Just another HiFi blog?

Rather not. This blog is intended to give my work on horns a suitable frame and to present information in a coherent form.

I remember very well my first experiences with horn loudspeakers and was fascinated by their sound from the first moment on. These experiences were based on the visit of various HiFi shows or special demonstrations. Inevitably one meets also the usual representatives of round horns, i.e. Tractrix, JMLC or similar/equal to Klangfilms spherical wave horn (Kugelwellenhorn). An awesome and almost comprehensive overview about the Kugelwellenhorn can be found here: Ref. 1.

Some time ago I decided to buy a pair of tractrix horns for my open baffle speakers to gain my own experiences and to play around with them as a potential replacement for the existing CD horns. In the course of the project, assembly in particular proved to be a real challenge, because the visual aspect should not be neglected. Here is a photo of my speakers with the original horn:

In order to install the tractrix horn in a sensible way, a mounting plate had to be planned and created first. For this I have resorted to a supplier who provides  software for his CNC machines, so it is possible to plan the boards at home and then send them over the net for printing. The results was this together with a test horn in raw finish:
And the same mounted for a test setup in my speakers:

Regarding the development of a cross-over network, I was somewhat naive in the review and have focused exclusively on the on-axis response. Anyway, the result sounded really good and natural and in my opinion an improvement compared to the CD horn. This round horn is still part of my current setup but or course with it’s final finish:

Although I liked the natural sound character very much, one thing has disturbed me more and more over time, namely that the horns showed a quite pronounced beaming. Maybe it is like complaining at a high level but one day I decided to investigate this issue further. I used my measuring equipment for this purpose and then carried out frequency response measurements at various angles what I had neglected before. Without having determined the exact angles, I estimate that the blue curve was approximately 30 degrees off-axis and the green curve about at the half of this angle:

What immediately springs to mind is that the beaming already starts very early between 1k and 2k. Although you will certainly find better and more precise angular measurements elsewhere the qualitative message should be reliable for a rating and I can only say and the amount of beaming shocked me a little bit. Probably I should have dealt with the theory more intensively before, but if I understood the matter to this extent, no cross-over network can turn a beaming horn into a less-beaming horn. At the same time this was the key moment that led to my decision to think about improving the round profile. If it is not about professional event or cinema sound, as it would be the case with a hi-fi home setup, then the listening position is rather in a very limited area to find. In addition, it is certainly the assumption legitimate that most listeners are more likely to sit on a chair or sofa and thus the requirement for the vertical radiation would be much lower than for the horizontal level, if possibly additional listeners are present. Now I let myself be led to the statement that round horns radiate something unmotivated or uncontrolled evenly into the room. But should uniform radiation not be good? Maybe not with what I have just described. In the end, the assumption has led me to deal with the topic and to create the first calculations of elliptical profiles for the Kugelwellenhorn. Since the first reasonable results were completed much faster than I thought at the beginning, I decided to continue working and incorporated the option to export point clouds for 3D printing.

My statements should by no means give the impression that I find round horns bad. In sum, I am simply not completely happy with them anymore.

Stay tuned for the ongoing posts!