Pros: natural sound, comfort, big soundstage
Cons: hard to drive
These headphones are very similar to the K501. They do similar natural, analytical sound, however they have different flawor.
The K401 have little bit more impact on the bass and have little more body, but they dont have the refined euphonic upper-mid-high K501 flawor.
The K401 is more all-around headphone than the K501, but still have the bass roll-off. For rock, hiphop the K401 is better choice, the K501 is better for classical, acoustical music.