artnoiNov 11, 2025
Never imagined myself writing consumer review for a 10 year-old in-ear monitors. But the Etymotic ER4SR is just too good to not have it in my digital footprint. My descendants will be proud of me, for the love I have for this pair of little ear dildos.
If I can only have 1 pair of earphones for my whole life, that will be Etymotic ER4SR. It singlehandedly killed my 2016-2017 passion for hunting for headphones/earphones, simply because other stuff was no where nearly as good or acceptably priced.
This is my tribute to one of the best engineered products from an engineering-first companu, the only one to do so in the bullshit ridden consumer audio space.
I like music, and I want to enjoy it with as much fidelity as possible (i.e. transparent). Normally, most parts in an audio chain are transparent, even the cheap ones.
For example, the Apple Lightning Dongle and MacBook outputs are considered transparent enough for driving its intended load.
The 3 points are my top 3 requirements for an audio system:
I have access to the music library (solved)
I have transparent audio devices
I have transparent enough drivers
Extra points if I can verify the gear performance from independent measurement, or salute to the manufacturers who publish these results objectively and professionally.
Bonus points if it’s also portable.
Although technology has made most audio devices transparent for 16-bit audio for ~10 years now, there’s one link in the audio chain has not yet become cheaply transparent - the speakers.
Speakers convert electrical electrical input signal into motion, which in turn moves air. This is why some calls the device “driver” - it drives air.
In other non-audio usage, devices such as the a speaker (receives electrical signal, outputs something else) are called transducers.
The speaker’s the last component of the playback chain, and it also happens to introduce a lot of artifacts and distortion. Usually, people have a very clean playback signal path (good source, D/A converters, amplifiers) only to get fucked by shitty speakers.
We can put these “speakers” into a box and listen to it directly (consumer speakers), or, if the speakers are small enough, we can build a miniature enclosure around it and strap it to our ears and boom we get headphones. or we can shove the speakers into the ear canal, and we call that earphones.
Sine the word ‘speaker’ is used everywhere, let’s call these barebone speakers, which could be built into headphones and earphones, “drivers”.
The term speaker will only be reserved for refering to speaker as an end-user product, e.g. shelf speakers or floor standing speakers.
There’re many ways to implement a driver. For example, the ER4SR has 1 speaker per channel, and that speaker is a of type balanced armature (BA), while normal free Samsung earbuds come with 1 dynamic driver. My custom monitors have 3 BAs per channel.
Since I’m not good with money and keeping my room tidy, I’ll never be able to build myself a listening room. I also have short attention span and would like to walk around with perfect music in my ear, all the time.
I’m thus left with only 2 options for transparent music listening: headphones and earphones. With these 2 implementation of transducers, I no longer have to care for “the room”.
Both headphones and earphones are just speakers placed very close to or in the ear. In terms of circuitry and how they work, both headphones and earphones are identical.
Very accurate/flat headphones and earphones for professional use are usually called monitors, just like monitor speakers and display monitors.
As of 2025, due to dumb buyers, most premium audiophile in-ears are marketed as monitors to distinguish themselves from AirPods or other in-ear earphones. And these IEM fans don’t actually like real monitors.
With headphones, some of the air (sound) pushed by the headphone drivers will hit our ear first, before going into the ear canal and finally hitting the eardrum. But unlike speakers, headphones drivers are placed directly in front of the ear canal, and the sound just goes straight into the canal, without room reflections and deflections inherent in speakers.
Earphones, whether earbuds or in-ears, do not have this ear gain effect as the sound originates from within the ear, hence no pinna amplification.
If the sound is coming in outside of the ear, as with headphones and speakers, the ear pinna will amplify sound within certain frequency range (1-5kHz). We call this phenomenon “ear gain”, or “pinna gain”. Ear gain was evolved to help channel more sound of that frequency range to help with our survival during the Unga Bunga period.
Knowing that our ear (the external part) has direct effect on sound heard at the eardrum means that when buying any in-ear earphones that bypass the ear, you’ll need some kind of artificial boost in that region.
A totally flat drivers will sound muffled when used as in-ear earphones, because our brain is used to that ear amplification effect
To understand why I love the Etys so much, let me show you my monitor collection, probably in chronological order of purchases:
Of all these monitors, I like Senn HD600 and Beyer DT880 the most, with HD600 being my “reference”, e.g. flattest headphones for 2 years. The midrange from HD600 is still my favorite implementation of “reference sound” in the headphone department.
But being very old, the HD600 still has some bass and treble rolloff. And it’s also open headphones, meaning noise gets in. Bad bad. This is why I kept buying new monitors every now and then during 2016-2018.
You can see how much I love the Etys. They’re the only one I bought twice.
Despite owning several “monitors” and non-monitor headphones/earphones, I still feel like something’s off. It’s like each of my other monitors will sound good overall, but lacking or having some problems in some frequency range.
Then one day I walked into a Korean audio shop, and happened to see a weird looking barrel-shaped Etymotic ER4SR. I suddenly remembered that I’ve read about it on online forums, since maybe 2011, and that people call it “too flat” or “too dry”.
The first one I tried at the shop was ER3SR, and boy was I blown away. It sounds right in every region - the bass, mid, and highs. It also sounds like my HD600 but with fuller sound across the spectrum.
And after hearing the ER4SR, I bought it right away (at the time, I can’t tell the differences ER4SR and ER3SR due to fatigue).
Well it turns out, a lot of things:
Very, very flat sound
Although engineered for decades already (ER4SR was released circa 2016, developed from earlier ER4S, which in turn was developed from the original ER4), no other IEMs come this close for sounding so boring for such a long time.
Being designed by the folks who make hearing-aid and first in-ears, it’s so surprise that the ER4SR sounds so damn good. It sounds good because of its transparency.
You’re almost listening to the music itself and not to the drivers. This is why I call the Etys “boring” in the sense that you almost forget about the monitors had they not penetrating you that deep.
Transparent bass
The bass response is superb. It’s not boosted, but it’s still flat down to 20Hz. That makes the bass very high quality, and you could hear everything including the lowest bass frequencies. People who say the Etys lack bass simply crave boosted bass response, and they don’t even know that their boosted bass is masking the lowest sub-bass.
I also have another pair of IEMs (custom too, in fact) that has some what similar looking flat bass performance: the 3BA UERR+.
Note: my UERR+ is a different model, not UERR as measured in the link above. However, they should sound close, considering UE did not even bother to put up a big marketing efforts for it.
Compared to the much more expensive (\(1000 customs vs \)200-310 universals), the ER4SR holds its own pretty well but still lacks the energy and details in lower frequencies. This might have to do with ER4SR’s single driver being stressed out, but who knows.
Natural mids, with proper ear gain
Because Etymotic knows about the ear amplification effect, they factor this phenomenon into their engineering process. The result? Excellent flat midrange that sounds very natural as if it comes from outside of the ear.
Compared to my CIEM UE RR+, which measures flat at the eardrum (does not factor in this ear amplification effect), the ER4SR mids are not muffled or laid-back, whereas the CIEM sounds like so despite it measuring flat.
Tonality wise this is the best sounding mids I’ve heard. Not too powerful, not too loud, not muffled - it’s just right.
Boring highs (good)
Highs are just right. No piercing and not rolled off. Not sure what’s more to say about this, I’m getting old, so let’s just say it’s not problematic and transparent enough for you to stop thinking about the trebles.
Certificate
Every box of ER4SR comes with a paper certificate hand signed by a human. The cert covers frequency response of both channels, and THD in %. Of all the monitors I’ve bought, only the ER4 family.
US designed, made, and binned (before 2025)
Etymotic has some serious QC pipeline that allows it to match both ER4SR channels to within 1dB.
The 2nd pair I bought in 2025 was made in Vietnam, but still comes with the certificate. Not sure where they measured the VN lot though.
Accessories
You’re for Right to Repair? If so, the Etys are for you. ER4SR comes with 2 sets of any type of tips included. Assume we have 5 types (yes they include that many), then we have 10 tips included.
The box also includes the replacement filter and high-quality metal precision tool to service the tiny earphones.
And this earphones include 2 cases! One rectangle hardcase and a smaller pouch.
Durability and longevity
THe ER4SR is designed for longevity. MMCX cables are replacable, so are the tips and internal tubes. It’s designed to last and be serviced.
I’ve stepped on the ER4SR once, droped it to concrete once, and there’s not a scratch on the barrel. After 7 years, my original pair of ER4SR is still going strong, except for broken cable. The cable broke because I wore them over-the-ear, though it’s designed to be worn normally. That puts extra stress on the cable and cause it break.
In fact, it’s because the cable broke and the replacement cable are somewhat pricey that led me to buy a 2nd pair in 2025.
After getting a 2nd pair, I can confirm that my original pair still work like it’s new.
Superb support
Etymotic replies my emails within 1 business day. I once accidentally put my ER4SR through very high volume (wasn’t listening) and was afraid I broke the drivers. Etymotic replies right away with technical information that basically just says “your pair is ok not fried).
After the assurance, Etymotic offers me to send my pair back to them to verify that it’s still good I did not, simply because I trust them
After 7 years, I asked them about replacement cables, and they replied right away. Last week, I contacted Etymotic asking them about new version of tips I included in the Vietnam version, and they gave me solid and detailed explanation.
Compare this to UE who not only misses deadlines but also not replying to any of my emails (they will direct me to my Thai dealer instead). UE fails to ship date, and when the date came, failed to notify me that the deadline was extended for 2 days after the deadline.
Due to current geopolitical climate, I’m not sure if we’ll be able to buy these fantastic ER4SR in the future. Which is why I bought the 2nd pair - to horde it for myself.
Owning a 2nd pair also combines their accessories to the point that I’ll not run out of tips within 10-20 years. And when I’m paranoid whether I’ve clogged the sound tubes, I can just use the other pair to confirm. If you gotta have reference, why not have 2 references?
In fact, after getting myself a custom UE RR+, I’ve been wanting to buy a 3rd pair for girl from Drop.com because $200 is such a great deal.
TLDR; It’s just that good. Buy before US implodes.