Any loudspeaker design programs that will calculate aperiodic vent and/or

[severedhead15]

transmission line type designs? Just wondering. I just bought a dayton mk III 15" subwoofer, and am interested in building some aperiodic vent type enclosures. I can't really afford any kind of transmission line setup, but it would be fun to look at how different drivers would perform within that type of setup.