I recently snapped up a Heil PR-22 just to see for myself. I had read that they are not quite as hyped/harsh sounding in the upper mid-range and highs, (4K to 10K). I wanted to try it out on 3 different female singers, one in the studio and 2 in live bands.
Over the last few weeks, I have directly compared it with SM58, N/D767a, Co7, and a few other dynamics which I can't recall right now. It does indeed make female vocals sound more natural and less harsh. It was just easier to find that "sweet spot" while EQing. While it wasn't a huge day-and-night difference, everyone could notice a different sound. All the right frequencies were present and I would describe it as being more like a good quality ribbon mic or something. It was full, rich, articulate, and elegant sounding without being sharp anywhere. Also, if you happen to go a bit heavy with compression to improve on intelligibility, it doesn't work against you quite as much as the other mics do when it comes to de-essing. Perhaps the larger diaphragm offers slightly slower transient response which tames the upper-mid. I don't know.
That was all live stage work and the singers have reported that it sounds better in their in-ear-monitors as well. I haven't tried it out in the studio just yet, but I am optimistic that it will do well.
It may not be the end-all cure-all to every problem but, I did find a new go-to mic for higher-pitched vocalists, both male and female.
