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Sunday, April 22, 2012

Etymotic Research ER-6: The TKer

Several weeks ago, I was able to grab a brand-new Etymotic Research ER-6 from m*xw**.com for $87. This is a discontinued item, and should have never been listed on the website. Well, I talked to the customer service, and they agreed to ship the very last item in the stock for me. Great service, indeed!

ER-6 was introduced in 2002, and it was to be an affordable version of ER-4S. According to Donald Wilson, the developer of ER-4 series:
"The new model will use completely different parts than the ER-4. The goal was to produce a device with a response close to the ER-4S with greater sensitivity, at about half the price. Because of price constraints the cable won't be removeable. Even if the response is close there is always the chance that it might not sound as good as the ER-4. I still plan to make a higher quality version of the ER-4 when I have more time."
And in 2009, upon the launching of HF-series, the end of ER-6 was finally confirmed by an user at Head-Fi. It was a very sad moment for all of us, the headphiles, and Etymotic enthusiasts.

PRO: The frequency response target is quite on the spot. Etymotic Research claim ER-6's accuracy is 90%, and the data just verify that. Moreover, the impedance is quite high; It is almost free from the portable source impedance-induced damping error, which is a common problem for IEMs available in the market today.

CON: It is a pain in the butt(or fingers) to insert this headphone to the proper insertion depth, not because its form factor is large, but because it is too small & short. It is so small, when it is time to pull the headphone out, there is almost nothing to grab onto. I am not sure why the polarity of this headphone is inverted. Also, the distortion figure is slightly higher than the ER-4 series.

ON SECOND THOUGHT: ER-6 is a team-killer. While the current HF-series closely matches the response of ER-4P, ER-6 matches ER-4S, which is more accurate to the reference diffuse field target. No wonder they discontinued this piece of gem.

Just out of curiosity, I did a simple test with different silicone sleeves:
And ER6I-18C, bi-flange sleeves for ER-6i, yields the flattest diffuse-field response! (almost as flat as MC5 with ER38-18)

ON SECOND THOUGHT #2: I completely forgot to mention ER-6 is an OEM product of a Japanese manufacturer, Star Micronics Ltd's PH-001A. In Mead C. Killion's 2003 interview with Audiology Online:

AO/Beck: Can you tell me a little bit about the ER-4 and ER-6?
Killion: Sure. The frequency response of both is very similar to that of the ER-1 from ten years before. Both the ER-4 and ER-6 attenuate outside sounds and mimic the open-ear response so the experience is as close to live music as possible. The ER-4 provides somewhat higher isolation and a slightly more accurate frequency response. We recently found a partner in Japan that had a manufacturing facility in China, which resulted in the lower-cost ER-6 model. 

However, Star Micronics' current official website does not have any information on PH-001A. It does not even seem they are manufacturing balanced armatures anymore. Does anybody know what actually happened to them?


  1. I question the efficacy of aiming for a diffuse field target curve for headphones used to playback music mixed over loudspeakers.

    We don't listen to music over speakers in diffuse fields so why should the headphones require diffuse field calibration? Diffuse field calibration makes no sense to me, and most headphones that fit the standard sound too thin and bright.

    1. Thnx for visiting my blog, Dr. Olive!

      If the diffuse-field reference is no more, headphone acoustics will fall into the even deeper audio's circle of confusion than loudspeaker acoustics.

      According to Theile and Ueda, in headphone acoustics, due to the orientation of drivers set up in a supra-aural configuration, a listener's perceived localization property is random-incidental. Thus, acknowledging such property as a technical reference shall be essential in dealing with binaurally treated applications, such as a BRS or a headphone measurement.

      However, as you have mentioned, a dead-flat diffuse field is definitely not an ideal condition for reproducing regular music materials: too thin and bright, depending on the recording engineer's preference. But since a headphone's transient property is not even close to that of a diffuse-field, headphone manufacturers, including AKG, usually tweak the frequency response to resolve the brightness issue.

      And it is not even worth to mention about a free-field equalization outlined in DIN45500, because it failed to demonstrate perceived tonal linearity more than 20 years ago. Currently available pseudo-free field synthesis products for headphone acoustics in the market are still far from perfect for substituting a loudspeaker environment either.


      G. Theile, "On the Standardization of the Frequency Response of High-Quality Studio Headphones," Journal of the Audio Engineering Society, Vol.34 No.12 (December 1986).

      K. Ueda, and T. Hirahara, "Frequency response of headphones measured in free field and diffuse field by loudness comparison," Journal of the Acoustical Society of Japan, Vol.12 No.3 (May 1991).

  2. You're absolutely right. I have been comparing my ER4-s and ER6 and they do indeed sound extremely similar after correcting volume levels and matching the ER6 with the dual flangers tips that places the drivers relatively close to my eardrum as the triple flanger tips does with the ER4-S. I also noticed the inversion of polarity, but again not important related to armature drivers. I have experienced other BA driver IEM's to be out of phase as well.

    I have noticed some slight distortion with the ER6 vs. ER4S listening to more complex type of music, meaning either orchestral type of music or just rock music with multiple layers of guitars and vocals. Then again I only hear this when I listen in an extremely critical mode, so it may not be there at all..

    Have you tried increasing the impedance of the ER6, bringing it closer to the ER4-S? I tried adding the "typical" 75 Ohm and I felt that it wasn't the right way to go.

    Anyway, the ER6 "was" most certainly an excellent gem and it is actually still out there.. Thanks for re-introducing it


    1. Hi, Finn. You know what, now you said it, I'll have to go back to my good old ER-6 and do a reanalysis with added serial resistance soon. Will it really match close to ER-4B?