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.

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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.

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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.