Anyone want to help with a 4th order?

[the727kid 1]

My buddy wanted to go from 2 12s to 1 12 in a sealed so I built him a box for free and he gave some cheapo 12" sub as a thanks. I would like to build a 4th order since I never have and see how loud I can get this guy for shits and giggles. Problem is I don't know where to start on designing one.

[ChrisAnglin 0]

http://dbdynamixaudio.com/4th-order-bandpass-enclosure-calculator/