Vertigo, please explain what you mean by "listener's fatigue". What exactly are the symptoms? How far away is the listening position from the speakers? Are the speakers toed-in? Are you on the vertical access of the tweeter? Do you experience fatigue every time you listen or only occasionally? Does it occur during specific recordings, or at random? I don't think you've given anywhere near enough info to adequately address your question.
Someone named Vertigo asking about fatigue -- there's a joke in there somewhere.
Someone named Vertigo asking about fatigue -- there's a joke in there somewhere.