[Selbi]

I absolutely love the sound of the Sennheiser Momentum In-Ear, even though they're pretty cheap. While I do love my Philips Fidelio X2, I see myself using the in-ears more often than those old cans. Something about the sound is just more pleasant. Maybe it's the sibillance of the X2, which has always been a problem of fatigue.

So I was looking for a pair of over-ears that would most closely resemble the sound of those in-ears., in terms of sound balance. Budget is barely an issue, although I got a feeling I won't be happy with the HD650's for what I'm specifically looking for. Anyone else got an idea?

 

[GREQ]

I honestly don't think you'll find a headphone that comes close to the Momentum IEi.
I just A/B'd mine with the HD650 and bass response was quite similar in volume.
HD650 treble was smoother and less pronounced; mostly because the Momentum IEi has a low-treble peak around 6kHz that is very weird and unnatural.

The Fidelio X2 should actually be closer to the IEi sound profile than HD650, since other graphs on the internet indicate treble peaks in the same region.
Overall, you might find the HD650 too 'boring' compared to the IEi.

If you're open to going the closed-back route, the Beyerdynamic DT770 Pro 80 is closer to the Momentum IEi sound than the HD650.
Some people find it's treble a little fatigueing, but is gets smoother the more you wear in the pads - this has actually been proven with frequency response graphs.

Or, DT1770 Pro is another option if you would like a more refined bass with a bit more of a thunderous sub-bass kick.
The extra bass naturally makes the treble appear less piercing, since you don't need to turn the volume as high to get it thumping.