but when I model a small horn there is no response in the bass region can one of your horns with desired cutoff be used for a box. Then adjust the tuning to get the responce you want.I know both programs and have been using Boxplot for awhile but horn responce is still new to me. But i still believe in trial and error for a box design but it helps to have a theory of how it will change then have a theory on why you got the change you did. for instance I built a fourth order bandpass that modeled good the the port was to small.