Angelo,
I have to disagree, go through the mathematics and you will see the difference. The tractrix contour will merge into a baffle by definition, the Kugelwellentrichter will form a shape that is closed at the back, if you go on calculating.
I know the Klang&Ton pretty well. Nice paper but I would not call it a reference. Concerning horns they are writing what others have done before. And the Kugelwellentrichter is mostly unknown in Germany - and elsewhere.
In your site you will find some links to original Kugelwellentrichter literature. (I have used your site to depose there a lot of links relating scientific reserches and implementations mainly connected with JBL - and KLANGFILM.)
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Peter