If I take a 12 inch woofer with these specs.

qts .32
vas 124 liters
fs 37hz
94db

Where exactly do I enter this numbers in pialign?
Low mid or high mid sections? What do I enter for low cut/high cut?
What if I want sealed not ported ?

After entering the data, the program will output the best box
dimensions? Will it tell me f3?

Confused

You'll need to enter Imperial measurements for Vas, so enter 4.34. Frd = Fts, so enter 37. Qts = 0.32 so enter 3.125 for Qd. If you're using a single woofer, enter 1 for "Qty."

No other items are really important for PiAlign's cabinet computation, except volume offset fields which are at the bottom right corner of your screen. Those can be calculated separately pretty easily, and all the rest of the items are informational only, so you can maintain a database of your designs.

PiAlign recommends a 1.4 cubic foot box, tuned to 45Hz for this woofer. To see the response curve of this alignment, use BoxPlot or something like that to model the cabinet and predict response.

So, you see, it is all related to beer.

Assuming a few hundred cubic inches are displaced by components inside and by wood thickness, your cabinet is 3.5 cubic feet. So to tune this for 40Hz, you'll need to shorten the port to 5" long, assuming the same rectangular W x H dimensions of 3.5" x 6.0."

That will tune it to the same frequency as the "stock" Professional Series four π speaker, and it will sound pretty good. A 2226 works very well in cabinets from 2.0ft3 to 5.0ft3 tuned to 40Hz.