I am trying to rebuild my box didnt know the best size and port size for the type r. I think my box right now is around 3 sq feet per sub with a 3x14 inch port that is shared between both subs.

 

Do a little Lookin on Alpine's site. If it's a couple years old, then u may have to do a little searching on the net to find their recommended volumes or find their T/S parameters and design via a computer program. The program should be available if you google it. it all depends on your desired tuning preferences and what you're lookin to do, SPL vs SQ.