Anyone here has experience of the Jabo horns made in Germany?

I am most likely going to update the xo's of my Altec/Onken speakers first but as idea of new horns as a reference to my original Altec H-811B cast aluminium ones intrigues me as well as later some diy option, the Jabo KH-55 model might be one solution to try on my way..

They would fit the system nicely also by the looks of the pis below found from internet