Sennheiser HD25-II is one of hot model in on-ear headphone. I buy it because of high rating from different users.
However, i feel very disappointed when I use it.
 
First of all, the headband structure is too tight. It makes my head painful and can't wear for more than 5 minutes, 1 song?!
 
Bass, quite strong
 
Mids - not natural
 
Highs - clear, but the highs are too aggressive. It hurts my ear when listening for long time.
 
I can't use it for more than 5 mins because of the headband pinching force. No matter how the sound is, the headphone is useless for a user if they can't use it daily.
 
Sorry about that. Sennheiser.

Too much bass, strident treble. I guess it could be worse. Midrange is not bad. It might sound OK straight out of my out of my cheap Android phone which lacks power and sounds kind of muddy.
 
The treble hurts me. I wouldn't keep them though, even if someone gave them to me for free. I wouldn't give them to my kids either because I don't want to destroy their high frequency hearing.
 
Really ugly too.

I have Grado SR60, SR225i, HD650 and HD25 II's, with an iBasso headphone amplifier, fed by an ipod dock cable. I principally bought the HD25's as a monitor headphone for video use but thought I would burn them in for 100 hours and see what they do with music. The reproduction is not what one would call subtle, the extreme frequencies are pronounced and there is little impression of ambience or imaging. It is like it is trying too hard to please.  I can imagine, for that reason, it suits loud rock music, but it tramples delicate good recordings.  The cable picks up some microphony.

These headphones are clearly designed for DJs in dance clubs and I can't recommend them for general or casual use.  They get 3 stars for doing what they're designed to do well enough but could be much better.
 
They are very isolating as a result of a strong clamping force that crushes my ears to the point of pain after 10-15 minutes.
 
The sound is very forward and punchy.  Good for techno/dance but lacks refinement, subtlety and space.
 
They are overly bright and there's a treble peak that causes sibilance and is very unattractive.  Though I didn't use a high quality amp this peak seems to be recognised in frequency response charts and other reviews here that state they can be too bright.  I'm not sure if this is a deliberate decision so that DJs will tend towards making club music darker but it could well be.
 
If using an iPhone or low-power analogue out you'll need to use a treble reducer or custom EQ to even listen to these without serious fatigue and pain, though bass response without amplification is still decent.
 
Overall these have a very specific application and purpose and unless you're a DJ that needs high isolation and a "club" sound you should steer clear.

I've owned 2 pairs of these headphones over the past 10 years so feel I've gotten to know them pretty well. Apart from the cheaper SP version these are the only decent headphones above a budget level that I've really tried.
 
Looks
 
I don't think this headphone is for the fashion conscious but they do have a cool look of its own in an industry standard geeky DJ kind of a way.
 
Durability
 
This is a mixed bag for me although maybe it is harsh to complain about a pair of headphones that last so long. Overall they are pretty indestructible and I regularly take them to the gym and put them in there and take them everywhere without a second thought. You don't need to treat them nicely for fear they will break. I've never had any problems with the headbands or drivers. However there is a fundamental design flaw with this product that has occurred with both of my units and is well documented by other users. After a while (often many years) one of the cups will develop issues with intermittent sound requiring you to wiggle the connector cable to try to make it work again on a regular basis. The problem is that the spring inside the ear cup which the headphone connector is placed inside become faulty. If it wasn't for this i'm pretty sure they would last forever which I doubt sennheiser would want - they want you to buy another set. I'm sure it could be easily remedied if they slightly altered the design. 
 
 
Replacement Parts
 
It's a positive that so much of the headphone is user replaceable. However, although readily available, they are also ridiculously expensive such as the £40 price tag for a new cable.
 
Comfort
 
There are definitely not the most comfortable headphones out of the box. They exert a significant amount of pressure on your ears although the do loosen up after a time and become comfortable. That coupled with their lightweight design does mean when they have broken in I do find the comfortable to wear for sustained periods. 
 
Impedance
 
These do go very loud when using a dj mixer, a sound card or my macbook pro laptop. When using portable devices such as android phones I find that they are only just loud enough for me so I need to push the gain of my music app to its maximum before distortion to get the level I desire. They are loud enough to use but I would prefer quite a bit more headroom so I would only half recommend them for portable devices. Something designed to be so portable and durable really should have been updated to be more compatible with phones and portable music players.
 
Sound
 
I do like the sound and they offer excellent isolation. They sound exciting but a bit harsh in the highs and boomy in the bass. They have almost a dark sound and sound very full and not at all tinny. I wouldn't call the neutral. They are great for djing especially since the kick is emphasised in the low mids but for producing I'm not convinced. When mixing with them I find I tend to end up with mixes that are dark in tone, overblown in the bass and quite dull and lifeless in the highs. I really find it hard to make informed decisions about what is happening in the low end and mix the bass and kick particularly. Maybe high end harshness is part of the problem that leaves me with dull mixes. 
 
Conclusion
 
I need to replace these now and I am tempted to get another pair because they are very versatile in that you can use them for djing, sport, sound design, and to a limited extent mixing. They are also durable, lightweight and comfortable after a while of breaking them in. However I can't help want more from them - a pair that are more comfortable from the outset, that I can reliably mix on and that don't develop a fault after so many years with the ear cup connectors. Maybe I should buy these for recreational/dj use and then another pair for mixing as I could end up disappointed trying to improve on them. 

I really like Sennheiser HD25, the sound is very detailed and balanced. I love the sound isolation which is I think the best from within all other closed headphones. They are very light and small which is great. The design would be superb if the cups could rotate 90 degrees but they cannot. I especially like that every single part is replaceable which I think is the reason why so many people buy these. 
You dont want to spend too much and be forced to throw them away or pay for expensive repair after couple of years. 
 
I would wear them in public but I dont like that the headband is sticking a bit outside from the cups which makes them wider than they are. Small design changes would bring these headphones back to the #1 position. 
 
So many times these headphones simply crush anything else around them in terms of sound quality. They are precise, detailed and well balanced. The bass is nice and punchy but I would prefer if it could go slightly deeper. But dont worry its still deeper than most of the headphones within this price range. They are very loud which is another reason why other djs and professionals buying these. If you like them then do not hesitate as I dont think you find better on ear headphones. Yes, maybe Beyerdynamics DT1350 but for some reason I dont think they are so cool than these are. 
 
If the soundstage would be slightly bigger that would be fantastic as comparing to the other headphones they might sound a bit in your face. These are great for work such mixing, editing, mastering etc. Specially if you use them in noisy environment. 
 
When I search for new headphones I often use the term I look for something like HD25 but around the ear  Definitely wear them / check them in terms of the comfort before you purchase. 

Sennheiser HD 25-1 II Review


Introduction
I bought these headphones about a year ago to enjoy my music with decent isolation, comfort and sound quality on my portable rig. I was very satisfied with them, and have been up until I got my IE80's. The IE80's are simply better in terms of sound quality and portability. However, these cans are still absolutely awesome in other aspects.

Before I'm going to do away with my trustworthy HD 25-1 II's, I thought it'd be worth the effort to write a review about them. I tried to keep this review short and clear, without leaving anything out. I'd like to think I succeeded, but like always I kindly ask for your input.


Listening setup
I wrote the sound quality impressions collectively from several setups:
Galaxy Note -> HD 25-1 II
Galaxy Note -> AMB Mini3 -> HD 25-1 II
Audio-GD NFB-12 -> HD 25-1 II
Audio-GD NFB-12 -> AMB Mini3 -> HD 25-1 II

If there is one thing I noticed from these comparisons, it'd be that this can is the furthest from picky; whatever you drive it from it'll be very near it's full potential. It has crazy high sensitivity as well, and I found myself listening to it one an airplane directly out of my phone or iPod with no need for extra volume.

I compared it to my IE80 primarily, but also did detailed comparisons with my HD650 and SR-202. I won't list the comparisons themselves, but rather what I found out through comparing them. If you're looking for the comparisons shoot me a PM.


Pictures




Build quality
The build quality of this can is legendary -- and rightfully so. There is simply no way you're going to break them, even if you tried. And if you're particularly vandalistic, you can still replace every single part of this headphone. They feel light in your hands, and are relatively small too. This makes them perfect for chucking them in your backpack.
These are labelled as professional DJ headphones, and are in fact used a lot by (famous) DJ's all over the world. And from a durability point of view I can definitely see why.


Cable & accessories
The cable is extremely good in terms of durability. The plug is very good in this regard as well, since it's right angled and very stiff. The included screw-on 6.3mm adapter is also very nifty.
However, there are a couple things which I don't like about this cable. For instance, while the cable never ties itself in knots, it does not stay straight either. It curls up awkwardly, which is not very pretty nor practical. Secondly the plug is too well-built; it is so stiff that it has destroyed multiple jacks of mobile devices, since it put too much stress on them. Eventually I started using this can with a 3.5mm extension cord just to relieve stress from my phone's jack, but this was a far from practical solution.

I personally bought the basic version, which only came with a 6.3mm adapter, and nothing else in terms of accessories. The complete version includes a pair of velour pads and a bag as well, but I doubt these are worth the extra price.

Not really an accessory, but I should also mention the swiveling ear cup. This is a feature meant of DJ's where they can swivel back one of the ear cups to hear the music from the headphones and speakers at the same time. I personally don't think this has much added value, since tilting the headphone works just as well. It also takes a bit of effort to get the fit perfect once you're swiveling it back to its original position.


Comfort
Comfort is surprisingly good. While the clamping force is still relatively high, I can comfortable wear them for several hours. They only start getting uncomfortable after the 3 hour mark, and more quickly if it's hot. They come with a split head band, and adjustable cups. There is a relatively comfortable cushion on the head band and the pads are quite comfortable too. Make no mistake -- these are far from as comfortable as a pair of full size cans like my HD650 or SR-202, but they are definitely not bad considering they're portable cans.

One annoying thing that should be noted is that it usually takes several seconds before I've found a comfortable fit. And putting the headphones on with only one hand is difficult, especially without practice. Though that's true for most headphones.


Sound quality
Overall I find this to be the most lacking area of the HD 25-1 II. For the price I'd like the sound quality to be a bit better, although all round they are decent enough for regular use by any audiophile.

Frequency response These cans have a recessed sub-bass, probably thanks to the small driver size. They are fairly flat in the mid-bass and mids, but have a recessed upper-mids/lower-treble with a massive spike at 10kHz. Overall I would describe these headphones as having a bit loose bass with a harsh treble, but with an overall feeling of neutrality.

Bass The bass packs quite a punch in terms of volume. More so than my HD650, but less than my IE80. The bass does sound a bit loose and uncontrolled, perhaps caused by the mediocre soundstage. In my experience these are well suited for electronic music, but aren't the best for things like conveying the energy of rumbling bass guitars with heavy distortion.
They do feel fairly neutral in terms of frequency response in the bass region. And for most smooth bass guitars used in rock they perform adequately.

Mids I find the mids to be decent with male and female vocals, and in general acceptable with piano, reed instruments and horns. Not too much to say about the mids since they sound fairly normal and neutral.

Treble One of the worst factors of the HD 25-1 II. Female vocals can sound a bit harsh when high pitched, cymbals sound tinny and just weird in general, they have noticeable sibilance, and are sonically fatiguing due to their harshness. The huge 10kHz thump in the FR can probably account for all of this, and I have found that EQ'ing helps to tame this beast. It's performing sub par in this area in my experience, although I may be making it sound a lot worse than it is. It should also be noted that these do not sound bright, but rather just harsh.

Soundstage The second bad factor. The soundstage is fairly small. Instruments sound like large sound sources, and are poorly separated. In the more chaotic passages all the sound is clumped up into one big ball. There is hardly any sense of distance either.
This is probably the same for most portable cans, and perhaps I'm spoiled by comparing to my IE80 and SR-202, but I do feel that this is the can's weakest area along with the harsh treble.


Conclusion
Overall these cans are pretty neutral. They do lack in energy, soundstage and treble. For the money they are pretty decent. But I wouldn't get them just for the sound quality; I'm sure there are better alternatives at this price. The fact that it's indestructible, portable and isolating are its main selling points.
They are pretty good value, but not if you go by sound alone.

Very Grado-y sound signature, but closed. An amazing portable headphone. Very easy to "personalize" with other colored pads and also very easy to disassemble. HD650 cable fits when flipped over. Amazing phone for the price and portability.
 
Unfortunately, comfort is an issue for some (myself included). I've had to return them because they clamp my head like a vice.

Good sound quality and good comfort. It is fairly lightweight but durable. The stock cable has some horrable mechanical transported contact noise (Some call it microphonics but microphonics is where mechanical vibration is transformed into electrical signal) so i replaced it with the HD650 stock cable. Yes i had to reverse the cups to make it fit.
I use it with a rockboxed iPod video and the RSA Hornet. Listening with crossfeed on i can listen to this combo for hours.
I listen mainly classical music. Opera, orchestral works, string quartets etc.
In my opinion, a closed can does not need to be perfect. i use a closed can to be isolated from outside noises but no passive closed headphone can isolate me for 100% so i will hear always hear some distracting noises
 
a great allrounder.
I do not really need a neutral sounding headphone since what is neutral nowadays? only my own ears listening to a live concert.
and my ears are not yours
 

The first song I listened to with the HD-25 (like with any new pair of heaphones) was Dizzee Rascal's "Bonkers". This is the one track that I know that feels like every audible and inaudible frequency is used in the bassline... It just surrounds you and therefore can be used as a benchmark tool to test audio hardware.
 
And boy was I convinced instantly, also the isolation is extremely good so all of that really set me on my way!
 
Definitely recommend!

My impressions is that these don’t sound significantly different than the cheaper SP version in terms of sound signature. The biggest difference is detail, more extended highs and smoother mid. If you didn’t like the SP version’s general sound you probably won’t like this either.

 

Comfort:
I personally don't like on-ear headphones that much because of sweat and heat reasons and this is no exception. These will keep my ears reasonably warm on a rainy day. Takes a little fiddling around to get a good seal. My ear gets warm over half an hour. The clamping force is just right, not loose or vice grip. 
 
Build:
Everyone says these are built like a tank and I agree. These headphones feel very solid and hard despite their plastic build. They will be able to withstand a good amount of abuse. I don’t suggest walking around with these in the rain though without an umbrella. Good headband construction. I like the two piece headband so it makes it easier for me to wear the headphone tilted back as the balance is better.
 
Isolation:
Not as good as my Westone IEMs but that is expected as these are on ears and not over the ears. If you’re a loud listener these are be ok on the bus or for walking around the city but for a really noisy subway train it might not be good enough as I found myself reaching for my IEMs.
 

High:

Sound somewhat rolled off. Cymbal hits decay fast. Snares sound a little thin and distant. As someone whose preferences are in a bright sound I would not say these headphones are bright as the HD558 sounds brighter to me and grados are far brighter than both. I would say in general these headphones don’t have any spike that would sound harsh; occasionally the upper range of female voices can sound a little scratchy and thin. I wouldn't listen to classical with these.

 

Mids are fairly forward even though it "sits behind" the bass often. Vocals sound quite close.  The mids sound smoother than the HD558 but in comparison it could sound more distant because of the bass presence. Male voices can sound nasally sometimes. I don’t hear any sibilance in voices. Midrange is pleasant to listen to most of the time, no harshness unless the recording was like that. HD25 does a lot good in this area with no glaring issues. 

 

Bass:

The midbass hump is prominent on every song and makes sounds sound warm. This can be good or bad depending on your preference. To me, it seems like the bass is the loudest part of all the whole frequency response. The mid bass is the body of the sound for these headphones. I notice it’s a little boomy as well.  These are good headphones for DJs as songs from deadmau5 or music in dubstep and trance genre will shine as the pacing of bass beat is very suited for these headphones. These are the headphones that your pop loving friend might like as well. Music with rhythmic repeating bass beats goes well with the HD25. Bass reaches depths that surprised me for the size of this headphone.

 

Soundstage:

Fair for a closed headphone, doesn't sound significantly wider or deeper than my Westone UM2. No artificial wideness or anything like that. I would not use these for gaming as pin pointing can be hard. I never get the feeling the sound is coming from outside my head but quite the opposite; the sound is coming from inside my head and stays there. A closed headphone like the ATH W1000 is much closer sounding to an open headphone than HD25 but that’s another discussion.

 

Detail:

Don't expect globs of micro detail but enough for enjoyment. You can hear nuisances but they are more blended in and again, the bass makes it harder to hear these small details. I wouldn't use these for mixing or for critical listening. Separation is reasonably acceptable but plucking of string instruments are not as distinct as grados for example.

 

These headphones are fun to listen to. If you are very critical of detail these are not for you. This is one of the closed back headphones everyone talks about so I figured I'd try it. These sound somewhat like Westone UM2 with a smoother midrange, more bass and midbass tossed in and less dry sounding. I will stick with my UM2 because I think the bass is a tad much for me but otherwise I can see why these are popular.

Good value for the use I get out of them professionally and personally.. A great all rounder Can and they make my ears happy

Summary: These headphones give an accurate picture of what the producers had in mind when they mixed their music because they have a well-balanced, present, but not over-powering bass.
 
Songs Used for Listening/Critiquing:

1. Stuck on You - Michiko
2. Unlike Any Other - Jeremy Ellis
3. Garden - Totally Enormous Extinct Dinosaurs
4. Basically, **** You - Deru
5. Flashlight - Parliament
6. Creator - Santigold
7. Petrified - Fort Minor
8. Jamba - Tyler, the Creator
9. Ballad of NGB - Stateless
10. I'll Never Leave You - Rogue Wave
11. BloodStream - Quartet Session - Stateless
12. Blue Ridge Mountains - Fleet Foxes
13. Sunburn - Muse
14. Rhino - Solander

 
I know that headphones are truly the best consumer audio market right now, and that's cuz I said so.
 
Just kidding.
 
But seriously, not a day goes by where I don't see at least 250+ people with headphones or earbuds on their heads, listening to these ridiculously leaky headphones that tell me more about their music taste than anything else.
 
Firstly, I think these headphones are quite something else. I can't put my finger on it exactly, but I know that they are amazing. Honestly, words can't describe the satisfaction these headphones bring to the table. I don't think I could describe the sound quite like others do (spacious soundstage, sweet treble, warm mids, supported bass, etc). On a side not, I work in the food industry, specifically coffee, and every day I have to work with coffee from Intelligentsia, people who describe their products with fluffy descriptive, pastoral, and picturesque diction and abstract syntax; I am not that kind of guy. I prefer to describe everything simply and with ease of understanding, so here goes.
 
These headphones are good. They get the job done. They are utilitarian. They are affordable. They are the PERFECT consumer product because they do everything that a consumer needs.
 
I own a pair of Sennheiser HD595's as well as Ultimate Ears Triple Hi Fi 10v (or something like that). I have also listened to the Senn. HD598, HiFi Man 500s, the Senn. OCX800, and a variety of Beats, Monsters, and other things. Of those, the HD598, HiFiman, and the Ultimate Ears were my favorite because they had noticeable clarity. They sounded good and didn't give me fatigue. I'm sure some have noticed that when listening to bad headphones, subconsciously or not, you get tired of listening to that music. I mean, if you listen trap music or like Blink 182, MUSE, and other high-gain songs that have massive compression and gain boost on the final mix, then duh of course you'll get fatigued, but I'm talking about Dave Brubeck, Kronos Quartet, and the Hilliard Ensemble. Listening to Stacey Kent's beautifully soft voice is tiresome when I have ****ty headphones on because those headphones don't sound natural, at all. The headphones that I liked were all natural-sounding headphones, with authentic sound that comes with quality engineering and technology.
 
Then come in the HD 25s. It is an amazing product because it sounds just like all the other headphones I listed above but with more bass. Why is that important? For me, it's very important; my mama always loved Earth, Wind, and Fire, Parliament, Chic, etc. and my dad loves Led Zeppelin, Deep Purple, Bread, America, Sultans of Swing, etc. My uncle loves Jimmy Hendrix, Beethoven, and Bach (weird mix right?), and I love electronica, rhythmic world music, and folk music. With all that exposure (and rest assured, I listen to all of those genres on all of my headphones, all day, every day), the one common factor between all of them, from Bob Marley to Aphex Twin, is bass. This is pretty obvious, considering the fact that bass notes hit harmonics with higher notes, immediately beefing up the overall density of sound that is produced. For example, when I was in a band and played one of my songs, I'd always incorporate a melodic bass line that runs against the upper register instruments (like the piano), and it never sounded thick or dense, but when the band played solid, unified chords, I was so astonished how much of a difference it made. This subtle, meticulous balance of bass and other frequencies is hard to accomplish, and that's where these headphones shine.
 
The bass on these headphones are not overpowering to the point where you can't hear other instruments, but they aren't thin like the HD595 to the point where Fleet Foxes sound wispy. They are perfect. They make the MUSIC sound BETTER. Now, I am not a pro audiologist, audiophile, whatever you wanna call it, but I can appreciate a well-balanced, supporting, not overwhelming, not nonexistent bass with a low range that goes all the way down to hit the sub-sonic frequencies in Tyler, the Creator's "Jamba," and these headphones are remarkable.
 
This is, again, my opinion however, and I think that is an important fact to consider. Some people like powerful bass, some don't, and I am neither of those, so consider my recommendation with a grain of salt. Furthermore, there is no such thing as "best" headphones; that's like saying there is such a thing like the "best" car, "best" steak, or whatever. It doesn't mean ****. Yet I can't help but appreciate how affordable these headphones are; they aren't, say, as cheap as some other headphones, but what you pay for and what you get is remarkable. On top of that, maintenance is super easy! Cables, ear cups, and other parts of the headphone are easily replaceable, a feature I love.
 
The worst part about these headphones? The looks. See, I think these headphones should be the standard headphone for everyday consumers; it gives accurate pictures of what the producers wanted to make in their labs, so you see an honest, untampered musical idea. Beats, for example, have a stronger emphasis on bass, and so every song will have a bass emphasis, even if the producer didn't want one. But they aren't pretty, and they aren't marketed well. They do really well with professionals, but I have such an itching to have my friends all listen to these side-by-side with their headphones just to open their "eyes" to what's out there. Clamp force is strong, but if adjusted well, it's fine (plus, a good seal on the ears = better bass).
 
Regardless, thanks for reading my ridiculously wordy, sarcastic, and boring review (just kidding, my reviews are the BEST). I recommend these headphones to anyone who's looking for something that is affordable, accurate, and eye-opening.

Happy Listening!

 

Specs​

 

 
I'm still burning my 25 in (and I do believe in burn in - partly because NwAvGuy says that he does, partly because I *thought* I noticed a difference with phones I burned in left connected to my PC when I picked them up a week later) but already I'm in love with them. 
 
They're often cited as being a superb rock phone and having a rather Grado-ish signature instead of the laid-back Sennheiser house style. I'm going to eschew words like "forward," "dark, aggressive" etc because they're meaningless, subjective, and subject to change by EQing. 
 
Instead:
 
- You can make the 25s sound bassy, mid-range dominated or trebleish by using your EQ. These things are very responsive to EQ!
 
- I literally heard things in tracks I'd never noticed before. Tracks I've listened to for years, often using my supposedly detail revealing Ety HF5s.
 
- For those who don't know, prAT! (I think I have the capitalization right - I didn't know the word yesterday myself, other than its English slang meaning) is a the ability handle sounds with lots of attack - ie sharp beginnings and ends - convincingly. So drums need prAT! big time, and human voices and acoustic guitar much less so. Electric guitar otoh needs it quite a bit - and so does piano. (Imo.) The 25s excel in prAT! Drums and electric guitar sound better than I've ever heard them before. And I've just switched to a Ben Folds album and the piano sound amazing.
 
 
- Soundstage is there, but it's ***tight***. You don't just feel that you're on stage instead of an auditorium seat (as people say of Grados) - you feel that the band has formed a tight cluster around you, and start wondering why can't smell Gillian Welch's breath and why you're not getting sprayed with sweat by the Replacements. You remember that story about John Cale beheading a (dead) chicken on stage and wonder if the blood will wash out of your clothes. The instruments separate out magnificently, and you have a feeling of intimacy with the performance. I love it - but you might not.
 
I didn't test with orchestral classical music - my classical tastes are more for piano and chamber music. If the Eroica is the sweet spot in your listening tastes, then I can imagine that the 25's presentation might seem rather bizarre.
 
- Vocals sound amazing. Ms Welch really does sound like she's standing beside me singing directly into my ear. From a range of about 5cm.
 
- I've heard people say that certain high end phones won't tolerate bad recordings and sound worse with them than cheap phones would. I have no idea if this is true, but to my ears it isn't the case at all with the 25. I have an awful bootleg concert recording of the Replacements and the 25s, in cooperation with the J3's EQ, let my ears cut through the fog and murkiness to hear hidden detail. The result was a recording that sounded better than my studio albums did yesterday - you can still hear a lot of the sonic flaws, but the good stuff dominates and that's what matters. 
 
- I bought the 25s looking for phones that would make music sound as exciting to me as my old Mission 70 speakers did (these things were real killers for their day...) They've done everything I hoped there, mostly by way of that prAT! thing, but they've also revealed so much I wasn't hearing before that a lot of music has changed for me - I can see myself buying a lot more jazz, for example. And some later Clash recordings have just opened up and revealed magnificent textures that I never suspected they had - stuff quite at odds with my assumptions about them.
 
- Comfort Mine are fresh and the ear clamping is a little hard - I'm feeling some real pinching at the top of my ears. I understand that it would be less if I swapped to the velour pads, and that the band will become a less aggressively springy in time. At the moment it is a small price to pay.
 
- A nice feature is that the band consists of two arms. You can adjust the gap between these from zero to lots - the idea is that the twin arm design will cradle your head keeping the phones on under all conditions - these things are designed for news pros and DJs.
 
- Useful hint picked up from the net: you're supposed to set these so that they're slightly loose and then tighten the fit by widening the headband split.If you do this they're much more comfortable - I can barely feel mine on my head now, although they've also had 12+ hours of wearing to break-in.  If you're a DJ or in a TV news team, then someone will tell you this, I suppose. But for everyone else Sennheiser  really should have included a manual...
 
- These things have a rep for toughness - news people and DJs use their gear hard and they survive it for years. And because they're meant for pros, all the parts are user replaceable - you can buy every component from Senn and swap out broken band or a driver for a fresh one.
 
!!!IMPORTANT WARNING!!! 
There's one spot on each side of the band where the cable running between the ear cups can get trapped and damaged if you completely close the two bands together. There's a notch to prevent this, but the cable might not stay in it. If you're going to repeated close and unclose the bands completely - which is pointless - then you will want to watch this or add a dab of tape or something.
 
 
- Sounded great on the Clip+ and J3. I *think* they sound better on the J3, but I didn't do an ABX test and really don't trust my own feelings on this sort of thing. There was no problem getting them loud enough on either player. I keep them at about 22-26 of the Cowon's 40 level volume control.
 
 
 
- Looks: Industrial in the functional rather than the designer sense. These things are designed to blend into the background of TV news and sports broadcasts.
 
But... the 25s are *very*  customizable. You can change pads and cables for coloured ones, and even paint the band and shells. Or you can buy some amazing pre-customized phones from http://www.customcans.co.uk/
 
The owner of Custom Cans posts on head-fi as jfunk, btw. They also sell coloured ear cushions and what have you - including from an ebay store. They're based in the UK, but I think they ship everywhere. They customize other several phones, but the 25 seems like the core of their business.
 
- I've avoided giving numerical scores but for those who must have them, choosing some widely known comparators: if I gave the HF5 a 5 for sound quality, then the EPH100s - which are widely being compared with some of the best IEMs around - would be a 6.5 to a 7 and my Superlux 668Bs a 6 or maybe a bit more. The 25s would be, oh, a 9.5. Maybe they'll be a 10 when they're burned in. But I'd be the last person to deny that a lot of what makes a good set of phones is subjective, so ymmv. 
 
***Postcript***
- The HD25-SP has different drivers and a simpler headband; I've no idea how close it sounds to the "real" 25
 
- The Standard edition comes with a (cheap, unpadded) bag and two pairs of cushions - pleather (fitted) and velour
 
- The Basic edition comes without the bag and velours
 
- The Adidas is a slightly prettified version of the standard edition.
 
If I  was buying again I'd go for the Basic and use the money saved to buy funkier velour cushions from Mr JFunk - he also sells what looks like a very nice bag. Or I might go crazy and buy one of JFunk's special editions.
 
Finally, as so often, UK buyers get an awful deal on the price of 25s compared to Americans. So if you're in the UK and making a trip to the US, you might put buying a pair of 25s on your to-do list. But also, as mean and obsessive about US-UK price differences as I can be, I am ***really*** glad that I bought these!
 
- The estimable Mr JFunk of Custom Cans has provided a guide to tweaking the 25s acoustics here:
 
http://www.head-fi.org/t/590995/some-diy-mods-for-the-for-the-sennheiser-hd25-1-hd25-13-hd25-c-hd25-hd25sp
 
..And a guide to painting them here:
 
http://www.head-fi.org/t/573845/heaphone-airbrushing-guide-with-lots-of-pics
 

The HD25-1 has been my favorite (trans)portable headphone for quite a few months. I spend a few nights a week away from my home rig and the HD25 works wonders with my iBasso D10 and netbook. Hi-fi on the go has never been so rugged and simple. Best of all is their sonic versatility – though my backup portables, the AKG K181Dj, excel with certain genres and recordings, the Sennheisers perform more than adequately with anything I can throw at them.



Build Quality: When it comes to build quality, Sennheiser’s flagship portables can do no wrong. The structure of the HD25 is painfully elementary. They are neither flat-folding nor collapsible, with very simple rotating joints and removable metal hardware. The rough black plastic is resistant to cracks and scratches. A thick and sturdy steel cable, terminated in a beefy L-plug, completes the picture. The headphones are also very light and not likely to get damaged from falls. Lastly, every single part of the headphones is user-replaceable. From the detachable cabling to the headband padding to the cups and joints, the HD25 can be disassembled completely in just a few minutes.

Comfort: The HD25 is surprisingly light compared to headphones such as the AKG K181 and M-Audio Q40. The adjustable dual headband exerts very little pressure – the majority of the force is applied by the supraaural coupling. Though clamping force is fairly strong in the HD25, the structure does a great job of distributing it over the entire surface of the pads. The cups have a good range of motion despite lacking any joints whatsoever and conform very well to the shape of one’s head. Vinyl pads come installed on stock HD25s but some versions include the optional velour pads as well. Even if that isn’t the case, at $7+shipping the velour pads are a worthy investment, providing a comfort improvement at the expense of a tiny bit of isolation. Overall comfort falls just behind the likes of the impossibly light Senn PX100s and the circumaural CAL!.

Isolation: Though in general portable headphones can never isolate as well as IEMs, the HD25 can compete with certain shallow-insertion in-ears. While the vinyl pads isolate just a bit more than the velour ones, the tradeoff is unlikely to be worth it for most users. Even with the velour pads the isolation crown of the HD25-1 can be usurped only the hard-clamping AKGs and only if you’re lucky enough to get the AKGs to seal properly.

Sound: Upon first hearing the HD25-1 I was absolutely convinced that I would be giving them a perfect score in sound quality. Having owned them for a while, however, I can’t help but notice that for $200 headphones they are just slightly lacking here and there. But the fact that I am still using them as my primary portables is certainly telling of the fact that they are a competitive product. They are well-balanced, have good clarity and detail, and are quite transparent when it comes to sources. The bass is tight and accurate. It’s hard-hitting in character and more punchy than powerful as opposed to something like the K181Dj or M-Audio Q40. It has impressive extension, though it won’t keep up with the M-Audios down to the lowest reaches. It is also well-textured and does not bleed into the midrange. For a portable headphone the quantity of bass is just right – a bit more than what one would expect from an analytical headphone but far from AKG K81/K181 quantity.

The mids are neutral, clear, and detailed. Articulation is very good and sounds are well-separated. However, the HD25 is lacking noticeably in both soundstage width and depth, at least when compared to most full-size headphones. Most of the other closed portables I own don’t exactly shine in soundstaging either but I can’t help but be disappointed that the smaller and cheaper PX200-II has a more spacious sound. Sheer size aside, soundstage positioning is fairly precise and instrumental separation is excellent on all but the densest tracks. Towards the upper midrange the HD25-1 struggles to stay smooth and as a result is very unforgiving of sibilant tracks. The high end is quite present and reasonably extended but comes off a bit edgy and clinical at times. The overall sound, though, is quite pleasant and works particularly well for genres not dependent on soundstage size for the full experience. All of my quibbles aside, the HD25 is as good for use on the go as any portable headphone I have heard.

Value. (MSRP: $299.95; Street Price: $199) By far the most expensive headphone of the bunch, both in street price and MSRP, the HD25-1 is on another level in terms of balance and detail compared to all of the other featured portables. Compared, however, to full-size cans in the price range, as it sometimes is, the HD25 can come off as dull and rather compressed-sounding because of the narrow stage. The hard treble can also be a bit fatiguing for home use. But of course such comparisons are unfair precisely because I am not comfortable wearing my full-size cans outside while using the HD25 comes naturally. It is this versatility that makes the Sennheisers well-worth the $200 price tag and one of the easiest portable headphones to recommend.

Manufacturer Specs:
Frequency Response:16-22,000 Hz
Impedance:70 Ω
Sensitivity:120 dB SPL/1mW
Cord:5ft (1.5m), single-sided; Angled Plug
Space-Saving Mechanism:N/A
 
 
-----------------------------------------------
To see how the HD25s compare to the other portables in my collection please see here.

I have own the Sennheiser HD 25-1 II for more than 6 years now, and everything is still in perfect condition. I have always love the analytical sound this unit delivers... These have turn to be my personal favorite headphones for tracking live instruments and recording vocals, but I use them to listen to music when traveling, and they are my favorite portable headphones as well.
 
They are not really that confortable, I find them to be a little uneasy to wear for long periods of time, but they isolate really well and sound great with theire slightly v shaped sound signature. I will recomend this headphones for anyone looking to something portable and with great sound isolation.

 
The HD 25-1 is more than a great sounding headphone, it has stood the test of time, and proved to be one of the worlds most durable and versatile headphones. There's many detailed reviews of this classic headphone, so I won't go too much into the details. In short, all I can say is the hype and praise these headphones have received is well deserved. After owning these, I began noticing professional DJ's and Sports Announcers on TV wearing these all the time. Funny I never noticed that before, but I can see now that they use them for a good reason. I think the reason these are so well regarded is more so because of their design/comfort/durability/versatility vs their sound quality (which is great too).
 
Sound (9/10)
 
The sound signature of these is quite balanced, with a slightly above average bass response, likely due to the above average isolation they provide. The sound stage is about average for a closed headphone in this price range, but the separation on more complex compositions is impressive to me. They are very sensitive and easy to drive, which makes them ideal for portable use. They get loud enough to be dangerous, even from portables. Like most higher end headphones, they also benefit from high end amplification, but it's by no means required to reach their potential. Due to their balanced sound signature, these will please lovers of any genre of music. They are equally suited for gaming or movies also. Gave it 9/10 due to the average sound stage, there's other closed headphones that do better in this regard.
 
Design/Comfort (10/10)
 
The reason Sennheiser built a reputation off this model is the design and versatility of it, it is a true feat of engineering. The plastic is of high quality, making them light and durable. The clasping force is moderate, and combined with the Velour ear pads, I notice no discomfort at all when wearing them all day, even with my glasses on. With the leatherette ear pads they come with, you will get warm after 1-2hrs, but you get a slightly better seal, which improves bass impact slightly. I think the added comfort of Velour more than makes up for the unnoticeable decrease in bass impact. It's easy to get the right seal on all head sizes/shapes. Once there on, they stay there, even when running/exercising. The split headband helps keep them from moving. 
 
They look good when there on, not overly stylish or big, a more minimalistic look. The cable is just the right length too (1.5m), and conveniently terminated to a 90 degree 3.5mm connector, with a screw on ¼ inch adapter too. For those who care, mine say Made In Ireland. Because these are so modular, you can easily take these apart and customize them with custom paint jobs or after market cables if that's your thing. All the parts are easily replaceable, and easily available, which is something no other headphone achieves in this price range with this sound quality and comfort/durability. For many, this headphone is the last one they ever purchase, simply because it won't break, sounds great, and is so versatile. For those who manage to break something, a replacement is easy to find. That's why you see so many professionals using these on a daily basis.
 
Verdict (9/10)
 
I highly recommend this headphone, for anyone. It will be the last headphone you buy. I can honestly say I was skeptical of the hype these had, but after owning them, I quit using all my other closed headphones in favor of this one, not just for the sound quality, but the versatility it provides. It's like a good ol' Acura; it might not look the most flashy, or perform spectacularly well in any one area, but it does everything well, takes a beating, and never lets you down. Gave it 9/10 due to the constantly raising price of this model.

I have had these headphones for a couple of days, and used/tested them intensely during that period.
I have a pair of mackie mr8 mk2 studio monitors, so this is the sound I am used to.
The sennheiser HD25-1 II are extremely populair, and this is one of the reasons i bought them, yet I was not satisfied at all.
First of all, the sound stage is extremely small, it actually sounds more like everything I was playing was in mono instead of stereo.
Also the headphone lacks in treble, and really does not have a lot of detail, this headphone is everything but balanced, so to call this a studio headphone is just wrong.
 
Don't get me wrong, it sounds good, has a lot of tight bass, really upfront (could be your taste) and goes really loud. And maybe if you are a pro and need a headphone that is built to last, and has an extremely high spl this is the headphone for you.
Otherwise, I think the headphone is a bit expensive.
 
Alternative: I have the beyerdynamic DT770 pro, these are closed, don't go as loud (as if you would ever need 120db in your ears), still more than loud enough though and have a huge sound space. Also I got them for 130 euro's, so that's 10 euro's cheaper than the sennheiser 25-1-II.
The only downside to these headphones is that they are quite a bit bigger than the sennheiser's 25-1-II.
Some people act like this is the best headphone in the whole world. With this review I am trying to tell that the 25-1-II really is not the best headphone, and that there are a a lot of alternatives.
 
EDIT
I actually have bought these headphones again, and love them!
My main headphone is the HD650, and I use the HD25-1 II for bass heavy music, portable uses and playing the drums. I actually don't mind the small soundstage for some reason, and love the sound.
I bought the velour pads for extra comfort, and the fiio e6 for portable uses.
 
Not sure if my first pair was falty or that my sound signature preferences has changed.