4th Order help for 2x RE Sxx 15"

[Ben Depellegrini]

Hi all,

First-time poster here. My name's Ben, and i've been fiddling with car audio for around 7 years now (since i was about 17). I've only recently decided to get a bit serious with it, and id love to enter a few competitions.

To cut a long story short, id like some help / direction with designing a 4th Order Bandpass enclosure for my sedan. I've got a desire to buy a wagon and make a dedicated spl-car out of that, but for now, id like to see what my two 15"s can do in a sedan.

I have two RE Sxx 15"s, each with 1200w rms @1ohm, in around 4.5cu ft with 2x 3"wide X 4"deep ports. Subs are facing the bootlid (rear). Im aware that the box isn't optimal for SPL, but it looks pretty... Made 136.2dB on a Termlab.

Anyway, for the sake of being competitive, boot-space isn't an issue, and im fairly handy with construction, so all I need to know is how to calculate volumes, dimensions and port area/depth for an SPL optimised box. I've noticed that my sedan has a resonance of about 45Hz, so i'd assume that I tune a box for around there?

Max dimensions for a box are: 35" wide, 16.5" high, and upto maybe 35" deep? The sealed section of the box can be upto these max dimensions, but the space under my parcel-shelf would limit the ported section to being about 13" high. (rectangular sealed section with a trapezoidal ported section). Forgot to mention, ive been told that a cabin-firing port works best for SPL.

Any and all help / advice would be appreciated.

Ben