4th Order SPL?

[Motorboat KER]

Hey guys! I want to get loud and low with a system I am planning. My trunk can handle 14.92 cubes if built inside (including displacement).

It is a '95 C220. So basically my box will look like a "L". My trunk has a section right behind the seats that can fit 7.08 cubes and the back half I will be removing my spare tire and using that area which added like 2.5-3 cubes. So the total back will be 6.6601 cubes.

I plan on getting 2 DC Level 2 15 running a RF 1200. I would like this setup to hit lows and still be pretty loud. Since my seats don't fold down, I will be cutting through my ski hole and ported through there.

I was thinking I will build the sealed part of the enclosure in the back "half" and the ported in the "front" so I can aero port it through easily.

Will a 4th get louder than a regular ported box? If so, what should I plan on tuning the ported portion to?

Thanks!