Pros: Fantastic sound. Amazing value. Premium build quality. Very comfortable for an on-ear headphone. Very portable.
Cons: Isolation is mediocre.
Until now, my pick for the best sounding portable headphone has been the Sennheiser Momentum. While slightly mellow overall with a noticeably forward bass and laid-back treble, until now the Momentum has provided a naturalness and transparency unrivaled by any competitor I've had the chance to try out. This includes Sony MDR-1R, Focal Spirit One, Logitech UE6000, B&W P5, Denon D600, Bose QC15, Sennheiser HD25, Amperior, Audio technica ATH-M50 and even the expensive Ultrasone Edition 8 (do I even need to include any of the Beats by Dre?). Until now, the Momentum has effortlessly wiped the floor with all else I've heard in it's class.
So! In case you forgot what product page you're on, the star of the show for this review, and the contender to throw the Momentum of the throne is the KEF M500. It's the first (!) headphone offering by KEF, a larger British manufacturer that has a long history in making great sounding speakers. They also ship an in-ear monitor called the M200, which I've not yet heard.
Let's talk hardware first!
The KEF M500 unboxes folded into a case that looks like an XL-version of a glasses case. This case is about half the size of that of the Momentum. Inside the box you'll find two cables (one with a remote, one without), two adapters and some instructions. And the headphone itself of course!
The first impression I got from holding the M500 was that it's solid. It's an all aluminum design which will feel right at home next to an Apple product of your choice and it has a nice, premium heft to it without being heavy to wear. The earpieces and headband are covered in a pleather material and the earpads are wonderfully soft. The cable goes into the back of the left earcup, instead of under it like most headphones. The pleather earpads do get a little warm and sweaty on a hot day.
In terms of comfort, the M500 is very comfortable for an on ear headphone. The earpads are so soft on the ears and the headphone puts a very gentle pressure on your head. I'm usually troubled by the headband pressing down on top, but that's not been an issue here. Take note though that because the headphone presses so gently, the fit is a little loose and I would not recommend it for headbanging. The headband also has a tendency to slide down when I'm lying in my bed listening, but a simple repositioning solves this.
Me personally, I've found the M500 to be a little picky about where you position it for maximum comfort. Sound wise, it's not position sensitive, but if I don't place them "just right", they will hurt a little on my ears after an hour or so. Luckily, I've now gotten used to how to position them and the fit seems to have bettered a little with use. So now, I can have them on for long periods without discomfort. Very nice!
Time to talk sound!
The M500 features an excellent bass response. It's impactful, has very good extension (those who worry because it's an on-ear design, don't!), it's very well defined and very well controlled. More so than the Momentum, which is a little less refined in the lows. Quantity wise, it's neutral-ish and offers a tad more than my LCD-2 which is completely flat. Compared to the Momentum, the KEF is a little heftier in the sub-bass, while the Momentum has more of a mid-bass bias which thickens the sound a tad. The bass of the KEF blends close to *perfectly* into the midrange and overall it's very flat for a headphone of this type. Impressive!
I'm actually really surprised at just how good the bass is on this headphone. I can nitpick and say that it's not quite as super-tight and natural as on my Audez'e LCD-2, but I see no point in doing so because the LCD-2 is a $1000 open, planar magnetic design and the M500 is a tiny little closed portable! The bass here has enough extension and impact to satisfy with electronic music, but make no mistake thinking these are bass-oriented like most of the competitors. This is natural, honest bass reproduction and bass-heads should definitely look into something else.
One area where the Momentum has been especially superior to the others mentioned above has been midrange performance. With a very nice smooth, open, unforced and rich sounding midrange the Momentum has given me many hours of musical enjoyment while on-the-go. Guess what, the M500 is even better!
The mids here are just wonderfully neutral, natural and open sounding! Not too thick yet not at all thin. Very clean yet not analytical. Very smooth, yet not overly so. Airy, yet full bodied. Neutral and transparent, these are the words that flow through my head when listening to the M500. On mids alone, the M500 is not that much less impressive than my LCD-2 in fact! Guitars, pianos, vocals (be it male or female) - they are all rendered very cleanly and realistically.
The midrange on the M500 is so good, I almost need to pinch myself every time I think of the price as this headphone doesn't embarrass itself among some well-regarded headphones multiple times the cost! This could be just the portable headphone audiophiles have been searching for. Truly among the best I've heard anywhere near this MSRP, regardless of headphone type!
The treble of the M500 is also very good. It's clean and detailed yet not harsh. I'm sensitive to brightness, and I feel the M500 avoids being bright sounding. But it's certainly not dark sounding either, it actually feels very neutral to my ears. Significantly more so than the Momentum. While the Momentum is preferable for poor recordings, the KEF does offer a clearer and more realistic presentation.
BUT, the one complaint I have with the M500 sonically is that I feel it has a slight edginess to the highs. Again, not bright in balance to my ears, but there is a slight sense of hardness present. For the most part, the M500 is just honest and revealing of flaws in the recording, but I've listened to some great quality audiophile recordings and compared side by side to my LCD-2 and I just find the M500 a bit untamed and forced compared. This slight "hot" nature to the treble also has an impact on certain female vocals, where things can sound a tad shouty.
To my ears, this is not a huge issue and it doesn't exactly bother me, even though I find myself very sensitive to treble issues. Sure, it's there and I definitely prefer the slightly smoother and more refined treble of the LCD-2, but again the LCD-2 is $1000 and the KEF is $300! I would feel bad about it if I let the overall impression of the M500 collapse just because it has one area where it's slightly less than phenomenal at it's price.
In summary, fans of laid-back treble should perhaps try this out first. Most other people will enjoy how clean, extended and neutral the treble is.
This headphone is surprisingly open and spacious sounding for an on-ear. It has a larger soundstage than the Momentum, especially in terms of depth. Just enough spaciousness and image specificity to not blur things together or making the singer sound right in your face. That's one thing that has bothered me with the Momentum, it has a fair amount of width but it really pushes things in your face and you feel you could use a little more breathing room. Well thanks KEF, problemo solved! My LCD-2, with it's angled drivers and open design does offer a greater sense of depth and image specificity, but the KEF puts on a surprisingly good show for what it is.
A word on isolation
This headphone truly doesn't isolate very well. It provides a mild isolation against outside noise (they leak very little though, so people around you will likely not hear much) and if you walk around a lot in traffic or you work in a loud environment, this below-average isolation coupled with the fact that the M500 doesn't overdo the bass much to compensate for it could be an issue.
So what's the TL;DR? In my humble opinion, the KEF M500 is up there on the top 3-list of best portable headphone I've listened to. Unless you want unnaturally emphasized lows or crave good isolation capabilities the M500 will deliver the goods in spades. I really hope more people get to experience this headphone because it's just that damn good and KEF deserves some serious credit for that accomplishment!