Pros: Warm, balanced, high fidelity audio. Gorgeous design with quality materials. Very comfortable (for me). Very portable.
Cons: Very slightly congested sounding. Remote volume up/down only usable on i-devices.
On sound alone, the Sennheiser Momentums are worth every penny and more. But aside from being wonderful sounding, the elegant design is beautiful and luxuriant with stainless steel band, real leather and quality plastic cups in a nice, dark bronze finish. The standard cable is also very high quality, with a substantial metal remote attached to it.
The case isn't as large and bulky as I expected from reviews, and it's sturdy enough to keep the headphones safe under most circumstances.
They are very comfortable. The light weight and the materials inside the earcups ensure the fit is great, with minimal headband pressure and without heating up your ears.
Sound wise, Sennheiser really nailed this one.
They have a balanced, natural sound free of grain, audible peaks and imperfections usually associated with small, sealed headphones.
They are a bit on the bass heavy side, but without ever sounding muffled or overbearing in the low end. Extension is superb and while it's not the best bass response I've heard, it's satisfying for acoustic as well as electronic music, giving a natural body to the music and being able to hit the low notes with some brute force when required.
The midrange is clear, full, rich and intimate without sounding forced. Vocals are smooth and thick, without sounding overly chesty. Acoustic instruments come through with great clarity and resolution for a closed can. Just a great midrange sound, perhaps the best I've ever heard from a sealed headphone of this size and intended application.
The treble is a bit laid-back, and lacks the sense of air and speed provided by electrostats or the flagship HD 800. Whereas the HD 800 exhibits a peak in the treble and can sound bright, and are ruthless with the source material, the Momentum sounds more polite and forgiving - which I greatly prefer for portable use, or general listening to sub-reference recordings. The treble is neither bright nor veiled to my ears, but neither was the treble of the HD 600..
The soundstage is fairly small, and compared to open headphones and the best closed ones, the Momentum sounds slightly congested. But they are small cans, and for the size the soundstage presentation is more than acceptable.
I'm surprised at how little failures the Momentum exhibits. While they are not really reference in any way they give a fabulous all-around performance. Many headphones a lot more expensive have greater flaws. For example, the HD 800 lacks some bass warmth and impact and has a slight peak in the treble. The Audez'e LCD-2 lacks treble air and soundstage definition. The Momentum, while not on par with the above in terms of overall performance, lack such significant issues. This great sound in a highly portable, practical and beautiful package makes them worthy of a perfect score in my book.
Great job, Sennheiser!
A side note:
I've listened to the Ultrasone Edition 8 (which many consider the best portable available), and frankly, the Momentum sounds better too me. I don't like the hard, aggressive sound of the Ultrasones and find the Momentum more natural. Based on memory, I also find the Momentum more comfortable than the ED8, which has a tighter clamping force. Lastly, the design of the Momentum appeals to me more. I find it more tasteful and elegant.
Of course these are my preferences only, but something worth mentioning.