I'll give a brief description of what I'm hearing so far with the ER3SR for those of you who may be interested. Keep in mind I've only been listening to them for a few hours. Also keep in mind I've had the ER4S for many years and the ER4SR/XR the day they were available and listen to both ALL the time, so I am very familiar with the sound of the ER4 line-up.
So... First I will just jump out and say this. If there is anyone out there that has EVER avoided buying an ER4 because perhaps it was "just" too expensive... Stop reading and go buy the ER3SR. You will not be disappointed.
Now, for everyone else, again keeping in mind the time I've spent so far, I would say these are every bit an ER4 in terms of their sound signature. Anyone familiar with the ER4 series in general will feel like these "fit right in." The housing, tips, cable, etc. are almost identical in basic design to the ER4SR/XR series. There are small differences, but nothing functionally altering. The cable centerpiece is actually smaller and the upper section of the cables is a single cable per side and not braided. Otherwise, the feel and basic design of everything is very much the same.
As for the sound, I haven't even got to the ER3XR yet. I've been comparing the ER3SR almost exclusively to the ER4XR, because oddly it seems to share a closer tonal similarity to my ER4XR than my ER4SR. The bass level for me is a bit hard to discern, because it is just a slightly "different" tuning to my ears. The bass "sounds" to me as though it is somewhere between the ER4SR and ER4XR level of bass. However, that could easily be because of a shift in some other part of the frequency spectrum giving that illusion. But it is definitely warmer and bassier in the lows than my ER4SR, however there isn't any drastic difference in muddiness or anything that would make you think "ew gross." The overall sound is very ER4-ish.
The main difference I believe I'm hearing (and this is to the best of my ability picking things our short term) is that the tonal balance is a bit more bass/treble than fully neutral, but only very very slightly.
It sounds to me as though the ER3SR probably does have more overall bass than the ER4SR and maybe even more mid bass than either ER4SR/XR model, however, there is a slight treble bump in the upper-mid treble that gives the illusion of balance and more details than even the former two models. I definitely sometimes get the impression that picked instruments low in a mix are easier to hear in the ER3SR. Small brightish sounds and textures appear more "in your face" and there is almost a more "dry" texture. I would describe it like listening to the ER4XR (since that sounds tonally more similar) is like listening to a very balanced and smooth sound. Smooth like glass perhaps. You can hear "through" the glass but you know you're looking through glass (bear with me here). With the ER3SR it is more like there is no glass. The sound is more transparent, however the sound is a bit more like there is the slightest bit of a rough texture. I would say sandpaper, but just a "dryer" texture.
I believe this is nothing more than the slightly uneven treble region adding a touch or "nasal air" as I'll call it. The ER4XR doesn't have this, so the entire treble region sounds very open and spacious. While the ER3SR may have more treble air and clarity in a certain region, but the "entire" treble region isn't as perfectly balanced and thus there is more of a slightly more narrow sense of hyper clarity while the ER4XR is more of a smooth wide clarity with less nasal tone.
Now, these difference are very minor in the scope of an ER series earphone. The difference between the ER4XR and ER4SR (so far as I can tell this early), sounds as though it is a similar "amount" of difference, but just in different frequency areas. So to me it literally sounds like an ER4SR/XR with some EQ applied somewhere. The noise isolation, dead silent background, low distortion, etc. are all similar so far to the former models. If there is more of anything it would probably be distortion, but that is incredibly hard to discern, because I don't perceive distortion, but rather more dry treble. It's possible though that the distortion could be higher and adding a bit of harmonic overtones to the sound. That would be a question for EtyDave perhaps.
The most noticeable difference in the treble response is that it is simultaneously darker and brighter. The mid treble may have a slight depression which gives the overall tone a more relaxed, dark tone, but then above that there may be the smallest bump, which does two things. First, in my opinion it almost gives a better, perhaps more "present" sense of the treble "details" area, making instruments almost sound more distinct and separate. Second, it gives the dynamic "snap" of certain things a boost. So whether these things are good or not I suppose is a personal choice.
I like both for different reasons. Again, the overall treble of the ER4XR sounds more coherent to me as a whole perhaps, but it also sounds ever so slightly glossy or smoothed (this isn't necessarily bad), while the ER3SR sometimes gives me the impression an instrument is more up front and dry and full bodied, though it lacks the blending smoothness of the former.
For instance, in some david benoit jazz songs like freedom at midnight, tropical breeze, or every step of the way, the drums sound more aggressive on the ER4SR having a more noticeable "snap" to the snares like they are smacking your ears a bit more. Also, the bass guitars have a bit more of a dry string sound like the string has a more "in your face" sound.
On the ER4XR the same songs have a more delicate sound in the cymbals and everything has a nice blended smoothness to it in the treble. The bass guitars sound more balanced in that they fit the overall mix better, but they sound a bit more "round" and lack the string clarity of the ER3SR.
On steven wilson albums, songs like first regrets, luminol, and my book of regrets,the drums are a bit more aggressive here as well and can almost sound "strident" if that's a good word, where at louder volumes they are ever so slightly more harsh or fatiguing. Where again, the ER4XR has a more delicate upper brightness and the treble is overall more balanced while being smoother. But the basses are a bit more distant sounding in that they are not as in your face.
In daft punk's random access memories, the song give life back to music, the quickly rotating/undulating keyboards in the side channel and the plucky sounds of everything in the intro are more distinct on the ER3SR a bit. As though they jump out of the song more dynamically/crisply, however the ER4XR makes the electric lead guitars at 1:21 sound more present, where the ER3SR makes them (at least one of them) sound a bit less present in the mix.
I stress again that these things in themselves are relative to the series. The ER3SR is not "strident" or "harsh" compared to 99% of other earphones. That would be like saying the ER4XR is too bassy. While it may be for some ER4 fans, in the scope of earphones it is not a bassy earphone by any means. So the ER3SR is just a slightly different ER beast.
I will also note that the volume on my devices is a bit more easy to drive the ER3SR. I can pop in the ER4XR and I need to turn it up maybe 5-8% on my volume slider to get an equivalent output level. This is very much a guess. I haven't paid a lot of attention to the volume differences, but they are a touch louder than my ER4XR.
To go a bit more into the treble difference. If you have a song where someone is tapping a bunch of cymbals consecutively, the ER4XR lets you hear all the delicate tss tss tss of the cymbals while the snare and everything else is balanced around it. The ER3SR sounds great, but there is less refinement there and the snare is the more apparent component for the same section of song with the cymbals just barely less finessed. However, the overall darkness of the ER3SR at moderate volumes can come across as more relaxing and revealing in a lot of ways.
For me it is a struggle between hear more "overall" details due to the balance of the ER4XR and hearing more distinct details in certain instruments due to the slightly contoured shape of the ER3SR.
I wouldn't be surprised if the differences between the two models were decibels all over the place, but if I had to guess I think the overall differences would be in the 2-3db range at a few key spots. So no drastic changes per se. Just a slightly warmer/darker tone, but with almost no lack of details.
I'll have to give them a listen for a lot longer. If the ER3XR are noticeably bassier, then they probably aren't my cup of tea. But we'll see. As for the difference between the ER4XR and the ER3SR, I'll have to give it time. I may find I prefer the 4XR balance, or I may find I prefer the 3SR relaxing yet detailed contour.
So what about the ER4SR? For me, the tonal difference is more noticeable. And as such I really think it wouldn't appeal as much to die-hard ER4S/SR fans. If the ER4XR is too much bass and the ER4SR is perfect, than you'll probably find the ER3SR to be too much bass, not enough mid treble and perhaps even too much nasally treble somewhere.
If you love the ER4SR, but think it doesn't have enough bass, the bass on the ER3SR is fantastic. At times I think I prefer it to the ER4XR, but again, time will tell. But if you absolutely love the ER4SR treble but find it has not enough bass, you probably want an ER4XR. The signature is practically identical with more bass. The signature of the ER3SR is slightly different.
If you have a low budget I wouldn't even hesitate to get the ER3SR. At half the price it's a no brainer. It does every single thing the ER4 series does with just a little less refinement perhaps, but I do believe that is really a lot about taste. I don't hear any objectionable differences between them all. It's not like the ER3SR has a huge peak or an enormous dip anywhere. It also doesn't have any obvious difference in hiss, noise, distortion, etc. Even in the quietest songs with soft lush vocal harmonies, the ER3SR picks out the individual voices incredibly clearly, maybe even more so than the ER4XR at the cost of some smoothness.
So maybe this wasn't exactly brief, and I know I sound like a broken record, but these are "initial" impressions after spending the entire evening listening to them all with a bunch of various genres. I'll give them a lot more time and try the ER3XR as well and report back. I'll also be making a youtube video once I have a more well rounded idea of the sound.
So many ER-earphones!!! (The ER4S and ER4B are in the other room)
