When Wayne announced his midrange horns last year, I spent a good afternoon going through my old math books, trying to figure out the angles. You know what I ended up doing? Built a mock up with 1/4" MDF to measure the angles directly off of it. Only took an hour to do the mock up.

With a mock up, you don't even have to "measure". Just copy the angle to a sliding bevel and transfer to the saw.

Gar.