12 alpine type r's box .

two 2 inch round ports are WAYYYY to small...I'd do atleast two 4 inch ports per woofer

i tried two 4" ports, and then the calculator says some obscene number, like 42 inches. my box is only 15" deep. I could use one 3" port. That works, but any bigger than 3", and the calculator gives me a length that wont fit into my box.Disturbin' Tha Peace

build a slot port and have it bend inside the enclosure 3 inches is too small...for ported I'd do 2-2.5 per sub net

Here is the skinny on the ported box questions that you have posted. If you are going to build a generic box like the type that Crutchfield or Alpine or anyone ells tells you to build, your best bet is to cut and install the ports as specified by that resource. Port volume like box volume has a sweet spot that is critical to its design. You can change the port diameter for instance and then calculate the new length for that same tuning frequency, but in doing so you change several parameters of your box other than the tuned frequency. Some examples are: cone displacement vs. frequency curve (including 3 db down point), achievable SPL, Vent velocity, impedance curve, power consumption vs. frequency curve, phase vs. frequency curve, and group delay not to mention port resonances that you may not want. All of which have a huge effect on how your box will perform. In short if you are willing to spend the time to experiment with various port volumes (diameter and lengths) go for it, but if you want the best chance of a good result the first time stick to the design that was designed by an educated audio engineer. The alternatives are to have someone with many years of experience optimizing and constructing (not just playing with share ware programs) actual boxes help you come to an educated decision. Or even better have a real pro plot the cabin gain of your vehicle and test the parameters of your actual drivers, then post that info here and you will get several valid designs to choose from. Regardless of what avenue you choose, this will require you to either absorb some knowledge of speaker design in order to make a decision or just trust the first Joe that responds to you.       I would like to also add that in my opinion the alpine type R is a great sub and performs the best in a ported box. SPL, deep articulate bass, efficiency, and transient response are all better in a ported box. The draw backs are that it is larger in size and will require you to do more homework. If you want a small, easy to build box that will give you good sound and mediocre output, go for the sealed box. And last but not least the type R subs have gone through generation changes, so be sure that any information that you receive about box design applies to the production date of your particular subs.