Car Stereos: Sub Enclosure, spectrum scope, port tubes

Question
I will be installing a 12" Fi Btl with Sundown 2000W amp. Im thinking of using 2.5cubic foot box and it recommends "12-16 square inches of vent area per cubic foot of volume." I was wondering how to exactly calculate port/vent size in constitution to the box. I want to tune it at 32Hz.

Much help is needed Thanks in advice for your time.

Answer
Oshea,

First, I am assuming you are tuning this sub for competition.  It will not have any recognizable sound quality whatsoever.  Knowing that, if you want to tune the Ported Box to 32hz, you need to have more information to calculate port size.  The sub should come with about 10 different sound specs.  You need those specs to determine box and port size.  Also, if you are tuning a box for SPL purposes only, you can get even more with an isobaric box, instead of just a ported box.  If you just want to build a ported box with 2.5 cubic feet, the port size should calculate out into cubic inches.  Not only will you have a certain size hole, but you will also have a specific length of pipe going into the box.  Using the information from the sub specs, you should be able to determine optimal box size in cubic feet and optimal port size in cubic inches.  Without a spectrum scope, you will not be able to specifically tune your box to 32hz.  Instead, you will need to buy a couple different lengths of port tubes and adjust the lengths until you are satisfied with the specific hertz response.  You will need a hertz drop cd to assist in hearing each specific hertz from 40 to 20.  Most of this tuning will need to be done at near max power, so I would recommend earplugs.  To get some of the tools needed for tuning, you may want to take it to a pro shop to get tuned.  I hope this gets you started.  If you have any further questions, please feel free to ask.  Hope this helps, Scott