Yep I'm not sure why as well. I was initially very worried about what I was getting myself into but comments from a_recording and a couple others who agreed with me on the EX1000 treble spike issues (yet who in turn loved the MDR-7550) made me take the risk. In the end I was very much happy with the purchase. I can't really fault the MDR-7550s. They sound great to me. Now at high volumes things could become an issue but the headroom in volume is very good, reasonable for listening to music in my case.
The thing is with the EX1000 depending on the tips I wore the treble spikes would get worse or slightly less invasive. I needed to use the hybrid tips combined with a custom tip in order to get a very good seal and in turn helped to tame the spikes to a certain extent. But it wasn't enough to cure the issue and it was still bad for me in the end. Funnily I found the hybrid tips on the MDR-7550s to accentuate treble spikes more and in that it was more noticeable (compared to using V-moda bass tips or JVC tips). I also noticed that it doesn't matter on how good the fit is on the MDR-7550s in regards to picking up treble spikes. A lose fit or tight fit it doesn't matter in my case... While on the EX1000 using those hybrid tips combined with another tip helped to lower treble spikes (yet having a lose fit with other tips would noticeably increase the issue)... In the end I much preferred the V-moda bass tips on the MDR-7550s which gives me the best fit and sound. The sound stage is more open and not so unnaturally narrow (which is a byproduct of the hybrid tips).
Edited by lee730 - 4/20/13 at 5:38am