the listening fatigue you are experiencing is likely due to the tweeters putting out too much sound. Consider it like if the treble setting on your receiver was too high. These resistors will lessen the dedibel level (volume output) of the tweeter. This would be like permanently reducing the treble setting.
Most listening fatigue occurs when speakers sound too bright to someone, which is quite likely what you are experiencing. I get that sometimes on my M22's when a recording is not very good. I also used to get it all the time from my computer speakers that had boomy, one-note bass.
