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

Phonak Audeo PFE122

Phonak is a renowned Swiss-based hearing-aid maker. The PFE is the company’s first foray into consumer audio. During several quick auditions at local meets, I was piqued by how smooth and pleasant sounding they made. Also, the comfort of the Phonak really won me over; I can easily sit back, relax, and enjoy its sound for a long time, though because of the shallow insertion, it can’t match the isolation of the ER4.

Phonak has included 2 different types of filters, grey and black, for the PFE, each giving a noticeably different sound. The black filter gives some loudness effect to the Phonak, adding some bass warmth at the expense of some upper mid resolution. It is not bad per se, actually quite good depending on the music, but for this review, I am using mostly the grey filter, since it really showcases what Phonak does best, which is midrange and upper midrange presentation.

A hearing aid is supposed to reproduce real life naturally to aid the hearing impaired; thus, I have great expectation for the Phonak to be natural-sounding. I was only half correct on that part. Voices sound great with this IEM, but not dead neutral life-like voices, the Phonak engineer adds some upper midrange emphasis, airiness, forwardness and liquid tonal character to the voices. Definitely one of the best mid and upper-mid oriented vocal presentations I have heard for the price. The Phonak is a fairly smooth and laidback sounding IEM, with a distinctive forward upper mid warmth. Grado has similar emphasis on mid and treble; however, they are not as smooth. To make an analogy, listening to the Fischer Audio Eterna is like taking a bite of a rich milk chocolate, the Phonak is like eating a nip of sweet dark chocolate. Rich, but only slightly so.

In some ways, The Phonak sounds like a much less clinical ER4, while maintaining good clarity. Voices reproduction stands out on both the ER4 and the Phonak, with the ER4 being sharper and more distinct, the Phonak smoother and more liquid. Unlike, the ER4, the very last bit of the treble sparkle is shaved off slightly earlier to give a smoother sound. The ER4’s reproduction of voices can be peaky and unforgiving with the wrong setups, tips, or songs. The Phonak on the other hand, is smoother and more forgiving to its source. Some peakiness is still noticeable but only on certain recordings. The bass though, lacks some impact and punch. It is there and still present in the music, but you hear it rather than feel it. The bass doesn’t snap like the ER4 though extension is comparable.

The Phonak can’t quite beat the ER4 technicalities bells and whistles, especially against the ER4S. The ER4 maintains an edge on instrument separation, transients, and imaging, but the Phonak is close enough while being less clinical, smoother and warmer. The music flows a little bit more as opposed to the surgical precision of the ER4. Soundstage-wise, the Phonak is slightly wider compared to the RE-0 and ER4; however, imaging-wise, the sound is a bit diffused in the soundscape. You trade off some of imaging precision for soundstage width. I was listening to this choir track, and I had some trouble imagining the localization of the sound, the size of the room; it just doesn’t add up to a clear image.

One strange thing about the Phonak was that it could sounds a bit mediocre and unfocused on some setups, like on my Ipod Nano. Though the signature upper mid warmth is maintained, it sounds a bit boring and uninspiring out of my Ipod Nano. Out of the Ipod, the transient attack of the Phonak is a bit on the slow and soft side. Some instruments lack a certain snap or crunch to it.

This is not caused by my ears adjusting to the Etymotic, because when I compared it to the Eterna, the Phonak has a muted sparkle, slower transient attack, a bit soft, dull, and too smooth out of the Ipod. The overhang from one note can clash a little with the soft attack of the next note. When the music gets really fast (like very fast up and down and change in volume between the notes), the Phonak has a hard time catching up. On the positive side, this give softness and pleasant decay overhang to the vocals. It’s a definitely preference thing, but I prefer a faster attack, and clearer decay stops. It is not a deal breaker but in the company of ER4S and RE-0, they sound a bit too unfocused.

Luckily, most of these problems were fixed out of my uDAC, which has a cleaner signal and beefier amp than Ipod Nano’s headphone out. Music has noticeably more snap, sparkle and focus to it. It’s not night and day. The improvement is subtle but enough to bring the Phonak to the level of focus competitive in this shootout.

One of my biggest discoveries while reviewing the Phonak, is the impact of adding a 75 ohm impedance adapter to the signal path. The impedance adapter gave the same effect to the Phonak like going from ER4P to ER4S. The guitar crunch comes alive. I like the sound of instruments better, but honestly, some of the warmth of vocal sound has been reduced as well to give a clearer focus to the sound, and this may not be preferable for some genre. Anyway, I recommend this to every Phonak user who has an amp if you want some more focus and sparkle to the sound. The change is subtle, just a nudge to a slightly more analytical direction, but not yet into the realm of extreme focus of the ER4.

The new Phonak Perfect Bass due to launch soon is more reason why you should try the Phonak if you have been waiting do so. Though the Perfect Bass maintains the same exact driver and design, it is cheaper and comes with a better cable and extra set of new bass-oriented filters, giving more option for sound-tuning.



  • Reply June 30, 2010


    Great review Hadi! Like it a lot 🙂

    From the three, which one has better bass?


    • Reply July 1, 2010


      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.

  • Reply June 30, 2010


    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.

  • Reply July 1, 2010


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

    • Reply June 30, 2010


      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.


    • Reply July 1, 2010


      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.

    • Reply July 2, 2010


      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

      • Reply July 2, 2010


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

  • Reply July 2, 2010


    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?

    • Reply July 4, 2010


      Thanks for the comments, rayk.

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

  • Reply July 9, 2010


    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

    • Reply July 13, 2010


      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 😀

      • Reply July 14, 2010


        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.

      • Reply July 14, 2010


        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.


        • Reply July 14, 2010


          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 😀

  • Reply July 10, 2010


    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.

  • Reply July 22, 2011


    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

    • Reply July 22, 2011


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

  • Reply August 17, 2011


    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.

    • Reply August 17, 2011


      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.

  • Reply January 2, 2014


    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.

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