2 x 8 verses 1 x 12 ??

Fine. But WHERE is the error? Is it in some of the pre-loaded driver data, is it in some of the parameters that WinISD automatically fills in? Do the errors only happen with sealed boxes? Ported? Saying, "this one time, when looking at this one calculation, with this one driver it was wrong" doesn't help me at all. :-) I'm not going to pirate Leap, JBL Speakerbox, or any other commercial software for that matter - and I won't recommend others do either. Please tell me what, specifically, is wrong with WinISD. New Project: 2003 Pathfinder

I wouldn't count errant pre-loaded driver data against any of the programs.  If the user doesn't have sense enough to check all the basic parameters against the ones he has from the manufacturer....then he more than likely doesn't have sense enough to use the program without error. Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.