Etymotic ER2SE and ER2XR Impressions and Discussion

I wanna thank everyone to allow me to be a part of this loaner tour. It has taken me awhile to get this impressions out due to work and business travel, but I have been able to sit down finally and get this impressions out.

When having the ER2XR and ER2SE in for loan, I also had the Moondrop Blessing 2 and the Thieaudio Legacy 3. I will be referencing those 2 in a shootout type scenario. I know ChiFi isn't popular here, but for those who might have listened or own these, it might serve as a good reference point in the "relative" price range that the ER2XR/SE occupy.

Chain
Samsung Note 8 -> ER2XR/SE + Blessing 2 + Legacy 3

Bass
When comparing the bass of these 4 IEMs, I found that obviously with IEMs the fit is a huge proponent with the bass response. I was using the triple flange tips on the Ety IEMs, and using wide bore silicon tips on the Blessing 2, and used a narrow bore silicon tip for the Legacy 3.

While the ER2XR was touted as a more "bassy" ER2SE, I found it to be only a slight tilt in the bass region that was noticeable but not dramatic. This does tilt it more into a "funner" IEM, but I prefer a more neutral signature so found the ER2SE with the slightly more linear bass response to be better for me.

The Blessing 2 and Legacy 3 seem to have a much higher bass shelf than the Ety IEMs, The Legacy 3 had much boomier bass, but this lead to fatigue and slight muddiness in the mids. As I have started to use more gear over the years I found that the more bass, especially in IEMs leads to headaches for me, so the Legacy 3 was something that I tried to avoid for more modern genres. It is great though if someone wants a bassy IEM, albeit with less bass detail than the Ety IEMs. The Blessing 2 was a more neutral IEM than the Legacy 3 in terms of quantity of bass, but was still above both the Ety IEMs; however, the Blessing 2 had the best quality of bass of the bunch. This is to be expected for the price, being much more expensive than the other 3.

Mids
The mids were much more close between the ER2XR and ER2SE. I found them to be almost identical with maybe slight differences? This could just be the ER2XR having elevated bass so it affected just the lower mids slightly, but I found them to be similar enough that I think they can both be classified as the same. I found them to be rather clear, but slightly recessed in the mix. This gave a nice sense of space, and I never felt that they were shouty in any way.

The same can not be said for the Legacy 3 and Blessing 2. I found the Blessing 2 to be rather shouty, especially in the upper mids. They got rather annoying to listen to with vocal heavy music. Both lack the clarity and cleanliness that I found in the Ety IEMs. The Legacy 3 mids seemed to be lost in the mix slightly, neither having their own space, nor having the ability to shine. It just got a bit muddied up with the rest of the mix. I was rather disappointed in these 2 with vocals, as most of my music is vocal driven.

Highs
The highs on the Ety IEMs are similar to the mids, in that they were remarkably similar. They were not hot or sibilant in any way, and would be good for long listening sessions without being fatigued. I am not a huge fan of treble personally, so I found this safe and reserved treble to be good for me. They had air, but nothing was ever hot which is what I found important.

Legacy 3 and Blessing 2. Blessing 2 reminds me slightly of the Andromeda in the sense that they straddle the line between just enough and too much treble. I think the difference between the Andromeda and Blessing 2 for me however is the detail. Blessing 2 is good for detail, but loses out to the Andromeda in my opinion. Legacy 3 is slightly rolled off in the treble in my opinion, which makes for a weird frequency response to me. Legacy 3 seemed to be too dark, and lacking in air. This makes the Legacy 3 to feel even more congested. Is this a trend with the Legacy 3? I guess so.

Detail Retrieval
Not much to say here, the Ety IEMs aren't extremely detailed, but for the price they have good detail retrieval and I wouldn't be mad having these. They beat out the Legacy 3 in detail retrieval, but lose to the Blessing 2 in detail retrieval. To be expected, but honestly the difference is rather close which I think is either a win in the Ety case, or a loss in the Blessing 2 case. Guess depends on how you look at it.

Soundstage/Imaging
This is an area that really separates the higher end IEMs from the more "budget" ones in my opinion. All 4 of these IEMs seem to be rather small in soundstage. I would say the Legacy 3 is the smallest, then the Ety IEMs, then the Blessing 2. But all together they seem rather confined to the width of your head, with no real depth or width to the stage. Imaging would follow the same ranking as soundstage, with the exception that the Ety would be similar to the Blessing 2 in quality of the imaging.

Fit
This is normally not something I touch on in my reviews since they are predominantly headphone related reviews, and most of the headphones I buy fit really well on my head. But IEMs are much more finicky and user dependent so YMMV, but I think it is still important to reference. For reference, my Andromedas fit perfectly in my ear, but in some positions, will rub on the back of my inner ear. This can be fixed by repositioning them so they aren't touching anything. With the Ety IEMs, I really dislike the feeling of how deep they are inserted into the ear canal. I was never able to get a fit I felt comfortable with, and always felt awkward and discomfort from having them so deep in. Some people love this, others don't.

Blessing 2 fit was terrible for me. The housing was way too large, and would create a complete seal in my ear from being pushed in and would create a weird suction in my ear. This would lead to headaches from this suction seal and would result in pain and discomfort within 20 minutes of using. Legacy 3 was better, but would have hotspots and areas it rubbed on the backside of my inner ear. Better than the Blessing 2 but not something I could wear for many hours. This could be to a weird size ear on my part, but wanted to still touch on this.

Conclusion
I know this is an ER2SE and ER2XR impression thread, but thought having the other IEMs in here for reference would be beneficial, especially given that I felt that the Ety IEMs were much better than the Legacy 3, given the same price range, and worth the buy over the Blessing 2 in my opinion as well, given the price of the Blessing 2. I think if you want a good quality IEM, with good clear sound for the $100 range, these are a go to. Just know that they have a deep insertion, but other than that anybody should be happy to have this as a commuter IEM, beater IEM, or just a really good IEM for the money that they can use until they decide to upgrade to a higher end IEM. I wish I could be okay with the fit, but even with the deep insertion I think they might be worth to pick up for me, and just get used to the insertion.

 

Just finished my loaner with the 2XR and 2SE. Amazingly these are the first Etymotics IEMs I've ever tried. The whole deep insertion thing was often uncomfortable for me and that alone would remove these from my to buy list, but I did like the sound, and they do isolate better than many IEMs if you can withstand the deep insertion sensation.

In terms of the whole diffuse field thing, I liked it. Both IEMs sounded spacious and open, albeit without necessarily a great sense of placement. These make for lovely late night non-critical listening as you drift off to sleep, as I did with my XD-05+ listening to The Zombies' masterpiece Odessey and Oracle. I also ran through both IEMs through my Lyr 3 being fed by a Modi Multibit via Eitr and Jriver. I know the forum favorite is going to be the XR with its more pronounced bass, but I actually preferred the SE. While I do think the bass quantity was not where I wanted it, the overall presentation felt more crisp and precise with the SE. It sounded like a studio monitor essentially, which isn't necessarily the presentation I always want but I can't fault it for doing what it's tuned to do.

The XR brought the bass but certainly not to the level of the FD-X1, which is my standard for IEM DD bass below $1k. For some reason I felt like the XR sounded more flat and less overall lively than the SE. I don't think this was a case of the bass overwhelming the rest of the FR or anything, and it was slight enough that it could have just been my ears on those days. Neither IEM was shouty in any way, or had anything particularly wonky in the FR. If it weren't for the deep insertion, I'd consider either of them to be strong candidates for a secondary/travel IEM.

In terms of total value, I'd say these are solid for the money. I'd like to hear the Moondrop Starfield which is only $10 more than these to see how it compares, as I think that might give me more of what I want and without the deep insertion. Of course I think the FD-X1 stomps all over these but at 2.5x the price I would hope that's the case. Still I'm glad I got to hear these as they were quite enjoyable while I had them and now I can cross them off my list.

 

These are Interesting iem’s, that I have wanted to try for a long time. I was quite surprised how tiny they really are when I first received them.

The fit for me is very good with the smaller trippleflanges.

These are less sensitive, than my other IEM's, but not outstandingly so. They have a smooth and clear sound that makes for a good allrounder. They are not warm nor cool sounding, but rather "gray" neutral. (their tonality reminds me of the the Focal Spirit Pro). It lacks extension on both ends of the of the frequency range, but the compromises here are well judged. It is a really even sound frequency response without sharp peaks, with a neutral bass, open detailed midrange and a smooth treble.

Compared to the HA-FDX1 you do get better technicalities, but compromise on weight, isolation and fit.
The ER20XR seems more subdued, compared to the more lively and exciting FDX1, however they do pack a pretty impressive dynamic punch when needed.

Their small size, light weight, excellent isolation and solid tuning with DD timbre
makes this a impressive IEM from a well established manufacturer, which I prefer over the HA-FDX1, since I always use IEMS on the go.

 

Well, I wanted to know what the deep inner ear sensation was all about. These IEMs have excellent isolation, and inner ear tingle. These felt a little scratchy to me. It would be embarrassing but I felt I wanted some middle ground, of semi clean ears to have enough lubrication to prevent the itchy inner feeling that can be very distracting.

Sound:
I felt they both perform exceptionally well, beating every chifi I have ever been peddled. These are really great for the price. My preference is the XR, the bass boost really helped me enjoy a lot of tracks I normally wouldn’t listen to. One of my new reference tracks was Bringing It Home - Son of Dave


The vocal performance is just spectacular on the XR. The SE left me wanting more, it was an easy choice for myself between the two. I can see why the SE will go on sale more frequently.

Ergonomics:
The major issue I had was I did not like the stock cable configuration. It was difficult to have the over the ear loop I prefer. In addition, the cable thickness has a lot to be desired. I felt very insecure but confidante on the fit. The unique mmcx receptacle made it impossible to try other cables I had on hand.

Sources:
LG v20, laptop with ifi IEMmatch, MOTU m2

Loved the sound of the XR, disliked the cable more than I would like to admit.

 

Eartips tip: after going through Comply T100, T100 Comfort, Etymotic foams and triple flange, Comply Pro I found my old Weston foam tips which are the worst design I have seen. Because the bore is too short, 2.5 mm short to be exact, squeezed foam would close the output in you ear, particularly with deep insert.
I cut the tip with a razor at exactly 2.5 mm so the bore goes all the way. Those shortened Weston eartips are the best I tried so far. Bass is touch less elevated but cleaner and, resolution in the rest of FR spectrum improved a bit. The cut tips have similar shape is Etymotic grey foams but are more comfortable.
They are a bit shorter, particularly recommend for the folks who are not comfortable with deep insert.
Not ideal with ER4SR, those do not need any more bass control and are resolving enough with Comply t100. or T100 comfort
Using IBasso DX220 and re-checking with BHA-1 low gain. Similar effect.

 

I have these on loaner now and should probably get them back to Marv soon since he's last up. I have heard many IEMs at trade shows, regularly hear all the CFA universal offerings (UA deals Campfire), own Tia Fourte (don't listen to them and won them in a raffle for free), modded IMR R1 ('fake but fun'), Periodic Be ('fake but fun' redux), Aurisonic Rockets (my 'reference'), and FDX1. And IE80 in the past, which I actually really miss.

In general I'd say I enjoy the sound of the 2XR over the 2SE (I like bass and they're pretty close to identical in every other way), so I'll focus my impressions on those. Regardless, I can't stand the fit with any of the tips. I always feel an edge or angle somewhere in my canal with deep insertion, and it gets itchy and makes me want to cough. I don't normally have issues with IEM comfort. It's a shame here because I think the ER2XR presents good value for a fairly balanced presentation.

The most obvious comparison for the 2XR is against the FDX1. I use my FDX1 with the heaviest nozzle damping, and I still hear them as VERY hot in the 4k area. Well, I'd say the bass and treble on the 2XR are strikingly similar to the FDX1, but that 4khz bump from the JVC is now shifted down to 2.5khz or so with a wider-Q emphasis and slightly lower amplitude. I would still say it's a distracting tonal deviation, but doesn't quite have the 'annoying' factor of the FDX1 with hotter-sounding music.

FDX1 is a bit tighter and more controlled dynamically, but not by much. 2XR does have a slightly smoother, less grey timbre overall. Still a bit of nasality and boxiness from that broad ~2.5k emphasis that really stuck out when coming from my full sized headphones, even those with a 3k bump like my modded HD580. I realize in theory a bump in this region should help simulate pinna gain, but the effect doesn't seem to work on me since I can clearly hear the emphasis. FDX1 is more comfortable short term and long term.

The Aurisonics Rocket is a forgotten IEM that I love aside from the slightly annoying fit and microphonic cable. Aside from it's lack of LF and HF extension and a slightly blurry dynamic response, I'd consider it tonally perfect through the midband and quite balanced overall. Rocket is still a league ahead of 2XR in terms of comfort, but the 2XR does have a bit more extension in the sub region and more colorful timbre with a less microphonic cable. The timbre coloration and 2.5khz push and extra sub of the 2XR is clear in direct comparison, making them sound a bit more fun but also more fatiguing in the long term.

Compared to Periodic Be, the Be is both more bassy with a a bit more mid treble presence and less of that 2.5k push. There is some tonal resemblance otherwise. I might prefer the Be for instrumentals and electronic, but the 2XR does have a slightly less opaque vocal rendering.

I think they're a good buy at the asking price, but I won't miss them with the other IEMs I have on hand. Then again, if they were comfortable, I could see them ticking off all the same boxes as the FDX1 and the Be while being a small bit more tonally accurate to my ears than either.

 

So my dear Massdrop Pluses developed a driver imbalance on the right side, coinciding with this lovely thread providing an excuse to get more gear. Looked up graph comparisons on @Crinacle 's site to corroborate what you all were saying, reminisced about my HF2s years ago, and I figured it wouldn't hurt.

VERY IMPORTANT NOTE: ER2XRs are US$80 on Amazon right now.

Basically, they're right up my alley. I've always preferred a peak at 2.5khz (might be my small ear canals) - I do love my FDX1s and agree with the others they are a fair bit better on technicalities, but MDPlus-like tonality with DD timbre is just too good to pass up. Such good value! Of course, this all assumes you don't mind Ety insertion. Not a problem for me - I lub dem deep deep. Great earwax cleaning routine too.

Cable could be a little better built though. Wire feels a little too thin for my liking.

AGAIN, VERY IMPORTANT NOTE: They're US$80 on Amazon right now. EIGHTY. Pitter patter.

Side rant: JVC has always had this weird thing with 4khz, seriously. I remember the FXT90s being my first fancy IEMs when I was a noob, and trying very hard to love them because of all the rave reviews online. But that peakiness was always there! Don't get me wrong - they were great in their own ways - but I know better now to trust my ears and corroborate with measurements/other impressions. FDX1s' peak became more bearable for me with an 18mm roll of gauze in the empty nozzle and @shotgunshane 's suggestion for a slight micropore covering.

 

You are right about this 2.5 kHz peak. It helps. Er4SR are the same way. I tried to EQ it down and it takes something away from the sound, adds some muddy feeling. So I left alone, it's better

 

Because I am a moron I ended up spending about $40 more on these than I might otherwise have had to had I ordered directly off Amazon, but even taking that into account these kick a fair bit of ass relative to loads of other somewhat-affordable IEMs in the sub-USD200 range.

Gear used: Samsung S9+, Schiit Fulla 2. I prefer the sound of the supplied foam tips but have settled on the large tri-flanges because I don't want to have to deal with replacing the former every few weeks.

UPDATE: Ahh bother. I don't know if I have wind tunnels for ear canals but I need the foams for a proper, more stable seal; minor prep isn't that much trouble. Sound and isolation get bonuses at least. Also telling L/R ch by feel is getting to be habitual— it's much easier to get proper channels in relatively quickly without looking.

UPDATE 2: It's couple months later now and the foams "snap" back too quickly for my liking so I've gone back to using the large tri-flanges. Pushing them even deeper in than I was initially comfortable with, enough so that I worry about impacted cerumen, the seal is more stable and the treble imbalance is somewhat less pronounced. Still a bit tizzy and bodiless, but not as much as before.


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My main point of comparison will be the FIIO EX1 which is a price bracket just beneath the ER2XRs I suppose. I got the FIIOs as a gift from a friend but they now belong to my one sister because I guess that's just how things turn out sometimes. I've been able to try out loads of other IEMs over the years in store and meet settings (CA, 64 Audio, Ortofon, JH, etc.) but I'm still primarily a headphone user because the chasses on most IEMs irritate my ears too much. Thankfully that isn't the case with Etymōtics, and that's the main reason I went and picked these up; I am happy to report that yep, they're easily among the most comfortable IEMs I've had and are in my use case ergonomically perfect other than they stick out a bit too much for me to be able to wear these with my head resting against a pillow.

Honestly I have no trouble with the L/R markings, though I can see how they'd be arse to put on in a hurry. Even without looking I can just about feel for the raised letter nubs and get them in the right ears, but that takes a few seconds so I usually just end up looking for the indicators anyway. If/when the cables wear out, I might pick up something with louder identifiers.

I do have other Etymōtics around the house (albeit ones in need of recabling...) but those never really made it to production and so are effectively useless as an impressions touchstone I think. Either way based on them and previous experiences with Ety's BA designs I was a bit pessimistic about the overall profile being to my liking but I was pleasantly surprised, really: out of the Galaxy S9+ simply running them with Bit and Bandwidth Upscaling mode through the baked-in UHQ upscaler makes them perfectly listenable, no EQ necessary. This mode adds a touch of body and warmth, improves imaging body, and opens the headstage up a bit at the expense of slightly more aggressive upper mids and some treble unrefinement relative to UHQ disabled.

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The headstage is crap, very much between-your-eyeballs, but the image delineation is much better than most IEMs around the price range despite the background being somewhat hazy. It's not the case that they sound like HD600s being powered by a smartphone mushy, it's just that there's a sense of a pervasive greyness from which sound emanates, but that's hardly a dealbreaker at this price and it's not all that pronounced to begin with. Imaging directionality is pretty excellent and hard-panned items seem exaggeratedly so, but it's not as excessively distinct between left-center-right as on the HiFiMAN HE4XX; the headstage tapestry remains very much cohesive, albeit compact. Though most sonic elements live quite upfront in the headspace, some of my "audiophile" (i.e. not crappy pop or weird genre music) recordings do present things as being further back.

@gixxerwimp mentioned that these appear to have a W-shaped profile and I really think that's the best way to describe it; per my ears midrange has a thinner skew and the bass sounds drier than what I consider to be "proper", not to mention there's some needling around the mid/upper treble. The screech at the beginning of Manic Street Preacher's The Intense Humming of Evil was... intense, but James Bradfield's vocals were kinda mud on both the UK and US versions. Guitars on the track had good crunch though, which was a genuine pleasure to listen to.

The birdsong at the beginning of TSwift+Bon Iver's exile was pushed way back to the point where I had to strain to hear them even at somewhat higher than typical-of-me SPLs. It's not just the birdsong either, there's a bit of a hollow and muffled character to the midrange that's pretty odd in contrast to how shouty and nasally it also is (slightly so), but I guess DF tuning isn't entirely my jam; the mids are a bit too anti-clockwise for me, but not enough so that it's outright offensive as, say, the ADX5000 was, though I wonder at how a clockwise correction might bury even more detail in goo.

The details that get buried seem oddly arbitrary. With some tracks it's easier to follow individual sonic elements than on my main headphone rig using either the HP-3 or the HD600 but other times things I expect to be there are... still there, but only just barely. Have to actively search and focus. The ER2XRs don't stumble when things get busy, to their credit.

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The treble is an odd thing. I hear it as being a bit recessed lower down after the upper midrange bump but having some tizz in the mid-high frequencies that make hi hats sound thin and splashy, almost unnaturally bodiless. Using the foam tips mitigates this somewhat— they level the upper frequencies out and make a better case for using them as a treble reference, but the foams don't resolve the matter entirely. It's not so much offensive as it is just mildly unnatural sounding, and it's thankfully leagues off from being harsh save for on really bad recordings. I'd definitely qualify it as a darker treble balance save for that slight tizz.

The lower end sounds like it's being played entirely straight without any added fanfare or flair. It's dry, as mentioned above, with adequate but generally unremarkable impact paired with surprisingly nice delineation on fast bass solos; it's remarkably easy to follow basslines during busier passages in a song. Not particularly lithe though. The FIIOs take the win for sheer slam and rumble as it likewise wins in headstage size, but that's probably unfair since they use a relatively large 13mm driver. Paul Simon's Under African Skies isn't as visceral and bouncy a listen and the rumble on Billie Eilish's xanny lacks the usual dirt and grit; the information is all there, sure, but it was just... present. Competent, but proper bassheads needn't consider this IEM (or... any Etymōtic, really).

On the whole the ER2XRs basically does what it says on the ad copy: they're well-balanced and resolve a fair bit of information, just that they gloss over most anything even moderately subtle in the mix. They lack viscerality and dance-ability but textures throughout the range are perfectly satisfactory for a daily driver and macrodetail is actually quite grand save for those odds and ends that inexplicably get buried.

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No measurements because a.) IEM squiggles are a hell of a lot more finicky, b.) there are loads of measurements just a quick Google search away, and c.) the ambient noise outside is jarringly high for obvious reasons.


Cheers, all. May 2021 suck less sweaty ball bearings.

 

Great write-up by the way, and very close to my impression of the sound, with exactly the same tips.
I tried some EQ but I could not exactly pinpoint what was wrong with treble. Then I tried using Moondrop Crinacle Blessing 2: Dusk as a reference. Green is ER2XR.
Funny but following the Dusk small peaks in 6-10 region helped a bit, clarity is better and instrument separation slightly improved. I left bass and mids alone as they align almost perfectly and sound right to me.

 

Thanks! Yeah I generally leave the FR balance well enough alone since I'm too lazy to use EQ most of the time and the overall balance isn't too bad unless I'm listening critically; in the months I've had this it just becomes more apparent that seemingly random odds and ends in familiar tracks become inexplicably difficult to make out, leading me to think it's more to do with the drivers' technical performance than the system's overall voicing.

Not gotten ears on the Moondrop/Crinacle Dusks since the price is slightly up there but I have found that treble elevations in IEMs are less immediately offensive to me than on headphones, probably on account of my ears being somewhat efficient at picking treble up (or I could just be deaf! ).

Checking out crin's comparison of the Dusk and the OG Solaris (which I adored, with a few caveats) I'm thinking that the Dusk might be a smidgen bright but have enough lower treble around 5kHz to level things out.

​

P.S.
You can click the "screenshot" button on crin's graph generator to save a PNG with labels to your device. It's pretty handy. I ended up archiving a few headphone measurements of interest back when I had an active subscription.

 

I got my ER Series tuning kit today and the good thing about it that, according to the description it includes filters to bring more details (white, brown) that could be useful for my ER2XR, and red, brown to worm up ER4SR.
But I do not understand the description that is referring filters in terms of resistance. Resistance of what?

What Etymotic is offering is the listener the ability to tune their Etymotic ER series earphones to their own tastes and hearing profile. By incorporating five different filters of varying resistance you can go from a more detailed sound using the white filters all the way to a warmer and darker sound if you go with the orange filters. Kit includes four filters of each color. The full specs of the included dampers are below.

White – 680 Ohms

Brown – 1000 Ohms

Green – 1500 Ohms

Red – 2200 Ohms

Orange – 3300 Ohms

 

Slightly off-topic but has anybody here tried the ER2SE/XR and any of the older Etymotic DD IEMs e.g. the MC5 or MK5?

I've had both the MC5 and MK5 over the years and the MK5 was a decent step ahead of the MC5 (kept MK5 and sold the MC5), just wondering if the ER2 is worth the upgrade over the MK5.

 

Based on how the filters were built I always thought it was referring to the resistance presented by the mesh layer protecting the diaphragm from ear gunk— a less dense mesh would mean that the diaphragm is able to move more freely and possibly resolve more low level information and textures at the expense of less damping, likely more elevated treble; conversely a denser mesh may offer more resistance, darkening the signature at the expense of smoothing over textures and tamping down low level information.

This is why I almost never front dampen headphones except as a very last resort, haha. I'd rather suffer harsher sound if it means keeping nuances intact. Not saying this is necessarily true of Etymōtic by the way since I've not get gotten to play with their filters, just armchair supposing based on what meager time I've spent playing with modding headphones.

 

If it was referring to the density of mesh layer how it would be measured in Ohm? They are talking resistance like in
V=A x Ohm. That is the part I do not understand

 

Facepalm, oh right. Kinda sharted that reply out while I was on break earlier with my brain undercaffeinated haha. The way I see it is they somehow went and assigned the additional resistance air damping a numerical equivalent in ohms; maybe adding an in-line resistor with those values will replicate the effects of the filters? My brain somehow forgot that an "ohm" is a standard unit specifically for electrical resistance; kinda got it mixed up with newtons (N). D'oh!

Did a quick search and I remember reading this a few months back, which likely contributed to the misunderstanding:
M.R.O.: The effect of acoustic dampers on IEMs (rinchoi.blogspot.com)

As far as I can tell there's no conversion between ohm and N so IDK what that's on about.

 

I used to own the EtyKids. I don't recall them being super resolving, but I liked that they would prevent me from turning them up so loud that I would deafen myself. Tonal balance was pleasing enough and clear. I used them for several years until they were stolen in Rome. If they still sold them, I'd buy another pair just for the safety feature.

 

https://en.wikipedia.org/wiki/Acoustic_ohm

 

Now it makes sense, one of the links on wiki page is really good https://www.animations.physics.unsw.edu.au/jw/sound-impedance-intensity.htm.
A filter cylinder can be treated as the simplest possible wind instrument and the density of the medium changes, different Etymotic filters) the sound speed and the volume passing though the pipe per second. More volume (lower acoustic impedance) more details, higher impedance - warmer sound, according to Etymotic.
In any case I applied those filters to ER4SR and ER2XR, they both come with green.

ER2XR is a good story. those filters can really bring some improvement. I listen to those mostly commuting or walking with DIY balanced cable and ES100 DAC/amp. I used the brown 1500 Ohm filter and it makes ER2XR a better in ears: bass level is touch lower with better definition, improved macro details without affecting the enjoyment of listening to ER2XR.

For reference ER4SR does not benefit much, at least to my ears. I started with 3300 Ohms and that created a warmer sound but somewhat diminished the monitoring qualities of the IEMs. I settled on red 2200Ohm and I have no complains, lower mids have a bit more substance, and I do not hear anything different in other areas. But the effect is really so minor that it can be just my imagination.