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

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.

final A4000 measurement (frequency response graphs) and comparison with Etymotic ER2XR

Please disregard this post and see the latest final A4000 measurements (frequency response graphs) and comparisons with Etymotic ER2XR using v1.0 of my IEM Measurement Rig.

These measurements are made on my DIY IEM measurement rig and are not accurate, and don’t necessarily represent what you might hear, especially before 60 Hz (huge sub-base roll-off) and after 10 kHz (and maybe even after 3 kHz as my ER2XR graph is very different compared to Crinacle’s post that). You can use it just to get a comparative idea, hence the comparison with ER2XR to give you a point of reference. Improving the rig is an ongoing process.

Here is Crinacle’s ER2XR graph for reference

It looks like final went with the mids to bass rise like in the E series and the highs of the A8000 on A4000.

Notes from InnerFidelity Podcast No. 10 with Dave Friesema, Lead Engineer at Etymotic

InnerFidelity Podcast No. 10 With Dave Friesema

In addition to its extensive hearing and testing products, Illinois-based Etymotic has won over the hearts of many audiophiles with their ER line of earphones. Lead Engineer Dave Friesema chats with us to discuss the company’s design approach to balanced armature headphones, consumer research and what’s next for the future of headphones.

Here are my notes on the stuff I found interesting in InnerFidelity’s Podcast no. 10 (May 1st 2019) with Dave Friesema, Lead Engineer at Etymotic:

  • About Dave
    • He has worked on the ER MMCX series (ER4, ER3, ER2), the first Bluetooth series, HF series and the MC series.
    • He is the project manager for the ER MMCX series.
    • He was a fan of the original ER4 before working at Etymotic.
  • About Etymotic
    • It’s a company of engineers.
    • They have always been a measurement heavy company and use KEMAR mannequins and lots of (single cavity) ear simulators (while at the desk).
    • They have their target for what they consider accurate.
    • Those who have been at the company for a long time know what the ear canal resonance is and they know what the right answer is at this point i.e., 15dB resonance between 2.6 – 2.8khz for insert earphones since the ear-canal is not flat and has this resonance built in. When sound hits your eardrums this resonance is built in so for insert earphones you have shifted that resonance so you have to put it back.
    • Etymotic has always been about hitting targets and is mathematical about it but they give importance to listening because you can’t hear with your eyes.
    • Lots of people in the company have good ears and their inputs are taken.
    • Etymotic traditionally moves very slowly.
  • On Keeping Things Simple
    • Etymotic has always been a single driver (no crossover) earphone company but it’s not to say they would never do multi-drivers. Dave can’t imagine doing something with 10 drivers but if he had to go down that path he would just use 2,3 or 4 drivers.
    • If you’re just putting in redundancy by taking the same driver and using two of them to cover the same frequency range, all you are doing is adding sensitivity and you’re not driving that large of a volume into the ear canal.
    • You don’t really need something that is a 120 dB sensitive with a 100 mW drive. You’ll just blow your ears out.
  • On Accuracy
    • If you have an accurate earphone then everything sounds the way it’s supposed to sound. As a guitar player you want your guitar to sound the way you are used to hearing them. You don’t want the frequency response massively changed to emphasize the frequencies of the guitar, you want it to sit in the mix the way you’re used to hearing it.
    • Years ago they used to go to trade shows and take the KEMAR mannequins with them. Somebody could bring their own earphone and they could play their own music that they would record through the KEMAR and then they would take the recording and play it again and repeat the process 3 times (like taking a photocopy of a photocopy of a photocopy). At the end of 3 loops the Etymotics would sound more or less the same (not perfect though) but with the colored earphones it would make a huge difference after just 3 loops. Either it would sound like it’s totally under water or thin and bright. Every coloration was emphasized with each replication.
  • On The New ER4 MMCX Series
    • Dave wanted to improve a few things with the original 4:
      • 4S was fairly inefficient (100 ohms).
      • 4P was more efficient and had lower impedance. When impedance goes down it tilts the frequency response so the 4P was considered a bass-boosted version but it wasn’t really. 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. It was warmer and wasn’t as detailed as the 4S.
    • With the new ER4SR they tweaked it to bring the accuracy where they wanted, making it more accurate than the original 4S and they were able to drop the impedance to 45ohms.
    • For the ER4XR they went with a different driver to hit the same mid-range and high frequency and get an actual bass-boost (instead of just tilting the frequency response) without compromising the mid-range and treble for it.
  • Studio (Reference|Edition) Series Vs. Extended Response Series
    • The Studio series (SR/SE) is accurate throughout and is flat in the bass
    • The Extended Response (XR) series is about making it as accurate as they could in the mid-range and higher frequencies with a little bit of low-end boost.
  • On Bass-Boost
    • In the ER4 and ER3 there were excursion limits to the BA driver and it wasn’t easy to add 10 dB of bass boost (it was more closer to 4 dB).
    • With ER2 which is a moving coil driver they could have added more bass but they kept it modest which is also a big change for them.
  • On Why Insertion Depth Is Important
    • Makes big difference to higher frequencies.
    • You avoid the occlusion effect with deep insertion.
  • On BAs
    • They source BA drivers from different people and they are all slightly customized but he won’t say if they are Knowles drives.
    • There are very few companies that manufacturer BA drivers and do it well because setting up the tooling for it is not an inconsequential thing (high-precision assembly and expensive).
    • BA drivers come in standard sizes and there’s customization that can be done within it.
  • On Future Plans
    • There might not be more earphone in the ER MMCX series. They went with a good (ER2), better (ER3), best (ER4) family in the series.
    • They might look at adding a higher end earphone as part of a different series.
    • No plans for circumaural and supra aural headphones.
  • Miscellaneous Stuff
    • Bluetooth stuff is disposable electronics. Etymotic users are about buying a few earphones and keeping it for years.
    • MC and MK series are the other moving coil driver earphone along with ER2.

Tyll would have loved the ER2XR

While reviewing the Etymotic ER4SR and ER4XR here is what Tyll had to say about bass response:

For me, the bass level on the ER4SR simply isn’t enough. Frankly, even the ER4XR doesn’t have enough bass for me, but it’s much better. I believe quite strongly that bass response on headphone should have about a 5dB bass boost below about 150Hz.

Tyll Hertsens in 25 Years of Making a Good Thing Better: The Etymotic ER4sr and ER4XR on Page 2

Tyll would have loved the ER2XR 🙂:

When the ER4XR was launched, Tyll applauded Etymotic for making the brave move of catering to user preferences and deviating from that they believed to be technically “accurate”. I think Etymotic went further with the ER2XR (and it’s almost like they took his feedback into account) and for that I am grateful as the ER2XR has just the right bass response for my preferences 🤗.

For me, having over 20 years of close experience interacting with Etymotic and the ER4 product evolution, I find it an interesting example of corporate learning at work. On the one hand, Etymotic has very strong reasons to believe they have a grip on what “accurate” means, on the other, they have 20 years of experience with customer feedback about the desire for more bass. Adding bass willy-nilly is simply not something this audiometry company would do; but having strong feedback that customers want more bass can’t be denied either. Making the corporate decision to deviate from technically accurate to cater to user preference is actually a pretty brave move from their point of view. I applaud this development!

Tyll Hertsens in 25 Years of Making a Good Thing Better: The Etymotic ER4sr and ER4XR on Page 2