This and That:
I don't even remember exactly why I bought the ER-4SR. I think two factors that contributed to it were the good price at that time (I got it for less than about $260 including taxes - brand new and from Amazon), and probably also because I just wanted to add it to my collection. While I don't remember all of the exact reasons, I know that I was quite late to the party and didn't really consider the Ety in all of the years, which was quite a shame. Whatever, I won't repeat the complete history of Etymotic.
Anyway - when it arrived, I didn't really use it, like at all. The included silicone tips didn't seal in my large ear canals, and as I hate playing the tip rolling game (I'm someone who prefers his audio gear without any modifications, if possible) and am not into foam tips (although those cylindrical ones provided by Etymotic are really comfy), my ER-4SR was put into the drawer and wasn't used for several weeks or months - I don't remember that anymore.
But when I decided to try it again, I started to modify the included silicone tips to fit my ears. My first tries didn't sound right, but eventually I modified the tips in a way that they sealed in my large ear canals but didn't alter the sound negatively: I removed the smallest of the three flanges, pulled it onto the nozzle, and only then pulled the other two, still connected, remaining flanges onto it. And that was it - the tip length remained about identical, however I was now able to insert my ER-4S properly and it sealed. And the sound I got out of it was also what sounded "right" to me using music, sine sweeps etc.
And to this day, I'm still using this ear tips modification with all of Etymotic's in-ears.
What else can be said about the ER-4S? It definitely needs to be inserted deep and seal in order to get the right sound out of it. The same goes for the ear tip length. Wrong insertion depth, bad seal or incorrect ear tip length = wrong tonality.
In terms of accessories, there are rather plenty, and it's obvious that the ER-4S was targeted more towards a Pro clientele.
The newer ER4SR received a better, more supple cable than that of the ER-4S and also incorporated a chin-slider, however what the ER-4S still does better is side indicators as the big red dot on the ER-4S's right side is difficult to oversee.
Sound:
I'm using my ER-4SR with the large triple-flange silicone tips that came included, modified as described above.
I've used several sources with my ER-4SR, most of which feature a low output impedance. For pure desktop use, that would be my RME ADI-2 DAC, primarily fed by my Pioneer PD-S701.
Tuning:
There are different approaches and studies on what is "neutral" in the realm of headphones and in-ears. I'm not going to repeat all of that.
What I can however say is that to me, the ER-4S (actually even more so the ER-4SR, but this very text is about my ER-4S) comes the closest to what I hear as neutral when listening to music and sine sweeps. All of my other in-ears that are heading into a quite neutral direction, such as my UERM, Fischer Amps FA-3E, InEar ProPhile 8, Shure SE425, or the UERR and others, sound slightly more coloured and/or less neutral in various areas to me. They always did to a small degree, even before I had my ER-4S. That said, to me, neither of these in-ears sound bad to me. In fact I'm still using my UERM as well as ProPhile 8, the latter more than the former, for critical, neutral stationary listening. It's just that, to me, all of the other neutral (/-ish) in-ears I own are like very well tuned, almost flat-neutral hi-fi speakers, but not 100% true, flat monitoring speakers.
When I first heard my ER-4S with correct seal and tip length, I thought "that's exactly it". And yes, this is the sound that I personally perceive as the flattest, most neutral out of the bunch. Period. It's the flattest, least coloured to my ears; the most neutral.
Flat bass that extends diffuse-field flat into the sub-bass without really rolling off. It's just flat to my ears. Really flat. No hint of warmth or (debatable) boost to compensate for the lack of mechanical vibrations coming from loudspeakers. No slight hint of bass lift, even if it's just very mild; no - just a flat, accurate bass reproduction.
The midrange sounds just as correct to my ears - perhaps with just a little to much level in the presence range that makes vocals probably a touch too close. But that was pretty much reduced by the newer ER4SR.
Then the treble - just beautifully flat, even and harmonious. The only area where it's just slightly too shy to my ears is around 6 kHz. Other than that, it is flatter and more even, more realistic, than the vast majority of in-ears I have heard and owned, regardless of price range.
In short, to my ears when using sine sweeps and listening to music, my ER-4S (the ER4SR even a little more so) is exactly what I hear as flat, neutral and uncoloured, just the way it should be.
Flat, "boring" and unexciting. And that's exactly what I love about it. Realistic. Authentic. Linear. Pro tool.
Resolution:
The ER-4S is probably one of the best resolving single-BA in-ears. Compared to several multi-BA in-ears though, it loses when it comes to ultimate resolution and separation, most audible in combination with very fast and busy tracks. I fully admit that.
On its own however, the ER-4S doesn't lack anything. At all. As I said, it's one of the best resolving single-BA in-ears. And it's plenty, and enough for me. It's not like the other in-ears in the $1000+ range were much better. They aren't (much better). They are somewhat better though. But that said, I'm not missing anything. There are also some multi-driver in-ears that resolve less well than the Ety.
Control and separation are good. Not as good as that of some of the more expensive multi-BA in-ears that I own, but good nonetheless. I don't miss anything, at least most of the time.
When was the first ER-4 introduced again? 1991? See, there haven't really been any real breakthroughs in (passive) headphone and in-ear development since then, unlike what the marketing wants you to believe. Some people also assume that a new in-ear is almost automatically better than a new one. But as the ER-4 and other models that seem "old" (but still young compared to the ER-4 line) show, that's absolutely not the case. Anyway, enough rant.
What the ER-4S does wonderfully is coherency. It super coherent. Not all that surprising considering it's a single-BA in-ear, is it? Anyway, this is where it beats most of the other sub-$100 models. And as it is basically perfect in this regard, other in-ears can only get on the same level of coherency. This is, I think, of course besides the flat tuning, one of the reasons why it sounds so authentic and realistic.
Bass speed and tightness are high by single-BA standards (and even beat the newer ER4SR), however just a little softer compared to the best multi-BA implementations.
Soundstage:
To my ears, the soundstage is pretty much perfectly circular and three-dimensional. However, it is only around average in dimensions and not as large as the most open sounding in-ears. Then again, because it is circular and three-dimensional, it sounds realistic to my ears.
Separation, precision and layering are definitely precise for a single-BA in-ear but, as with the resolution, a little behind that of better multi-BA in-ears once very fast and busy tracks are being played.
Conclusion:
When it comes to tuning, the ER-4S is the flattest and most neutral, accurate sounding in-ear to me. Sure, in terms of comfort, resolution, bass speed and tightness or instrument separation, there's still a little room for improvement that one can find in several more expensive multi-BA in-ears, not that the ER-4S were bad as they're among the very best single-BA in-ears ever made, if not even the very best, however when it comes to naturalness, neutrality and treble evenness, Etymotic's ER-4S is a diamond and a true reference.
Grand Daddy ER-4S is King.