box for jeep gc

Hello everyone, I have been doing ALOT of research and, of course, am getting different options from everywhere, so I thought I would turn to some others who may be able to help. I have a 2003 Jeep Grand Cherokee, the measurements of the back hatch area are 29"(back of seat to where hatch closes), 40"wide, and 14" up is as high as i can go and still use the cover to hide the system. I have two memphis mojo 12s and my bass amp is a PPI PC2350, 1400 watts at 4ohm mono....4 ohm mono is as low as I can go, so I have to buy a third sub to get my four ohm load, or a third and fourth sub...either way I need help. I am sure I can do four 12s, BUT I know three would be an easier fit. Im looking for some possible measurements for sealed and/or ported boxes for my subs...the mounting depth is 8 inches. Please help, anybody....OH, btw. Im trying to build for SPL and hope to tune the box, if ported, to the current IASCA regulation of 60Hz. After help with this question, If im not mistaken the formula is LxWxH divided by 1728 to get airspace....my question about this formula is this...are the LxWxH measurements the INNER or OUTER measurements of the box? thanks again. Taw P.

I think your just gonna have to experiment until you get it right or maybe google a some sort of volume calculator, i found some good triangle calculators that let you reverse stuff if you know area but not dimensions etc.

The formula would need the INNER measurements of the box (if thats the correct formula) otherwise the outer measurements would measure the volume of space of the wood + the air. Would it also need to consider the volume of space taken up by the rear of the speakers? You could always follow archimedes trick and stick them in a bucket of water and measure the increase in water volume and add that to the box.... you'd have a stuffed speaker though.

thank you for the reply. honestly i expected a bunch of people saying a lot of bad things....lol. I really want to do four subs, but dang, just not sure if i want to loose my hatch cover...starting to look like im going to have to go taller than fourteen inches and custom cut alot of pieces of MDF to form fit everything in the rear. I also really wanted to face the subs to the rear, but again...with my space and what i want, looks like all four will be facing upward and maybe put two subs per chamber with ports facing rear....thanks for the reply, I will still be checking in here to see what anyone else has to say.

PS....ive already measured the displacement of the sub and I didnt even use water to do it...LMAO!

Not sure if this helps you much but I built a box for my grand cherokee to make the most use of the space back there. Our goals are different, but I'm happy to share what I learned if you need help. this threadMalcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.