My battle with sibilance.

jdjohn, sibilance and miss tracking distortion are two separate problems.
Even the best, perfectly maintained systems can have recording induced sibilance. Miss tracking distortion certainly sounds terrible and can be do to bad styli and cartridges but it is not sibilance even though it makes you squint just as bad. The easiest response to sibilance is just to turn the volume down a little. This will not get rid of miss tracking.

Mijostyn, you cannot assess whether any speaker has a deliberate gundry dip incorporated into the crossover simply by measuring the response of the speaker, because there are natural dips that occur in association with a crossover from one Driver to another. So you can not know whether that is an incidental artifact of the crossover or a deliberate dip. Further, the very benefit of a loudness control is that by turning the control one way or the other you are adjusting the level of the compensation for the Fletcher Munson curve. Because the degree of loss of sensitivity to bass and treble frequencies relative to midrange varies with sound pressure levels, the adjustability of a loudness control affords much more flexibility  than incorporating a fixed Gundry dip into the crossover network. Did you actually inquire whether  Wilson incorporates a gundry  dip into their crossover networks?

Mc low gain  is always much longer settling time. even just changing the stylus only.

and the cable burn in etc is much more difficult due to low gain. also if it's hot sounding.. check the capacitance and loading make sure it's in range. nothing to it really.. patience. 

@lewm , the dip is there. Now, you could argue as to whether or not it was intentional. Would Wilson do something that was not intentional? 
Most loudness controls I am familiar with are just on/off switches with only one curve. It would be very complicated and expensive to rig an analog variable control. My TacT is the only unit I know of that has dynamic loudness compensation. It hops from one curved to the next with output level. It happens automatically. I love it. But, no other digital preamp with the power do do this has the programming. I suspect (but do not know for a fact) that Bozevick had a patent or copywrite on this programming. Others will institute it in time. 
By the way, there is no one Fletchur-Munson curve. It is a continuum that is outlined by a set of curves that vary with sound pressure levels. Your ears do not hop from one curve to the next.

Most loudness controls on old school preamplifiers and receivers were continuously variable, sort of like bass and treble attenuators combined into one circuit.  So, for example, if you rotated them to left of center, you got a reduction in compensation for the Fletcher-Munson curve.  If you rotated them to the right of center, you got enhanced compensation.  Center detente could be the off position.  (I am not claiming that every Loudness control operated exactly like this; just giving an example.) This allowed for variable correction based on the SPLs at the listening seat.  You see such controls on Japanese equipment right up to this century.  40-50 years ago they were standard on some Harmon Kardon, Marantz, Fisher, Sherwood, etc. gear.  Would you agree that that would be better than one fixed Gundry dip built into a crossover?  Further, the complex network required in the speaker crossover to effect the Gundry dip would require inductors and capacitors, bound to muddy up the SQ.  Let's see, when you personally measured a Wilson speaker, was it in an anechoic chamber?  Could you rule out room effects to help produce the dip you may have observed?  But easiest of all, ask Wilson. I strongly doubt they would introduce such a complex network into their crossovers; it's tough enough to build a linear and transparent crossover network successfully, especially for the 3-, 4- and 5-way speakers built by Wilson.