Read somewhere that sibilance is in the 5 to 7 kHz region. That's the same area where metal midrange/midwoofer breakup occurs. Easily compensated with a (LRC) parallel notch filter after the low pass. With the value of the inductor being low (.08 to .12), timing/phase issues minimal. But that's only one of many possible causes. Heard it happen with just the wrong choice of speaker wire for a particular setup.
How does excessive sibilance measure?
I am super sensitive to excessive sibilance as I am sure most of us are, but I know very little about whether this can be formally measured on test equipment like one sees in Stereophile's reviews. I do know, however, that it is about much more that simple frequency boosts in the sibilant range. Are there any techies out there than can shed light on this?