What causes listener fatique? cure?

I find that most metal or inverted dome tweeters cause me listening fatique. Of course, there are exceptions. But, I haven't come across a lot of soft dome tweeters that irritate me. I find that I am becoming increasingly prone to the ill effects of a harsh system(headache, dizzyness, ringing, etc) as time goes by. Not sure if the reason is age, or being around systems that are tube/soft dome tweeter based. The cure is usually available. Either a speaker that features this type of tweeter, or retrofitting your speakers with a good soft dome(have done this). I don't believe that a lower priced speaker has to cause listener fatique. A great example would be the Coincident Triumph. A $1000 speaker featuring the fabulous Vifa D26 silk dome(my FAVORITE cheap tweeter). I have listened to this speaker in a system using an NAD integrated(with the treble set at +6 db), all StraightWire cabling, and budget CD players(Marantz, Pioneer, Sony), and it was still listenable(I didn't say good - but it didn't send me running, which I often do from a bright system) after an extended period.

I guess we all have different interpretations on things. I am glad you like the Focal Ti tweeters, Sedond. While I simply love the woofers/midwoofers/midranges from Focal, I absolutely abhor their tweeters. Be they Ti, TiO2, or Kevlar. The Ti in particular are the worst sounding tweeters I have ever come across. Perhaps in your speaker, the designer was able to make them listenable ala the crossover design or whatever. I have not encountered any listening fatigue in drivers operating above their ideal frequency range OTHER than metal coned drivers. The metal drivers are quite succeptible to audible, irritating ringing.