Recs.
Updated
These closed back, over the ear headphones have an almost flat sound signature, making them a good choice if you prefer neutral/accurate audio. Passive noise isolation is great, which makes them good for studios, for noisy or for quiet environments.
SpecsUpdate
Pros
Pro Balanced sound, solid build and effective noise isolation at a great price
The M40x can be used for casual music listening, studio tracking or on the go. The fairly balanced sound signature is versatile and works well with virtually all music genres. Build is solid, comfort top notch, with removable cables and foldable yokes for easy transport. This feature set is one of the best in the price range.
Pro Fairly neutral sound signature
Sound signature is quite accurate, almost flat. Bass is much more controlled instead of boomy, while there is a slight elevation on the highs, resulting in extra energy and detail up top. These offer a nice middle ground between a fun sound and a more reference/analytical sound signature. This sound quality makes the headphones quite versatile as music enjoyment headphones or studio-use cans.