If anyone wants, I'll give a quick tutorial on how to design sub boxes. Topics to be covered would include speaker selection, box designs, construction techniques and testing. I will not cover horns. I will cover sealed, ported, dual reflex ported, bandpass(4th order only), and transmission lines. This can be for home or car.
To get the ball rolling, a good program to use for designing your own enclosures is called WinISD. The current version is WinISD Beta and is freely distributed by LinearTeam(x). It has a decent database of existing drivers and is a fairly complete program.
If anyone needs help designing a box, please post here and I'll follow-up with you. Remember to link to the speakers Thiele-Small parameters. They are listed as: Fs, Qts, Vas, Sd. These are the bare essentials. Addiotional parameters include: Qes, Qms, Le, Re, power handling, BL, Xmax.