A New Kind Of Reversal

But look carefully, with $d=10$, $r=\sqrt{\cfrac{d}{x}}$

which section of the Horn should it be?  Maybe, a cup formed by rotating the r-axis arm, sucks energy into the cup instead and directs the energy down the apex.  In which case, $x$ and $r$ is swapped; a new kind of reversal.

May God help us all...