Cures for Vocal Sibilance?

Best of luck.

There remain various avenues to explore, including cables, jitter, power and swapping out speakers

How about some measurements?
(Like REW sweeps, or multi tone measurements?) 

@slaw 

Thanks!

@holmz 

I lack any experience in that regard but I could consult with local audiophiles who are more capable in this regard. 

Update: I no longer hear the sibilance. 

It would have been nice to have before and after sweep measurements.

I guess we should conclude that it was the ears?
If so, then it is good news that the situation has abated.
That is what happened when I saw the audiologist, way back when… but maybe I am projecting?

It is great news in any case.