Box Design for 2 SSA Xcon 18's @ 30hz S-10 Blazer 4dr.

[RedFred]

I'm looking for some suggestions on how to calculate the math and set up this box.

I've got 2 SSA XCon 18" subwoofers, going behind the rear seats of a 4dr 99 S-10 Blazer.

I've been told to tune the box to 30hz with about 200 square inches of port and 14 cubes net. I'll be running them off a SoundQubed 2200 @ 1 ohm currently, and may upgrade to a SoundQubed 3500 in the future.

I've come up with exterior dimensions of 44.25" wide x 25" tall x 31.25" deep. I want the top to be double baffled. (The base will be 38" wide x 29.75" deep, and the top will be 44.25" wide x 31.25" deep, in order to overcome the wheel wells.)

Using this box calculator - http://www.the12volt.com/caraudio/boxcalcs.asp

I came up with about 16.75 cubes gross. Does this seem right? (I used 44.25" wide x 24.25" tall [to account for .75" of 2nd baffle] x 31.25" deep, with a thickness of .75")

A big question is that I have to build up over the wheel wedges. The dimensions I will be using are 3.875" wide x 7" tall x 31.25" deep on each side to overcome this. How do I calculate how much volume this will take up? I got 0.98 cubes. Is that anywhere close?

Any tips in the right direction would be greatly appreciated.

[RedFred]

This box is turning out to be much more difficult than I originally anticipated. I should've done more research on these SSA Xcon's before picking them up haha. They want huge boxes with lots of port.

Looks like I'm going to have to make some sacrifices.

Even moving up to 26" tall, I'll only have about 12.5 cu net if I go with 200 square inches of port tuned to 30hz.

I'll either have to:

1) tune higher

2) less port area

3) build higher

4) have less air space

I'm thinking I'll just stick to 26", 200 square inches of port, and tune to 32-34hz.

[RedFred]

This is what I came up with

44.25" wide x 26" tall x 31.25" deep - .75" MDF everywhere except 1.5" on top - 17.48 cubes gross

-0.5 cubes for woofer displacement

-0.98 wedge displacement

-0.07 bracing displacement (2" x 4" with dimensions 1.5" x 3.5" x 23.75")

15.93 cubes

Port - 8" wide x 25" long x 22" deep (200 square inches)

-2.55 cubes for port

13.38 cubes net, 200 square inches of port, tuned to 34hz.

If anyone could double check my math, or give any tips, I would really appreciate it.