HiFiMan RE-400 Waterline and RE-600 Songbird Dynamic In-Ear Monitors Measurements

HiFiMAN RE-400

HiFiMAN RE-600

Click on graphs image to download .pdf for closer inspection.

Other than the significantly different impedance figures (36 vs. 17 Ohms), measurements of the RE-400 and RE-600 are extremely similar so I'll discuss both simultaneously commenting on differences when aplicable.

Compensated frequency response is fairly flat to about 2kHz, which is right on-target. Thereafter response falls roughly 10-15dB to 10kHz, and then an additional 5dB in the top octave. while the treble balance from 3kHz to 20kHz is good, this region may be a few dB lower than perfectly neutral. The RE-600 is slightly more recessed in this area than the RE-400 as ljokerl note in his listening tests.

30Hz square wave shape is near ideal with excellent linearity and little tilt indicating tight well extended bass. Similarly, the THD+noise remains level in the lower frequencies echoing the indications of excellent bass response.

THD+noise is low for both models, with the RE-600 showing slightly lower numbers at 100dB indicating the slightly better power handling capabilities of the more expensive model as noted by ljokerl in the review.

Both the 300Hz square wave shape and impulse response seem a bit slow to me. The first overshoot of the 300Hz square wave is nicely under control, but the subsequent cycle of ringing is slightly excessive. But while slightly slow and lacking control compared to the ideal, this response is substantially better than average for this type of headphone. It does appear to me that the RE-400 measures slightly better than the RE-600 with regard to these measures.

Impedance response for both cans is quite even with the RE-400 showing a 36 Ohm figure and the RE-600 clocking in at 17 Ohms. 17 Ohms is pretty low, so it's not unlikely that the RE-600 will begin to sound a little loose if the output impedance of the driving amplifier goes above three or four Ohms. Fortunately, evenness of frequency response should be little effected as the impedance is quite flat.

Both headphones isolate quite well and are efficient making them well suited as a traveling and portable can.


hatman's picture

Thank you for the excellent review and the measurements. I am trying out the RE-400s as we speak, as part of the Great Earphone Hunt to replace phones that were lost or stolen.

So far, I've been disappointed with models from Shure, Westone, Klipsch and a host of other brands. Either the sound is lacking, or they don't fit, or they aren't durable.

Out-of-the-box, the sound of the RE-400s is everything you say. The Cowboy Junkies, Sarah McLachlan and Norah Jones sound much as they do on my big rig with Vandersteen speakers or on my Sennheiser 600s and 650s. Percussion is plentiful. Sound stage is just OK.

Nits: The cords look and feel cheap and are tangle-prone, but are easy to loop over the ear for a better fit. Speaking of which, none of the included tips is a good fit for me.

I resorted to a set of Sony hybrids, which increased the cost of these otherwise good-value earphones. No hardshell case was included in my Amazon purchase.

Overall, a very pleasant surprise. Unlike the other tryouts, I'm keeping the HiFiMan RE-400s.

Thanks, Joker and Tyll!

ljokerl's picture

Can't comment on the long-term durability of these yet (my RE-400 is still less than year old) but it really is amazing what they offer for the money otherwise. Of course those who are looking for enhanced bass or sparkly, energetic treble may find other sets more impressive even in the same price range but I wouldn't trade the RE-400 for any other $99 set.

melvin's picture

I've been eyeing some of the Hifiman IEMs for quite a while now but have not gotten it still for various reasons. I know VSonic VC02 is below the level of either of these but how far is the RE-400 from the VC02 sonic-wise? I like VC02's sound sig a lot that I postponed getting an Etymotic iem so I wonder if it's worth the price diff for RE400.

Thanks in advanced.

ljokerl's picture

They're not as far apart as one might think based on price alone - clarity, detail level, etc are all about on-par. They do differ in signature, though. The VC02 is actually more armature-like, with a thinner and brighter overall sound. Definitely more treble sparkle at the expense of being more sibilance-prone than the RE-400. The HiFiMan set on the other hand has less treble but also sounds a little more natural overall (IMO) with its warmer tone and more full-bodied midrange. 

Type35's picture

On your recommended list of IEMs, you mentioned that if you were to choose only two models, you'd pick the Hifiman RE-400 and Yamaha EPH-100 to cover all bases (linearity and transparency for the RE-400 and bass boost and euphonic sound signature for the EPH-100). I was curious to see what your preference would be if you could only select one IEM (no custom) to play any music genre and carry in all situations (work, travel, gym, nightime, etc.) - a jack of all trade of sort (and probably master of none at the same time)?

ljokerl's picture

...it would be the RE-400 (or the Etymotic HF5 as an alternative) - I'd just have the one balanced-sounding earphone. In most cases a balanced sound is an asset and for situations when I simply want more bass punch I can get a $10 Philips SHE3580. Or just suck it up and deal with the RE-400 - it doesn't lack bass, it just doesn't have the low end boosted.

Bennyboy's picture

The Re-400 is definitely bass shy, and that doesnt mean I'm a bass head.

The Re-400 is too small and weak to accurately portray the right level of bass in the music.  It's the same with all HiFiMan IEMs. 

Music in real life has bass and quite a lot of it, if you listen with your ears. IEMs dont generally get the balance of the bottom end right - either its too bloated or its too feeble.

HifiMan probably need to go dual driver to get that sorted.

Try the KEF M200s if you want to hear bass as it should be done.



Alondite's picture

Actually, they're not bass shy, and the measurements prove it. When listening through speakers, a significant amount of bass is actually perceived by feeling it rather than hearing it (or hearing it through bone conduction). This isn't possible with headphones (for the most part), particularly IEMs, because the sound is projected directly into your ear. 

With live music you experience more bass, but it doesn't color the overall sound because the actual quantity of bass isn't boosted. With headphones you cannot add more bass without coloring the overall tonality, because again, much of the bass from speakers or a live performance is felt rather than heard. 

Bennyboy's picture

So how can it be then that my KEF M200s produce much richer, deeper bass that is perfectly balanced against the rest of the spectrum compared to the RE400s?

I don't buy the argument at all. Yes, of course you get more bass impact at a live performance, but that doesnt mean you shouldn't expect a reasonable approximation of that through an IEM. I go to a few jazz gigs - in fact, was at one last night - and I'd say that the KEFs do a brilliant job of reproducing bass tones both on studio and live recordings.


Alondite's picture

Can you prove that the bass is more properly balanced within the spectrum using something more reliable and objective than your own ears? Measurements may not tell the whole truth, but they don't lie, and the RE-400s are almost ruler-flat in the bass region with essentially perfect 30 Hz square wave performance. Were they lacking bass relative to the rest of the spectrum, the 30 Hz graph would bow down to indicate such. 

And whether or not you buy the argument doesn't matter because it's scientifically proven fact. You can pump up the bass in heaphones to approximate the perceived bass from a live performance, but because you're adding more of a particular frequency than the recording calls for, you're goingt to disrupt the natural tonality of the recording. 

Speaker bass is perceived as being more than is actually there, but it doesn't affect tonality because there isn't actually any more of a particularly frequency, you're simply perceiving it in a different way. 

Bennyboy's picture

Yes I can prove it -  I made a drawing of how the music makes me feel. It's a big smiley face. 

oldmantone's picture

As with most IEMs, the factor that influences the bass response is the quality of the seal in your ear canal. If the KEF can get a better seal for you than the HiFiMan, then that would account for your perceived differences.

sp3llv3xit's picture

Hi Type35,

Did Tyll say that if he was given a choice to keep 2 IEMs, he'd choose the RE400 and the EPH100?



sp3llv3xit's picture


Who said that if he was down to two IEMs, he'd choose the RE400 and the Yamaha EPH100?


JoetheArachnid's picture

I have one of the earliest pairs of RE-ZEROs and I will be incredibly sad when they eventually fall apart from their years of service. From what you've said hopefully the RE-400 will capture everything I love in the ZERO; the neutral presntation with just a hint of warmth, overall smoothness and mids that I love but can't entirely put my finger on why. I own a 262 as well but they're not as special to me.

ljokerl's picture

I would consider the RE-272 to be the spiritual successor to the RE-ZERO. The RE-400 is a little different but still hit all of your requisites as well as anything in that price range currently on the market. Who knows, maybe your RE-ZERO will last through the next generation of HiFiMan IEMs.

Bennyboy's picture

Every pair of HifiMan iems I've owned have broken on me pretty soon after buying them. RE-252, RE-262, RE-272, and yep, the RE-400 - they've all been pretty shoddily built if you ask me.

Anyway, putting that to one side, I think the RE-272 was the pinnacle of sound quality from those I've tried.  The RE-400 just didnt do it for me - couldnt get a great fit with any of the supplied tips. When I did finally find a pair of tips that worked, the sound wasn't anything to write home about. Not enough bass, smallish soundstage. The rest was ok, but only ok.

Pretty much a 'meh' IEM for me.

I sold my pair (technically the second pair I had, after the first ones were replaced when the left speaker started cutting out due to connection problems near the jack) to a mate of mine and got the new KEF M200s instead.  Waaaaay better purchase all round.


me1337je's picture

So the 400s are actually even more smooth and easy sounding than the Fidelios? How would you compare the two mid-ranges?

ljokerl's picture

The sound of the S1 is akin to applying a slightly v-shaped EQ curve to the RE-400. You get more of both bass and treble. The bass boost is not a bad thing but the treble makes it less forgiving compared to the HiFiMan set (also not innately a bad thing, but not a plus, either). More importantly, the midrange on the RE-400 is more prominent in comparison to its bass and treble than on the Philips set. I prefer the mids of the RE-400 - they are more capable of the type of intimate vocal presentation I like and the slightly warmer overall tone works for me.

time9000's picture

Decent earphones for the price, but not in the same class as my B&W C-5, which is admittedly more expensive. I also own a couple of the Shure 100 series as well as a 300 series, three different Skullcandy, including the FMJ, and none really compete with the C-5. When I read reviews of the C-5, is was concerned over the comments about fit problems, but this has not been an issue at all for me. The C-5 wins in almost every parameter, tighter, well-proportioned bass, extended, but not brittle highs and a very neutral, clear midrange.  The Re-400 is second in this group, but pretty distant. I've been tempted to give the Grado 10 a listen, but haven't had acces to it yet. Would love to hear comments from anyone who may have had the chance to compare it to the above phones. 

Alondite's picture

I'm not sure what you're hearing with the C5, but it's really not close to the same level of fidelity as the RE-400. The bass isn't more "well-proportioned," it's heavily boosted and is neither tight nor fast. In fact, it's downright muddy. The midrange and treble are also very recessed in comparison, so the whole presentation lacks organic body and air, coming off as little more than a constant bass hum. 

Bennyboy's picture

See my reply to your other point above.

The RE-400 lack bass. Its simple really.  When you hear music done properly with an IEM, that much is glaringly obvious.

Don't get me wrong - the RE-400s are ok, but they're not the new sliced bread that everyone seems to be making them out to be.

Don't believe the hype.

Alondite's picture

If reproducing the exact same amount of bass as called for by the recording is "lacking bass," then what exactly is the "correct" amount of bass?

And I'm not buying the hype, I've heard the RE-400, and they absolutely are deserving of every bit of praise they get. For a measley $100, there isn't a better deal in the entire world of headphones.

Bennyboy's picture

Where on the CD or LP does it say how much bass is supposed to be in the recording?

Please, put away your silly graphs and rulers and theories. Put music in your ears and listen to it - you can quite easily tell if its got the right amount of stuff in it.

Seriously, those RE-400s are way too small to work properly - anyone with eyes can work that out.

Also, $100 (or £100, as the RE-400 cost over here in UK) is not 'measly' - in case you hadnt noticed, a lot of us are not exactly in clover right now. Maybe in the deluded fantasy world of Audiophilia, that amount of cash is just a drop in the ocean, but in the real world its a serious thing.

Alondite's picture

...you're not serious, are you? Every album is mastered with a specific EQ that determines the given ratio of one frequency to another. Open up an audio track in Audacity and you can use the "plot spectrum" too actually see the frequency spectrum. Proper reproduction keeps all frequencies at the same relative volume as mastered in the recording.  

This is the thing that proved that you're an outright fool:

"Please, put away your silly graphs and rulers and theories."

Again, you're not serious, are you? You probably believe that gravity is made up, too. Graphs literally represent measurements of what actually exists, and in what quantity, and scientific theories are factual concluisions made by observing reality. And you're telling me to trust my own perception, which can change radically based on an infinite number of factors? 

If you think the RE-400 objectively have too little bass, then you are absolutely not qualified to claim what proper frequency balance is. The FACTs (not opinions, like what you're trying to push as fact), prove that the RE-400 is nearly perfect with regards to bass quantity and linearity. 

And what does the size have anything to do with it? Have you seen a balanced armature driver? They're minescule, and yet BA sets are capable of delivering exaggurated bass gobs of impact and overwhelming body. 

If $100 is a lot of money to spend on headphones worth twice that, then you've probably made some wrong decisions in your life. Seriously, I spend more than that a week in groceries. 


Bennyboy's picture

Nah,  you can't get away with comments like that. Who cares whether an IEM somehow measures 'nearly perfect'  on a theoretical graph,  when experience demonstrates this is patently not true? Look,  no offence mate but I checked out some of your other comments on this site and it would seem you also think the Ety ER4s have enough bass. Ha,  what a total joke. If there's something fundamentally lacking with thos, iit's the bass. Any 'fool' with half a brain can tell you that. 

As for BA earphones,  I am yet to hear a single BA,  or indeed multi BA IEM that properly reproduce bass frequencies. 

I dunno man -  maybe you ought to go listen to more music and stop looking at dots and lines. 

Denis's picture

You know there is a difference between a fun and an accurate headphone. And yes Ety ER4s has plenty of bass but ONLY when you get the correct fit, otherwise it sounds very thin(weak bass). All reports on RE-400 having weak bass response stem from a bad fit. Many don't get the correct fit with the original tips. Sound also changes a lot depending on how they are inserted - how far from the reference point.

"Who cares whether an IEM somehow measures 'nearly perfect'  on a theoretical graph"?

Maybe most people that visit Innerfidelity? If it weren't for the graphs and other great technical information it would be like most other sites - "I give these headphones 5 out of 5" -why? because I like it's sound signature and it's the perfect headphone for me. With graphs you can make your own decisions to conclude whether it's good or bad for you.

Bennyboy's picture

Having owned the Etys, I can't agree.  I raped m ears repeatedly and tried all sorts of tips on them and still they were way too weak in the low end. 

Same with the RE400 -  tried countless different tips and fittings and still didn't wow me. 

Accurate vs fun music?  Ha,  what an insane concept. If your music isn't fun, what's the point? It's not an academic exercise. The minute you try and reduce music to that, you might as well pack up and move on to a new hobby. 

You seem like the kind of bloke who might enjoy crown green bowls. 




Denis's picture

"Accurate vs fun music?  Ha,  what an insane concept. If your music isn't fun, what's the point? It's not an academic exercise. The minute you try and reduce music to that, you might as well pack up and move on to a new hobby."

What are you talking about?! Who said anything about music. I said there is a difference between a fun and an accurate "headphone". Still, I understand what you are saying, but I won't agree that RE-400 has weak bass. More doesn't always mean better (like in my Sennheiser IE-80 vs. RE-400).

Bennyboy's picture

"What are you talking about?! Who said anything about music. I said there is a difference between a fun and an accurate "headphone". Still, I understand what you are saying, but I won't agree that RE-400 has weak bass. More doesn't always mean better (like in my Sennheiser IE-80 vs. RE-400)."

Um, sorry to have to point this out, but without music going through them, headphones dont have a 'sound'.   Its a bit like that tree in the forest.

The whole concept of 'fun' vs 'accurate' is complete bollocks and just shows how snobbish and up themselves audiophiles can be.  The inference is that somehow wanting to get fun from music is a base pursuit, something that the plebs do, while the Audiophile Gods sit on their acoustically treated clouds and listen to the real, 'accurate' and 'neutral' music.

Do you know how utterly ridiculous that idea is, with its presumption that there is somehow an indivisible truth to listening, that subjectivity can be eliminated and what will be left will be the glorious holy grail of perfect noise?  Insanity.

The only aim should be to have kit that makes your music sound good to your ears.

As for the comment about more not always meaning better - well, duh. Who's saying thats not the case? I was merely pointing out that the RE-400s reproduction of bass frequencies is poor compared to other IEMs out there.  Its pretty weak really.

If you dont get that, try listening to more music through speakers or at live performances (which might be piped through speakers anyway, but you get my point). Bass is just as important as other parts of the spectrum, and if you think otherwise, you're deluded.



Denis's picture

Of course bass is important. That's what usually makes music sound "fun". Billie Jean would be boring without the classical bassline. I'm not sure what IEM's you are comparing the RE-400 to (KEF? and what else) bass wise.

Really, if they were that bass weak (according to you) wouldn't joker say something about that - he has tried hundreds of IEM's you know (aka experience). I've done my share of listening too and they don't come off as bass weak. Yes there are IEM's that have more bass quantity and what not, but there is no way they will be considered bass weak in general public. I'm done commenting on this subject. It's no use. Have a great one..

Bennyboy's picture

Joker?  I dont know, he seems like a nice enough bloke, but having tried and reviewed 300+ IEMs does not automatically make you a guru or confer taste.  It just means you've tried a lot of IEMs. 

I too have tried a lot of IEMs, and I'm prepared to say that to my ears, the RE400 didnt cut the mustard.  They are not so much giant killers and giant ankle kickers.





cyh03176's picture

I totally agree with you, Bennyboy. C5 sounds good for every kind of music and it's best when listening to classical music. I play piano myself and often participate in some performances myself and I can tell everyone that C5 sounds very lively and it makes me feel like I am on the stage. The bass might be boosted according to the graph but I totally I agree with you, these people have to throw away their rulers and starts listening to the music itself. I say the bass adds some weight to the music as to when the piano is played and the string instrument are pulled or picked, the bass about right to makes it sound real. I owned se535 and I sold it after a month because it just doesn't sound right. Honestly, these people who says c5 has too much bass should go and learn to play some musical instrument or go listen to a real orchestra then only come back and post their silly comments. Well, they probably only listen to the pink noise. -_-|||

bikermanlax's picture

I'm wondering whether to replace my 262's with the 600's .  I have an ALO RXMKB amp that uses that TRRS type balanced plug.  While I liked the 262's for more mainstream rock, etc. they didn't work so well for classical/jazz, which is what I primarily use the ALO for.  Any thoughts?

ljokerl's picture

what did you find lacking for classical/jazz reproduction from the RE262? 

bikermanlax's picture

Lack of clarity in the treble, especially orchestral pieces.  Muddiness for piano.  They did well for brass, esp. jazz saxophone.

ljokerl's picture

In that case I would go for something with a balanced armature driver. The RE-600 is an improvement on the RE262 in that regard, but you'll notice a larger difference going to something like an Ety ER4. 

AstralStorm's picture

Just use a trivial equalizer. A simple 6 dB/oct boost with knee at 2500 Hz will do the trick.

This will rid them of all the darkness and will not damage the qualities in the slightest.

If you really unreasonably hate equalizers, order RE-272 set of tips and filters, remove original filters and apply RE-272 ones. A tiny bit more peakiness but a lot more air and brightness.

notraces's picture

I have to agree the RE-400s are fantastic at just 99 bucks. I didn't like them at first -- it took me some time to find some tips to give a good seal - and about 10 hours of burn-in made a huge difference.

I also agree they can get a little harsh at louder volumes -- especially with compressed audio files from the iPod. I just ordered the RE-600's to see what the difference is -- Hifiman has a liberal return policy - but I'm hoping I won't have to return them!

Up until now I've been thrashing around with Senn IE-80's -- somedays I like them -- others I hate them -- but with the RE-400's - they're just smooth and accurate and great amp'd or not...


Great review...

chahahc's picture

Is it just me or do these iems have an uncanny resemblance to the brainwavz m2...

Their impedance curves are similar, all 3 have a minor blip at 2khz

Their impulse responses all resemble each other

Their frequency responses are similar. They have the same hum at around 2khz, the same hump around 5.5khz and the same spike a little above 10khz

I wonder if they took the brainwavz and tweaked and repackaged them... indecision

ljokerl's picture

the M2 is bassier than these, with more of a mid-bass hump and poorer bass control. Altogether this skews the overall balance and performance quite a lot. 


As far as I know HiFiMan and Brainwavz earphones are manufactured by different OEMs so the resemblance should be just a coincidence of two different engineering teams having with similar goals.

nicdub's picture

With the Black Friday deal, the RE-600 is $199. I wonder whether it would have made its way to the Wall of Fame at that price, since it seems to be considered the better of the two. Seems like most people found $400 too much, but $200...

Alberto Martinez's picture

Hi, I need help to finish my decision.
I am getting rid of of big and bulky noise canceling full size Senn PXC450 when traveling weekly by high speed train or airplane with an average duration of 2 hours.
I am looking for best balance in comfort (my ears are very sensitive using small and medium tips), noise isolation and sound quality (new IEMs will be connected to Audioquest DragonFly v1.2 FLAC 24/96 mainly).
Price range $200-400
By now options are HiFiMAN RE-600, Aurosincs Rockets and Etymotics ER4-PT/ER4S (in near feature I will have and iFi micro iDSD o Centrance M8),
Music 70% classic and progressive rock and 30% jazz guitar.
Which one of these 3 do you recommend? Thanks a lot
Please indicate other models of other brands.

IkSak's picture

Hi. First of all, this are great IEM, I've owned them for almost 9 months and the sound is really good. My wife really loves them and I've been thinking of buying an Etymotic 4RPT.

Has anyone tried both and can tell me how are they better and your personal opinion if the 200 price difference is justified.

Thanks in advanced.