For any Xelento owners that might be stuck at home (for whatever reason) with some time to kill, I've got something for you to try.
I recently learned something interesting about the Xelento's vents.
@earfonia pointed this out to me, so I should give him credit for this little discovery. I'd not even bothered testing this before because vents and ports are usually there for a good reason, and it's usually wise to not mess with them. Case in point - this is the effect if you take a piece of electrical or packing tape and completely cover the entire back faceplate and all around its seam:
You now get an almost perfectly linear bass response from 20 -> 500 Hz. That's interesting, but if you like that kind of sound you're probably in the wrong place and should probably be browsing this thread instead:
https://www.head-fi.org/threads/if-you-still-love-etymotic-er4-this-is-the-thread-for-you.538615/. The thumping sub-bass is one of the coolest features of the Xelento and most of us probably don't want to lose that. But here's the interesting part. There's a very consistent plateau region of the FR that we can reach if we tape over both port holes (to the left and right of the word "Beyerdynamic" on the face plate, but leave a tiny gap exposing approximately 1 mm of the seam between the faceplate and the IEM body above the lettering, like so:
Within quite a margin of play on the packing tape, I'm able to get a very consistent response, which now looks like this:
This is magical
The main weakness with the Xelento for me has always been its slightly heavy mid-bass. This port mod fixes that. It's now objectively a better headphone, measuring closer to the Harman target, meaning ~2/3rds of you ought to prefer this sound signature over that of the unmodified Xelento. If anybody's feeling brave, it's just a one-minute modification and it's easily reversible if you decide you prefer the original level of mid-bass. I'd be curious to hear people's impressions of this mod.
As I said, statistically, more people ought to like this change than not, so it's a bit of a head-scratcher that Beyerdynamic didn't give us a tuning like this to begin with.