So when I got my HD800, they were so good from the first hour with every song and genre, when compared to other top tier flagship headphones, that I wrote a quick review to give them a no brainer five stars and then filled that review in slowly. Same deal here. These are getting close to the resolution, spatials and sound quality of a good full sized headphone. Not quite there yet -- for example, they're not as detailed, e.g., as my HD800 driven by a Burson Conductor ES9018, and they're similarly noticeably deficient in other respects when compared to a proper full sized -- but they're better than other high end IEMs in this respect, such as the Shure SE846 and IE800. I'll add more to this later, but basically right now every dimension of sound is better with these. Detail, spatials, treble (although these have a warmer sound signature than those other two), mids, bass (the SE846 has good sub-bass, but the Roxanne's bass is better defined; yes, there's detail in bass), balance between the frequencies, everything  . . . 
 
On comfort, they are definitely big (maybe twice the size of the SE846 in terms of volume? and much much bigger than the IE800) but I am having no problems whatsoever fitting them and so on. They're like the SE846 in that respect (but not as good as the IE800, which are super easy to pop in and out).
 
Edit1: They're clearly "warm" on the frequency scale, sort of like an Audeze LCD2. So if you want a bright headphone you may not like these. This is true even if you turn the bass all the way down (which you do via two screws on the line, one for the left ear and the other for the right ear). If I were designing them, I would have moved them a tad bit up on the frequency chart, but I can't criticize JH for that decision since you can't please everyone on the warm/neutral/bright debate. Note this is very slightly exacerbated if you move from the rubber/silicone type tips to the comply foam tips, which create a super air-tight seal and thus magnify the bass (and consequently cause you to perceive less treble).
 
Edit2: If you like the fact that IEMs put the music right  in your head, and you don't like the way full-sized headphones create some imagined distance between you and the sound, then you won't like these. It occurs to me that some people might like that closed in feel of a traditional IEM. It's a little odd listening to an IEM that presents music in this way.
 
 

First a bit of background on my experiences with headphone amps. I have tried the Fiio E17, Objective 2, the 2.3W amp built into my laptop, my Yamaha receiver's headphone out and a cheap $40 Chinese tube amplifier. I got rid of the E17 and Objective 2 because after careful listening, they did nothing my 2.3W laptop amp couldn't do and so were a pointless waste of money. The tube amplifier though did impress me, it was super powerful, brought out deep bass that none of the other amps could do (although the Yamaha receiver got close), and added a nice warming effect which blended well with the HD800. I have also tried a number of DACs all of which had their own sound and I heard that the ES9018 sabre is the best DAC out there. I was investigating $1,000 well implemented ES9018 DACs when I decided to bite the bullet and buy what audiophiles said was the best ES9018 DAC/amp combination out there under $2,000.
 
Now let me go through the problems with this product one step at a time.
 
You need to leave it on -- The first thing I noticed was that right out the box it sounded slightly but annoyingly airy and tinny. I thought this thing had 4 watts. That should be more than enough to deliver deep thumping bass to my HD800. I was quite shocked at the subpar sound, until it started to slowly improve over the hours. I thought it was my imagination but then I read the manual which confirmed that this improves the longer you leave it on, even over days. I imagine that has something to do with the way heat affects the conductive ability of metal. The manual says that once you start it, you should give it a minimum of 30 minutes to warm up before listening, and suggests that it should be on for days to achieve its best sound. Any way, after it was on for hours, the bass/warmth were acceptable. Still not as good as the tube amplifier or Yamaha, but at this point it was simply a subjective matter of tastes vs. a clearly deficient product.
 
You might hate the amplifier -- Having said the above about subjective vs. objective bass tastes, even after it's fully hot and operating for three days, I can't help but to conclude that this could be a warmer sounding amp with more bass impact. This might not matter as much if you're driving, say, an Audeze (I didn't test that, by the way), but it does matter if you're driving something like an HD800 and you want an amp that really brings out the HD800's secret warmth and subwoofer capabilities without sacrificing the treble. This thing has like a $1,000 solid state amp built into it with all this fancy "no IC" components blah blah blah and a whole bunch of other rhetoric that you can find on their website. But who gives a crap if its frequency distribution is off? Burson, why don't you worry a little less about ICs and a little more making sure that you go the frequency response right? This supposed 4 watt amp can't even outperform a cheap $40 Chinese tube amp when it comes to delivering the warmth, exhilaration and bass necessary for some songs. For example, Al Jarreau's "Morning" is unlistenable on this. How did you suck the warmth out of Al Jarreau's voice?! The song sounds dry and irritating to the ear. I could list numerous other examples. I think it's amps like the Conductor that give the HD800 its reputation as a headphone that can't deliver top-tier bass/warmth. I often wound up connecting the Conductor to that cheap $40 tube amp to enjoy its ES9018 DAC with a proper amp. To its credit, the Conductor delivers sound transparently and clearly with no line noise (when using a headphone), and the tube amp is muddier -- but why can't we both micro-analyze the music and enjoy it too? Bottom line is that a $1,800 amp should handle every genre of music, and it should never be beaten by a $40 Chinese tube amp, ever, not with any song. I will never put my HD800 down to wear a $50 headphone and the same should hold for an equivalently priced amp. I don't know how much better a proper tube amplifier such as the Valhalla will sound, but I'll update this when I get such an amp. It's not only tube amps though. Even my Yamaha receiver sounds better at times, and that's solid state, and even my laptop's amp/Realtek 269 sometimes sounds better. Any way, since this is more of a niche amp designed to present some warped dry, cold, "reference" version of songs and not a song you would enjoy -- I feel I have to deduct 2 stars.
 
Edit: Eventually I got used to its "style" of presenting music and I guess diversity in musical flavoring isn't a bad thing so long as the buyer knows what they are getting, so I'm not going to deduct anything for this. This was clearly an amp designed to optimally present classical music: piano, violin, harp, horns -- not much of a focus on bass and warmth in those instruments. Rather, those instruments have a lot of mid/high treble and the Conductor's revealing nature is very well suited for such sounds. And to be fair, it's called the "Conductor" not the "Rock star," so it's not like they're trying to mislead the buyer. In addition, although it doesn't have a ton of bass, the bass it has is very detailed and revealing. This is the system to listen to if you want to hear the polar opposite of "muddy" bass.
 
The ES9018's boost in detail won't be worth the price for all but the most nitpicky consumers -- After lots of careful listening, the ES9018 does have a slight detail boost over my other DACs with most songs. You can hear tiny background things, or details in foreground sounds, that weren't as noticeable on the other DACs. I say as noticeable because once I try to listen to them on the other DACs, I can often see that they were there, but those DACs didn't separate the detail push it forward as well. The problem with this is diminishing returns. Any modern DAC worth its salt will deliver enough detail to allow you to thoroughly and fully enjoy the song. Sure, back in 1991 when soundblaster had that awful sound card that couldn't handle anything more than I think 8 bit / 16khz, DACs were bad. But those days are gone. All of my phone DACs, my $87 Chinese PCM5102 DAC, and my laptop's Realtek 269 put out perhaps 90-99%% of the detail that this puts out depending on the song and your setup. Is it worth it to spend $500 to $1,000 to get an ES9018 that puts out a few extra irrelevant sounds? Let me compare it to an analogous decision you'll have to make: Was it worth it to get an HD800 to plug into my laptop, vs. plugging a $300 headphone into the laptop? Hell yes, absolutely, I recommend that purchase for everyone who wants good sound. Or if you don't like the HD800 get some other high end headphone. Those are a good buy. Consider it a 10 year investment costing you $12 a month or so. There is a huge and noticeable improvement when moving to an HD800. But don't overestimate the improvement in detail created by the ES9018.
 
The USB driver is defective -- Sometimes, when you finish a song and a new one starts, or a new youtube starts, all you'll hear is silence and occasional random bits of a sort of static popping sound. Well eventually I figured out that in these situations you need to restart the music player a few times and the USB will fix itself, but this is not a problem I have ever had with any other DAC in any way, ever, in decades of computer audio. Hey Burson, why don't you spend a little less time bashing ICs, whatever they are, and a little more time competently programming your USB driver? Even my cheap $87 Chinese PCM5102 xmos DAC doesn't have this problem and that was essentially built by a DIYer selling stuff on Ebay. I'm deducting 1/2 star for this.
 
Edit: The USB issues is now a much rarer occurrence, for whatever reason, so I won't deduct any points for this.
 
Line noise -- This has three ways to output sound: a DAC out RCA, preamp out RCA and of course the headphone out. The preamp out has a faint high pitched squeal that is tolerable but annoying, and the DAC out has even more line noise that in my opinion is intolerable. These were tested by plugging those sources into my Yamaha receiver's line in or the Chinese tube amplifier's line in. I know what you're going to say -- there's probably something wrong with my power strip or power line conditioning or whatever, and that indeed probably is the actual culprit here, but regardless some of my other sources on the same setup do not have the line noise and I expected more from a product this expensive. Ultimately, I wound up connecting it to the receiver by using the headphone out and converting that into an RCA L/R, which had the least line noise (although even that had a very slight high pitched squeal). However, since I don't hear any line noise when using it purely as a headphone amplifier, which is its purpose, I won't subtract any points for this.
 
On the positives -- I guess it's a good "reference" dac/amp. Good if you want to study the music. The build quality is also obviously excellent as you can see in the pictures, and it looks really good sitting on your desk. It also has a ton of inputs and outputs (but again the output might create line noise in your system). Overall, this would be a good addition to your mix of amps and DACs. That's how I'll use it -- it'll my hyper revealing technical DAC setup. But at the same time, depending on your tastes, there could be much more important audio products to spend on.

Just doing a quick review of this amplifier that I got from China. If you look at my other amp reviews, you'll see that I have tried the Alpen E17 which I thought was underpowered and had an average DAC making it a total waste of money, and that I also tried the Objective 2 which wasn't underpowered, but wasn't something I would call powerful either.
 
Please note I tested this with a $14 bulb I purchased off of Ebay, an RCA model. So I'm not using the bulb it came with although I didn't listen to see if that made a difference.
 
Well this thing is SUPER powerful. To listen to it without hurting my ears, I have to set the source's volume (my laptop headphone jack or my phone headphone jack) to like 5-10% and then I set the volume on this to about 25%. This would almost certainly make my ears bleed if I turned its volume to the max and turned my source volume to the max. So it does the most basic thing an amp is supposed to do: deliver as much power as you could possibly want. It's rated at "450mW" based on the ebay site, but it doesn't say what impedance this was measured at. It does say it can handle a 600 ohm headphone, though, so perhaps it was 450mW @ 600 ohms, which would make this quite a powerful amp. I wish I had an HE-6 to see how much power this can really put out.
 
It also does its job in delivering bass and warm frequencies. I don't know if the tube is doing anything; but the sounds do sound slightly warm and aged, i.e. it makes it sound like what you might hear from an old jukebox or stereo system..
 
I also hear very little line noise and it's easily ignorable (you have to really listen for it), although there is a lot of loud cracking (probably due to its power) when you plug and unplug the source and there is a little bit of cracking noise as you turn the knob to adjust the volume.
 
Overall, though, due to its very low price, its high power, its decent sound and its ability to let you enjoy a tube amp for a measily $45, it deserves 5 stars. I think I would recommend this over the objective 2 amplifier, for example.
 
Last thing. At first, the sound in the left side was louder than the right, by a lot, but there are two orange screws near the tube that you can adjust to fix this.

First the preliminaries, like, where do you find this and does it work? You can find this on ebay by searching for PCM5102 (called that because it has the high-end Burr Brown i.e. Texas Instrument PCM5102 chip), and you get the drivers from the link below (the purple baidu link) http://item.taobao.com/item.htm?id=35324113465 which work fine with both windows 7 and windows 8. I don't even know if the brand is really Breeze Audio but that's what it says on the case.
 
As another preliminary, please note that I am reviewing this amped. I connected its coaxial/SPDIF out to the coaxial in of my 500W yamaha stereo receiver, and plugged my Sennheiser HD800 into the receiver's headphone jack. Unamped this sounds listenable, I guess, but it also sounds intolerably bright and it's missing warmth. It's really a severely distorted listing experience unamped; an amp makes a night and day difference and I would not recommend buying it if you don't have an amplifier. Its built in amp is the worst amp I have ever heard, including all of my cell phone and laptop amps. But I can't penalize it for that because it's sold as a DAC not an amp. I'm also powering it via an external 9v power supply (not a fancy one) but I haven't tested if that makes any difference relative to using USB power, which you can also use.
 
Eventually, I learned that if I connect the coax/SPDIF out of this DAC to the coax/SPDIF in of my Yamaha receiver, then I am really using my Yamaha receiver's DAC, and this DAC is being bypassed. The maker built this into this DAC to let you use it as a means of converting a USB signal into a SPDIF/coax signal, for high-end DACs that only have a SPDIF/coax input. If you use the SPDIF/coax output of this DAC you are completely bypassing its DAC. So the review I originally wrote was for my Yamaha receiver's DAC, lol, which I have updated below. I now connect the headphone out of this DAC to the RCA L/R in of my Yamaha stereo receiver, to make sure that it's this DAC, and not the Yamaha's DAC, that is being used to convert the digital signal to analog. This method still warms up the sound significantly. Edit: Note you can get away with not having an amp if you drive a low impedance headphone, which I verified by connecting this to my SE846 and my SRH940. But you need an amp if driving a high impedance headphone like the HD800.
 
Now that I was actually listening to this DAC -- in summary, I'm not sure this DAC sounds better than my other DACs. It's OK, but a modern laptop/phone already has a pretty good DAC. I'm not sure you gain much if anything buy using this thing. Also, I heard some line noise. Very slight line noise but I can hear it if I try. Edit: Actually I later hooked this up to a different headphone amp and discovered that the line noise was caused by my stereo receiver and not the DAC. The receiver doesn't cause line noise with other DACs but for some reason when combined with this it created line noise.
 
At $80 + $7 shipping, due to its lack of remarkable characteristics and a terrible amplifier, this is a 1 star product. But I guess it has value in that its SPDIF out allows me to use the DAC of my Yamaha receiver, which was previously inaccessible.

Let me start with the good, and then explain why you should never buy this IEM.
 
Sound signature: The treble, mids and bass are sort of like that of an HD800, except downgraded. For example, one of the songs I use to test headphones is Michael Jackson's The Way You Make Me Feel. One of the key parts I listen for is that initial drum blast. On this, it sounds very close to the way it sounds on the HD800, except it's just missing a little bit. Moving on to a treble heavy song, it sounds similar to the HD800, but slightly muddier and the highs seem a little rolled off. Something is missing with the mids/voices as well -- they seem a little bit more distant. In general, it sounds like the HD800 but it's missing a little of that oomph, exhilaration or spine tingle that the HD800 gives (and a little is a lot when you're comparing headphones in this price range). Despite the fact that I keep noting differences between the IE800 and HD800, I do definitely sense a similar sound signature. For example, like the HD800, voices, instruments and all sound "natural" (they way they would sound right in front of you) as opposed to that synthetic and adulterated sound you hear in so many headphones. Well this is the best I can do now but when I can better articulate the similarities and differences I'll edit. But please do not misunderstand, this is a downgraded HD800, not at all an HD800. They're similar, yet also quite different.
 
Comparisons with Shure SE846: Is the bass as good as with the Shure Se846? No. Shure has invented a magical device in the SE846 that delivers beautiful, clean, tight and undistorted bass of whatever degree you want (depending on the filter you use). This is pretty good, not nonexistent bass (like, say, the Shure SE425), but I would compare it to something between the white and blue SE846 filters and even then the SE846 might be very slightly better in terms of quality. Is the treble as sparkly as the Se846 with a white filter? I'm not even sure about that; I would have to think about it a bit and do careful tests. But I disagree with reviewers I've seen that claim the Se846 sounds like its treble was rolled off relative to IE800. The IE800 has OK treble, but it also feels slightly rolled off relative to sparkly treble kings (like the HD800 and Audeze LCD XC).
 
Spatial imaging: For an IEM, the spatial imaging on this is amazing, better than the imaging of the Shure SE846 (but it's still no where near the spatial imaging of the HD800, and other over the ear cans can also do better; ultimately this is still just an IEM). It achieves that effect of making certain things feel closer and certain things feel farther away. On some songs you get a version of that cool echo/spaced out effect you get on the HD800, which is impressive in an IEM.
 
Detail and instrument separation: Detail and instrument separation is very good. Again this is not as crisp sounding as the HD800, but it does have a lot of detail. It's quite good. Of course, the cool aspect of the HD800's detail/separation is that the detail is placed in a certain virtual location, and as noted above this can't do that as well as the HD800.
 
Comfort: You do not need to go through an ordeal to insert these, unlike the Shures mentioned above. In addition, the wires are not stiff like the Shure wires which has to be another advantage. It's really hard to read which is left and which is right (but after you find out once you'll know forever based on their shape). In addition, it has a hole that equalizes the pressure between your ears and the outside, which is a good feature. Consistent with Sennheiser's other cans, this is extremely comfortable and easy to wear. I guess that deserves a 1/2 star boost.
 
Now for the negatives.
 
Design flaw #1: Isolation: I decided to take it outside near cars and busy activity to see how well it isolates. The first alarming thing I noticed was how loudly I heard the door close on my way out; not a good start. But I readjusted the tips and remained hopeful and optimistic . . . until I hit the street, when I was overcome with disappointment after hearing everything. I stopped, played with the tips, did every trick I could think of. Nothing. This isn't as bad as an open back headphone, but it's only a little better than a closed back. Sennheiser, don't you think that, perhaps, people wear IEMs to block out noise? If they want to hear outside noise they could easily wean an over the ear or on the ear can. Eventually, the only way I could listen to the music was to turn the volume up to a level that I later measured as 70-75 dbA (for comparison, the Shure SE846 isolate well enough to easily listen at 60-65 dbA). Thanks for the hearing loss Sennheiser!!! All the outside noise of an over the ear and the "pumping music directly into your ear canal to destroy your auditory hairs" dangers of an IEM. Great lose-lose combination you got there! Due to the risk of permanent hearing deterioration caused by this unacceptable and inexplicable design feature, it has to lose 1 1/2 points. (Edit: I measure dbA by putting the IEM tip right up against the port of a decibel meter).
 
Design flaw #2: Line noise. At first I decided to try it with the line hanging under my chin, the way you're supposed to wear it. But as soon as I started walking, it sounded like I was in a wind storm! There was no wind, but every time I would move, the chord would move, and apparently when the chord moves it has to let me know by sending this loud sound up and into my ear canal. Thud, thud, thud, thud. I get it chord, we're moving. You don't have to tell me every half-second. Let me move a bit without you machine gunning my ears. Sennheiser, did you even put this on and go for a walk with it before you decided to sell it to the public?! I wasn’t even exercising heavily. This is unacceptable, it has to lose 1 star over this. Edit: Sometimes I wonder if Sennheiser is playing a joke on us with this product. I say that because I just discovered that the Sennheiser HD800 has absolutely zero line noise. I tapped its line, shook it, whipped it . . . but I couldn't get it to produce even a tiny bit of line noise. So the HD800, which is designed for stationary use, has absolutely zero line noise, and the IE800, which is designed to be used while active, has insufferable line noise? Really Sennheiser? The fact that Sennheiser knows how to completely eliminate line noise means this flaw deserves another 1/2 star deduction.
 
Design flaw #3: So to cure the slight bit of chord noise you hear in every IEM, I discovered this trick I do whereby I let the IEM hang behind my head instead of under my chin. With the SE846 you hear nothing if you do this. I think your hair acts as some sort of sound baffle or cushion or something; whatever it is it works, and it helped a good amount with the IE800 too, but not as much as with the SE846 and the IE800 wasn’t as comfortable hanging behind your head. But whatever it's tolerable now and so I'm walking along and . . . I decide to put my player into my pocket, at which point I discover that the chord, from your ear to the jack, is only about 3 1/2 feet long! Sennheiser, did you test this on little people?! Did you think that perhaps customers would like just one measily foot of extra chord?!?! What terrible thing did you think would happen if you included a five foot chord like Shure? Fine, keep your chord short, but if I'm paying you $1,000, could you at least have thrown in an extra chord of a longer length? Shure includes two chords with the SE846 and their chords look to be of higher quality than yours, so why can't you? This inexcusable chintziness and lack of thought has to cost it 1/2 star.
 
Design flaw #4: This is minor but it shows how inconsiderate Sennheiser was when designing this. The case has no room to insert your extra tips. This four inch, by 3.5 inch, by one inch case (measure that out so you know how big it is) doesn't have room for the extra tips. The inside of the case is almost entirely foam, with a little groove where you insert the IE800 (you don't put the IE800's wire in the case, by the way, rather you must wrap the wire around the case). First of all, what happened to just being able to throw your IEM into a case and take it out with ease, rather than having to perform a complex lego piece insertion and removal each time? Back to the main point, Sennheier, if you're going to make a gigantic case as big as a fat wallet, could you let us use some of that room?! Cut a little area out of that foam where we can insert the extra tips you gave us. This is a small thing, but it shows such a lack of consideration and thought. It has to lose 1/4 star.
 
Conclusion: Ultimately, I am not going to keep these. Although I love the sound signature of the HD800 and this reminds me of that, I can't support a product engineered this poorly. It's of no use to me because if I'm in a loud area, I'll use my beautiful SE846 and if I'm in a quiet area I'll just use my HD800. This leaves the question of what rating to give these. Although the sound is very good, based on its hefty price tag it can't get more than 4 1/2 stars on sound (I have to save 5 stars for something that really wows you). Subtract 1 1/2 stars for lack of isolation, add 1/2 star on comfort, subtract 1 star for line noise, another 1/2 star for having line noise even though Sennheiser knows how to completely eliminate it, subtract 1/2 star for the chord, subtract 1/4 star for the case, and (this is very subjective) add 1/2 star for having something close to the HD800 sound signature (which I like) and for being made by Sennheiser, a very ethical headphone company that lets you return things you don't like for a full refund. So 4.5 -1.5 +.5 -1 -.5 -.5 -.25 +.5 = 1.75 stars, which I’ll round down to 1.5 stars because I expected better from a $1,000 headphone. For comparison, I gave the SE846 5 1/2 stars (capped at 5 stars). As anyone who has spoken to me on this board knows, I am a huge Sennheiser fan so I wanted to like this but this is just pointless.

The only other IEM I've ever tried is the Shure SE425. The SE846 has not only better bass (obviously) but I confirmed that it has better treble and mids. The SE425 sounds downright muddy relative to these. The treble is very slightly rolled off on the SE846, I think, but that's subjective so it might be just right for you. The bass on these is like everyone says, tight, deep, natural and undistorted. But it's not at all like beats or other boomy headphones. Play a bass heavy track and you'll hear it with quality, but it doesn't inject bass where it doesn't belong and it is not excessive. It also sounds nothing like a proper subwoofer; it's no where near that impactful and strong (you can feel a subwoofer in your body) so let's dispense with that bit of marketing right now. However, it delivers bass similar to what you would expect from a quality neutral full sized headphone, with very little distortion and very cleanly. It was unusual to hear that sound from a tiny IEM; at first I found it kind of disturbing, sort of like how you would feel if you saw an ant carrying a rock on its back, lol.
 
The above was with the blue filter, which leads us the reason why this is one of the greatest headphones ever made: its filter system. When I moved to the white filter, the bass seemed much lower. I say seemed, because the manual says that all the white filter does is raise the volume between 1khz and 8khz by 2.5db, so it shouldn't affect the bass. Any way, that extra treble sort of drowns out the bass I guess. After about 3 hours on each, I think I'd like something between the white and the blue (can we get a light blue filter Shure?) But since that's not available I'll spend most of my time with the white. Regardless of what you like, the three filter thing is a very cool innovation by Shure which deserves praise. The only problem with it, is that you might find yourself constantly wanting to switch, to hear how the other filter sounds with a particular song, and I'm guessing I'll be losing/breaking these filters at some point from all the changes, lol. Not sure what the replacement cost is. But this feature, which will probably be copied by others, deserves a 1 star boost. It's like getting three headphones in one.
 
One last comment on the bass -- it's very DAC (and amp, if your amp adulterates the signal) dependent. I say this because the bass output is much much higher when I plug this into my LG G Flex phone, than it is when I plug it into my Note 2 phone. The Note 2's DAC is much brighter but that causes the bass to almost disappear. If you're not hearing bass, switch DACs by trying it on another phone, or your laptop.
 
As far as fit, if you buy a professional tip from Comply, I don't think it's possible to get an improvement by purchasing a custom molded sleeve. Shure IEMs + comply tips go deep into your ears, they are comfortable and they fit every nook and cranny of your ear canal. Just get the right size. I have never tried a custom made IEM but I would not be surprised if they didn't fit as well as Comply tips. The tips supplied by Shure are not as good for comfort or isolation, and I will never use them, but you can buy Comply tips for $20 which isn't much relative to the price of these things.
 
Moving on to the isolation. First of all, Shure is misleading customers when they claim that the SE425 and SE846 provide the same isolation (its website states that both "provide up to 37 dB of isolation" without distinguishing between the two). The SE425 with professional Comply tips is like wearing hearos ear plugs. A car can go by you at 35mph and it'll sound like a very light whispery vroosh. You can't make out what people are saying, even if they're right in front of you. With the SE846, the car is louder and you can hear people's voices a little better. If you look at the innerfidelity charts, they confirm that the SE425 isolate better than the SE846. At first I was annoyed by this slight downgrade in isolation, but then again the isolation of the SE425 might be dangerous. It's kind of odd walking next to a busy street and barely hearing anything. Very risky if you're bicycling or something. Plus, once I find where the noise is leaking into the SE846 I can put tape over  it or do another mod (I think the noise might be coming in from that mechanism they use to let you change tips, perhaps it needs a gasket that I can easily craft). I was going to take off 1/2 star for the downgrade in isolation, but now I'm not sure. I think the Etymotics isolate sound excessively and are unsafe, but I'm not sure whether the SE425 or SE846 have it right. Edit: I created a gasket out of about a 2mm thick slice of a hearos earplug (when compressed it's about as thick as a hair), and inserted it between the base and the screw you use to attach the filter to the base. After doing so, I can no longer hear people talk in front of me; I think the SE425 might still have a tiny bit better isolation but I would have to do careful listening tests to be sure.
 
Getting back to the sound quality, the SE846 still generally doesn't sound better than a solid $300-$500 over the ear headphone. It is NOT EVEN CLOSE to the sound of a flagship over the ear. If I were to start comparing this to the HD800 I would trash this a hundred ways, relatively unresolved and sloppy bass, relatively unresolved treble, treble roll off, lack of spatial imaging, I could go on and on. The first company that makes an IEM that is objectively indistinguishable from an HD800 in blind tests will make a fortune. These are only worth it if you listen to music with a ton of ambient sound that you need to block out or if you don't like the looks of a big headphone; otherwise always buy a full sized headphone. At the same time, it's in another universe relative to the SE425. Those sound awful once you wear the SE846. I really need to try the IE800 (which I didn't buy because it doesn't accept Comply tips, and it has much worse isolation than the SE846 according to the innerfidelity charts) to compare the two [Edit: I purchased and reviewed the IE800 which you can find in my reviews]. But since the reviewers who compare this to the IE800, JH13/16 etc. and other $1,000 IEMs aren't sure which is best, I think this is about as good as it is going to get with IEMs -- which is  disappointing.
 
One other observation is that these are louder than the SE425. With one volume bar, this is like having two volume bars with the SE425 (I checked with a decibel meter, measuring dbA slow). Similarly, with two volume bars, this is like having three volume bars with the SE425. I hear Shure didn't do this on purpose to fool customers with the "louder = better" trick. But please keep this in mind. These have virtually no resistance and they put you at greater risk of hearing loss if you're not careful with the volume. But also keep in mind that the increased bass response of these might be affecting dbA measurements; I would have to dig into the dbA formula to confirm.
 
Due to the high expectations from a $1,000 price, this isn't quite a 5 star product, but I'm keeping them because when a song with bass comes on, I want to hear it, rather than hear that lame tapping sound the SE425 calls bass, and overall I think they deserve 4 1/2 stars. Add the 1 star boost due to the filter innovation and it's 5 1/2 stars (capped at 5 stars).

Please be advised that I am only writing this review to help other buyers. I am not trying to upset any T1 owners and it's my honest opinion. If you think it's unfair please state so in the comments and I can reconsider although I have enough experience with headphones now to know what I like.
 
First, let me note for the reader that if you google the three words beyerdynamic t1 deal, you'll see that every month or so an internet retailer sells brand new T1s for $750 to $780 (and these seem to be authorized retailers, for example one deal was from Buydig which is Beach Camera if I understand correctly, which is listed as an authorized retailer on Beyer's website; that deal even included free overnight shipping and no tax). These constant deals beg the question of why these "flagships" consistently go for mid-tier prices; The answer became apparent when mine arrived.
 
The only other top tier headphones that I have ever tried were the Sennheiser HD800 and the Audeze LCD XC. I preferred the HD800's sound signature, but I could appreciate the quality of the Audeze. For example, if you play the sound of a single guitar string being picked, you'll see that it's a noise which starts somewhat low in the frequency range, and rapidly, very rapidly, goes smoothly up in frequency until it reaches a high note. It takes a fast and capable driver to reproduce that well, and the XC could do that; it would send a chill up my spine. The HD800, well, I shouldn't have to explain why it's a flagship but let's just say its spatial imaging and magic are renowned.
 
The T1, though, is not even close to being in the neighborhood of those two. The best way I could explain the sound of this headphone in a relatable way, is to say they are an upgraded Shure SRH840. The way I tested them is to spend hours listening to and re-listening to my set of favorite songs, songs which I have played dozens of times and essentially memorized. I also listened to and relistened to very specific parts of songs, such as the sound of that guitar string being picked. The headphone was powered by a JDS Labs Objective 2 amplifier and I was generous with the volume, playing it at about 65-68 db ear level.

1. The bass, while relatively strong and booming, is distorted at the very low bass frequencies, which is less than you would expect from a flagship. There is a distinct way that the HD800 and especially the Audeze hit low frequency bass notes that distinguished them from mid-tier headphones. If you've heard it you know what I'm referring to (the SE846 is another example of clean undistorted low frequency bass). The T1s have plenty of bass, they're kind of boomy actually relative to what I normally listen to, but they hit bass notes in a subtly distorted and less than satisfying way. The measurement charts from innerfidelity objectively confirm the T1's bass distortion. Very common in $500 and under headphones; unacceptable for a $1,400 flagship.

2. The treble sometimes has what I can best describe as a subtle but annoying form of that "listening to treble on a cheap pair of ear buds, or a clock radio" effect. I'm obviously not saying it sounds like a clock radio, but let me see if I can put it another way. If you were to play a tone that smoothly goes up in frequency, it would not sound smooth on the T1. The T1 produces some treble frequencies at much higher DBs than others and this is not flagship sound. Very rarely it produces a particular treble frequency at such an unexpectedly high volume level that it causes that fingernails on a chalkboard effect. Good treble should be smooth, not jarring. Listening to classical music on an HD800 will exhilarate you. The Audeze wasn't as good as the HD800 in this respect, but it was no slouch and played smooth treble. When it comes time to play those songs and parts of a song on the T1, all it does is cause you to purse your face in disappointment. Again, if you read the innerfidelity charts for the T1 it's all there in objective science. The treble response is a mess with these, and my ears confirmed it. One important note about this issue: please keep in mind that one, just one, "fingernails on a chalk board" treble note can ruin an entire song for you. That noise stays with you. Mid-tier headphones either try to be airy, and have this effect or, more commonly, they just punt and roll off the treble. That's fine at that price range, but I don't ever want to hear that uncomfortable sound out of a flagship.

3. The midrange, to its credit, is very good, maybe even slightly better than the Audeze and the HD800. I couldn't definitively say which was better, but I had no complaints about the way the T1 reproduced voices, and I was impressed by the detail of its voice reproduction at times as it did things the other two could not do, in certain spots, particularly with a mid or deeper female vocals. So I will give it that. If I were just listening to people talk, or singing acapella in a middle range octave, I might choose the T1 over the HD800 and LCD XC.
 
4. Its detail is excellent, better than even the HD800. But since the HD800 was getting close to that "maybe this is so much detail that you're taking away from the joy of the music" territory, this may have gone over that threshold. I actually really like detail, but combined with the T1's other problems the excess detail was too much. But if you need to do an auditory detail spotting test, use these.

5. Instrument separation is also excellent for the same reasons as above. The way those instruments sound, though, is another matter as described above. But they're separated well.

6. Spatial imaging is, as expected, not anywhere near as good as the HD800 but better than the closed back LCD XC.
 
7. With its somewhat punchy bass and erratic treble, the T1 is more fatiguing than the HD800 or LCD XC.
 
A few other notes. For some reason people had me expecting these to be heavy like the Aude'ze but they're not heavy at all. They're in the HD800 territory in terms of comfort; very comfortable, so don't let that be an issue. They not made of fancy material, unlike the Aude'ze. They seem to have the build quality of your average $100 headphone. The cables are also not detachable which is very unusual. The case is a beautiful and compact aluminum. Very nice case. I uploaded a picture of the case so you can see. Much smaller and lighter than the needlessly big and heavy HD800 case and much nicer than the plastic audeze case. The T1 is also not unusual looking like those other two so you won't attract attention to yourself by wearing it.
 
If I could summarize by analogy, a Mercedes E-Class is a great car in its peer group, but if it tries to compare itself to S-Class AMGs, Bentleys and so on, it's a low performer. Same with this. It would get a higher rating if its MSRP were lower, but I have to rate it like a $1,400 headphone.
 
And to settle that mystery alluded to earlier, there is a perfectly logical explanation for why Beyerdynamic allows authorized retailers to sell this for $750, it's the only way they can clear inventory when trying to sell this for $1,400.

As I noted in my reviews of the Alpen E17 and the O2 amp, those two did nothing that my laptop couldn't do. However, unlike those two products, this thing might actually be doing something. I sense a little more bass and treble coming out of my HD800 which makes some songs a little bit more interesting. Not all songs -- for example, Swan Lake definitely sounds better on my laptop's dac -- but certain pop songs sound better on this.
 
To give you a few technicals, this has the same DAC chip (ESS9023) as these much more expensive DACs http://www.alldacinfo.com/?tag=es9023/
 
I don't have specs on its wattage output, but my ears can confirm that it is incredibly powerful and loud, so I would guess its wattage is impressive.
 
Due to its $40 or so price, this is a no brainer 5 stars.

The objective facts
 
Background: I listen to music on a higher-end (purchased for $800) Asus laptop, or my Galaxy Note 2 smartphone. With my SRH940s, the phone sounds better in terms of sound signature, but with my Sennheiser HD800s, the laptop sounds better for some reason. But they're both very close. All of these experiments were done listening to music on Spotify 320kbps; that's how I listen to headphones 99% of the time so that's the only way to test for my purposes.
 
How I tested this: I connected the O2 amp, with low gain, to my laptop's output jack. I set the volume of the O2 amp to its highest level (in other words, I controlled the volume of the music from my laptop's volume meter). The playback was set at 24bit / 192 khz (basic windows audio lets you pick this option). I plugged the HD800 into the amplifier.
 
The first thing I noticed was that this setup didn't cause the HD800 to be that much louder than it was when I simply plugged it directly into the laptop. In other words, with the O2 amp's volume set at max, and my laptop volume set at 25%, the headphones had close to the same volume as when I plugged the HD800 directly into my laptop and set the volume to 25%. So my laptop has as much power as this thing. Then I turned up the volume to the maximum and used a decibel meter to see how loud the two could make the headphones, and again, very similar. I repeated the above with the phone and got more or less similar results. 
 
Subjective observations
 
Next I cycled through a few songs that are very well recorded, to see if they sound better on one vs. the other. I listened once, twice, three times, again, again, focusing on very specific parts of the song, often playing 10 second portions of a song and repeatedly alternating between the two sources. I could find nothing. I would often focus on one tiny detail in a song, to see if the O2 and computer produce it the same, and they could. When the O2 was driving the phone, it had the phone's less desirable sound signature, and when it was driving the laptop, it had the laptop's sound signature, but the O2 didn't change the sound at all. I thought an amp was supposed to improve the sound of my "power hungry" HD800, but this did nothing. However, commenters say that this is exactly how it's supposed to work. In other words, it's not supposed to change the sound at all. So I guess I can't rate it poorly for doing what it's supposed to do.
 
Conclusion: If you have a severely underpowered source and need power, this will deliver it. But it could do more in this respect. It's not underpowered like some of those pathetic portable amps you see out there. But in my opinion, a $130 desktop headphone amp should provide boundless power, as much as you could ever want. When you buy a desktop amp, you should no longer be concerned about not having enough power. You should be concerned about keeping the volume low so as not to blow out your ears. To provide technical stats, on its website, it states that the O2 can only deliver a maximum of 88mW at 600 ohms. Well what if you're trying to drive a T1 or another 600 ohm headphone? Is 0.09 of a watt enough? Again, it has power, but you might not need the little bit of extra power this provides, and you might be fine sticking with your laptop or phone's amplifier. In light of the fact that it costs $130 and sits on your desktop, but doesn't have huge bountiful power, I'll subtract 2 stars. I'm just not sure why you would buy this if you want a desktop amp.

Will fill this in later but based on the fact that it absolutely kills every single song and genre of music that I've throw at it, the final rating is clear.
 
Edit 1: After listening to this and the Aude'ze LCD XC for four days, I've reached a point where I will never grab for the LCD XC if the HD800 are available. The HD800 simply sound more natural (all of the other headphones I have sound "synthetic," like they almost auto-tune or digitize the sounds very slightly if that makes any sense. With the HD800 it sounds like the band is singing and playing right in front of you.). The imaging on the HD800 is also incredible. It's like there are 10 speakers spaced all around your ears, each firing off in turn. Therefore, I called Aude'ze and the retailer and asked if I could please return them. The Aude'ze person said I would have to pay a 15% ($300) restocking fee, which I mention here only because it shows Sennheiser's superiority (they don't charge a restocking fee if you return the item within their 30 day money back guaranty period). Sennheiser is first class all the way.
 
Edit 2: OK I found a design flaw. On the outside of the headphones, around the drivers, there is this very thin aluminum foil type cover/enclosure that I keep accidentally touching with my fingers when taking the headhones on and off, and which seems like a weak material that will eventually tear as a result of this touching.
 
Edit3: To give you an example of the auditory magic performed by the HD800, open "the way you make me feel" by michael jackson, bad 25th ann. album, on spotify at 320 kbps. The whole song sounds great but focus especially on the drum that kicks in every 10 seconds or so. You hear this particular drum beat in the first four seconds of the song, at about 11 seconds, at 20 seconds, at 27 seconds. . . . The HD800 reproduces it amazingly, even providing that special and very faint echo that is produced by a real drum. If you can find a headphone that produces that drum beat better, please post it in the comments. The reason I like the HD800 is that it can make well recorded music like this shine like no other headphone.
 
Edit4: On the other hand, with the HD800 you'll find yourself opening your favorite song from the past, hoping for the magic described above, only to discover that the song was poorly recorded. In these cases you need the right amp to mellow things down. Perhaps a tube; for me my Yamaha stereo receiver's output jack works well. But I am not going to ding the HD800 for making bad recordings sound bad, because I think it's solely the fault of the recording engineer but it's a complaint you'll hear from many HD800 users. Fortunately, there are enough very well recorded songs out there for me to enjoy the HD800.
 
Edit5: I just discovered a great use for its super long wire, using it to listen to TV and movies! More outstanding sound.
 
Edit6: One other advantage of this headphone is that, because its drivers are so far from your ears, there is less risk noise induced hearing loss.They are more like speakers in that sense.
 
Edit7: Out of curiosity, I took the time to set up my stereo receiver properly in 5.1 surround mode. I used its microphone to perfectly calibrate each of the speakers, placed all around me, left/right rear each 3 feet away, and the others 10 feet in front, all perfectly calibrated so that no one sounds louder than the other. There is also a subwoofer in this mix. What did I learn? That this setup (which costs about $1,000 total including the receiver) beats the HD800 in every song. The HD800's benefit is that it sounds more "natural" and realistic than other headphones, but if that's what you want you should just stick with speakers, which offer better detail (and details are presented in proportion, not like headphones which make details sound louder than they should), better spatials, better sound -- just better. My conclusion from this is that although the HD800 are the best headphones I've ever tried, they can't beat a proper speaker system, which makes sense because no amount of magic engineering could turn a 1-2" driver into something that can compete with perfectly placed full sized speakers. I include this so that no one, who has the room and privacy to enjoy speakers, wastes their money on an HD800. Headphones are for people in apartments, people with families and people on the move. If you have the room, go with speakers.

I have an odd history with these headphones, which I'll explain in detail so no one is misled by my rating. If after reading it, you think the rating is unfair please let me know in a comment.
 
My first headphones were in the sub $500 range, and I have always wanted to own one "best" headphone so that I could stop wondering if my music could sound better. I went around my city investigating options. In doing so, I listened to the LCD XC at a store where they sounded amazing. Great bass, mids and treble. I was really impressed. However, that store didn't have inventory. After that experience, I wrote an earlier review on head-fi giving these five stars, which people didn’t like because it was based on only five minutes of use (see comments below) and so I took that review down.
 
I spent the next week debating whether I should buy them. Eventually I saw them new at another retailer and pulled the trigger. I took them home and they were ultimately good, clearly better than anything in the sub-$500 range that I used to listen to.
 
Now here's the first disclosure. I primarily listen to all of my headphones from my portable MP3 player and my laptop. I used the MP3 player when trying the LCD XCs at the first store and these two items are what I use 99% of the time. I have a large receiver with a 300 ohm high powered headphone jack, but I don't notice enough of a difference in the quality of the music to use that instead of my portable items. Please keep in mind that Audeze's website claims the headphones are easy to drive, they have low impedance, and I confirmed in speaking to their tech support that they were designed to be driven by things like Ipods (although that person also said they will sound a little better if powered by a high-end amp/dac). So if this kills the credibility of my review then stop here and move onto a more helpful review, but I'll go on for others who might be interested in what happened next.
 
I still had a nagging feeling that there was a better headphone out there. I noticed that Sennheiser had a no questions asked 30 day money back guaranty on the HD800s – and I decided to order them, planning to return them if I didn’t like them. Long story short, after four days with the HD800 and the LDC XC, it became clear that based on my personal tastes, I would never use the XC if the HD800s were available. That's why I deducted 1/2 star from the LCD XC. If a headphone isn't the best in its price range, it can't get five stars. That being said, there is no way I would give this less than 4 1/2 stars on sound, and it is entirely possible that based on your tastes you would prefer this over the HD800. The LCD XC did magic with a few songs and performed excellently on all. It's like a Rolls Royce vs. Bentley thing. Both are excellent but you may have a preference. The fact that the HD800 is open back may also have made this an unfair comparison.
 
Now let me explain why I took another 1/2 star off. When I realized that I would never use the LCD XC, I went back and forth a bit over what to do, wondering if I could just leave them on the shelf as a decoration, ultimately deciding there was no point to keeping them. I planned to try the retailer, and if that didn't work, then I would sell them on Ebay. I called the retailer and asked if I could please return them, since I had only used them for a few days. He said he would only give me store credit. Then I tried the Audeze corporate headquarters to see if they could take them back. At first their manager said there is nothing she can do because it's the retailer's decision. I asked her why Audeze doesn't have Sennheiser's satisfaction guaranteed policy and she said that Audeze does have such a policy. She said if I had purchased from the Audeze website, then I could return them in 30 days with a 15% restocking fee. I then asked why it should be any different if I buy from an authorized retailer and she kindly agreed. She spoke with the retailer who matched the Audeze company policy. I gladly paid the 15% restocking fee (a total of about $300 due to tax). I'm very happy to pay only $300 to unload these because had I sold them on Ebay there would be a 10-15% Ebay/Paypal fee, I would have to ship them and I would have to deal with a potentially dishonest buyer. So thank you to Audeze for accommodating me.
 
But that leaves the question of why Audeze charges a 15% restocking fee if you don't like their headphone. On the one hand I can understand how it's designed to deter looky loos who buy stuff, try them out and return them. But then again, if you are operating in the $2,000 to $3,000 headphone space, that should be a cost of doing business. You should not charge this much for a headphone unless you are confident enough in your product that you will let people try them out for free, like Sennheiser does. For that reason, I felt these should lose half a star.
 
Finally, the reason why I tool another 1/2 star off. Those in the headphone community know that you can easily pick up a open-box Sennheiser HD800 (see Sennheiser's own website or Crutchfield), or Hifiman HE-6 (these are harder to find but you can get them from authorized retailers) for a huge (20-25% or so) discount. These have been fully inspected by the factory and come with a warranty. However, I have never seen such offers with Aude'ze headphones. Which raises the question of what Aude'ze does with all the headphones that are returned to them, and implies that they sell them as new. Now I want to be clear that I could not confirm this inference and so I may be completely wrong, and Aude'ze may not be selling returned headphones as new headphones. If anyone has an answer please post it in the comment. But from what I can see that seems to be the case.
 
One note about comfort. I'm not at all a super muscular, but my average neck is strong enough to easily support this for hours and hours of listening without any annoyance. They're clearly heavier than the HD800, which feel like a feather, but the extra weight really wasn't an issue with me.
 
Finally, on those beautiful looks. As you can see in the pictures this is a very attractive headphone. This could be the nicest looking headphone made today. In general, all of Audeze's headphones are these huge wooden monsters that look impressive (and do not underestimate how big this is, this is much bigger than your average over the ear headphones, which are already big). However, you should consider whether that's something you want because it will definitely bring attention to you if you wear these anywhere in public.
 
I hope this was helpful to readers.
 
Edit: I just discovered that I need to credit this headphone for its efficiency. I could get this to put out ear thumping bass, screeching (in a good way) treble and solid mids with my cell phone (a Note 2) and my laptop (a Realtek 269 DAC + 2.3 W amplifier). I didn't see much of a benefit by moving to my receiver's powerful jack. That's apparently a major engineering feat in a planar magnetic, that I did not appreciate, so adding 1/2 star.

I use these when exercising next to cars. I used to use sealed closed back headphones which didn't block out noise well, but these definitely do. When outside in a loud environment and wearing these, I set the MP3 player's volume to the same level I use when listening to these IEMs in a quiet room. The isolation is that good (I use comply sleeves, but the sleeves included were also pretty decent).
 
However, I was definitely disappointed by the sound quality, relative to a $300 over the ear headphone. I will never choose this over a headphone if listening to music in a quiet environment. The selling point on these isn't sound quality, but rather noise isolation. I won't take more than 1/2 point off for sound, though, because I imagine all IEMs are like this and that this is good IEM sound for $300.
 
One other problem is that the wires are really stiff, a design feature I don't understand. Lastly, putting these on isn't as simple as putting on a pair of regular headphones, you'll have to spend 15 seconds or so seating them correctly to get a proper seal.

These headphones should be valued for providing an ultra-bright sound signature not offered by any other headphone that I'm aware of.

Comparisons with the HD800: If you compare the 30hz and 300hz square wave measurements from the innerfidelity charts between these and the Sennheiser HD800, you'll see that the two are almost identical. I own the HD800s and this, and I can say that the SRH940s are much much closer to the HD800s than their prices would suggest. The HD800s handle bass and mids better, and their treble is a little smoother, and they have better spatial characteristics, but the two are close, with the SRH940 being brighter.

More on their brightness: These are possibly the brightest headphones made today, which is something I appreciate. They are almost like taking the tweeter out of your stereo speakers and putting them up to your ears. OK that's an exaggeration but do not underestimate how bright these are. On their bass output, they're not like a clock radio that can't put out bass. If you play a bass heavy song you'll hear the bass notes and they can go quite deep on the frequency chart. But if you like to hear a bunch of bass on all your songs, then you'll need to use the equalizer to turn these into the headphones you want.

Ultimately, if you want to know what your music sounds like with excess exaggerated treble (and sometimes it sounds better) these are the headphones to own.

The only problem is that they put pressure on one spot on the top of my head if I wear them for a long time (the cushions were designed poorly and they focus the weight on one spot).