Detail Experts: Etymotics ER4, Phonak PFE122, and Hifiman RE-0

The idea of writing this review came up after we have finished writing the review on the Fischer Audio Eterna. The Eterna opened my eyes how I was able to get so much sound for not so much money. IEMs are getting cheaper and sounding better, on a different level from 4 years ago when IEM market were dominated by Shure, Etymotic, and Ultimate Ears. New IEM manufacturers like Phonak, Fischer Audio, Hifiman Sleek, Jays, many others, and even Monster have produced IEMs that can be mentioned in the same sentence as the offerings from more established companies.

Since the last review we had done was on relatively bassy IEMs, for this review I am assembling a trio of relatively detail-oriented IEMs that shines on the mid to upper part of the frequency range, while keeping the bass on the tight side, a nice way of saying not so much bass. They are not going to produce thumping bass, but I will take good sound across the frequency range anyday over a one-trick bass pony. Keep in mind that if you are listening to a lot of dance, trance, and bass beats driven music, the bass presentation of these three IEMs may not be optimal for those music, as it punches more than it thumps.

Etymotic Research ER4

First one up is the Etymotic ER4, which I owned for 3 good years till I sold it last year. One of the first mass-produced IEM, the ER4 has been an old mainstay in the IEM market. It has amazingly retained the same technology and design since the first time it was introduced in 1991. And they are still considered by some to be among the best-sounding IEM in what they do. The version I’m using for this review is the ER4P, pairing it with a DIY 75 ohm impedance adapter to turn it into an ER4S. Etymotic Research has acknowledged that the difference between the ER4P and ER4S models is just their impedance rating. So basically, by adding impedance in the signal path, you can virtually convert an ER4P into ER4S.

One of the features that I like about the ER4 has that is still unmatched by other universal-fit IEMs is its great isolation to outside noise, 35-42db outside noise reduction as claimed by Etymotic. Because of this, they are ideal for subways and airplane flights, but walking around in the street with the ER4 on is hazardous as you’ll be partially unaware of your surroundings. Its sheer isolation really transports you to a music chamber of your own. This tradeoff is that the ER4 is not terribly comfortable. Microphonic is also an issue with the ER4, and you can hear some sound your foot stomp if you’re walking with the ER4 on.

With the RE-0 being priced at $79 and the planned lowered price of the Phonak, the ER4 is the most expensive IEM in this comparison. However, I would say that the extra money might be worth it for Etymotic’s warranty and service. I have excellent experience with Etymotic’s repair service; they have lots of ER4 parts ready and offer all kinds of repair at reasonable price even for out of warranty ER4s. However, the reliable service center is located in U.S., and outside U.S., you may have to ship your ER4 in, adding to the cost.

Detail Experts: Etymotics ER4, Phonak PFE122, and Hifiman RE-0
3 (60%) 2 votes

  • Earfonia

    Great review Hadi! Like it a lot 🙂

    From the three, which one has better bass?


    • Hadi

      Thanks, Earfonia :). I'm partial toward the ER4's bass for its surprising punch and vivid texture (easier to imagine the actual drum being hit) though extension is not the greatest. Some people may prefer the RE0's bass presentation.

  • HC

    Thank you for the nice review Hadi,

    I've read quite a few rave reviews for the RE0 but remained skeptical at best.

    Recently i tried out the RE0, the unit very new but it immediately caught my attention with its clarity. Its like you mentioned, the details are all there but it is smooth, refined and in no way fatiguing after prolonged usage.

    The next thing was the bass, there was much less quantity compared to my Eterna but it is much tighter and detailed. Not to say the Eterna's bass is bad but the RE0 presented it in a whole new way all together and they are definitely not bass lite. It provides just the right amount of warmth and does not flood into other regions of the sound. It is tight yet very gentle to the listener.

    Besides that, i've been trying hard but i could not find anything that really stands out from the sound. Its like they don't have a signature of their own. I think they may have a hint of warmth making their treble sound smooth and relaxing while still retaining all the details.

    Also, i noticed that they are not very efficient but can be played directly from a portable player such as an Ipod and still sound good. I wouldn't say an amp is an absolute necessity but it certainly sounds better with one. I've been pairing them with the Asus Xonar U1. I know its only a budget dac/amp with a usb connection. However they pair up pretty nicely with each other. The Xonar U1 complements the RE0 by not adding anything else but actually refining the way it sounds. Thus giving better bass control, impact and cleans up the overall sound produced.

    I bought them almost immediately after auditioning due to the fact that details are presented so effortlessly yet managing to sound relaxing. You can really just sit back and let them do the rest of the job of presenting the music to you without having to strain your ears to hear the details.

    At this point, some may think that the RE0 will sound boring on Pop and RnB or other types of bassier songs. I was worried about the same at first but after giving them a chance i loved the end result, it was very refreshing.

    In conclusion, the RE0 sounds neutral maybe with a hint of warmth. There is no real emphasis to any spectrum of the sound. Vocals and instruments produced sound are complemented with just the right amount of bass making them sound real and natural. In simple words, everything sounds just as it is, nothing less nothing more.

    Everytime, i try my best to listen with a clean state of mind and not biased towards any type of sound signature. What i've mentioned above is based purely on my honest and humble opinion and is subjective to each individual. I'm open to criticism and please forgive me if i applied any audio terms wrongly as i'm still new and inexperienced.

    Thank you.

  • HC

    Sorry about hogging the comment section, i just wanted to share my opinion and clearly got carried away.

    • That’s cool, HC. It’s always good to hear other people’s thoughts on the subject.

      We don’t put limits on the comments section, especially when they are honest and thoughtful such as yours.


    • Hadi

      Thank you for the comments, HC. I think you made some very well-thought points about the RE-0 ;), thanks for posting it up. Enjoy your RE-0, you have quite a nice combo there with the RE-0 and the Eterna.

    • HC

      Thank you very much Mike and Hadi,

      The Eterna and RE0 seems to compliment each other.

      They are both enjoyable in their own way and i often find myself swapping between them whichever suits my mood best.

      Now eagerly awaiting the long anticipated comparison between the HD800 & T1. =D

      • I've finished the HD800 & T1 comparison, and it'll be published tomorrow (Friday) :D.

  • Nice review. I have both the RE0s, and now the ER4P. Really enjoy the ER4s over the RE0, they just do everything better while being a little smoother sounding – but that could also be because I get a far better fit with ER4s which go deeper inside.

    Any chance of doing a review of earsonic SM3s?

    • Hadi

      Thanks for the comments, rayk.

      I heard good things about the SM3. No definite plan for now, but we might consider it.

  • jendol

    good review Hadi, I have all three IEMs that you compared here, I prefer er4p over the other two, it has better bass presentation and good seal for my ears. I am intrigue by your impedance adapter, may want to try that and experience how it can improve the sound qualities for the IEMs that I have

    • orz

      Hi; i'm not an expert but this is what I have,

      "impedance adapter" for audio signal works as a "low-pass filter" (, but it's different in my own experience; with low impedance, ER4 has more bass quantity… and so for another phones; if you combine with impedance adapter, your phone's bass quantity would be reduced.

      btw Hadi, would you like to add e-Q7 as comparison for ER4?

      I'm interested on it 😀

      • Hadi

        Yes, that is also what I'm hearing. The 75 ohm impedance adapter takes off some bass quantity (mainly midbass) from the ER4P and the Phonak. Surprisingly, it's harder to notice the difference when I pair the adapter with the Eterna and the DT531.

        Maybe we should let Mike chime in on that :D. I haven't had the chance to listen to the e-Q7.

      • Yes, adding a resistor between a headphone and amp will make the sound more bassy. I tried it before with the HD650, but I was using something in the range of 470 Ohms. A 75 Ohms resistor is barely felt.

        The ER4 is quite the opposite in this sense. I really don't know why specifically. Different driver I guess. I also tried the 75 Ohms adapter on the JH customs, and I didn't like the effect. It was more congested with the added impedance.

        Ortofon eQ-7 is totally different sounding than the ER4. The ER4 is superb on clarity, technicalities, separation. The e-Q7 is more midrange oriented, mellow, great vocals, though instrument separation is not so great.


        • orz

          I've test using a 75ohm adapter to my CK10… results: the high become less edgy; harsh & piercing sound of cymbals and female vocals never bother my hearing anymore…

          Just as Mike says, It's totally opposite of ER4.

          In my own conclusion; if resistor works alone without capacitor, it won't act as filter, neither low-pass or high-pass(mistake on my early statement). I want to catch up more clue about it.

          cheers 😀

  • Hadi

    Thanks, jendol. Impedance adapter may or may not be useful depending on your IEM and/or synergy with your setup. But it's fun and always worth a try since it's relatively easy to get :D.

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  • leonsphinx

    Very well said. Really comprehensive, “direct-to-the-point”  review. I own both the REO and ER4 and have the same observations. Hope to see more reviews from HADI

    • Anonymous

      Yes, Hadi does have that kind of clinical precision when he writes. 🙂

  • BDias

    Using the ER4S without proper external amplification is no good.
    Furthermore, I found the review too lengthy at times (to much text to explain simple things), and not that coherent.  For example, criticizing the Etys for fucusing on a narrow frequency bandwidth: mids and highs (hmmm, that’s seems at least 2/3 of the bandwidth !?) 
    I found the ER4S much better than the other two when amplified. It makes a real difference. Not so much width the ER4P. Also, proper ear canal seal is of great importance to get that wonderful bass. It takes some experimentation and it may well be impossible for some to get that seal. That is the real problem with the Etys: if you don’t seal the ear canal as it should you loose bass extension, power and definition and a lot of soundstage. When properly used (correct seal and decent amplification) the ER4S are as good as any top earphone/headphone, except of course, those exotic and very expensive  offerings from Grado, Stax, Ultrasone, Westone and the like…


    PS: My comment is, of course, biased, but I have seen to many people/critics to jump to conclusions without proper use of the marvelous ER4S.

    • Anonymous

      Thanks, Bruno.

      I think your points are valid, and the ER4S is indeed truly remarkable, and still one of the best IEMs around. I didn’t write this review though, Hadi did, and he is not so much of an amplifier guy.

  • Io

    I hate to say this but really, the ER4S really performs in every way better when amped or at least with a decent source like the fiio x3. I admit the bass quantity is lesser but I find the ER4P bass almost muddy. I agree totally with BDias about the fact that a proper seal is very important. I used it the first time with a bad seal and said it was bassless but remember this is coming from a guy who used the kilpsch s4 which have quite a lot of sub bass thus my basshead needs :d But after a while, I fell in love with the er4s and my friends when he tried it just went ‘yucks, this sucks man, how do you even endure them’ So I guess sometimes it’s just personal preference.

    PS: I insert the er4s seriously deep.