EX1000 doesn't change much with fit/tips, it's of very low acoustic impedance. The tips James made will help with seal rather than to tame the midhighs, matter of fact tips mostly just change the very high treble as Anaxilus pointed out a while back. The 7550's weakness is actually in that very high treble, so wide-bore tips help it more than it does the EX1000. Rin will measuring the 7550 soon, he says that based on his subjective listening it sounds quite neutral, but misses that bandwidth/air of the EX1000, no surprise.
Surprised you get no sibilance at all James, maybe your listening is just all done in quieter environments where the lower volume levels helps tame that peak. Even raising it up a notch *(not to excessive levels, mind you), doesn't yield anything?
Very surprising as James is the only extensive EX1000 user that has had no issue whatsoever, recordings will have a say as well though.
I will say that the EX1000 is the best dynamic IEM I have heard, it just has that weakness in just one spike, though again, it's of low isolation anyway so I used them in quieter environments where that peak is tamed by lower volume levels (yet not too low to sound dull). I haven't heard the GR07MKII, haven't done an A/B with the 7550 (though have heard them before) and the RE272 can also be contenders for the best performance dynamic IME. But I am going to get a chance to try all these soon ;)
Edited by Inks - 10/16/12 at 5:47pm