I just got this program and when ever I open a sub on its data base or enter my own I look and the box volume and for like a sub that uses a 1.25ft^3 box its tell in me to use like a 6-13ft^3 box!! I just want to know if I did somehting wronge or if its just messed up or what??
Usually WinISD uses a box size that will yield the flattest response...
What sub are you trying to plot? Go with what the manufacturer recommends for now, then try different sizes and take a look at the freq. response and SPL curves. See how they change.