I am with Mapman and Ryder's rationale. Simply excessive energy in upper mids and lower highs in general. But it could be the entire midrange, if excessive. You would want as flat as possible in the mids and lower highs, then roll off is preferable in highs. Find a component in your system that is the culprit. It could be speakers, source or preamp or even cables. Look to the room in the end unless it obviously has overtly exposed reflective areas. In any case make your evaluation in near field listening to rule the room out. For now.
Where does fatique come from?
I've heard systems in the past (also owned them ) that would fatique your ears after a certain amount of time. Always thought this was the speakers fault. Is this right? or a combination of Speakers, Receivers, Cd players, Etc. How much do you have to spend to get over the fatique factor, or is just personal to each person?
Gary
Gary