TS Parameters

I was playing around with WINisd the other day and I started thinking. How does WINisd take the TS parameters and turn them into a simulated frequency response? Other than plugging TS Parameters into some kind of software application and getting a curve on a graph I don't really know much about them. I looked them up online and I mostly understand what all of the parameters mean. But I don't understand how they work.

Example: I have a box that is 2 cuft with port tuned to 30 hz. I drop some random driver into that box and I get an f3 from WINisd. What happens if the driver VAS increases by 10%? How does something like that change the f3 and the rate of the roll off?

I am seriously thinking about digging out the original papers written by T and S and digging into the math. But, I thought I would ask in case somebody here already has.