I am by no means an expert audiophile, but in my humble opinion these IEMs sound exceedingly well. I have read the rave reviews of other Noble Audio IEMs (mainly their old flagship Kaiser 10), and I was quite ready to plump for their current Sage product ($600), so this drop came at a really good time. According to online reviews from real experts, these $250 Massdrop X can match the audio quality of the Sages for less than half the price, which makes them a real bargain.
Some issues that other reviewers have mentioned (but are minor quibbles to me): the fit is a little particular, with the nozzle being quite wide (I have used the big foams provided with the IEMs, but am waiting for my 500 Comply Foams to improve the fit) and the big body of the IEMs is unable to entirely fit in the ear cavity. I have found that this creates a little bit of drag on the top of my ears, and the contact of the wire gets a little painful - but I am sure I will get used to it.
In terms of sound, I find they outclass both the Grado GR 10 and the Shure SE 215 that I was previously using: they are indeed very musical, and I do not experience the bass problems indicated by other users (probably because of fit issues?). The amount of details that can be heard is quite amazing, similar to what I get in my quiet home evening sessions with my Beyers t50p, but with a sound that is less analytical than the Beyers, and more ‘musical’.
I use them for my daily commute, with my iPhone 7 Plus and a Dragonfly Black (using VOX Cloud for my FLAC library), and honestly I am simply amazed at the sound I am getting with a rig that has a total cost of around 400$ (not including the cost of the iPhone, of course).
The isolation is quite good, almost on par with the one of the Shures (which are known to be very good at this), and I have no problem getting fully immersed in my music even in the middle of the relatively noisy Geneva tramway.
This may sound like a cliché, but currently I am in the process of listening again to my whole library, and rediscovering hitherto ignored details in my favorite albums.
To me, an excellent purchase, that I do not regret at all, quite the contrary: I think I got a real bargain here (so thank you Massdrop!!)