas you guys can shoot at me?

That vent CV recommends tunes the box to 43hz. A little high IMO. You want something more like 14" in length.

As the vent gets bigger (more area) it will also get longer for the same tuning frequency. Ideally you want to keep port velocity below abut 100feet/second.

If you keep the box to the same volume, the shape does not matter so much.

I was going to use those subs and had worked on a box for them. I found a box that was 3.5 cubes, that used a single slot port (12.5" tall x 2.5" wide x 17.5" deep) worked well. Combined with a subsonic (infrasonic) filter set at 25hz and 12db/oct, it tuned the box to 33 hz, and had a port velocity peak of about 82 ft/s @ 30hz with 1000watts. It had good group delay, and cone excursion was under xmax at all frequencies. Spl was above 120 db from 40hz-80hz with a smooth frequency response. You can use any dimensions you want as long as the box volume is the same and the port opening area (31.25 square inches) and length (17.5") are the same. Alternatively, 2 round ports 4" diameter x 14.5-15" will be about the same.

Thanks so much! I've got a real good idea of what I'm going to do now.
I'll try to post my design and take some pictures as I build it.
Hopefully it's just as loud as I want it to be!

Renders of the box!
 

I've designed the box using Rhino to spec. heres the renders!
Note: The top piece that hangs over is not to spec, i left it long, because i want to cut it so that it will fit perfectly

files are attached here