First, I was supposed to get email notifications of responses to this post. I didn’t get any, so sorry for the late reply. Thanks to everyone for their input.
I think that this is a break in issue, I just need to give things more time. Only about 75 hours on the speakers and less on the new cartridge. Things are improving. I did try repositioning the speakers a bit and it did not make much difference. The problem was worse with digital (CD) playback and tube rolling to a less microphonic pair has helped. Also the alnicos are a faster speaker than my old Mac hemps, that might contribute to a perceived sense of sibilance. I do like how the alnicos play acoustic music (classical, jazz, etc). Though I can see why they would not be for everyone. The Zyx ultimate 100 is going through growing pains as well, some times can sound very strange for a several hours. Narrow part of frequency band just kind of “disappear” and then reappear. Just purchased a lightly used Zyx UNIverse so we’ll see how a broken in cart with a boron cantilever sounds.
Lastly, I have sent about 200 records out to Steve at Perfect Vinyl Forever for cleaning and that has been a remarkable change as well. It sounds crazy, but that service has made more of a sonic difference for the better than any tweak or upgrade I’ve ever tried. More of everything, detail, imaging, soundstage, timbre, I would never have believed it if I had not heard it myself. On a wonderful recording of Aaron Copeland conducting his works celebrating his 75th birthday, the change was so startling that I actually jumped almost out of my chair. I know it is expensive, and I would highly recommend giving it a try. Even made a difference on new and records that had been well cleaned by other methods.