Etymotic ER4 over the years

Released in 1991, the ER4 was the world’s first noise-isolating high-fidelity in-ear earphone that became the basis of all subsequent in-ear earphones and in-ear monitors worldwide, creating an entire category of consumer electronics. 30 years later, the ER4 is still produced and while it’s changed over the years, it is still channel-balanced to within 1 dB by Etymotic.

If any earphone was to be considered the most significant in earphone history, it would be the ER4, the one that started it all. So I thought it would be interesting to see how it has evolved over the years.

1991 – ER4 (no suffix)

This was the OG. A number of consumers felt they were too bright with recordings that were mixed for playback on loudspeakers. Based on consumer feedback this was split into two different models: ER-4B and ER-4S.

1991 -ER4B (Binaural, 100 ohm)

The original ER-4 was renamed to ER-4B and was meant for use with binaural recordings as with them it was generally not perceived as bright.

1991 -ER4S (Stereo, 100 ohm)

Etymotic reshaped their target curve to adjust for brightness on commercial mixes and the ER4S was tuned to this new target. From an accuracy perspective, technically the ER4B is the most accurate in reproducing the average response of the human ear canal, but the modified curve that the ER4S was based on is what all of Etymotic’s consumer earphones (sans ER4B) conform to.

1992 -ER4L (Low impedance, 18 ohm)

This was a lower impedance version (hence the L) that was never released as ER4L and eventually became the ER4P.

1994 – ER4P (Portable/Power, 27 ohm)

The ER4P had a lower impedance (and thus more sensitivity) to work with the output stages of portable players of that era. There is some internal debate within Etymotic if the P stood for “power” or “portable”. Most people within Etymotic remember it as “power” but outside of Etymotic it is widely assumed to stand for “portable”.

The ER4P and ER4S share the same driver and the difference in frequency response is achieved by reducing the impedance which in turn results in a tilt in the frequency response. So while the 4P was considered a bass-boosted version, it really wasn’t. It just had a tilted frequency response where the bass and lower mid-range tiled up a little bit and the peak and higher frequencies tilted down a little bit. This made it warmer, which many users liked, but it wasn’t as detailed as the ER4S. Since the only difference between them was the impedance, it meant you could convert an ER4P to an ER4S by increasing the impedance (using an impedance adapter or changing the cable to one with the required resistors) and convert the ER4SR to ER4P by decreasing the impedance.

2016 – ER4SR/ER4XR (Studio Reference/eXtended Response, 45 ohm)

Product Review: ETYMOTIC ER4SR Studio Reference and ER4XR Extended Release  In-Ear Earphones

The latest iteration was the first full redesign of the ER4 and is offered in two tunings: The ER4SR (for studio reference) and the ER4XR (for eXtended Response).

The accuracy of the ER4SR to the Etymotic target curve is slightly better than the ER4S and is Etymotic’s current reference model for accuracy. The ER4XR on the other hand loses accuracy because of a bass-boost (to cater to consumer preference for more bass), but unlike the ER4S/ER4P, the bass-boost is not achieved by a difference in impedance (or sensitivity) and is done instead by using a different driver.

This was also the first time Etymotic switched to using MMCX connectors from the 2 pin one they had earlier.

The test of time

Considering it was the first IEM, the ER4 is the oldest IEM still in production, 3 decades later and a testament to how keeping things simple (with its full-range single-BA driver) can withstand the test of time. Over the years, Etymotic has stayed true to it’s idea of technical accuracy while also catering to consumer feedback for more bass. If the last 30 years are anything to go by, the ER4 isn’t going anywhere anytime soon and it’s here to stay, a true classic.


Grateful to Jeb Pasillas and Dave Friesema from Lucid Audio / Etymotic for all their help in ensuring this post is accurate.

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Etymotic EVO – What We Know So Far

On 1 Jan 2021, Etymotic announced they will be releasing a new multi-driver earphone, a first for them. Here is what we know so far about it.

  • It’s a 2-way, 3 BA driver configuration (2 for bass and 1 for mid/high).
  • It’s voiced more like the XR series and will have around a 5dB bass-boost with the corner frequency at 100Hz or lower (which is lower than the ER2XR)
  • It’s been in development for 2 years and has a custom stainless steel PVD-coated housing that utilizes the Estron T2 connector system and will ship with an Estron BaX cable.
  • It will be blue in color and come with the familiar combination of 2-flange, 3-flange and foam tips.
  • It will have the green damper in the nozzle.
  • It doesn’t have an ambient filter and is an isolating IEM design like the other Etys.
  • It won’t have the channel-matching compliance graph which is exclusive to ER4.
  • According to their social media posts, it’s supposed to be “designed for supreme accuracy and ultimate durability” and it’s “sound signature takes the ER4 to the next level with less canal resonance, increased sound stage and a faster response.”
  • As per Blake Gaiser, Director of Consumer Audio at Lucid, “The soundstage is wider, responsiveness is faster, clarity is better and ergonomics are more comfortable.”
  • On the new connector, Blake Gaiser, Director of Consumer Audio at Lucid, said “(MMCX) was never the right connector for earphones. Excited to share this new connector and we’re definitely looking at balanced variances.”
  • EtyMotion will have a version with the T2 connector that will work with EVO.
  • It won’t be priced under ER4, so price will be $300 or more.
  • Will realistically release in May.
  • You can register to get notified when it becomes available on the official EVO product page.

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final A4000 / Etymotic ER2XR – Listening Session

Note: This is NOT a review.

Setup: DAP [Sony NW-A105] ➞ Music [Spotify (Downloaded at Very High Quality)] ➞ IEM [final A4000 / Etymotic ER2XR]

Track: Misty by Tsuyoshi Yamamoto Trio

  • Track: Misty
  • Album: Misty – Live At Jazz Is
  • Artist: Tsuyoshi Yamamoto Trio
  • Listening Volume:
    • A4000: 76
    • ER2XR: 80

What I hear on this track

  • On A4000, starting at around 0:01, I hear the drummer making what sounds like 2 circles on the snare with brushes which I hadn’t paid attention to on ER2XR. Once I knew it was there I could faintly hear it on ER2XR as well and by increasing volume I could hear it clearly but at the expense of making everything louder.
  • The piano sounds warmer, fuller and rounded/blunted on A4000 while on ER2XR the attack is more defined/sharper, has nice decay and sounding tonally richer and more “real” (actually sounds like piano keys being struck).
  • On A4000, cymbals and hi-hats sound more emphasized, splashy and have a lot of sizzle, drawing attention to them in the mix while on ER2XR they are just there, are more articulate and cymbal strikes actually sound like wood (drumsticks) hitting metal.
  • The upright bass is more emphasized and has more body and mid-bass on A4000. It stands out more in the mix than on ER2XR.
  • Imaging seems more precise on ER2XR, for example with the piano and especially on hi-hat, cymbal strikes and snare hits.
  • While the instruments seem to be panned to similar width on both IEMs, on A4000 the cymbal strikes sound closer and higher. I assume this is because of the boost in the highs. The A4000 also has a larger “sense of space” (wet/reverb).

Track Verdict

With ER2XR, the piano is the star of this track (which is how I think it’s mixed), while on A4000 the trio seem to be fighting for attention. The A4000 has what I call “emphasized detail” on this track where certain sounds/instruments are emphasized (which might make it interesting for some people) at the cost of tonal richness and sounding “natural”. This track is more engaging, immersive and richer on ER2XR for me.

See Also

Interview with Demond, the CEO and Product Manager at ddHiFi, about the companies first IEM, E2020A (Janus)

Editor’s Notes

To truly understand a product I feel it’s important to know the context in which the product was built and what the creators were aiming for, or intended. This is my attempt to learn more about the creator’s perspective and also share it with a wider audience. Hope you like it.

Please bear in mind that the text below is translated by a translator and some nuances might be lost in the translation. If you have any followup questions please feel free to comment on this post and I’ll try to get them answered.

The Interview

Demond, CEO & Product Manager, ddHifi.

Hi, what is your name and what do you do at ddHiFi?

My name is Demond, I am the CEO of ddHiFi, and also the Product Manager.

ddHiFi seems to be a company that creates solutions to problems with great design. What problems were you trying to solve with the Janus?

In our opinion, some HiFi products have gradually deviated from life. They are very bulky and expensive because of unnecessary gimmicks and functions. For the design of Janus, we mainly focused on solving two problems: one is to make it possible to allow two styles of wearing: to hang down naturally or hook it over-the-ear; the other one is to achieve the aesthetics of the overall collection design.

Janus can we worn two ways, hanging down or over-the-ear.

Janus is endowed with ddHiFi’s original design language, which is very important for a brand. Through the overall collection of materials, colors, accessories and packaging, we want to convey a sense of fashion and classic in the color of Morandi. In addition, Janus’s tuning is mainly developed for mobile phones, since we have developed a variety of audio adapters for mobile phones, and we hope Janus and our audio adapters would be an added bonus for mobile phone users.

What design and technical challenges did you face while developing Janus?

During the design process, it’s quite critical to control the overall weight. In order to ensure the stability of the front cavity sound quality, metal materials are indispensable. So the weight of the shell and the speaker need to be controlled reasonably, since light weight can improve the wearing comfort.

The technical challenge is of course the speaker tuning. We first confirmed the design or appearance, so the key element to tuning is the design of the speaker itself with no change to the cavity. During this period, we’ve done a lot of trials and selections.

What design and technical innovations have you done in Janus?

Janus’s dual-socket design is an innovation. It has obtained a utility model invention patent (ZL 2020203726919) in China. In addition to function, we also made technological innovations in the design of the speaker, using a flexible PCB directly connected to the speaker coil, which reduced transmission distortion and also reduced volume and weight.

Flexible PCB connecting the speaker coil and sockets.

Were you aiming for a specific sound and target with Janus?

When developing Janus, there are many retro elements, including the transparent shell. I also hope to find the sound in the memory. It is very pleasant to hear and suitable to convey music, but without an absolute style label.

What sort of users did you have in mind while developing Janus?

When Janus was developed, just like other ddHiFi products, we hope that our products will be used by users who enjoy life. If you already have a lot of headphones or earphones, Janus can still be a present that you can share with your family or friends, so that HiFi music can be integrated into your family life, rather than a toy for yourself.

Is there something about Janus I didn’t ask that you want to talk about?

The development of Janus started one month before Christmas in 2019. At the beginning, we made some metal earphones that looked like Christmas bells and gave them to some friends as Christmas gifts. It’s only around 1 year until its official release by the middle of November 2020. This is a carefully prepared and highly integrated product. We are very confident in Janus. Thank you.

The “Christmas Bell” precursor to Janus.

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final A4000 Measurements (Frequency Response Graphs) and Comparisons with Etymotic ER2XR

I had posted measurements (frequency response graphs) earlier for final A4000 based on my old rig. Here are the latest measurements based on v1.0 of my IEM Measurement Rig.

final A4000 Left and Right Channel Frequency Responses

3 samples each of the left and right channel. For each sample I remove and re-insert the IEM.

final A4000 Average Frequency Response

Average of 6 samples (3 samples of left channel plus 3 samples of right channel).

final A4000 vs Etymotic ER2XR (normalized at 85dB@1kHz)

final A4000 vs Etymotic ER2XR (normalized at 85dB@200Hz)

Etymotic ER2R Measurements (Frequency Response Graphs)

These are the first measurements from v1.0 of my IEM Measurement Rig.

Etymotic ER2XR Left and Right Channel Frequency Responses

3 samples each of the left and right channel. For each sample I remove and re-insert the IEM.

Etymotic ER2XR Average Frequency Response

Average of 6 samples (3 samples of left channel plus 3 samples of right channel).

Compared to KopiOKaya’s ER2XR Frequency Response (Average)

KopiOKaya was kind enough to share his ER2XR measurements (from his rig) with me for comparison and our measurements are pretty close.

Crinacle’s ER2XR Measurement

There are some differences but overall it’s pretty comparable.

IEM Measurement Rig v1.0

After struggling quite a bit with the DIY tube-coupler and in the interest of making my graphs compatible with other graphs out there for easy comparison, I decided to get an IEC6038-4/IEC60711/IEC711 coupler. This is a Chinese knockoff which is supposed to be pretty close to the real deal.


  • Hardware: Laptop > USB Audio Interface > Sound Card (Mic In) > IEM > IEC711 coupler > Sound Card (Front Out) > USB Audio Interface > Laptop.
  • Software: Room EQ Wizard (REW)

Colored earphones and headphones are destructive for certain types of music

To understand this, we need to first understand how records are mixed and mastered.


Mixing is the process of taking raw recorded tracks and using tools like compression, EQ and reverb along with adjusting levels and panning to create a finished stereo mix.


Mastering is the final step in the production process that takes the finished stereo mix and optimizes it for playback on a variety of devices.

EQing individual instruments

Mix engineers first work on the individual tracks to make them sound right and then put them together to make a record. For acoustic music, the mix engineers (especially when they are also the producers or have access) sometimes go into the recording booth to hear what an instrument actually sounds like and then try to replicate that while mixing with the instruments raw tracks using EQ (among other things) before putting all the tracks together to create the final record. The important thing to note here is that the EQ is done for each individual instrument.

Earphones and Headphones as EQ

One way to think about the things in your chain when listening to music, is to think of them as EQ devices (among other things). A colored earphone/headphone in that sense is the same as applying EQ but this EQ is done on the final record (similar to mastering) and there’s a reason the first rule of mastering is “do no harm” and why mastering is all about making subtle changes. An EQ applied to the final record is destructive, especially for well recorded acoustic music where authentic replay matters, because it changes the sound of the individual instruments in different ways and an EQ that works for one instrument might not work for another.


This is also the reason why most earphones and headphones (since they are all colored in some way, some more than others) can’t do justice to all instruments and can at best be good for certain instruments on certain records, and why neutrally-tuned earphones and headphones might be better for well-recorded acoustic music where authentic replay matters (for some definition of neutral, which is a post for another day 🙂).

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