Dave,
Instead of messing around with XLR cables - get a PEQ and just cut the mid range by about 6 db SPL from 1 to 5 Khz - that should do the trick to get rid of harshness, as this is the range where your hearing is the most sensitive to nasty distortion and loudness.
By the way, your speakers are probably very efficient - in which case your powerful Krell may be overdriving them into distortion due to exceeding their linear excursion range of the driver (at very high levels only of course). If I recall these speakers are often mated to lower power tube amps which would be less likely to cause this kind of extreme issue...
Instead of messing around with XLR cables - get a PEQ and just cut the mid range by about 6 db SPL from 1 to 5 Khz - that should do the trick to get rid of harshness, as this is the range where your hearing is the most sensitive to nasty distortion and loudness.
By the way, your speakers are probably very efficient - in which case your powerful Krell may be overdriving them into distortion due to exceeding their linear excursion range of the driver (at very high levels only of course). If I recall these speakers are often mated to lower power tube amps which would be less likely to cause this kind of extreme issue...