This first part is more background info than anything, my actual thoughts on the headphones are about halfway down the post..
I'm always on the lookout for the best sound I can get out of my portable setup. I posted a thread over a year ago comparing a few portable models Here, and a few months later I ultimately found the headphone I was looking for in the Sennheiser Momentum and posted on those HERE and in several other threads.
Things changed rapidly in the market between when I started my search and when I found the Momentum, and since the Momentum were released things have continued to evolve. In the last year lots of new options have hit the market, but none have yet replaced the Momentum as my everyday go-to headphone.
A few very brief thoughts on models I've since tried and compared with the Momentum:
The B&O BeoPlay H6 had great looks and a nice flat sound signature, but were not very efficient and a bit more difficult to drive making them less ideal as a portable can. The V-Moda M100 had great looks and build quality and were exciting and fun to listen to, but ultimately not very balanced or accurate sounding and ultimately just not 'hifi' enough for me. The KEF M500 are a very accurate and balanced headphone and are probably the best sounding portable headphone I've found, but I just could not force myself back into an on-ear style of headphone. The PSB M4U 1 like it's bigger brother was just a bit forward sounding for me when compared to the sound signature I'm looking for but is still a great sounding can, and to be honest I'm a little put off by the plastic construction and bulky size. The Harman Kardon NC are a great noise cancelling headphone and I would argue they're the best option for people needing NC cans, they're almost as good as the Bose QC for NC and they sound better by a mile. I've tried lots of others as well, but those are the better options I've tried and my thoughts on them.
But after trying ALL those models the Momentum were still at the top of the heap for me and have continued serving as my daily driver.
Enter the Bowers & Wilkins P7
When I first heard about the B&W P7 I was only very mildly interested. I'd heard their P3 and P5 headphones and really wasn't impressed with either one. While I found the P5 tolerable and really liked the looks and comfort the P3 was really not very good in any respect. Ultimately both those headphones were too colored for my tastes and just didn't do it for me, so when the P7 was announced I expected more of the same in a larger form factor. As it would turn out, I could not have been more wrong.
I decided to pick these up though at the Apple store. Ultimately the look and feel was enough to entice me into trying this new model, so I decided to risk it and take the plunge knowing that I'd be able to send them back if I absolutely hated them.
Initial impressions were very good, so I decided to do a full comparison with the Momentum
Looks and build quality
I'll post a few pictures below which include the Momentum for comparison, but these are premium headphones in every sense of the word. The build quality feels superb and I like the fact that they fold up for travel. I love the metal and leather design. I prefer the looks of these slightly over the P5, and though I could see someone preferring one over the other they're very similar. These are a little bulkier than the Momentum so in that respect I prefer the Momentum. I would give the slight edge to the Momentum for looks and the slight edge to the P7 for build quality since they feel so solid and have no plastic.
This is where things can vary a bit from person to person. If you have small ears I would give a slight edge to the Momentum since they're so lightweight, they really do just disappear once you put them on. The P7 are heavier and you know when you're wearing them, but their pads are larger and they will fit most people. Also, even though my ears do fit well inside the Momentum, I find that the larger pads on the P7 allow my ears just a little more room to breathe and keep things a tad cooler so I prefer the pads on the P7.
So if you have larger ears I'd say the P7 easily wins, if you have smaller ears then the Momentum is lighter and puts less weight on your head but the P7 still has more comfortable pads - so its a matter of which you prefer.
The overall sound is very comparable between the two, with the verdict coming down to personal preference as I don't believe either is a clear winner across the board.
In terms of FR - the B&W have more sub-bass, tighter performance throughout the bass frequencies, mids that are slightly less present, and a high end with more sparkle but still never harsh. I have not seen a direct FR curve comparison between the two, but my guess is that the Momentum would have a more flat FR curve.
The low end has a bit more impact on the Momentum, thumps a bit more, but can also sound a tad loose at times. You give up some of that impact with the P7 but you get bass response that's more controlled, and you get more sub-bass as well. Don't get me wrong though, the P7 still has a great bass response and is among the best headphones out there in this respect.
The highs are more present on the P7. The Momentum has highs that are fairly laid back, while the P7 brings them forward a bit and adds some sparkle. They never become harsh though. They make the P7 sound a bit more lively and fun than the Momentum, which is a good thing for me but some may prefer the more laid back treble on the Momentum.
The midrange is really where the Momentum wins IMO. I think the highs on the P7 pull that headphone a bit and as a result the lower midrange (male vocals) tend to sound more present on the Momentum. It sounds slightly recessed on the P7, though not terribly so. In fact, it's only when I do a direct comparison with the Momentum where I can heard what the P7 is missing. Mark Knopfler on 'El Macho' sounds a tad thin on the P7 when compared to the Momentum, as an example.
Soundstage is where the P7 wins IMO. The P7 has a much wider and open soundstage, and in that respect sounds much more like an open back headphone. The Momentum sounds more intimate and may work better for some recordings, but for most of what I listen to the P7 is the better fit. Stuff like jazz, prog rock, classical and movie scores make up most of my music collection, and music like this with alot of instruments really favors the wider soundstage. On the P7, it sounds much wider and open, I can hear air around the instruments, and most importantly the instruments maintain their separation. On the Momentum those same recordings at times can sound congested and the instruments can tend to bleed together, in some cases because of the presence of the lower midrange the instruments can even blend in with the vocals. If you listen to alot of 'wall-of-sound' music like Metallica and alot of hard rock that's out there then the Momentum may be the better fit in terms of soundstage. If you listen to alot of more complex music or music with alot of instruments then I think the P7 is a better fit.
Overall it's hard to pick a winner based on sound quality. The P7 works better for more of the music I listen to, but there are selections where the Momentum still sounds better. Alot of country or straight ahead rock would get my nod on the Momentum, with the rest getting my vote on the P7.
Overall it's hard to pick a winner here, but at the very least the Momentum now has a true direct competitor in the P7. If I had to have only one right now I'm leaning more towards the P7, but I like them both enough that I'll be keeping the P7 and a pair of my Momentum (going to sell the second Momentum that I hardly ever use to help fund the purchase of the P7). This is a great headphone, and should be on your short list if you're looking.
I'm posting a link to pictures below, fair warning that I'm in a couple of them so brace yourself!