no, no such problem what so ever :| I even cranked up highs by 3 db to get some more sparkle but no sibilance. there could be three reasons for that: recording is sibilant, source has some problems, or as already mentioned - there is poor seal going on. these iems are quite laid back, with rolled of highs, so the fact that you hear sibilance is strange. maybe you are too sensitive to high frequencies? how old are you?
Thanks for your responses guys.
I eliminated recording and source from the equation by trying different songs, different sources and also cross-referencing with the MH1C and S500. So seal seems to be indeed part of the problem. Until now I used the large (light blue) hybrid tips because I also use the large tips on the MH1C and that is the best seal I ever got from an IEM. But those are meant to have a shallow insertion, which doesn't seem to work with the XB90EX. After a bit of trying, I settled for the smaller green hybrid. The seal with those is better but still not perfect and the highs do seem to relax a bit and make it more bearable. The seal is still not as good as with the MH1C however (nice 'plop' when pulling them out), so which tips would you recommend I should try to improve that?