Originally Posted by ZilchLab
Yes, doable, but the transition between a round compression driver exit and elliptical flare is critical; that's where the action is, and I think it's also going to vary depending upon the driver exit angle, as well. Doing a two-piece design, throat adapter plus flare, may comprise the most rational course, at least at the prototype stage, until the variable detail is defined....
In simple terms this is what I'm thinking:
You determine a specific ellipse shape that is the mouth of the horn. At its tallest and widest extents it is a 90x60 (or whatever flavor you want) horn.
The profile at the widest extent can be calculated as a 90 deg flare at a certain radius plugged into the OS profile formula.
The profile at the tallest extent is similar but with a 60 deg flare and smaller radius.
For all points between the tallest and widest, you can calculate the flare and radius to be used. It will terminate to a circle at the throat because the same throat diameter value is always used.
I could easily be mistaken in my assessment as I haven't tested it thoroughly. Please point out where it is more complex.
Edit: Forgot to address driver exit angle. I agree, each OS profile, in order to be optimal is setup for a specific CD exit angle. IMO, the DE250 is the best exit to go with because I believe it is documented, the driver is readily available, moderately priced and well accepted as a top notch CD.