This is odd coming from apple to have one of the cheapest and best sounding usb c to 3.5mm adapters on the market. It is significantly better than some phones with crappy 3.5mm output quality. This is an easy way to give your phone or your computer a good improvement in sound. It works flawlessly on my phone and computer. Durability remains to be seen but so far I am happy with the sound. Hearing no obvious flaws, I am only using this to drive my low impedance headphones like my grados, ksc75 and westone iems. Some 3.5mm ports on phones that I have plugged my IEMs into make a pop sound but not for this adapter which is good.

A must try for anyone curious about usb c to 3.5mm audio.

Source and amp: Using the Objective O2 amp and ODAC combo
 
Build quality and comfort:
 
Headband pad is a little too firm, may need break in. Initially putting them on, the headband is feeling is evidently there but with time it slowly disappears. Earpads are not the softest nor particularly t thick but the low clamping force and lightness of the headphones make it acceptable.
 
Build quality is ok but reasonable in keeping the headphone light weight. Only the cup holder part of the headphone is magnesium, the rest is plastic.
 
Good driver depth for people with dumbo-like ears as they are angled steeper than the HD558 and AD900X.
 
Sound:
 
When I put these , I was quickly reminded of my HD558 upgraded in almost every aspect. The sound signature is similar; forward and engaging but not in your face like grados. As someone who mostly uses Grados, I did not get the impression that these are dark sounding at all; HD558 is darker sounding. The highs may not be the most extended but it is not offensive making it well rounded for just about anything thrown at it. The sound is more crisp sounding than the HD558; clarity across the board is an improvement on the MA900. There is a good amount of detail but do not expect micro detail level extraction. The midrange sounds lively and works quite well with voices without sounding nasally for both female and male voices; I thought it worked well with both. The midrange sounds layered and is transparent; it is not thick sounding. The midrange is evidently clearer than the HD558,  especially vocals on the MA900 I much prefer over the HD558. The whole sound in general sounds more open and spaced apart. Sometimes vocals on the HD558 sound like they come from 1 point in the middle where as it doesn't on the MA900. The highs and mids work well together and sound balanced to me without one being too overly powering. In the bass region though, the HD558 hits harder and the low frequencies are louder. Low bass rumble is hard to hear on the Sony; maybe it is due to the housing enclosures as the HD558 is more encapsulating than the MA900 in physical design. I find the bass even lighter than the AD900X on the low end. I can totally picture a new buyer asking where the bass is; the only clear weakness. For me, it is fine but I can see someone wanting more. Both have a good midbass impact to make them enjoyable with pop music. The sound stage is not significantly wider than the HD558 but expect some improvement in depth and width just don't expect a world's difference. There is definitely a better sense of air. The separation is better on the MA900 vs the HD558; it is simply easier to differentiate fore ground and background. Also maybe for some office users, it's important to note that the MA900 leaks out sound more than the HD558 so you may annoy some coworkers nearby almost as much as Grados.
 
Conclusion:
 
Would I buy these again? Yes I would. I may be looking to sell my HD558 now. I like the whole sound and wasn't sure what to expect in terms of sound. They met my expectations for the price and in some aspects exceeded. I thought the sound stage would be wider but I can't imagine anything wider than the AD900X. Not 100% sold on the general consensus that these are the most comfortable headphones ever but we'll see what happens through pad break-in although they are certainly light but weight alone does not determine comfort. If you like the HD558 but didn't like the midrange much, you may want to give these a try. Other than the bass, it's a clear step above the HD558 in every aspect in terms of sound. Crispy is the one word I would use to describe these.

Note that my impression is with the foam removed from behind the grills.
 
HD558 is a very good headphone that I would recommend to everyone to listen to. Easy to listen to, not offensive sounding or dark sounding. Good price.
 
No amp required.
 
I have had the HD25-II before and the HD558 excels in every aspect except in the bass region.
 
Comfort: Pads could be softer, feels noticeably firmer than the pads on a ATH AD900X. Weight is ~260g which is not very light nor heavy, similar to that of the AD900X. Low clamping force. There is a little bulge on the rear side of the inner cups that may touch your ear creating discomfort over long listening sessions but should be fine for most people with flatter ears. Coming from Grado, this is noticeably more comfortable but not as comfortable as my AD900X mainly due to the pads' softness and the steeper angled drivers. HD600 and higher pads are noticeable softer. The pads collect lint quite easily. Acceptable comfort.
 
Highs: Does not stand out; does not irritate. Not the loudness nor does it have that sparkle a AD900X does. Cymbal shimmers are not as clear or obvious as on my Grado SR325 or AD900X. I don't think anyone who listens to classical a lot will enjoy these headphones. Highs do not try to grab your attention, not very extended. The highs suit others genres quite well as they are not offending. The highs combined with the forward midrange makes this headphone sound bright. I never get the sense that this is a dark sounding headphone at all. HD 558 is the less fatiguing headphone compared to the AD900x as the highs are not quite as loud.
 
Midrange: Forward sounding but not in your face or shouty. Can sound somewhat dry judging from vocals; don't expect liquid mids. For the price , the level of refinement is expected. Not very transparent sounding . There is some graininess and sibilance compared to some higher priced Sennheisers like the HD600. Higher end headphones sound more rich and resolving; it is hard to mistake the mids of the HD 558 as high end but again, considering the price I think most will be happy with the performance. 
 
Bass: Midbass is good to add to the engagement of the sound signature however don't expect to hear anything below 50 Hz very clearly and evidently. The bass texture and decay in the lower end is hard to hear but it can be hard for most open headphones to be great in this area. Don't expect these to make your head rumble. 
 
Details: Not the headphone that will make small details pop; it's there but I will have to listen to it a little closer compared to a AD900X which reveals tiny nuisances more effortlessly. When the track gets quite busy there is some smearing which is expected for a headphone of this price but really it is not bad at all. I think those who are looking for their first decent cans will be satisfied.
 
Soundstage: Not super wide or narrow, could be considered just right depending on where you're coming from. It does not sound artificial like some 3D effect and there is decent depth as well but not very deep. No obvious flaws or gaps. The AD900x is an example of a headphone with a wide soundstage however I feel the HD558 has a more balanced soundstage meaning that the soundstage is more evenly spaced out. The AD900x can make things sound as if the sound is only coming from the extreme end of the soundstage with some voids between the center of my head to the edge of the soundstage. Despite this, the AD900x can sound incredible with the right music sounding completely encompassing where the HD558 will fall behind. It is sort of like a movie theatre experience vs a home theatre surround sound experience.
 
I do not like the build quality very much. There are small cracks developing which is a very common issue on the side of the headphones where the Sennheiser logo is near the headband. It is disappointing this has not be resolved since the HD 555 headphones.

Note: Impressions based on using new bowl pads as worn in bowl pads can change the sound significantly.
 
RS2i reminds me of the SR125 I once had, bright and not as full bodied sounding as the RS1. My first impression was that it sounded quite detailed then I realized it is because the bass presence is not as strong as the RS1 so I was a little fooled at the beginning. It is not any less aggressive than what you'd expect from a grado headphone.
 
I will be comparing against a buttonless RS1 (not RS1i or RS1e) for this quick review using bowl pads.
 
Highs: Pretty much right up there with the RS1, well extended and detailed. It doesn't sound less refined. I could not tell if there's any difference in this category. This aspect is the closest to the RS1, the mids and lows is where things start to separate the RS1 from the RS2i.
 
Mids: The presentation is a little different. The midrange sound thinner on the RS2i so it seems a tad recessed to the RS1. It sounds a little more "hollow" compared to the RS1; imagine a somewhat V shape where the mid and bass is a 0dB and the mid is minus a few dB. This is most noticeable when comparing vocals as I find myself needing to turn the volume up so the vocals sound as loud as on the RS1 but the highs become too much. Guitars still sound great though, but again thinner on the RS2e compared to RS1. Cymbals sound more distant and slightly less refined as I heard some graininess. Since the mids are more recessed the highs are more evident, making it sound brighter than the RS1.
 
Lows: RS1 slams harder here and the mid bass is more present as well. It is easy to hear the difference for the kick drum; it's more quiet on the RS2i. Bass guitar is very easy to follow on the RS1 compared to the RS2i. This could be the difference in cup height difference as the RS1 has deeper cups. This makes the RS1 have more body than the RS2i which sounds lighter in comparison. To me this category combined with the midrange difference is what is most obvious. The RS1 simply has a fuller sound than the RS2i and the RS2i does not excel in any aspect in regards to bass vs the RS1. 
 
Summary vs RS1:
Highs = Equal
Mids = RS1
Lows = RS1
Bright = RS2i
Soundstage = RS1
Detail = Equal
Comfort = Equal 
Build quality = RS1
 
I think someone who hasn't heard the RS1 compared to the RS2i will be very happy with it compared to the prestige series plastic headphones. I just wished the midrange was fuller but I guess that's what the RS1 is for.
 
I feel like the RS2i is more suited with comfie pads from the 90's that are much closer to the ear than today's comfie pads. The midrange is much fuller as well as the bass presence. It makes a massive difference to the whole sound presentation. No longer do I hear a weaker and bright sounding headphone compared to the RS1. What I heard is a more forward midrange with great vocals and full body midbass. I am not sure where these comfie pads can be obtained as I have them from my headphones that are quite old. The old comfie pads do not sound the same as modern day comfie pads at all; modern comfies sound pretty much the same as with bowl pads.

This little player can take a beating. I am not careful with this device and I've dropped it many times on all types of surfaces and it keeps going. I have had my player for nearly 3 years now and the menu button now requires a harder press to respond. Headphone jack will be looser with wear and tear, it should be fine if you do not change headphones much or if you don't tug on the headphone cable to pull the clip zip out of your pocket.
 
This player has a OLED screen, which is immediately apparent when using it at night as black does not emit light.
 
Sansa clips have measured well historically in the past and this is no different. It has an output impedance of less than 2 ohms which is great for low impedance headphones as it does not change the frequency response of my headphones. I pair this up with my Westone UM2 and it sounds great. You do not need to spend a lot for great sound; only if you are driving something that is likely not very portable for outdoor usage. I do not feel compelled to buy anything else until this thing is dead. I don't need a multi hundred dollar "audiophile" player to improve my UM2. My UM2 sounds just as good out of this player compared to my desktop O2+ODAC combo. 
 
I also installed rockbox. I cannot think of a better player for the price that has rockbox compatibility let alone expandable storage (I am using a 64GB card) . Having rockbox makes this player very flexible in terms of settings. This makes the player superb and greatly improves its usability from its basic stock UI. I really like the settings to change the screen time out length as well as where the player loads to when powered on; I chose to go to database. I never changed the volume by accident in my pocket when it is not locked. My microsd card stays in just fine, never popped out by accident and I didn't tape it in or anything.
 
I think I wish I could do is remove the clip part as I usually just leave this player in my pockets.
 
They've dumbed down the new clip sport to support only 4000 files (2000 from sd and 2000 from  internal) which is more reason to buy another clip zip! Also the new clip sport is not rockbox compatible!!
 
I will be glad to buy this player again without hesitation.

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.

Note: This headphone is for music that does not rely heavily on bass for enjoyment; it doesn’t have that body at the lower end that is for that genre. If you listen to mainstream pop a lot, these are likely not for you. These headphones are not all rounder headphones like the HD558 which can sound good with everything but does not wow me in ways the AD900X can.
 
These headphones do not have that metallic sheen over the upper midrange and highs like the AD700 which turned me off. That was the least enjoyable aspect for the AD700, not sure if it is fixed on the AD700X .
 
First thing I thought was that these headphones lacked dynamics when I put them on because they sound light in the sense that they don’t exert the authority in bass. My first day with them I did not like them but that’s because my mind did not yet adjust to its sound signature. It took a week for my ears to adjust and to enjoy these headphones. I am glad I did as I know where the headphones excel .
 
Comfort:
The comfort is excellent and these headphones simply disappear overtime. I never felt the clamping force was too much at all. The drivers are angled and the pads are firmer than the AD2000X which is great as my ears do not touch the driver grill. These are probably the most comfortable headphones I have ever owned.
 
Build quality:
Feels solid, looks appealing. Not much to complain about, no creaking anywhere.  I prefer they didn't cover the "headband" with rubber but I guess ATH wanted to make users spend on th AD2000x for that...
 
Sound
 
Mid:
These headphones have a bright sound signature and lush mids; AD2000x is even more so. Some people like the mids to sound a little more recessed as it lets them perceive it as clarity since the mids are more in balance. The midrange is forward on these; just like how I like it on my grado but the mids sound thicker meaning at times it could sound very rich or muddy depending on the song.  As mentioned many many times already, these truly excel with female vocals; sound very lifelike because it does not sound sibilant with female voices. Female voices sound breathy Male voices sound quite good as well but nothing truly out of the ordinary which is perfectly fine. If you really like listening to female singers, I highly suggest trying a ATH AD headphone sometime.
These headphones offer a good amount of detail, better than the HD558 at picking out nuisances for example plucking on guitar strings is more distinct and edgy. The soundstage also helps with these as the spacing makes things seem less blended in. The background seems more obviously separated from the vocals. Since the midrange is forward, I feel it is hard to perceive depth with these. The soundstage is fairly wide left and right, almost right up there with the K701. Listening to music which already has a wide soundstage because of the way it was mixed will sound quite good on these. I don’t think these headphones sound particularly good with rock music but it is acceptable as the midrange makes the guitars sound too thick for my liking.  
 
High:
The highs give everything that crisp top end but depending on the song it could be overwhelming but I am personally used to it by now as I am with more bright headphones. The higher end ATH AD headphones have toned down the highs quite a bit, doesn’t sound nearly as bright but further improves the midrange and bass impact. AD2000x highs sound blanketed compared to AD900X; it doesn’t stand out. I am personally not sure if I want to give away the soundstage and highs going to the AD2000x for its magic mids and better bass.
 
Bass:
Do not expect it to amaze you in anyway. Expect light sounding headphones and keep expectations of bass very low. Of the mids and highs, bass is the frequency range I personally care least about which is why I decided to give ATH a try.
 
If you listen to the right songs (such as songs from M83, Explosions In The Sky, She & Him, Sara Bareilles, Lindsey Stirling) these can wow you but on the other hand, listen to something it is not suited (Bullet For My Valentine, Linkin Park,  Lady Gaga, Sum 41)  for then the wow factor is gone and it becomes an average sounding headphone. You can cripple these headphones by playing the wrong music really. When it sound good it is amazing but when it’s bad it’s not pretty at all. 

This is the best grado I have owned and I put these about any RS1i/RS1e and RS1 I have heard (I didn't hear the pink driver RS1 yet). 
 
The SR325 was purchased in 1995, SR125 roughly 1997
 
First thing I will talk about is the bass not because I'm a bass head but because there is a very big difference between the two that even words can't quite seem to describe correctly and precisely.
 
Bass:
When I first put on the SR325 for the first time, it didn't seem that much more bassy but at the time it was only for a minute at most which is not enough to make a valid impression at all. I listened to them for awhile then I stepped down to the SR125 , all of the a sudden the SR125 sound too light and weightless. The difference in bass in easily heard when comparing the two. I always thought the SR125 lacks in the low end and the SR325 is exactly the answer to it. The SR325 has a nice bass presence when a song calls for it, it slams hard and I can hear some of the low rumbling in some songs. There really is no comparison between the two, the SR325 do anything bass related better than the SR125. There is more bass texture and quantity; I never felt a lack of bass with the SR325 in any song. The bass gives the music a nice weight and body not present on the SR125. I have never heard the bass guitar so easily as I have on the SR325 of all the grados I have owned. The bass follows the rhythm of the song effortlessly; the SR125 on certain songs sounds like it has holes as it follows a rhythm because it  can suddenly dive off when low bass can't be reproduced loud enough to be heard. The SR325 with authority makes the SR125 lack bass; never again did I yearn for more bass after putting on the SR325 right after using the SR125. PRaT in this category is unmatched by the SR125. The SR325 bass is not bloated in any way; it is full,solid and possess a lot of weight. It keeps up with fast and tight bass rhythms with no effort. Bass slams and decays; something not easily heard on the SR125.
 
Midrange:
SR125 has a more modern grado sound, yet they don't sound harsh at reasonable listening volumes. I can hear that the upper mids are noticeably boosted; on the SR325 it's not like that. The SR325 only has a slight upper mid boost. The SR325 has a certain smoothness in the midrange that makes it sound transparent. It is not very colored at all compared to the SR125. The SR125 sounds very hyped compared to the SR325 which is more mellow. The midrange on the SR325 is full and lush, the lower midrange is more plenty than the SR125. Voices on the SR125 can sound thin but on the SR325, it is the best I have heard out of all the headphones I've owned. I never really thought a grado can present vocals in such a way the SR325 does; the RS1i does not compete against the SR325 in this area. The vocals on the SR325 is simply pleasing to listen to, something I couldn't always say even on a classic RS1 which is one of my top favorites of all time. The weight of the vocals is spot on. I have never cared much for vocals over guitars but this grado really changed my perspective; I now appreciate the beauty of vocals almost just as much as electric guitar performance. The midrange on the SR325 has a slight warmth, not overly warm like the RS1i. The SR325 is only sibilant if the recording has it; it will not create sibilance like the SR125 can. The SR325 sounds more mellow whereas the SR125 has some more excitement because of the upper mids. The SR325 does not present anything in a manner of extremely colorization, only just enough to give singers for example some emotion. The metal cups do not give the SR325 a cold steely sound characteristic at all. Electric guitars sound like they really grind and crunch on the SR125 and is definitely on the thinner and bright side; SR325 on the other hands sounds more full and rich again while being non offensive but not being polite and shy either. The midrange is where the SR325 and SR125 share most of the similarities despite SR325's better low midrange presence and SR125 upper mid peak differences; they both really do sound great for different things. The midrange on these vintage grados are very close to perfection for me; they really both do sound beautiful in this region. Sibilance is really a rarity on both cans 95% of the time. On the RS1, the guitars would sound great but sibilance in vocals (harsh shh) was the cost; I'm still wondering how these SR125/SR325 can sound great at electric guitars but with no sibilance in vocals or why the RS1 has sibilance in vocals if it's not caused by he upper mid spikes. SR125 sounds like the RS1 in upper mid peak in terms frequency response but the SR125 doesn't seem to compromise anything. The SR325 is probably the grado that also made me realize just how good everything sounds when weight of instruments in the recording to me sounds like it has its proper weight.
 
SR125 midrange may sound too thin on bowls. Comfie pads are more suited for the SR125 since it brings up the bass and midrange so it does not have a thin sound.
 
Treble:
The SR125 has a very evident boost. On a few occasions, highs can sound shrill. The highs on the SR125 tend to stick out more than the SR325. The SR325 treble does not sound boosted or emphasized in any way. The aluminum cup doesn't make the SR325 sound brighter than the SR125 at all. Does the SR325 sound bright? Maybe coming from a HD600 but not from a SR60i. The treble is very pleasant to listen to, it is not very aggressive and would never annoy or offend me in any way. SR325 is not harsh at all; no ears will cringe from the sound produced by these. The treble is very refined; it sounds true to the recording over the SR125; the SR125 can exaggerate the highs.  The decay in micro details can be heard easier on the SR325. The SR125 I feel is a headphone that most people can agree to it being bright when heard. It would definitely need more time to get used to than the SR325 but once I did get used to the SR125, I found it acceptable. Some of the plucky of an acoustic guitar is more edgy on the SR125; it sounds more hard where the SR325 is simply "natural" because there really is no exaggeration to be heard on the SR325. The SR325 really reminds me a lot of the vintage SR60 I had, the treble between those two sound very realistic compared to the SR125. HD600 sounds like its treble is just there, just enough to be heard; the SR325 isn't recessed. Its treble simply doesn't demand for attention by becoming all splashy and peaky but it is easily heard without trying to listen for it (not that you ever need to for a grado)
 
The balance between the midrange and the highs on the SR325 is perfect. The SR125 sounds tipped towards treble. The bass on the SR325 does not overwhelm or hide any of the midrange or treble detail. The SR325 makes the SR125 sound like it could use a little more meat on the bottom end.
 
Soundstage:
Both are still in the realm of a grado but the SR325 is slightly wider and deeper because of the cup dimensions
 
Conclusion:
 
SR325 is one of the best grados I have ever heard and the SR125 is surprisingly very enjoyable to listen to and is no slouch either but the SR325 simply does a lot more right than wrong compared to the SR125 over a broad number of music genres. The SR325 is what I could call versatile compared to the SR125. The SR325 needs to be heard to be believed; you will know why this vintage sound is so sought after by some. After hearing the SR325, I wonder why grado moved away from this sound. Sometimes a person's tastes changes as quick as the tides in an ocean; in this case it might be John  . I feel that the modern sound has taken a step backwards from what it once was in the past from all the grados I have heard or owned so far in my life. I think anyone who is a fan of the grado brand should at least hear a vintage grado once in a life time, to know and appreciate the sound of the past. Does it sound better than its modern version? That's for you to decide upon listening but to me, it's a yes for both the SR125 and SR325. It would be a steal if vintage grados of their modern models were priced the same and sold today.
 
The comfort on the SR325 is somewhat less than satisfactory for me, the weight doesn't allow me to listen to them for a long time (which is a big bummer for me) but I enjoy every second and bit of sound I hear reproduced by it. I never thought I could say this about a grado without hearing a HP1000 but the SR325 presents sound with grace and power while being the most natural grado I have heard. ( I don't like using the word "natural" but that's all I could think of at the moment )
 
Vintage SR125 vs Vintage B RS1:
 
After listening to the RS1, the SR125 sounds thin and quite bright. SR125 sounds more airy though
 
Treble : SR125's boosted treble makes micro it sound more detailed but it can be fatiguing after some time. The highs on the RS1 is not hyped up but they both are still bright headphones. SR125 has a certain crispness to the sound the RS1 doesn't have, some may like this while some may not.
 
Midrange : The midrange on the RS1 is thick lush and colored compared to the SR125. I'm not 100% it is the wood but the tonality is not quite to my taste on the RS1. The SR125 midrange sounds thin in comparison. Vocals surprisingly sound better on the SR125, the RS1 is a little too thick for my liking. The vocals on the RS1 don't sound quite realistic to me at all, not as transparent as I would like it to me. What I hear on the RS1 is a bigger sound, definitely more full. The upper midrange is thicker on the RS1, but not as boosted as the SR125. Guitars sound good on both, depending on taste either can be preferred. I feel the upper midrange spike on the RS1 covers too much detail; when the guitar kicks in it sounds too dominant over anything else being played. I like electric guitars but this trait actually annoyed me the most when listening to the RS1. The midrange on both is more forward than the SR325 with bowls.
 
Bass : RS1 has more bass than the SR125 and has more body. The SR125 sounds quite tame here; it doesn't quite have the warmth and punch of the RS1. They both have less bass than the SR325.
 
Which one do I prefer? Hard to say, I like the bass and treble on the RS1 but I like the midrange presentation better on the SR125.
 
Vintage SR325 vs Vintage B RS1:
 
RS1 makes the SR325 sound like the SR325 is the most balanced and transparent sounding headphone of the two. I have stated above that the SR325 is one of the most "natural" sounding grados I have heard meaning it sounds the most uncolored and realistic.  The RS1 just reaffirms what I stated about the SR325. The SR325 sounds very airy compared to the RS1 without sounding weightless.
 
Treble : Where to begin, the treble on the SR325 sounds very refined compared to the RS1. It is like listening to a 128kbps mp3 file then going to lossless. The resolution of the treble on the SR325 is on another level. The SR325 has a crisp and clear treble that does not sound harsh; not a hint of grain. The RS1 treble sounds a little muted and due to the upper mid/lower treble spike it makes it very difficult for me to pick out details.  The details on the SR325 I can hear very effortlessly; I don't need to strain to hear them. The way the treble is presented with the midrange on the SR325 also gives the perception of a larger and wider soundstage. The RS1 sounds more closed in and intimate. The SR325's treble is capable of being sparkly not overly exaggerated but helped by the aluminum cups. Something as simple as a triangle sounds realistic and metallic like it should on the SR325.
 
Midrange: SR325 wins in transparency, this is the area that really beats out the RS1 the most. Any voice produced on the RS1, undoubtedly sounds better on the SR325; simply lifelike on the SR325. The SR325 never seems to sound sibilant with vocals at all. If the singer's voice is dry then it will sound dry on the SR325; it will not pave a smoothness over it.There's a certain colorization that makes vocals sound a little nasally on the RS1; the switch to the SR325 makes it more obvious.There is no weird colorization on the SR325; the RS1 sounds like it tries to make everything sound sweet and warm. It is similar to wanting to just drink water, but someone always adds some flavor to the water when I don't want flavored water. The RS1 has a certain warmth in the midrange not present on the SR325; this might be from the wood housing.The midrange on the RS1 is more aggressive than the SR325 and is more forward. RS1 sounds like I am in the singers' face, the SR325 sounds like I am in the first row. The layering on the RS1 is not quite the level of the SR325. The forwardness of the midrange combined with the upper mid spike makes the sound somewhat more two dimensional; sometimes it's hard to hear behind the vocals,guitars,drums. When everything gets too busy, the RS1 sounds like it blends everything together instead of separating it out like the SR325. I can always listen "deeper" into the music with the SR325 changing my focus into the background sounds or foreground vocals because of the layering on the SR325.  I actually hear the distortion on the guitars much easier on the SR325 than the RS1 even though the RS1 makes guitars sound louder. The RS1 makes nearly anything that sits between the upper mid and low treble sound loud enough to the point where it can sound grainy and lose its texture; I'm not hearing quality but rather quantity. The plucking and individual strokes on the SR325 are distinct. Everytime I switch from the RS1 back to the SR325, it sounds like the balance and clarity has been restored. I never thought I could say this about a RS1 but the SR325 makes it sound muddy and sloppy at times. The RS1 can sound grainy on recordings the SR325 plays back with no grain because of certain peaks and emphasized loudness of frequencies to a flaw.
 
Bass : The bass on the SR325 is more and it goes lower as well.  The bass on the SR325 is very solid and punchy on the SR325, the RS1 is slightly more loose and wolly sounding. Both have noticeable more bass than the SR125
 
Soundstage : RS1 sounds more closed in from the forwardness of the midrange and a lack of transparency in the midrange. SR325 sounds noticeably more open with more depth and width; spacious is the word. Audible differences but SR325 is not like a K701 in soundstage width just for perspective sake.
 
Weight : RS1 weighs almost identical to the plastic SR125. An aluminum cup is about 2oz heavier which does not seem like much but it is definitely noticeable when worn. I would preferably like to have the SR325 weigh lighter but the sound makes up for it.
 
I have yet to find another Grado that will make me give this up.

I have a pair of vintage SR60 with pink drivers dark driver cloth. They also have a black magnet. These headphones simply at the best value headphones I've ever owned.
 
Vintage SR60 sound smoother than current day SR60i and SR60e yet still maintain the same engaging sound. I found the best pads for these are the original comfie pads and these pads put my ear closer to the driver opposed to today's comfies which create a greater distance making them sound more similar to bowl.
 
Using new bowl pads will make the highs sound a little strident. It is more obvious the highs have some roughness and edginess to it. The bass impact will be reduced and the bass slam is gone from comfies. The midrange sounds will sound thin with new bowl pads. Once the pads are broken in, they sound closer to comfies except comfies still excel in all areas related to bass and the midrange is full on comfies.
 
On first listen I thought it sounded oh so similar to my vintage SR325 however upon further listening I found the biggest difference between the two is refinement and bass. High end grados will sound higher resolution meaning there is less sibilance to voices and cymbal hits while retaining the same signature. It will be like going to 128kbps mp3 to flac with more bass and stronger impact with a slight hint of a warmer / colder sound depending whether the upgrade is to wooden housings or aluminium ones.
 
Cannot go wrong with the SR60 if you want to hear what Grado is all about.

Intro:
I must say the UM2 sounds better than the UM3x which I sold shortly after few months. In short; it sounds more articulate,airy and more expansive. The UM3x sounded too bloated,closed in and collapsed to me; the soundstage was too narrow and the UM2 doesn't share the same trait which is great. The mids were too forward and the bass was too much, the highs are too soft and delicate on the UM3x; it didn't have the balance the Westone 2 does. UM2 sounds quite different from the UM3x and I can't see how anyone can say the UM3x is a definite upgrade from the UM2 in sound other than having one extra driver which doesn't mean much. The Westone 2 is probably the IEM I've kept longest, longer than the Westone 3 and the UM3x; I am quite fond of it. If I had to rate all the Westone IEMs I owned it would be UM2 >= Westone 2 > UM3x >= Westone 3 >>>>UM1
 
Note that I have seen two versions of the UM2, whether they sound different I have no idea.
The first revision has clear stress relief strains with orange comply tips while the latest ones have black stress relief strains with gray comply tips.
 
Physical differences
 
Shell size: The UM2 and UM3x share the same shell I believe and it is noticeably bulkier than the Westone 2; I could lay down on the bed with the Westone 2 and not feel a thing and I can't say the same with the UM2. If I had to estimate, I would say the UM2 is at least 33% bigger than the Westone 2. It is quite a bit thicker than the Westone 2. The glossy finish on the Westone 2 is more prone to scratches than the matte texture finish on the UM2 shell. Comfort I'd say the Westone 2 is definitely better, just plain smaller and lighter.
 
Cable: The Westone 2 and UM3x both uses braided cables but the Westone 2 is more tightly braided while the UM2 is not so. The cable on the UM2 is definitely softer and flexible than the Westone 2. If I coil up the cable on the Westone 2, it is harder to straighten compared to the UM2 meaning it likes to retain its previous shape. The plug on the two are different; UM2 being bulkier and Westone 2 being thin to fit on the devices where the 3.5mm socket is recessed.
 
 
Sound Analysis
 
I find the sound didn't change much at all using different silicon tips so I stuck with medium sized gray silicon tips
 
Highs: The extremes of the Westone 2 extend better than the UM2. The highs on the Westone 2 is more pleasant to listen to; it is quite safe sounding and is never offensive. The biggest difference I notice is that the highs are more articulate on the UM2 and I hear some low treble boost on the UM2 which makes snare drum hits and rolls more lively. Cymbals sound more lively on the UM2 and triangle sounds sparkly on the UM2. The cymbals also sound more splashy, which can be fatiguing on the UM2 compared to the Westone 2. I have no real complaints about the somewhat common feedback of roll of highs on the UM2 but then again I do not listen to classical.
 
Mids: Vocals on the UM2 sound thinner and doesn't have the warmth of the Westone 2. However the vocals on the UM2 sound more real and live; it is more revealing. I notice that sometimes the UM2 can sound sibilant on the S's from the singer's voice which is a surprise; the Westone 2 does not sound sibilant at all. Sibilance is the biggest problem I have with the UM2 right now on specific tracks and as far as I know; armatures do not require burn-in. Vocals are more dry sounding the UM2. The midrange on the Westone 2 has a certain smoothness and warmth over it and it is more forward sounding than the UM2. The midrange on the UM2 does not sound warm, it is on the neutral side and it sounds more transparent.  Guitars sound more crunchy on the UM2 than the Westone 2. This part is definitely a preference thing, some may like a warm midrange which the Westone 2 but the UM2 resembles my Grado SR325 a little more which is a good thing for me though I still think my vintage SR325 is simply way better in the midrange than any IEM I've owned but that's a different story. Too much warmth to me means it doesn't sound live anymore.
 
Low: Definitely more bass on the UM2 and on the lower extreme as well; not boomy and quite controlled. The speed is quite similar. Because of the bass presence, the UM2 sounds bigger than the Westone 2. It doesn't mean the Westone 2 has no bass; it's there but not as loud as the UM2. The UM2 can slam while the Westone 2 can hit. The UM2 does not have as much bass as the UM3x that's for sure but the sound is definitely more balanced. From the day I had the Westone 2, I really did feel it could use a bit more bass and the UM2 does it right.
 
Soundstage: The soundstage on the Westone 2 is slightly wider than the UM2 but the depth of the UM2 is deeper than the Westone 2.
 
Detail/Separation: There is noticeably more detail on the UM2 than the Westone 2. Everything sounds more blended in on the Westone 2. On the UM2, the details in the background jump out more and plucking on an acoustic for example, is noticeably more distinctive and edgy. UM2 is more analytical and is more capable of exposing flaws than the Westone 2. Westone 2 is more forgiving, and just makes everything sound great.
 
Misc:
The UM2 sounds bright compared to the Westone 2 which is a surprise. I almost felt fatigued after hearing the UM2 for the first time but my ears adjusted; somewhere in the upper mid and low highs can sound harsh depending on the song. The Westone 2 has a safe warm sound; works well with everything but doesn't excel at anything in particular. UM2 takes more chances but like a double edge sword; sometimes it's great and there are times it is harsh and fatiguing. Everything sounds more raw and articulate on the UM2; it sounds more open despite having a slightly narrower soundstage than the Westone 2. I still need to use the UM2 more to see if I could get use to the certain harshness or brightness I hear in the 7kHz-10kHz region area based on listening to percussion frequencies from various cymbals but other than that I am liking these so far. It sounds musical to me which is good as these are stage monitors after all.
 
(11/20) Update with shure black olive foam tips on UM2
 
I have been using the shure black olive foam tips with the UM2. I notice it will tame any peakiness, give a fuller smoother midrange but the bass impact has suffered without a doubt. There is no more sibilance with the foam tips but sibilance with the silicon tips is only noticeable on bright recordings. Just about every con I mentioned earlier about the UM2 has subsided except the weaker bass has become a new con with these foam tips. The articulate sound and separation remains strong, which is on a different level beyond the Westone 2. To me the better value IEM is the UM2 at $279 vs the Westone 2 at $249; I would pay the extra $30 every time for the separation and non-congested sound.
 
2014: Update
I've kept this IEM for a very long time. I still get goosebumps in some songs I listen to. I have not been so content with any IEM like I have with the UM2. I know its flaws but the pros of it outweigh the cons for me. I listen to a lot of modern rock and I feel these sound a little bit like Grados in some way. The midrange is forward and the guitars crunch. I have not thought about upgrading at all and I am still listening to it everyday to this day. I have gotten the cable replaced because something was loose on one side so it has the thinner headphone stress relief strain now like the Westone 2. I prefer the older one. I have not been content with the UM3x and Westone 3 but this one IEM is a keeper!

I have owned 3 RS1i, yes 3 because they sounded so different from a SR60i that I had to be sure I didn't get odd balls. I've come to the conclusion it's just the way it is. It has a serious level of warmth that prevents any harshness, only smoothness. Poor recordings won't sound so bad on the RS1i unlike all the other grados.
 
My first listening impression was,
 
"...err what the heck is this??"
 
I'm a huge fan of the bright grado house sound and I cannot deny that I was disappointed in hearing the RS1i. Any non ""i models possess that bright grado house sound if you want to know what I mean.
 
The RS1i strays away from the house sound found on the SR60i. If you are expecting a bright live performance like the SR60i then do not get the RS1i, but get the buttoned RS1. The RS1i instead makes everything sound very smooth, too smooth. To say the RS1i sounds bright is laughable (with comfies,bowls and flat pads), it's a big downgrade in treble hotness from the SR60i. RS1i leans more towards the bass and midrange rather than the usual treble and midrange.
 
Do not buy the RS1i as your first grado, you will be missing out. Buy the SR60i first and if you find that it is too hot sounding then you can try the RS1i.
 
The highs are very smooth and delicate. I never get irritated by this presentation but it sounds too safe. Zero shrillness, if you dislike how all the other grado's treble sound then there is a good chance the RS1i will be for you
 
The midrange is very warm and lush. It does not possess the high mid spike found on the SR60i that makes rock music shine but instead, Grado has changed the RS1i to be more of a all arounder. SR60i excels at rock over a RS1i because of its frequency response even though the RS1i is more about the quality. The RS1i frequency response is different from the graph shown at Headroom, imagine all the peaks just tamed down by 10db or more. Any song I listen to, I always hear the midrange warmth. Some people will not like this thick sound as it takes away transparency. I would not dare us a tube amp with the RS1i, the midrange does not need to be any thicker because it's already too much. The RS1i will never ever sound thin no matter what I threw at it compared to the SR60i, that's how dense the midrange is. The RS1i is not the headphone for rock sadly, no high mid spike energy for guitars and drums. I would say Grados are the rock headphones, however for the RS1i I felt rock is the genre it seemed the least impressive at which is quite shocking. I would say the RS1i was better for pop than rock. The RS1 buttoned is simply better in that genre.
 
The soundstage depth is considerably better than a SR60i. The width is largely unchanged. A lot of layering can be heard.
 
The bass is noticeable more and better. The bass has body but there is a lot of midbass presence in a lot of songs that may make the song sound a little odd and congested. These can go low. In a lot of ways the bass is better but some may not like it.
 
To some it may seem like the sound is refined  but to me , it is too tame. I don't think this is the right step as an improvement over the RS1 because clearly, the sound has taken a big change. I hesitate to recommend the RS1i as an upgrade. However, the RS1i is amazing in its own way even though it wasn't the exact sound I was looking for. For some songs, I do enjoy its fullness and warmth as well as its strong bass slam. It still has the speed of a grado and the pacing. The RS1i is by no means a bad headphone, there are many others who enjoy the RS1i. The sound signature I am chasing needs to remain the same as the SR60i without a large change.
 
On the other hand, if you're in pursuit of the smoothest sounding grado headphone then the RS1i is the jackpot. It is just not capable of sounding harsh, no exaggeration.
 
Extra notes:
 
Now trying jumbos on...
 
Pads make a big difference on the RS1i. If you put on the jumbo pads found on the GS1000i and PS1000i, the RS1i sounds ridiculously close to a PS1000i except for the amount of bass which the PS1000i is dominant in. The treble stands out so very clearly, pushing the mids back so it does not sound so thick. The whole sound in general becomes very transparent sounding. I was very impressed with Jumbos on the RS1i much more than bowls. I did not try a PS1000i with bowl pads so I can't say how closely related the drivers may be.
 
Interestingly using bowls,if remove the bowls and place them on top of the drivers the bright sound is there but the upper mid spike is not.

Features (listed from coolfungadgets)
•High speed USB connection
•Independent power module provides pure and strong power supply
•Independent APU MU6010 for 24 bit/192kHz audio processing
•High quality S/PDIF transmitter
•Optical toslink & coaxial RCA digital output
•Stereo RCA, 3.5mm headphone analog output
•Headphone 1 is for medium/high resistance headphones
•Headphone 2 is for low resistance headphones
•Support 24bit/192kHz digital output
•Specialized ASIO driver - support Windows XP, Windows Vista and Windows 7
•Aluminum alloy chassis for minimum interference


I have been using my X-Fi for 3 or 4 years now. I've also upgraded the opamps to LM4562 (improved high end details and transparency over onboard sound, less edgy but vocals still sounded a bit "digitalized" if you get me) and decoupled the capacitors for about 2 years now. The 02 US sounds like an improvement far greater than the jump from onboard sound to a modded X-Fi, to me it really felt like the next step.

I don't really feel like there's any point in comparing my onboard realtek "high definition" audio as it's fairly low end (harsh, lack of resolution and dry) such that my zune and sansa clip sound better (greater dynamics , greater soundstage and generally more detailed)

I mainly listen to rock,alternative,classic,electronic,piano pieces and once in a while pop just for the heck of it
It has a very solid casing, very study and not made of thin metal.
 
Sound comparison
02US vs opamp upgraded X-Fi Xtrememusic

Headphone used : Grado SR-225 (X-Fi cannot drive my HD580 adequately, sounds quite anemic I should say)
No dedicated amp was used

Speakers : M-Audio BX5a

The first thing apparent between the two is the instrument decay and texture. For the X-Fi I can't distinguish timbre well at all , the 02US really fleshes it out for a violin,saxophone,flute,clarinet and piano for example. As I know, it is not only the pitch or tone that makes me able to distinguish an instrument, it's much of the texture. The X-Fi has wide soundstage compared to onboard, however the depth is further improved on the 02US as well as the width ( the depth was a more noticeable change than width). Instruments have a more apparent occupation in space; X-Fi sounds cluttered in comparison. The vocals on the 02US are great, and sound natural without a hint of edginess or graininess. The X-Fi presentation of vocals ( can be smooth and rough at times) vary through a variety of recordings but the 02 US manages to keep its smooth vocal characteristic a constant. I didn't notice anything too different about the distance of vocals between the two sources. Everything sounds so well together, the layers of instruments and vocals blend in together well without losing any detail and does not become a mess. It is really a bliss listening to vocals on the 02US unlike any other sources I have

The 02US is able to be very detailed (again the decay and timbre is beyond the X-Fi) and crisp in even complex passages where the X-Fi loses midrange detail and separation creating a small mess. Like many source upgrades, I find myself hearing new details and for details that were already there, stood out even more. The separation in the strumming of an acoustic guitar for example is good on the X-Fi but 02US manages to bring out even more distinction between each pluck. Also passages of music pieces when the choir comes in, the 02US makes it noticeable there are more singers there with the choir; the X-Fi makes it seem as if the choir is short a few voices. The 02US is easily able to dissect small details and present them, where the X-Fi isn't able to discern them at all.

The 02US is able to keep its composure of sounding smooth, detailed and transparent at all times. Although the 02US is smooth sounding, it is capable of making guitars in rock sound lively. Drums have a dynamic snap and cymbals actually shimmer. Pianos notes have body, tone and decay not distinctively apparent on the X-Fi. I can't stress how smooth flowing the sound is compared to the X-Fi, it really needs to be heard than described. It does so without being mellow,boring,overly gentle or lacking in dynamics, and has rhythm. I can even listen to the 02US at a slightly higher volume because of how non-fatiguing it sounds.

Regarding the highs, I have always wanted more out of the X-Fi despite the improvement by replacing the opamps. It didn't have that sparkle and is tad shrill. 02US remedied this for me, violins really "sing" and something like a triangle instrument had the sparkle on its initial hit. Lastly, the low end frequencies on both are comparable but in terms of impact the 02US has the edge creating greater dynamics which is nice for kick drums for one. Bass in some songs had a tighter and more controlled punch to it compared to my X-Fi which is more loose.

If I had to pick a word to roughly sum up both sources

X-Fi : Artificial
02US : Natural
 
Musiland 02US is competitive to the uDac. Musiland 02US has slightly more forward vocals, more extended high and better bass impact and depth. This comparison was made through my Arietta amp
 
02US is one of the best value DACs I have owned. Those with harder to drive cans may want to pair this up with a proper amplifier.

After having a few dacs and amps , I wanted an all-in-one package that would leave me happy for a very long time. The size of this thing is small and portable which is an added bonus. I didn't like dealing with interconnects with amps and dacs so this thing was a blessing.
 
I only owned a handful of amps but I compared this Meier Corda Arietta and from what I was hearing out of my RS1 was better attack and speed. It is not as warm as the Arietta but for me this is a good thing. The transparency and soundstage depth is improved over the Arietta as well. I felt the HDP amp is a better match for my RS1 than the Arietta. If there was one thing that I wished it could improve on would be the width of the soundstage but this is minor for me since my AD700 already offers a huge soundstage.
 
I did not get a chance to compare with my other DACs since I sold them all betting that the HDP would triumph them all . Clearly it does not disappoint when I received it.
 
There is no hissing on my unit with my AD700 and RS1. The unit runs cool all day and never gets hot, but lukewarm leaving it on 24/7.
 
Overall I'm impressed by the price and the features of the HDP, it's hard to find anything with all the features at the same price. I feel as an headphone amplifier, it could very well be worth the entire price of the HDP at $449 but Nuforce managed to fit an excellent DAC packed with features all for the price of one. Like some have already said, this entire package offers a lot of bang per buck.