JBL Subwoofer Box Specs / Measurements

I've searched high and low for the box volume of these factor JBL boxes but have never seen it posted. So, I pulled mine out and filled it with water! I also took some depth measurements while I was in there. Just wanted to throw this post up so others can find it if they're also looking for this info. I think the box is a lot larger than anyone originally estimated.

Here you can see the box shape and design. In this pic it's filled to the brim with water. But, there's some additional volume that sits above the water level in this pic so there's definitely more volume than the 0.6185 cuft of water that's in the box in the picture. But it's not a lot more.





Another angle. Still full of water. Here you can better see the areas that sit above the mounting hole and thus are filled with air, not water.




Interior with webbing on backside. Hard to tell at first from these pics but the face where the sub mounts is not parallel with the back of the box. So, there is not a constant depth. At one side, close to the outer edge of the mounting hole there's a minimum of 3" depth. At the center it's ~3.75" and on the other side there's probably 4-5" of depth as the box just keeps getting deeper and deeper the further down you go due to the angle of the woofer compared to the back of the box itself.













The factory sub is 3.5625" deep but it has a very small magnet and is very narrow in the center. So the fact that the box is very shallow near the top isn't an issue since the thickest part of the sub is only in the center. Many shallow mount aftermarket subs have almost a uniform thickness from outside to inside so YMMV on what fits.






If anyone wants any additional info/pics/measurements you've got a few days to hit me up and ask while this box sits here drying out before I reinstall.

 

what diameter is the sub(inside mounting hole and outside perimeter)?

i'm wondering if a ford dvc 8" sub would be a simple upgrade for a lot of people. they're pretty easy to come by, and spec out reasonable.
https://www.ebay.com/itm/114417862996

 

That sub seems a bit expensive for what it is. For round about that same cost you can get a

$170 Rockford Fosgate P3SD2-8 8" Dual 2-Ohm Punch Series Shallow Mount Car Subwoofer

Rockford Fosgate P3SD2-8 which others have had decent luck using with the stock amp.

The factory opening is 7.375" diameter.




Overall recess in the box (maximum overall diameter of outside of subwoofer) is 9.0" diameter.

 

yeah i was trying to dig in my saved sites, there used to be a link i had somewhere they were selling for $25/ea.

they're at least readily available from junk yards for scrap value, ford put them in a good part of their lineup '06-12. i got 3 of them through 2 different yards. 2 of mine were out of a 2010 mustang, 3rd was out of an explorer or excursion, i think.

they're made really nice, bumped back plate, rubber surround, thick pressed pulp paper cone, even has coil venting. magnets a little small and the 1.6ohm per coil is odd, but series the coils, and it'd be close enough to 3 ohms most amps would be happy running it. with the jl system, a single coil might even be what the amp is needing, iirc, those were 1 ohm speakers in a lot of that setup.

i just checked the dimensions-- 7-1/4" cutout, 8-3/4" overall, and 3-1/4" depth. they would work.

 

Yeah, if you could get them cheap then it may be worth testing out. Cheap replacement if your stock JBL is blown but seems unlikely it'd be a huge upgrade - but who knows.

Also, the stock JBL sub is a dual ohm unit. Not sure how picky the stock amp is about impedance but that Ford one is pretty close and just a little on the low side.

 

Nicely done sir! This should answer a lot of questions for people in the future.

 

Wow! This is great info! I was just thinking about filling the box with water to test volume. I picked up the p3s and I'm getting ready to swap it out. The specs on the p3s call for a 0.25cuft sealed box. This box is nearly double the size, and that will contribute to low output. Has anyone tried putting something in the box to reduce the volume and tested output?

 

I had been looking at the Rockford P3S but got some feedback that it may not be ideal. Post #19 in this old thread of mine will link you to DIYMobileAudio where some guys ran simulations but looking back on it now it seems I removed the P3S from my list early on due to very minimal power handling. But maybe there's some info in there for ya.
https://www.tacomaworld.com/threads/help-me-pick-a-subwoofer.786161/

Also, I haven't gotten around to finishing this project. At one point I was hoping to get the sub setup but when I went to do so it became immediately obvious that it wasn't going to be a basic bolt on affair. My IDQS sub will need to use some sort of MDF trim or somethign to get it to fit. None of the screw holes line up and I feel like there was one other issue to overcome too. This audio install has had more starts and stalls than I'd care to remember at this point, lol.