Anybody with any modeling programs want to help me out here? I've been researching tapped horns (with no success) and transmission lines and I've came up with this. I think it would be more of an expanding transmission line. The "throat" area is equal to the cone area of the speakers and it expands from 8" to 16.5" Maybe I should have a more gradual expansion? I don't know, I've never been able to model TL's and horns. The drivers are Mach 5 Audio SPL 12's and the red line is the line length of ~88 inches which is right around 7 feet for a 1/4 wavelength of 40 hz. Any help would be greatly appreciated.