TubeNet

That seems very awkward. Interesting though.

The angle of rotation may rather be chosen for the photographic display. To me a more forward direction would be better for actual playing.

The reason I relayed this link is about the almost flareless bell, which also may be seen in an old Kruspe double tuba with forward bell. This shape of bell reminds of the passive vents seen especially on older steel ships.

Klaus