I just got these in the mail today. I bought them used, and the guy assured me they had 150+ hours on them (including several uninterrupted days of 24/7 burn-in playlist), so burn-in would seem unnecessary.
I also have some "balanced" M9 tips, and UE compatible tips, that I bought to use with them. They are my first IEM. I have tried them with and without the foam mod. With the M9 tips, the foam mod is not really necessary, because for me they live up to their name and balance out the sound pretty nicely (these tips also put the drivers an extra cm away from your ear canal). With the UE tips I find the mod is necessary to avoid shrillness. Overall I prefer the balanced tips - the sound signature is just best to my ears, though the UE tips do widen the sound stage a little and still sound pretty nice.
What do I think of them? They're okay. I do feel a bit disappointed, but only because I had built up a lot of anticipation, I think. They are certainly a big step up from the stock iPhone earbuds, but also certainly a major step down from the K701's I am used to. I guess this is not surprising, since their price ($80 used) falls about in the middle.
I hear quite strong, boomy bass, even with the foam mod. This is a little problematic for me, because to my ears these are a "basshead" headphone, which is not what I wanted. I was expecting something that was relatively neutral, just with a minor boost in the low end and highs. To my ears they have a pretty major boost in those areas, and while the right tips even this out a lot, they are still pretty boomy in the bass to me. To think that people are seeking out IEMs with a lot more bass than these, is kind of ridiculous. Overall there's a kind of muddiness to them that I'm not thrilled about; I think this is what many others mean when they say the detail is "smoothed over" with these IEMs. It's strange that some detail does stand out that even the K701s don't catch - like a bassoon player's keys clicking in one very well-recorded classical disc I have - but if I choose to focus on any one thing (like the actual sound from the bassoon), the detail is nothing special.
I've only spent about two hours listening so far, so my ears will probably adjust. I know they have a bit already. But so far I think they are merely good; I'm not about to sell them off in disgust or anything, I'll keep them a while, but at the same time it's a little baffling how much some people love these. I don't think they're THAT good.
Is this thread supposed to contain only gushing reviews?
Sorry if that's the case, though I DO appreciate them, just not to the extent of some. This seems like the dominant HJE900 thread at the moment which is why I put my thoughts here.
