[Benas09]

Originally Posted by Billfitz

Hiss comes from the electronics. Crossover filters don't add anything to the signal being reproduced. They only remove frequencies that are outside the speaker pass bands.

Thank you for response. I understand, that crossovers do not create hiss itself. But my question is what can cause ear pain after they are installed? Maybe some high frequencies going to tweeters which were "eaten" by mids before crossovers were installed?

[Billfitz]

That can't happen. Ear pain is typically caused by distortion that results from tweeters receiving too much power below where they're supposed to be working. The crossover high pass filter reduces, by a large amount, the power to the tweeters below their operating frequency, so distortion is significantly reduced. An error in the wiring could be the problem.