To the best of my knowledge, sibilance is used to categorically describe a certain type of sound ie a hiss, whistle, s, sh, and in the case of audio, perhaps including certain sounds that certain cymbal strikes make or perhaps sandpaper blocks.
There is nothing wrong with sibilance in one's system or speech. The problem is negative sibilance ie where an 's' is now pronounced as 'sh'.
Assuming the negative sibilance is not in the recording, based on my own experience, I would attest that negative sibilance is entirely based on the quality of AC electrical and whether it is purified and/or conditioned.
A reviewer/columnist who evaluated my system last summer noticed immediately that there was no negative sibilance and he inquired about my passive line conditioners.
In addition, as an experiment about a year ago, I removed only my amplifier's dedicated passive in-line conditioner and installed a 20amp Hubbell IEC connector at the end of my 10 gauge 6N OFC solid core romex. The romex was connected at one end to a dedicated 20amp circuit breaker in my service panel and the other end now plugged directly into the amplifier.
Among other negative effects induced, the most prominant was negative sibilance. And this was noticeable within seconds after making the switch. Upon switching back, the negative sibilance was gone.
Therefore, at least in my experience, I feel confident quite stating that negative sibilance is induced entirely by the noise generated in my AC and without my line-conditioners.
-IMO
