Well, the main reason for this review is that these have been in and out of my grasp at least once (as in I've had them, then debated and lost against myself at keeping them and gave them back) At very least, I thought I'd share my thoughts on them against what are the legendary QC15s to help everyone out a little bit. So.....let's go!
Design (and Portability)
A very useful and notable change with the QC25s (other than the change to how they look) is that they fold inside to help them fit into their smaller case compared to the QC15s, with a case that will fit them to the extent that they can fold; flat, not inside. Also, the case has a purpose made space for the airline adapter and spare battery you'd most probably (and I'd reccomend you to) take with you.
From left to right: QC15 Case, QC25 Case
The QC25s' case being smaller does make it slightly easier to put in a bag and take around with you, especially if space is a premium on any long trips, although if you're travel is the hour or two of commuting to work on the train then you may not notice a huge real-life difference between the two. The main reason the smaller case is both a pro and a con is that inside the new case, after the headphone (folded) is in there and you've got the cable to sit somewhere nice, there's only really space for one spare battery and the airline adapter, whereas in the QC15 case, you have a little pocket that can hold quite a few (I count 5 or so) AAA batteries, and the void where the headphones are still nets you some space for a cable, and maybe some jack adapters and your airline adapter too.
Other than the case, the QC25s opt for a fabric cover on the headband as opposed to the leather that the QC15s had, and a black-and-blue striped liner inside the earpads, with a huge L or R on them. The second is something I don't like when looking at them, but perfectly honest is something that's a bit of a non-problem, because nobody (including you) will see them once you're wearing them. Also, the QC25 come in white and cream, or black and slate. At least there's a choice rather than having to wait for limited editions to the "anything, as long as it's silver" on the QC15. They also use a simpler cable that doesn't have, or need, overmolds to fit in to the shape of the headphone. The cable's thicker as well, although now you have to have a remote and mic cable with them. I can see an issue with earlier Android devices that may decide not to output audio to them. Best bet is to try a set with your phone before buying just in case.
The cable is still removable but these aren't wireless for audio. You can use them for my sleeping analogy (especially sleeping while travelling if you're brave) in noise cancelling mode without the cable, but if you want some tasty beats, you'll want that cable in
Comfort
Comfort between the two is pretty similar. Never a bad thing with what I could easily class as some of the most comfortable headphones I've used, and tried. 15s are good when I need to make sure I'm getting good rest so I still look "acceptable" while there's a party next door and I could easily imagine doing the same with 25s. The QC25s ear pads feel slightly different, and clamping force feels ever so slightly tougher on the 25s, but that could easily be attributed to new vs "weathered" sets of headphones. I still wouldn't call these "uncomfortable" in any way, even after a long listening session at home or out and about.
Features
25s work when they're off! If I'm honest, I personally am not excited a huge amount about this. Yeah, they work when they're off but think of it this way. QC25s and QC15s last for arouns 25-35 hours on a single AAA. If you have a spare battery/spare batteries with you, you're minimum looking at around 55-70 hours of play time with them. That's difficult to burn through unless you forget to turn them off and investing in some good rechargables (eneloops) will mean you're hardly every gonna use them when they're off. This is the non-caveat I have with QC15s and why I prefer they're larger case. I can take three or four of my spare eneloops as well as the one in the headphone with me. Total time - 150-170 hours over 5 batteries. I struggle to be completely out of battery with them, so I never "run out forever." With 25s, you can maybe get three (if you don't mind leaving the battery loose and knocking next to the heaphones) batteries with you (one in the headphone, one in the insert, one somewhere in the case) so you can still get your decent 65-100 hours taking them with you. On a day out, unless you've used a lot of the battery life, you'll only need one.
Noise Cancellation
Here in London, we have one of the noisiest things in the world. Yep, the Underground. QC15s are already quite good at cutting through most of the background noise and putting your music front and center. On the noisier parts of the tube, the spikes from outside will still seep in, but if you're volumes at a semi-decent level (halfway on my iPhone 5) it really won't bother you. This is where the 25s start to show off what they can do. They're quieter - much quieter. The tube is challenging for lots of things because the sound is never constant, but if the 15s slightly push those spikes back, the 25s do that slightly further, and smooth over them a little bit more. You're music definitely feels more present when there's lots of disruptive noise.
I haven't had the financial opportunity to try them on a plane, although I'd imagine that with the constant sound you get on both, you'd mainly see the 25s will definitely quieten down the engine a lot more then 15s will. It's not chalk and cheese, but I'd much rather have a plate of 25 if this was the only metric.
Sound
This is the deciding one. How do these headphones stack up compared to the 15s. Remember people, this is very subjective, so let me explain my music taste. I'm on the side of R&B, Soul, Hip-Hop and the like, as well as a bit of Jazz, Classical, and probably some Electronic music thrown in there. I'm definitely partial to the warmer, darker side of sound, with a bit of a bite in the midrange and treble, and that's what made me love the 15s. Neither of these are basshead, or analytical headphones as a quick one; they're pleasant and most people will appreciate both of them.
The 25s still have that slight sharpness at the treble end, with a slight push forward on the bass response. On the bass response, they're a bit on the loose side compared to other things I've listened to. Voices can sometimes get pushed back into the middle of the instrumentation if the track gives them the opportunity. It gives them a "nice" warm sound with a little bit of a snap to it.
With one of my favourite soul tracks, "Drive All Night" by Joss Stone, the kick drum definitely has that smoother punch I'd expect, while Stone's sultry voice still seems to float around slightly more front and center. There is nice refinement to her voice that does give it that slightly lifelike and live feel to make them quite enjoyable. Those keyboard sounds that you get in the background also float around, almost setting the scene of a purple jazz lounge in your head (and with my Afro, there's a lot of space in that lounge.....you guys want to visit?)
If you want bass, "A Dream Within A Dream" by The Glitch Mob can get them moving quite a lot of air in that little bubble they make. Soundstaging, the sense of space from the sound, is where a headphone can make this song sound awesome. At a midpoint in the song, a synthesized "saxophone" (if you can call it that) plays in the background. It doesn't seem to have an etheral feel to it as it has on many headphones I'll listen to with this song. They're not completely direct as in "shooting sound directly into your head" but the soungstage doesn't extend as far back as you imagine it could. Some of Bose's on-ear headphones will soundstage to a similar, if not only slightly lesser extent to these which is slightly scary. The bass response is controlled compared to a lot of other headphones in this bracket. Forward given the type of song, but with a fast enough decay not to get in the way of anything else which, with the amount of drums you have in this song, is great. The "glitchy guitar" (that's what I'm calling it!) has a slightly softened timbre to it. I like this, some people may want the slightly harsher sound thrown in. If you're the second type, a quick EQ on the higher frequencies should give that a quick fix.
To get more critical with them, with Nils Frahm's "Says," the texture of the synthesizer he's using just about comes through - remember these aren't analytical, there's definitely some detail that gets smoothed over - compared to what I'd get out of my Denon AH-D5000's at home - the Denon's are about one and a half times to twice as expensive though. This is quite a good thing in a way with this song because at moderately loud to loud volumes, it doesn't become completely unchained and assault you with what can be harsh tones on sharper headphones. The soundstaging from the headphones, although wider than expected, isn't as expansive as I thought it could be again. The notes on the synthesizer, especially as the song builds to the end, all seem to be coming from the same-ish place on the left and the right with the bass from the lower notes becoming, strangely, subtly pushed further back within the complex arrangement. The headphones are still enjoyable with this song unless you decide you want to listen critically, in which you turn into what I do; someone who looks for anything you didn't like (I had to re-listen a lot before these things started to get me)
Overall, for a Noise Canceller, these sound good enough to use as your dual use home headphone for many genres of music, as well as your travel, commute, and general "shut-up world" headphone. And they can become a very enjoyable headphone to have a listen to, with enough detail and push to get you through some semi-speedy rock music, as well as refinement that works well for your jazz or soul. You have enough punch for your electronic music too. The only thing you may not get is a huge soundstage. It's acceptable and will be "good enough" for most of your musical needs however.
How about when they're off?
When they're off, you'll lose a lot of the top end, and a lot of the bottom end. They'll sound slightly muffled. Bass won't be muddy, it'll just be reduced in it's overall quantity. This doesn't make them analytical, they're just not as clear and not as heavy. A lot of the soul that makes them legendary kind of goes away, so this isn't a mode you'll "want" to listen to, but one you'll listen to inbetween changes of batteries, or recharges of your eneloops or other rechargable AAAs
Sound - Compared to their Dad
25s replace 15s. 15s are definitely in two of my lists. They're my favourite Noise Cancelling headphone, and they're among my favourite headband style headphone with the only things better being those that are both more expensive and don't actively cancel noise. So, how are they when faced off against each other?
Remember, this is my subjective afro-based opinion.
I prefer the 15s
Honestly, I listened to the 25s and felt that there was "something missing" rather than a difference. The 15s, although less forward with their bass, seemed to have a bit more refinement and a more laid back feel which I love. The detail on them was slightly better; the mids on the 15s seem a bit less forward than the 25s which doesn't mean you lose mids - it means you gain a bit more detail and crispness. Most important to me is that these both come in with a noticeably different soundstage. They're wide enough that you do feel that bit more immersed. To me, you gain utility but go sideways or, in my opinion, slightly downards in sound.
Summary - The "Short Review"
You're going to love the 25s, just as much as you'd love 15s if I'm completely honest with you. Best bet, if you have the opportunity go out and try them with your own stuff. My opinions are based on the fact that I'm particular with the sound of them, and that I still expect my NC headphones to blow my socks off. After having the 15s do that, I expect the same from the 25s and you probably won't get that. You're talking two headphones that are very similar. Once you pick one that becomes you're blueprint at this level of NC, and differences can easily become negative rather than positive.
I'd definitely say the foldability of the 25s is good, even if it means you can't fit as much into there now. The thicker cable also means you're gonna be spending less on maintenance on the headphones. The NC is also a big boost compared to what they've done before; enjoy the even quieter silence.
Sound wise, you've got a slightly more direct, less "dark" and more "warm" headphone compared to previous QC around ears. Soundstaging exists, it's just not as prominent as you may have previously experiences. An ever so slightly more "common denominator" rather than "niche" type of sound overall I would say. Minor differences to most of the community. Treble is still in the same amount in a way, if not slightly reduced, and you're mids and bass go up a bit more in quantity. Not basshead, but you end up with a less detailed and rounder sound as a result. When they're off, everything becomes masked under a cloud of not being powered (and therefore actively equalised)
Content with your 15s? You
might be better off keeping them and spend that money on a new set of ear pads and a cable. (unless you try them and prefer the 25s) If you don't own either one, I'd say it'd be worth getting the 25s. The little additions for utility, ability to work when you've forgotten to charge up, and possibly more "universal" cable make them better than having to try to find a good condition 15.