Subwoofer Design/Modeling Software

Hi folks, i currently design and build subwoofers as a hobby. I have built maybe 50 overall and my designs have performed well. I use winisd and sketchup to accomplish what i need to accomplish to this point. I do get requests for me esoteric designs like quarter wavelength and series tuned 6th order. I have used math and winisd to accomplish some good performing designs of this type but i would like some acoustical prediction. I have tried hornresp, i know its powerful but to this point i am not able to model anything accurately in it. I will keep trying.

In the meantime what other software are folks using for series 6th order and possibly other more advanced designs?