I've looked around for a definition of this phrase:  driver flex.  Used in conjunction with descriptions of IEM earphones.   Is there a commonly accepted definition?   

Updated the title.     Also: after more time with the Klipsch I would report that the sound does not seem veiled after all.  Bass is more pronounced, certainly.   Any suggestions for other headsets to consider?   Any suggestions for methods to make the mc3 more comfortable?  

first post: I've been reviewing the material in the forum.  It's very extensive, and I've tried to take advantage of all of your knowledge and experience.  It has been interesting translating all this information into a purchase decision.   I'm looking for a headset for iPhone4.  I want...