@mapman
"... not fatiguing."
A buddy of mine has the III and giddy about getting the IV. I've not heard it myself. Wondering if the difference is more than subtle. I've heard the new Tractrix® horn midrange and noting the Hersey IV has a titanium diaphragm high-frequency driver. Former versions always sounded piercing to me.
If you can share - Is it quite different from the former version of itself, across low, med, high freq?