I Have a 2005 Magnum and i wanna know can i fit 3 JL Audio 13W7 sub in the back, you only need 2 ft per sub so i was wondering can i do this.

 

Here is a website with great info on stereo system building Stereo systems. There is a box size calulator there.

The back of the magnum is 39"wide and the speakers are 14" overall wide (14*3=42"). What you would have to do is a pryamid(triangle) arangement of the speakers if you want them to fire rearward/forward. So 15" tall and you should be able to stagger the speakers. OR have the speakers fire upward and things are alot easier.

What you will need is 1.985ft^3 per sub + .21ft^3 per sub for displacement = 6.585 ft^3 total sealed. Now you have to design the box and then add the dimensions for the bracing/seperators.

A sealed box 39wX14hX27.25d = 6.98513ft^3.
6.585ft^3 + .33ft^3 (dividers/braces)= 6.915ft^3 leaves .06653ft^3 (6.98513-6.915) extra space and the wiring should take care of that. Pretty dang close! The 14" height should allow you to pull the rear cover over to hide when parked.

JL recommends 1.0" for the front panel that the speakers mount to. What I do is use .75" for the caculators, then for construction, mount (glue and screw)another .75" to the face. This gives a 1.5" panel up front.

A sealed box will give you tighter response, a ported box will give you boom. I dont know what you are looking for, better music or pure boom.

For ported you will need a 7.755ft^3 box before braces/dividers.
A ported box 39wX14hX31.5d would give you the size that you need for a ported box including the bracing but not the wood displacement for the port. I would guess that you would need a box around 33"d. Now you have basically taken the whole back end up. Plus trying to get the battery would require removal of the box (assuming you dont even worry about the spare tire). Plus the box and speakers would be very heavy.

Now I did these boxes quickly and dont take any responsibility for accuracy. What I would do is take the measurements to a stereo shop and ask them how much to build and have them double check the figures. If the cost is $$$, and it will be, you can go to cabinet maker and have them do it at a fraction of the the cost. Just make sure that they use 3/4" MDF. Hope this helps some.

I have a single 12"TREO with 600w Alpine amp in a ported box and it shakes the car big time. You can see the install on my website in the signature. Seems now that every panel in the car rattles hahaha. This spring I am going to have a lot a deadening to do.

 

Here is the quick version...it will fit.....
http://www.cardomain.com/ride/2081440

We also just finished an install with (4) 12" Eclipse woofers. The pics should be up soon.

 

Yes you can. We did a similiar setup at my work a few weeks back. The thing was sick loud, but be sure to use plenty of dyanamat to dampen any rattling.