Like Bower's and Wilkins, KEF is a British company that was known for its loudspeakers before entering the consumer headphones arena. We were pretty impressed by its first on-ear headphone, the somewhat pricey M500, and also like the model reviewed here, the M400, which may not sound quite as good but costs a little less at $250 (£200 UK, AU$300).
With its metal chassis and sturdy headband, the build quality offers little to complain about, and the headphones fold up to fit in a nice neoprene carrying case. That case comes with a small V-shaped free-floating divider to keep the headphones finish from getting scratched up (the M400 comes in blue, orange, black and white), which is a bit awkward and easy to lose. The headphone cord is detachable and comes with an Apple-friendly inline remote/microphone.
Overall, we liked the sound (I also had CNET editor Ty Pendelbury and CNET contributor Steve Guttenberg have a listen). The bass will perhaps be a little too prominent for some listeners -- you can really hear how much of it there is on Nine Inch Nails tracks, for instance -- but the treble and midrange were pleasing and the headphone comes across on the warm side. It's fairly forgiving -- it works well with all types of music -- and in many ways has a similar sound profile to Bowers and Wilkins' P5 Series 2, but it isn't quite as comfortable or quite as swanky. But it's close.
In the end, the M400 one of those headphones that's quite likable, particularly for an on-ear, but doesn't necessarily blow you away for the money. It's also doesn't cost that much less than the step-up M500. In other words, this should be a $200 headphone to provide a little more delta between the two models.