"Ad Hoc" is the Lowther Club of Norway's own horn calculation software. Written in MS ACCESS, it will run on any modern PC. "Ad Hoc" calculates front- and back- loaded hyperbolic, exponential, and tractrix horns.
In addition to calculating the expansion curves, it will also calculate the cavity volume for back-loaded horns (based on upper cut-off freq) and back chamber volume for frontloaded horns (based on T/S parameters).
"Ad Hoc" works in both metric and english measurements, and performs expansion math to any desired precision. (1/1 inches/centimeters, 1/10 inches/centimeters, 1/100 inches/centimeters, and so on...)