[Mike P.]

For the life of me I can't figure out how to get WinISD to model SPL or cone excursion.

You need the Sd for that, it's not listed so use 800 cm2 which is about right for a 15 inch sub. Modeling shows 2 subs in 12 cu.ft. tuned to 18 hz looks good. Input power is 1200 watts with a high pass filter at 15 hz to prevent over excursion. Porting would be a 8 inch diameter tube 29 inches long to keep the port air speed at 27 m/s.

 

[Mike P.]

The HPF would be an add on unit like the Reckhorn B1 from CSS, about $100. It also has the ability to boost the input voltage to the amp if that's an issue with your receiver.

 

[Mike P.]

With a HPF added at 15 hz cone excursion is not a problem with 1200 watts input.

At 26 m/s port compression starts and air speeds up to 30 m/s usually aren't a problem noise wise in most cases. Remember that a HPF affects the port air speed when you're modeling.