K518 is no doubt a legend - killer sound and decent isolation for a portable cans, together with the most badass clamping force ever.
 
K67 is one full class above in sound, and maybe two in comfort. Funny though, the K618/619 siblings exerts a MUCH stronger clamping force on the skull than the K67, despite the seemingly similar design.
 
Bass: As deep as you can hear, and as deep as you can feel as well. This is definitely THE cans to produce clubsound in terms of bass, but with much better everything else. The K618/619 can reach just as deep but while K67 emphasize sub-bass while keeping mid-bass less prominent, the K618/619 exhibits a tamer sub-bass but with more mid-bass emphasize.
 
Mids: Lush and clear. The K618/619 siblings sound a bit more open in mids, but the K67 sounds quite a bit more warm, natural, and easy to the ears.
 
Highs: Both the K67 and the K618/619 produce some twinkles and shimmers in the highs, but they do roll off gradually. You won't find the last bit of high pitch overtones in these, but in exchange you won't find them screechy or harsh.
 
Conclusion: Competition is stiff for the portable headphones market these days - Senn got two killer cans in the Amperior and the Momentum in their arsenal, each got its own appeals. AKG, instead of pulling out completely new concepts like the Momentum, chose to keep its winning formula from the K518 days and improve on it, while keeping the price VERY budget friendly, contrary to Senn's take. To be completely honest I'd take the K67's sound over the Momentum any day - I've never liked its overly warm tones and all-engulfing, but not deep enough bass. The amperior is superior in most aspects BUT for the capability to produce deep bass from a non-amped source. The K67 is a revelation - at its price point it's hard to beat. At twice (or more than twice) its price point, where you'd find the Momentum and the beats and the B&Ws, it still holds its own very admirably. Time will tell whether it makes it to the legendary status of the K518s.

Taking size, weight, shape, design, sound quality, and other pluses (EQduo, good looks, German engineering), this is up till now my ultimate choice (I STRESS: up till now) for portable amps.
 
Bass boost is a dream comes true even for a non-basshead like me.............it raises the level of the bass fairly linearly from the very bottom to midbass without sacrificing any bit of the bass details. It offers a real tight bass with plenty of oomph and slam, without any hint of flabbiness.
 
Treble boost, on the other hand, works not to extend the highs into the cloud........rather it serves mainly to raise sharpness and musicality.............emotional info in vocals (especially female vocals) get across more freely. It MUST be noted that the treble boost attracts a noticeable amount of hiss - it is not really discernable when the music is on but it is definitely there.
 
(Coming from RSAssss, 2Stepdance, ADL Cruise, GSlee Voyager, L3, and tried uHA120)
 
P.S. With all its goodness..........I'd say it's still a bit on the pricey side............hence -1 star for value. It's worth its price, yes, but definitely not the bargain of the year.

Well, I just had a rather special experience with the P5 which results in me selling my T50p and ESW10jpns while retaining the much battered P5. Here it goes -
 
I haven't thought of getting the P5 after Skylab's comprehensive write-up, and other concurring views from other members. I was rather happy with my ESW10s, and later the T50p. I mostly use ER4S and Monster MDs these days, but there are times when I'd like to reach for a headphone. I just grew curious about the P5 after someone, who is a known Bose hater, asked me to try them. He himself got a little surprise with them. I didn't asked him in details and thought I'd come up with my own conclusion. Luckily the P5s are relatively easily available for trial.
 
I brought with me a light setup, just my iPod Classic and SR-71A, with my iPhone and the iQube loaned by the shopowner being guest performers. My music is mainly classical orchestral pieces, with plenty of pop to supplement that. Rock is scarce but also available.
 
Maybe my review would be better understood if I begin by saying what I DON'T LIKE about my own portable cans, namely T50p and ESW10:
 
T50p: I absolutely HATES its bass. Overpowering, embracing YET lacks impact and bite. The lower half of the spectrum is a bit too lush and mushed, while the upper half is a dry-ish and rather coarse presentation. Does that sound awful? Well no I like its presentation of slower, lazier music like jazz and small-scaled classical pieces, mostly solo works, but in larger-scaled works they sound a bit bland and lacks transparency. It shows its weakness in tonal coherence when there was an upward swoosh in strings in an orchestral piece (forgot which one now) where the lower notes and the latter upper notes sound like they come from different instruments, which was not true. Soundstage is quite disappointing, and details are present but drowned out by the all-embracing fat bass. One thing the T50p really stands out is its isolation - until its release only the HD25 performs well in that department.
 
ESW10: I have no gripe about its sound - it's simply 1st class, period. A bit coloured in the mids (but less so than other ATH phones), its detail rendition is jaw-droppingly good and is nicely extended at both ends of the spectrum. The one and only one possible deal-breaker is its isolation - it's almost non-existent in noisy environment, like on the underground or on buses, not to say on a flight.
 
OK so I know the perfect portable can would be a ESW10+T50p mixture, which is a distant dream. I'm not saying the P5 is anywhere near that dream. But, as a portable can (ultimate one maybe, as I've been looking for the ultimate one for a long time), I think it does wonders in every department in a portable can. And the obvious caveat when judging a portable can is that sound quality must be balanced with other factors, such as build quality and durability, looks (for some), weight, size, isolation, practicality in general, etc.
 
When I first put on the P5, I immediately searched in my memory for something similar in the sound signature, and if my memory serves me good the can appeared first in my mind was the PX200-II. Both sounds pretty balanced, but nothing excels. Both suffered from a lack of extension at both ends of the spectrum. That said, I was expecting a very, very dark sound from the P5 after all the others have said here, but the sound I got from the P5 out of my iPod directly is far from being dark. There is a peak somewhere in the mid-high region, creating a pseudo-high-extension feel - actually this feeling is quite similar to the Monster tuning in the MD and the Copper Pro, the difference being the P5's peak is located a bit lower in the spectrum, while the Monster peak is located a bit higher up. This renders the sound somewhat coloured, but not overwhelmingly so.
 
Besides this peak, the P5's sound is pretty balanced overall. I don't find it muffled - in fact I find its detail rendition at least on par with the T50p, which is very surprising considering Beyer's claim of the driver technology and T1's track record. When listening to classical symphonies the P5 reminds me of my bedroom Onkyo system - a rich, warm sound, with bite and grit, but not too weighty. And P5 is very good in soundstaging and presenting layers of instruments in the correct orientation with transparency and clarity. This even the ESW10 fails to satisfy me, and the T50p is a complete failure in this area.
 
The bass is good, not overwhelmingly deep, but comes with details and impact. Definitely not overpowering, and not lacking.
 
Needless to say, P5 excels in build quality and comfort, and I do not intend to repeat what others have said in these areas. What proved it to me as the able partner to my iems is its isolation - it is not iem-good, but it is miles ahead of PX200 and ESW10. It IS usable on trains and flights. And its size, together with the more reasonable approach in its method of stowing away, adds up to a winner, not in the sound department perhaps, but in the overall package.
 
Is the MSRP justified? As I've mentioned its sound is PX200-II-ish and though it betters the PX200, it isn't a night and day difference. I think it is difficult, if not impossible, to consider this question solely on sound quality. For the listed MSRP I think the isolation alone worths 20%, the design/looks/size/weight/comfort worths another 20%, the brand (yes I think that's the part which haters hate most) worths maybe 10-20% (though trust me the B&W brand is not THAT marketing oriented and not THAT well-known here in Asia, at least their campaigns are way less aggressive than Bose, Sony and Shure, and their showrooms are located in obscure places). The rest goes to the sound. Fair enough, eh? Yes it is way more expensive than the PX200 but doesn't offer too much improvement in sound, but to sum it up in one word: PRACTICALITY, makes it all worthwhile IMHO. It is small (relatively), extremely simple to handle, extremely intuitive in folding and storing (by contrast the T50p case, thought handsome, was HUGE and occupies too much space in my briefcase, while it's always a hassle to tug the cable of the ESW10 into the seperate cable pouch to protect the wood from scratch), great isolation making it usable in many difficult situations, the single-sided cable is very handy in everyday life situations, and the Apple-friendly remote/mic cable, if you can stand a very slight deterioration in sound, is again very handy if you use a iPhone. Even when i'm listening to music on my iPod (not my iPhone), i can just yank out the cable and plug it into the iPhone in no time if a call comes in. And if I want to listen to the broadcasting on the underground, I can turn down the volumne or stop the track in no time. Practicality may not be for all audiophiles or head-fiers, but for myself, I know there are times when I'm chilling out with my ER4S and some Mahler, I become desperate when a call comes in and I wanna fetch my hands-free buried somewhere deep in my bag.
 
And it sounds good, not jawdroppingly good, not $299 good, but plain good. You know what you're paying for, and that's fine.

After around 50 hours burn-in: - Muddy, fat yet shallow bass, recessed mids, non-existent highs. if the mids aren't this recessed it is actually quite smooth, and there/s no sibliance problem cos there's no highs. one should not underestimate the power of burn-in but if burn-in can turn this into something half-decent i'd be really pleasantly surprised. i'll do another review after maybe a few hundreds of hours if there's any such surprise.
 
Terrible build quality: there is glue mark ON BOTH SIDES and the right panel (the blue part) cannot sit in place, thus flapping outwards a bit. I can put a blind eye on the glue mark but the panel is really disturbing, it's like i'd lose it any second. The ear gels included are simply horrible: hard and refusing to fit in the ear canal - in fact I haven't seen any sleeves this bad in these few years when every iem manufacturer knows how to make (or from which source to get) quality sleeves.
 
Terrible package, with a printer-quality cardboard box, a so-so velvet-like pouch, and 2 pairs of hard, silicon-like sleeves of similar size but different color (what's the pt?). The earphones themselves look OK actually, but for the loose panel.
 
I have absolutely no complaints on Rudi's amps but this........no Rudi should go back to the design table and work on it from scrap again. I'm saying this while trying my best to put its striking resemblance to Sony's EX700 out of context.