I am still working at the pressure minimum for the 150 Hz dip, which might be all wrong.
Let’s take the out the damping and construct a couple of paddles to fit in the holes, by doing so I obstruct approximately half of the horn area. The bends seam to help create standing waves in the horn. By cutting the cross section by half I hoped to induce the same effect as a bend tend to do.
Unfortunately my idea didn’t work at all.
Have I cut the cross section down too little? Or am I trying to address the problem at the wrong place in the horn, should I maybe aim for the pressure maximum at 150 Hz instead?