Now I'd read on a post about three years ago, or perhaps a little longer, that the Pixies-or rather a little critter with a Scottish name or herritage, similar to Pixies, was originally intended for the M22s(a small speaker more suited for the littler of the little people)and the M2s, but quite addaptable to the M60s, were being utilized to help control higher freq (Short wavelength)sound problems.
As they are not too bright themselves, they tend to attack and absorb "Bright"to compensate. They are also not timid, but perhaps just a little bit foreward or aggesive, just a bit.

I'm not sure who posted it, someone with a Scots/Canadian background, I believe.