Alpine Type E 12's
 

i got two alpine type e's in a bass works ported box and they sound great. But all u guys say if u can get a custom one built subs always sound better. So how would i go about figuring out how to design a box with ports?

first off search in google for an enclosure program that will get far :) you type in your pax dimensions and what you want the box tuned to and your subs and then it generates a os for you

RE Enclosure Calculator
http://www.carstereo.com/help/Articles.cfm?id=31

i would upgrade your subs if you are going to pay alot for a custom box

My old opinion = don't mess with what's good you like your boom car box how it is leave it upgrade other areas, its hard to get a box right, if I'm not mistachen you can pay some one on this site like 10$ and they will completely desighn a box for you?

BMW is right man, upgrade the subwoofers...the custom box would cost more than the sub...type e's aren't all that great either...my girl has 3 and compared to my one sub...cant match

A box built by yourself will usually cost about $40.... Cheaper than two new subs.

Use the RE audio calculator

Try to make the box about 3 to 3.5 cubic feet, with around 50-60 square inches of port

EDIT: If you want a hand with a design just let me know.