ill define ported enclosures in the easiest way possible
The basics of ported enclosures which i learnt from my own experience
1- if a box is tuned to 32hz , it will generally be peaking 6 to 8hz above tuning frequency that is 37-42hz range depending upon port area and cabin gain
e.g mehran has extreme gains in 45 to 50hz range, i-e a box tuned to 38hz can probably gain arnd 6db boost just due to nature of box and cabin gained combined at peak frequency
2- Now coming to port area, the basics are
the lesser the port area , the more range enclosure will have, will play flat , smooth. Uniform excursion at the cost of extreme spl
the more the port area, the faster the subwoofer will go out of balance below tuning, will b almost still playing at tuning frequency, will have alot of over power margin above tuning and at peak frequency due high excursion cooling it down
sound will b peaky and rough but loud
9-16sq inches is advisable for slot port, i prefer to keep 14sq inches per net cuft as its a decent compromise between extreme spl and quality
Regards 
