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HiFiMAN RE-400

91% Positive Reviews
Rated #12 in Universal Fit


Pros: Magical mids. Warm lilt in the neutral sig. Fast, accurate and punchy mid-bass. Extremely comfortable. Easily driven,

Cons: Sub-bass presence is low. Treble might be too smooth for some. Isolation is average

Packaging and build

The packaging is minimal and exquisitely so. The extra tips filters and manual are behind the felt coated foam holding the earphones. As I gingerly dislodged them from the grooves, I was struck by how tiny they are. I always try to avoid gripping the strain relief as a precaution, but it was difficult considering the size. The shiny bead blasted aluminium back goes well with the brushed aluminium housing. Which brings me to the build. This is the most common qualm people have reported. The plug is beefy, the y split seems sturdy enough. However, I noticed that some free movement of the cable is possible at the entry point of the strain relief. As long as the cable is secured properly within the main housing this shouldn't be an issue. (I was tempted to add a dab of glue at the strain relief end to restrict that free movement).

The half and half cable is… okay. The cloth half is a little kinky (pun not intended). The sticky half is thin and flexible making it very comfortable when worn over ear. Apparently, the hybrid design serves to reduce weight among other benefits.


Accessories, Comfort and Isolation:

Tips galore but an odd assortment. Anyway, I have very narrow ear canals and the smaller tips gave me a good seal. The pseudo-double bump tips gave me pressure problems, so I settled for the bar-tips. The complys are good, but the foam overhangs (ahead of the rubber tube) get scrunched. (I have modified them by cutting off the overhangs) Cable noise is more than present when worn cable-down. Almost disappears when worn over-ear. Can hardly feel then in my ears after a while. It is evident that the HiFiman team has paid a lot of attention to ergonomics. Other accessories include a shirt clip, 5 pairs of stock filters. I have dry wax so I won’t be changing them out anytime soon. Perhaps I could use them to hard EQ them (doubling the filters, felt mod etc.) Maybe later.

Isolation is average, even with a good fit. But maybe that’s about as good as it gets for vented earphones. The vent is placed ventrally and only the deepest fit might shield it partially.



A short intro/disclaimer My experience when it comes to iems is very limited. The RE400 is my first foray into audiophile territory. I’ve been in a V/U-shaped bassy world thus far. 

Chronologically....Sony MDR-E818LP>Sony MDR-EX35LP>Creative EP-630>Xears TD4 Ebony Blackwood>Brainwavz R1>HiFiman RE-400

I’ve loved and hated every set. So I set my sights higher and decided to bravely plunge into a neutral world just to see if that was the right direction for me.

Doing an A:B comparison doesn't make much sense with iems that differ this widely.

My impressions may seem overblown to some. But such a drastic change in direction can do that. Back to the review I expected to be disappointed by the RE-400 in the bass department. I like a little rumble and feel in my bass. But given my inexperience, I was very curious about bass quality vs quantity.


Fast forward to my impressions… I initially thought of describing it by music genre. But after a week with them, I’ve decided to go ahead with the classic break-up.



I’ve always found sharp treble to be off-putting. There is a (false?) sense of enhanced clarity that comes with sparkly treble. But for me, the overall enjoyability dips. I’m absolutely amazed by how smooth the treble is on the RE-400. Some may like a little more sparkle, its sooo perfectly where I want it to be. It may lack some bite with fast electronic music. I found no nasty peaks or dips. To me, the detail and clarity was eye widening (considering my experience or lack thereof).



I was expecting to be impressed. But not blindsided like this. It felt like I had suddenly switched from 192kbps to a vinyl track. The first thing that struck me was how much more life-like it felt. The vocals had a certain texture. Simply put, if that texture was absent, the vocals wouldn't be as immersive. A striking feature was the depth to the vocals (not necessarily to the soundstage). It sounded “wholesome”(male and female alike). I’m finding this very hard to describe but I must persist, because it’s that important. I am able to gauge how much breath and effort the singer is taking. Apart from the core vocals I hear a lot of nuances and details that contribute to that sense of “completion”. This particular feature impressed me the most in this iem. Another thing I noticed is how untouched and unaffected the mids are. No matter how busy rest of the spectrum gets, the mids always come through unadulterated. Like I had a separate pair of ears for the mids. And it seemed like the bass and highs complemented it nicely. Like they were all on the same plane of preference.



I will have to divide this segment into two. Initial impressions and Brain-burnt–in impressions.

Initial: Sub-bass felt non-existent. Some tracks need that sub-bass to sound right. It adds to the ‘natural, warm’ feeling. Sub-bass is more ‘feeling’ than ‘hearing’. Tracks that had a strong mid-bass component were handled beautifully. I couldn’t believe the detail and how fast it sounded. But I would have liked some more punch. Sadly the mids keep grabbing the spotlight therefore I didn’t get to try many bass heavy tracks.

Brain-burnt in: Sub-bass still felt weak. I do see they measure near flat through the bass, but they could do with more presence in the sub-bass. I did find out at higher listening volumes, that the RE-400 extends pretty deep. I feel the punch in the mid-bass now(I think it feels more apparent when you get accustomed to the signature). I find the quantity sufficient(not lacking) now. Surprisingly enough, I’m actually enjoying them immensely. I love the attack speed and the detail, even when it gets busy. I want to say “resolving” but I’m not sure if it is the correct term. I’m quite stunned to find myself enjoying this “type” of bass. The initial disappointment only surfaces when I find the sub-bass lacking. ljokerl advised me to try a “narrow” lift of a few dB in the sub-bass. This improves presence without affecting the mid-bass or the mids. The RE-400 is a very capable iem in this respect. The overall tonality has warmed and I’m not disappointed as often. I still find myself wanting a bit more presence but I don’t think EQing it in is the answer. (Perhaps a vent redesign, dampers coupled with a sub-bass lift). Drums sound very natural (except the deepest reaching ones). It’s easy to differentiate between the types of drums. The bass conveys that much detail.

Bottom line: Bass enjoyment is very track subjective. EQing helps because the drivers are capable

Extra tip: The EQ in Poweramp for Android (with the DVC audio setting enabled) is very effective in boosting the sub-bass without "upsetting the tonal balance"

Other miscellaneous rambling:

The soundstage isn't the widest. The Brainwavz R1 has spoiled me in this regard. But it isn’t congested either. It conveys a good sense of space. Vocals can be very very intimate. And orchestras can be sufficiently spacious. No complaints there. All the music components are clearly positioned and layered without any interference. I believe that is good “imaging”?


Like I mentioned before, I sense an overall “completion” in the music. Vocals will have a ‘bass’ component and a ‘lower highs’ component in addition to the core “mid” component. The RE-400 delivers all of it in equal measure (just a tad more in the mids). I have observed that they sound even better at higher volumes (+1/2 dB above normal listening volume).


I am curious to as to how the RE-400 will perform when powered by a better source. That will have to wait as I don’t have the resources :(


Some have reported good results by using dampers to add a little warmth and presence (even going as far to comparing it to the 400$ RE-600). I will try these mods later on.


Conclusion: This iem was meant to be a test, an experiment. My first foray into neutral audiophile territory. And they have surprised me. They have made me second guess my sound sig preference. I know what I want now (until the next revelation). But what I want now is so different from what I wanted, I doubt I’ll ever have such a drastic change of heart.

I expected it to fit a small segment of my music but I’m shocked at the versatility and satisfaction it has given me in most of my music.


I have a very non-technical way of knowing when music sounds really good to me. It has nothing to do with genre, mood or content. It depends solely on raw music quality. This happens to me with “certain tracks” that span a wide genre(Examples: Imogen Heap- Let go, Jasmine Thompson - Home, Mick MCauley & Winifred Horan - A Daisy in December, Eminem- Sing for the moment etc). Well….. My eyes well up. Not related to feelings of sadness, happiness etc. My eyes simply leak a lot of tears without warning(freaked me out the first time). Let’s just say, I can’t see through the haze of tears when I have the RE-400 on. It’s only happened with the Fidelio L1, some active speaker I can’t remember, rarely with the Brainwavz R1.


The RE-400s have set the bar very high for me. If these had a more sub-bass presence I would have absolutely nothing to complain about. I think finding something much better will be very difficult unless I burn my wallet, so I will now look for an iem to complement (not beat) the RE-400.



@esantosh for all the advice he’s given me. And for replying to my monotonous PMs.

@modulor@Tom22 for their detailed and comforting words from a very understanding POV.

Big ups to HiFinage for bringing HiFiman to India.


Edit: I have rephrased by impressions of the sub-bass. It is my first review, and a year and a lot more experience later, I do feel my wording was not an accurate representation of what I felt regarding the sub-bass.

HiFiMAN has now reduced the price to 79$. The 100$ market is very competitive and the new price gives it even better value.


Pros: Neutral, good to have, 45 degree plug

Cons: Neutral, could use a bit more bass, Microphonics

Build / Fit

They are much smaller than I expected. The aluminum casing is nothing too special, it looks very clean, and simple. The wires above the split are very thin with a feel like they could break easily if you use then regularly on the go. But, below the split is a very nice cloth cable that leads into a 45 degree plug. The fit seemed very loose, even with the comply tips.



Neutral with a very slight rise in a bass. For the price, even for the $99 MSRP, they are incredible. The detail and sound stage are as good or better than some full sized headphones I've listen to. IMO the bass could use just a bit more impact?, not too much though. The Highs were just great, non-fatiguing, but still held the detail very well. The mids are neutral, nothing sounded too out of place. Again, for the price you can not get better than this. There is a reason why HiFiMan calls them the waterline.



I guess this is something take into consideration? I thought is was very simple, clean, like the headphones that lay inside. There is a thick plastic sleeve that I thought was neat.



They are fantastic pair of IEMs to keep in your collection, I will be using them when I am too lazy to put on my SE-215s or is a rush. BTW, Microphonics are a thing. I love the RE-400s, but they feel like something was holding them back from being spectacular.


Pros: smooth sound, good detail retrieval, forward midrange, tight bass, extended smooth highs, excellent imaging and separation, decent soundstage width

Cons: bass a bit soft in punch at times, initial build quality

HiFiMAN RE-400 Waterline - Ultimate Review w/ pictures


1)Equipment and cabling




HiFiMAN RE-400 Waterline


Type: Closed, tiny, in-ear, dynamic driver monitor

Frequency response: 15 - 22.000 Hz

Impedance: 32 Ω (may vary by up to 10%)

Efficiency: 102 dB

Weight: 16 g (with cable)




This was my first in-ear-monitor purchase. Also the very first IEM made by HiFiMAN. Their cheapest headphone yet, priced at 100 USD. How will these compare? They share the general HiFiMAN house sound and neutrality and offerarrow-10x10.png good build quality as well. There is a dedicated RE-400 review below where all will be discussed and compared.


b)Amplifiers, Digital to Analog Converters, Preamplifiers and more


Fiio X1



The X1 is an amazing little unit. In fact, that is an understatement. It's been a very long time since last time I was this overwhelmingly impressed by a $100 unit. The UI is excellent. Very intuitive, rather snappy and easy to navigate. Honestly, I was not expecting an in-house developed UI to be this good, but it every bit is, and it also reads all the formats that I've tried without any hiccups, including associated CUE files. The DAC is absolutely stellar, using an impressive Texas-Instruments PCM5142 DAC chip. The amp section is also pretty good, utilizing an Intersil ISL28291 amplifier buffer. The 2.4" TFT display is plenty big and easy to read, providing all the necessary information even in direct sunlight. It is slightly washed but still plenty good for the price. Among other things the player offers a 7-band equalizer [from -6 to +6 each], gapless playback, sleep timer, usable buttons when screen's off or volume limiting. There's no date and time yet though, which I find a bit strange though not all that important.

The build quality is perhaps the most spectacular aspect - holding the unit in your hand boasts confidence and there's good heft to the unit. The X1 features a fully-aluminium body with very tactile buttons and quality that's hard to find on products costing much more. The Fiio also comes with a screen protector and a rubber protective case, along with a charging cable. The battery life is around 12 hours a run, for a 4 hour's full charge.

There's also the line-out function using the headphone jack, which offers the possibility to use just the player's DAC with a more beefy portable amp. Although I already found the X1's amplifier to perform favorably with reasonable headphones from IEMs to full-sized cans.

I am really struggling to find anything to criticize here... Did I mention it was a hundred bucks?! In a long time, I am left with only fuzzy and completely positive feelings, while using the unit feels just as enjoyable. I really don't understand how Fiio did this, but currently I consider the Fiio X1 a jack-of-all-trades and wouldn't hesitate recommending it to anyone looking for a lovely little DAP and as someone coming from the pretty good, very-happy-with and tried-and-proved Sansa Clip+, I think this is some very high praise.

There's more competition on the way, however :)



+ build quality

+ performance

+ User Interface

+ price, price, price!

+ line-out function



- no time & date, slightly washed-out display


Overall 9.5/10


Fiio E11




A very versatile little amp.

Slightly warmer tonality with smooth highs. Decent instrument separation and soundstage. Ideal for most portable headphones. Fits your pocket nicely. The stockarrow-10x10.png battery lasts about 8 hours.

Packs lots of power. For 60 bucks it is hard to beat. Fully aluminium casing (like all amps here). Has a bass boost switch as well as a low/high gain one. Fiio is getting very popular among audiophiles these days because it offersarrow-10x10.png good quality throughout for the price. The E11 is no exception



+ Small

+ Decent battery life

+ Price

+ Works with most headphones



- Cannot charge while playing


Overall 9/10


[A/N - The amplifier was not tested with this IEM and this was only meant as an informative review. An amplifier is not needed for these if you already own a decent DAP]




The RE-400 cable (not removable)




2)Unboxing and accessories



The RE-400 comes in a rectangular shaped glass-like box. The inside of the box is cut for the individual pieces found inside, that is the headphone, 6 different tips (one comes pre-installed) a clip and that’s about it. The box itself is made from two pieces and these like to fall apart a lot. It doesn’t really hold together well and it really contains only the most basic things. Although they come cheap, a better box would be nice.


Update: Now comes with a nice hard-shell carrying case, more ear-tips and even two pairs of foam tips [all reflected in comfort/fit]. Packaging rating improved.


Package overall 8.5/10






3)Design, build quality and comfort


a)Design/Build quality


I am glad I can say that the build quality of the RE-400 is the best yet of all the HiFiMAN headphones. The headphones look finished and sturdy and could definitely take some abuse. The only issue I had was with the jack of the cable, which snapped, but this was mainly my fault and was briskly replaced with a different jack by my local dealer.

The cable is a bit kinky and likes to get stuck on clothing but is in turn rubberized and of nice quality.

I am definitely happy with the overall feel of these headphones, from top to bottom they feel like a well-made product.

The shells are made of aluminium and feel great in the hand. The cable, on the other hand, ...


Update: The [cable's] build quality unfortunately did not hold up to initial expectations. The shells are not to blame, they are made from aluminium and feel very sturdy the cable, however, is a different story. I had the jack break once and the internals of the cable [meaning the thin wires that are underneath the sleeves] are probably significantly damaged. I need to stress that I took very good care of the IEM, but the cable has a will of its own and it coils down all the town, which is probably the culprit of it. Still it is a thing worth mentioning and a nominal design flaw. I'll bump the build quality down by 3. 


Update 2: Since my inititial issue many months back, these headphones have been holding rather well, though the cable is still microphonic and tangly... I will boost the build quality up for now, assuming the teething problems have been fixed by now.


Build overall 8.5/10 (Build quality 8/10 Design 9/10)










Only one of the 4 stockarrow-10x10.png tips fit me. They came preinstalled on the monitors. Changing the tips is not that hard but since I don’t have any other tips available right now, the stocks will have to do. They isolate quite well. Medium insertion seems best for sound quality and comfort, isolation. They fit in nicely so I can wear them for hours, adjusting here and there. I was worried about the fit a little, but everything seems ok. Decent comfort and fit.


Update: It now comes with more tips, including a two pairs of foam ones.

With them, the white middle-sized tips [pictures further down] currently offer the best comfort/fit ratio. I want to stress out that fit is really important for the overall balance and bass presence. Luckily, there're many tips included now, so finding the ones that fit shouldn't be a problem anymore.


Comfort/Fit overall 9/10


White Tips




Stock tips






4)First and further impressions


There wasn’t much burn-in with this IEM so to speak. Back then I still used my trusty Samsung Wave I (S8500). For now, there is no external amplifier to speak of. I am considering one for the future, as I will probably need one for the RE-600, which I’ll be buying (and subsequently reviewing) most likely. Initially, I was really surprised by how good the sound was. The vocals were butter smooth, midrange was full and lush, bass was nicely detailed, slightly lacking in depth and punch, but very nice. Highs were very smooth but still didn’t lack excitement. Soundstage width was great, extending even out of my head slightly. Instrument separation was still top notch like with all other HiFiMAN. I didn’t perceive any burn-in with these, really, other than changing my phone for a Galaxy Ace II.

They certainly didn’t disappoint.


First impressions overall 9/10




Update: I am now using a Sansa Clip+ and the RE-400 are great with it!

Update 2: I've now purchased the Fiio X1 and the RE-400 is simply stupendously great with it. I will change the review scores and corresponding sections slightly to reflect this marked perceived improvement. I am also using a different set of ear-tips, which come with them now [see pictures] and those give me nearly perfect seal. This, coupled with the X1

makes the RE-400 a seriously amazing pair of IEMs for the asking price.






+ Tight

+ Lots of detail

+ Non-intrusive



- Can be a bit soft at times


Overall 8.5/10 – The low-end of this headphone is pretty good, sounding pretty much tight and punchy, very much in line with the bigger HiFiMAN headphones. As such, it also bears the same relative shortcomings - coming off a bit soft in weight and punch at times, with a bit less oomph than I'd like. But the reward is that the bass always remains tight and in line with the other frequencies, never sounding overbearing but not sounding deficient either. The IEM is certainly potent and depending on the recording it can drop some serious bass, punchy and extended, but still controlled, mind you. Now that I've achieved a proper seal, I don't think the bass is lacking or weak anymore. Instead, it is just the traditional HiFiMAN signature bass I learn to really appreciate.





+ Balanced across

+ Natural and sweet

+ Instruments have their space

+ Pretty great detail retrieval



- None


Overall 9.5/10 – I don’t personally take any issues with the midrange. In many aspects, it is like a full-sized HiFiMAN lite. It lacks the ultimate spaciousness and air of the full-sizes, but it still offers an absolutely even instrument reproduction across, with a balanced but still dynamic sound. The midrange is slightly forward, just enough to keep its bite but smooth enough to not be fatiguing and providing hours on end of enjoyment. This is the area where this headphone definitely shines. 





+ Nicely extended

+ Sufficient presence

+ Absolutely non-sibilant

+ Clean



- Lacks some air


Overall 9/10 – The vocals work rather well for my tastes. They are present at all times, without ever sounding muted or constrained and still very much smooth and sweet. There is not a massive amount air but there is a enough to make this IEM sound more airy than most sealed headphones. They have a fair amount of extension, but not overly so and this contributes well to the smooth signature of the RE-400. These IEMs are not bright by any means, but they aren't dark either. Still, they play nice with everything I've thrown at them, producing a slightly warmer but still fairly neutral sound.





+ Natural

+ No added presence

+ Just enough extension

+ No harsh moments



- Lacks the last bit of extension and air


Overall 9/10 – The highs work the same way as the vocals and midrange. They are sufficiently extended with some slight roll-off to prevent them from ever sounding harsh with cymbals for instance but there is enough presence there to carry all the necessary information without overdoing it. Electric guitars never sound edgy either. Together with the rest of the frequencies they offer a smooth, balanced and forgiving experience ideal for traveling or relaxing at home or work. They do many things right without doing any obvious wrongs and as such they are hard to put down.


e)Soundstage/Instrument separation/Imaging



+ Great width

+ Stellar instrument separation

+ Smooth and even tonality

+ Plays nice with everything

+ Detailed



- Lacks depth and height


Overall 9/10 – As I said, the tonality of the RE-400 is very smooth, while offering great detail retrieval and musicality. Due to the tight bass, I wouldn’t recommend them solely for hip-hop or rap, though they still perform reasonably. These offer just a sibilance-free, engaging but relaxing experience. Basically a toned down full-size HiFiMAN in all aspects with some slight roll-off at both ends. The instrument separation is excellent and the soundstage width is likewise great. Center stage is very coherent and does not exhibit any oddities or unevenness and nor does the rest of the stage. The imaging is likewise excellent. 


f)Recordings sensitivity


Overall 10/10 – These belong among the more forgiving headphones for sure, and they're probably  the most forgiving “audiophile” headphone I have heard so far. I never had to turn the volume down with these because of harshness or sibilance. The interesting thing is that it still extracts a very fair amount of details and it does it really well without any obvious peaks or recesses, which usually isn’t the case with other headphones. HiFiMAN has managed to master the balancing act with these, offering great detail retrieval with a smooth tonality - something that is very hard to achieve.


Overall Sound


As such the RE-400 belongs among my favorite headphones - with tight and punchy bass, present mids and smooth and extended highs. Coupled with good detail retrieval, good soundstaging and remarkable imaging and separation, these fit right into my favorite sound signature, with very few minor imperfections that are easily forgivable based on the price/performance ratio these little puppies offer.


Sound overall 9/10




RE-400  N/A (I wouldn’t consider an IEM for gaming, really. Feel freearrow-10x10.png to give it a try if you want though and report back :})


[HE-6 and Pro 900 have been reviewed for gaming, to see the gamesarrow-10x10.png that I've tested and how those did, check their individual reviews on pages 1 & 6]




The RE-400 would be my top pick for portable headphones. It doesn’t really need any sort of amplifier to sound top notch. The signature also works really well when you want to focus on other things or just relax. Every song works here so you don’t have to worry too much about quality and specific playlists and as such it could very well be your perfect travelling companion.


Portability overall 10/10


8)Unique trait




The tonality of the RE-400 is one of smooth nature and rich detail. This tonality is particularly inviting to me because there are not all that many headphones with such traits. There is a bit less highs and vocals presence and bass than with the HE-6, making it similar enough in tonality but different enough in presentation. If you want a totally smooth pair of in-ear monitors this is the right one to choose. The RE-600 should offerarrow-10x10.png similar tonality as well with more body and less roll-off at either end. W will soon find out :)




9)Songs and genres


[see HE-6 Ultimate Review, page 1]




This was my very first serious IEM purchase. I was a bit skeptical about just how good such a tiny driverlike this one can sound. I was quickly reminded that at HiFiMAN they simply know what they are doing and how to produce top notch sounding products. Even in direct comparison with full-size offerings, this little fellow muscles up and certainly holds its own ground. It is not as extended or airy or spacious as its higher brethren but the price is much more feasible and honestly, an IEM just cannot sound that way. Still, for just around 100 USD you get a sneak-peak into the HiIFiMAN house sound. The performance was smooth throughout coupled with a highly enjoyable signature straight off your DAP's jack. I've tried an amplifier to see how much difference it would make, and there was none - the X1 just sounds phenomenal with these. As is, this headphone is simply too good to resist at the price point and everyone who is looking for a very decently priced, neutral-warmish IEM to get, you might as well pick this one up. You certainly won’t regret it.


Overall value 9.5/10




The joint point






This is a seriously good IEM, absolutely suitable for portable use. I am not a huge fan of IEM due to their inherent shortcomings [lacks the soundstage of full-sized headphones, etc].

I am one of the few who don't mind carrying around full-sized headphones, provided they are not difficult to amplify well.

Still the RE-400, being a bit of my IEM premiere, did not disappoint me and I sometimes prefer it to full-sized headphones when I want that smooth, detailed yet non-fatiguing sound.

For a hundred bucks, this is a great, great IEM, even though the cable could have definitely been better made, at least initially.


RE-400 final score 9/10


12)Special thanks: 


[See HE-6 Ultimate Review, page 1] 


Kindest regards and thanks to anyone reading this. Hope you liked it!

Luke, the reviewer


Pros: Exceptional tonal balance and clarity, not boring or overly bright, build quality, comfort

Cons: Sound is not for the bassheads, cable feels a bit delicate but it's probably nothing to worry about


CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 90




HiFiMAN needs no introduction around here, so I'll simply share my opinion briefly. In my mind, not only are they one of the premier manufacturers of headphones and related gear, but - and this is possibly more important - they deserve a lot of credit for helping advance the headphone industry in general. Of course, they aren't alone in this category. Plenty of others have done amazing things over the last few years. But I can't think of anyone who even approaches the broad portfolio of HiFiMAN. They have gear competing for best-in-class in a variety of categories - their HE series of planar magnetic headphones, their RE series of IEMs, their EF series desktop amps, their HM series of portable players... all that remains is a dedicated DAC or two to completely cover the full range of HeadFi hear. 

I've reviewed the HE-400 headphones and loved them. I also use the HE-500 and those are great too. But this is my first time actually having a HiFiMAN IEM of my own. I've heard some of the older models like the classic RE-0 and RE-ZERO, as well as the more recent RE-262, but never got to know them well enough to really form a solid opinion other than "they seem good". HiFiMAN contacted me and asked if I'd like to review their newRE-400 Waterline IEM ($99). Since I write for InnerFidelity as well and have plenty of reviews on deck, I wasn't sure if I would have time for this one. But I decided to work it in and boy am I glad I did. 
Like all the prior RE models, RE-400 uses a dynamic driver. In this case HiFiMAN uses an advanced 8.5mm unit with a titanium driver. Impedance is rated at 32 ohm, sensitivity 102dB/1mW, max power 30mW. So don't try running this on HiFiMAN's powerful EF6 amp as it probably won't be ideal....
The cable is made from OFC copper and has a cloth sleeve leading from the 3.5mm, semi-angled plug to the Y split. From there it uses a soft rubber material leading to the earpieces themselves. I speculate this section was left "unsleeved" to minimize microphonics. It feels kind of flimsy but also strong at the same time and very flexible which is a good thing. Having been in the IEM game for a few years now, I'm sure HiFiMAN knows what they are doing with respect to making sure cables are appropriately durable. Bonus points are awarded for the slider which appears to match the silver shells of the IEMs. 
The IEM body itself is made from a metallic substance (aluminum?) and feels durable yet lightweight. There's a very small port on the bottom of each earpiece which is fairly common for dynamic based designs. Isolation doesn't seem to suffer - while these are no Etymotic ER4s, they do have moderate isolation as could be expected from a design like this that seems designed for medium insertion. I can get them to go in rather deep if forced but the sound gets worse - I don't think they were intended to be used in that way. 
Looking at the pictures, or even seeing them in person, these don't seem like tiny IEMs. The Ultimate Ears UE700 or the Jays Q-jays are the two smallest models I can think of, and the RE-400 doesn't strike me as being in the same category with regards to size. Even so, it's definitely on the small side, and real life shows them to be smaller than I had expected. Even with medium insertion the shell nearly disappears into my ear and is hardly visible from the outside. This makes the RE-400 one of the few IEMs to be suitable for listening while laying down. 
The RE-400 comes with a rather nice assortment of tips - think quality over quantity. I got good results with the typical medium sized single flange tip. But I got even better results from the medium biflange tips. I don't normally get along very well when it comes to dual or triple flange tips so I was surprised at this. These tips have each "layer" closer together than most biflages, and the insertion is barely deeper than the basic single flange tip, so perhaps that's why it works so well for me. 




I listened to the RE-400 on a variety of equipment including:
Sansa Clip+
HiFi E.T. MA9
I also used my big home setup based around an Auraliti PK90 player and a Resonessence Labs Invicta DAC/amp. The RE-400 hits the "sweet spot" of usability - it doesn't sound terrible on a basic player, but does scale reasonably well as your source and amplification improves. I appreciate this as some of my IEMs sound miserable on a basic DAP, and others top off too quickly. The RE-400 seems to have something for everyone. 



The first thing that struck me about the RE-400 was the clarity. It's got a very clean, accurate presentation which defies any attempt to stereotype IEMs based on a "dynamic driver sound". If I believed the stereotypes, I would probably think this was an armature design but that just isn't the case. If you think all dynamic IEMs have thumping bass and somewhat slow or muffled highs, you obviously haven't heard enough of them to know better (and specifically, you haven't heard anything in the RE-series).
The overall sound falls slightly onto the analytical side. It doesn't go as far as something like an Etymotic, but it does tend towards neutrality and precision rather than relaxed fun. Bass doesn't thunder but what's there is tight and accurate. I find that most of the time it is plenty satisfying for me - any type of rock or jazz, or practically any music using real drums, sounds very nice. Only when trying some hip-hop and electronic music where exaggerated bass is the focus, does the RE-400 seem occasionally lacking. What's there is great - there just sometimes isn't enough of it to rattle your ears in the way you might want. Again, this is a tuning choice rather than a deficiency, and the RE-400 joins the Sennheiser HD800, AKG K701, and many other models with deliberately non-bass-heavy sound signatures. But I don't want to make it sound too bass light - the RE-400 is plenty satisfying for me in all but a few cases. 
Mids on the RE-400 are really the star of the whole show. Open, clear, and very transparent, they carry the listener further into the music than any $99 headphone has a right to. Vocals sound clear and lifelike. Snare drums have appropriate snap. Everything sounds "real" for lack of a better word. It's quite intoxicating, and forces me to cast an accusatory glace at some of my other (more expensive) IEMs like the $399 Westone AC2. The AC2 has some great bass but could definitely learn a thing or two from the RE-400 in terms of midrange transparency. 
Because of this excellent midrange, the RE-400 works well with "audiophile" grade recordings. I had a great time listening to Marta Gomez - Cantos De Agua Dulce, Livingston Taylor - Ink, Oscar Peterson Trio - Night Train, and a boatload of classical works from a variety of labels. I even tried some DSD tracks through my Resonessence Labs Invicta and they sounded stunning. I can't think of a better $99 headphone or IEM with which to listen to great recordings. 
The top end of the RE-400 is extended and clear, but not overly sparkly. For some people this will be very welcome - hot treble is something that really bothers certain people, and can kill an otherwise great listening experience. The RE-400 is nicely balanced - fairly clean and extended without being harsh or overly emphasized. The downside is that some people might find it a little boring. I personally don't hear it this way but I can see how someone else might. If your preference is geared towards the super-exciting, you may find the RE-400 a tad bland. 
The good part about the highs being the way they are - this is not a completely unforgiving IEM. Sure, it sounds better with quality equipment and recordings. But it rarely becomes completely unlistenable. That's not the case with some of my high-end custom IEMs which practically demand a good source. I recently listened to a flagship custom (which shall remain nameless) on a Sansa Fuze - playing Mastodon's Crack The Skye, I could only handle a few tracks before I had to turn it off. It just sounded like a blurry, harsh mess. I'm very familiar with that album on my home setup and while it isn't exactly a Steve Hoffman masterpiece, it normally sounds far less strained. So I switched to the RE-400 and bingo! I could actually enjoy the music once more. There's a headline in there somewhere: "Extra! Extra! HiFiMAN RE-400 superior to $1,000+ 6 driver CIEM! Read all about it!" This is deceiving of course, because switch to a better source and that flagship custom completely dominates the RE-400 - as it should for the price. But what I'm getting at is this: the RE-400 is not overly analytical and actually does a great job with average quality sources. 



I'll keep this fairly simple - the RE-400 is not a massive deviation from the earlier RE-series models. I'd call it more of an evolution than a revolution. It hasn't turned into a bass monster, nor has it gone completely ER-4S all over the place. Still, in some ways it does seem to have developed a more "universal" sound. I suspect the even response and clean sound will work for more people, though a few who previously loved the RE-0 might find RE-400 too homogenized for their taste.
As far as I'm concerned, the RE-400 is about as good as it gets for $99, and then some. That includes IEMs and full sized headphones too. I can think of nothing else in the price range that has such smooth, transparent sound, and still remains engaging. Add in the quality build, excellent fit, and well-proven history of customer support, and it seems like an easy recommendation. HiFiMAN does it again!


Pros: Balanced yet slightly warm and sweet, beautiful and realistic mids, price

Cons: Lack of sub-bass and a tad sparkle, microphonics

After I bought the HD 598s, I was soon looking for a portable set of headphones or IEMs for casual use on the bus or outside. Sure enough, I found the lauded HifiMAN RE-400 to be an interesting option and even with concerns of durability and the possibility that a neutral sound signature wasn't for me, I bit the bullet. Were they worth it? 


Comfort, Design and Accessories:


I found the RE-400's to be well-designed overall, featuring a rather large plug and a cable comprised of both cloth and rubber. The drivers and the casings surrounding the drivers are rather small, which is a definite plus for portability. They also come with a wide array of tips and a rather convenient little case that can hold some extra tips and the RE-400 itself. I myself found most of the tips uncomfortable and stuck with the smallest tips but with the plethora of choices at hand, one can easily find a fit comfortable for them. To note, the RE-400's can sometimes be annoyingly microphonic at the rubber part of the cable in particular but this can be somewhat avoided by wearing them over the ear.


Though I've heard the cases of unpleasant durability, so far that doesn't seem to be true and these seem like they'll last easily for another two years. As far as comfort goes, I find the RE-400 to be satisfactory but not perfect. The fit is fairly comfortable but over time it can get warm and unpleasant in my experience for listening sessions over an hour or two. Perhaps with other tips this can be remedied but I haven't found that to be the case. Isolation for the RE-400's is average for the most part and even with a good fit, much of the background noise around myself is still discernible.



Sound Quality:


Overall, I found the RE-400's to be easily satisfactory for my musical listening purposes. The sound signature of the RE-400's does seem to be neutral and balanced but as many have noted, is also warm and sweet which makes the RE-400's sound detailed yet not analytical.


The treble of the IEMs is well-extended and definitely unfatiguing with a small amount of sparkle in the upper regions of frequencies. Drums and cymbals sound detailed and well-presented without being overly detailed and sibilant. However, this can at times sound a bit too smooth and without more sparkle, instruments and electric guitars in particular don't sound completely realistic. (when I hear a violin, I expect to hear some bite on the sustained, higher notes but the RE-400's present them without much harshness)


Mids on the IEMs are wonderful, bring very realistic and slightly forward in its presentation. In particular, guitars and vocals sound beautiful and almost immersive with detail to attention in the depth of vocals and string instruments such as violins and cellos. Most impressively, I can hear the breaths of vocals and little footsteps which I hadn't heard before in my music. However, male vocals, though sounding beautiful can come off as a tad dry and not quite as lush as I'd like but at this price point, it's to be expected and so this is a very small concern.


Initially, the bass of the RE-400's seemed far too anemic and lacking, especially the sub-bass. I expected this and waited to burn them in for about 50-100 hours before deciding my feelings on the bass. After burning them in and getting used to the sound signature, bass seemed much more present than beforehand and even though I still feel there is a lack of sub-bass, I'm pleased. Bass overall is well extended (perhaps even more than my HD598!) and is tight and fast, which I appreciate.


The soundstage on the RE-400's is slightly better than what I expected pretty much at the price point and the design and it does seem reasonably wide and tall enough. Curiously enough, the soundstage seems to be slightly angled. I don't know if I'm imagining this but it really does seem to be angled and it sounds a bit more 3-D than what I expected from these. 


In short, the RE-400's sound wonderful with a warm, sweet neutral sound signature and a satisfactory soundstage. Though I have minor problems with the treble, mids and the bass, this is due more to the fact I prefer a slightly more colored presentation and so these are really good all-rounder portable IEMs at this price especially. The RE-400's are great all-rounders but if you are looking for a headphone/IEM that can deal with more electronic and hip hop music of that sort, you're better off looking for something else.




To conclude, the RE-400's are most definitely worth the $99 price tag. These don't require an amp but it does benefit a bit from amping if you wish from my own experience. More to the point, these are a great value and it does seem like HifiMAN has made a new waterline for the $99 IEM. These hit a rare balance in sound, good overall balance and detail yet pleasantly warm with an angled soundstage. Companies will be surely trying for years before they succeed in producing an IEM equal or better to the RE-400's. Right now these are only $99, a price that HifiMAN could've made $199 and costumers would still be satisfied. 



Albums Used:


Belle and Sebastion- If You're Feeling Sinister

Daft Punk- Discovery

Jeff Buckley- Grace

Living Stereo: Bruch Violin Concerto No.1; Scottish Fantasy & Vieuxtemps: Violin Concerto No. 5

Nirvana- In Utero

Radiohead- In Rainbows

Wilco- Yankee Hotel Foxtrot


Pros: Delicate and trully musical, timbres, fatigueless

Cons: Very slightly warm sounding, not as spacious as other's

I am only listening to acoustic music, So I had no issue with the amount of bass (only plugged to my FIIO X5II, Flac, APE, Highres and DSD files). Even though they are not as tight as on my Shure's Se425 they are well balanced with the rest of the spectrum.

Slightly on the warm side but perfectly balanced, not in the face , musical, smooth apart from a little peak on the high mids, they have an amazing respect for the timbres, which is for me the main point.

The relative lack of definition participate to how "liquid" the music is just like in concert. Everything is integrated in a delightfull way, not much sticks out.

On some tracks I was expecting a little bit more dynamics but I have never heard a pair of IEM's that accomodate so many different style of recordings. 

Bought second hand (perfect condition) for 40€, it's the bargain of the century.

Higly recommended for classical music lovers.


Pros: Smooth neutral sound, amazing soundstage, very detailed yet not fatiguing at all.

Cons: Supplied ear tips may not get a comfortable seal.

Where do I start? These honestly sound like the HD600/650 in IEM form. My previous go to IEM was the Klipsch X10 ($100), followed by the Klipsch X20i ($539). What is amazing, is that the RE-400 sound smoother, are more realistic, have better treble extension, AND have better soundstage than the X20i. And these cost just $79! I am continually impressed by these the more I listen to them. They seem to work with every genre too. For classical, they bring out every instrument texture to make them sound realistic. For pop and EDM, they have decent impact and sub bass extension, but are not for bassheads. I would describe them as neutral, and very slightly warm. Some may say they don't have good sub bass, but I disagree. If you are used to Hifiman's planars like the HE-400i and HE-560, you will notice these have extremely similar bass presentation. Mids are fantastic, very realistic and right where they sound be. Maybe slightly elevated compared to most IEMs, but only very slightly. Treble is so smooth, no peaks at all. I must say, the tonal balance is smoother and more realistic than many over ear headphones such as the Beyer DT800 and T1, Hifiman HE-400i, and Shure SRH-940, and sound very similar to the Sennheiser HD600/650 in the mid and treble regions.

The only con I can think of is the supplied ear tips may not fit people with smaller ear canals like me. The smallest size is ok for me, but doesn't seal as well as foam tips, and the next size up is too big. So I ordered Comply foam tips (the TS-400 size) and hopefully those will get a better seal. However, even without the best seal, it doesn't seem to affect the sound that much, because they already sound fantastic. 

Considering these sound significantly more balanced and natural than what the Klipsch IEMs have to offer, at under the $100 price point, is a huge accomplishment in my book. You probably wont find a better sounding audiophile IEM under $100, or maybe even up to $300. I wouldn't be surprised if these match the performance of the king of dynamic IEMs, the Sennheiser IE800. Hifiman sure knew what they were doing with these, and I can't recommend them highly enough!


Pros: Good balanced sound, Solid build, Comfortable

Cons: No in-line controls

Source: Macbook 12 with Audioquest DragonFly v1.2


Comfort and Construction:


Overall the comfort level was good to me for an in-ear monitor. The key is to correctly size the inserts. Cord length is good for this type of ear monitor. Ended into a 1/4” plug with a 45 degree angl. For use on an iPhone or iPod, this may be a slight distraction. The cord is sturdy. Seemed to have good thickness without being too thick. There are no controls on the cord. This could be a deal-breaker for some.




Overall, the RE-400 has a good sound. The highs are crisp and detailed. The mids are solid. It does lack base, but most in-ear monitors will be the same. Isolation is good for an in-ear monitor. No active noise cancellation, but with a good fit using the correct inserts, the isolation is satisfactory. I was impressed with the clarity of these. Good sound separation.




Easy to recommend if you are looking for a reasonably priced in-ear monitor. Good sound and comfort. Need to decide if the angled plug will detract or lack of in-line control forces another choice.


Pros: flat frequency response, excellent timbre, quick, very clean decay, inexpensive, comfortable, discrete fit, impact, not BA, responds well to EQ

Cons: benefits from EQ, not much high treble extension

A bit of background:

Warning: Spoiler! (Click to show)

I have never really been that into portable gear.  I have already sunk a lot of money into my home setup, it is more comfortable to use than in ears, more conducive to critical listening, and generally I like to be aware of my surroundings when walking around in public.  I am however well past the point of diminishing returns with my home setup, and occasionally its nice to tune out from the unpleasantness of public transport, plane travel etc. and still have an acceptably engaging and truthful sound quality from portable equipment.


In any case I am used to over ear desktop sound.  Relative to my desktop gear in the price range I am looking at is compromised in one way or another.  More often than not with multi balanced armature in ear monitors there are certain colourations due to the BA drivers themselves, crossovers, peaks and dips in frequency response.  More often than not the BA headphones I have tried exhibit an airy sound quality that sounds nice and detailed, have excellent separation and detail.  More often than not though you know you are listening to a multi BA earphone.  The JH Layla was an exception, showing little of the usual BA colourations (not airy or soft), having excellent dynamic impact and incredible imaging.  Eventually though I tired from the lack of micro detail resolution and poor fit, and incredible local cost (our currency in Australia has dropped in value).  I sold them and went back to my Westone 4's.


Anyway the trend with multi BA earphones seems to be stacking more and more drivers to develop a more forceful detail presentation and dynamic impact, and get away from that sort of vapid airy BA sound.  This however is very costly and more often than not still results in peaks and dips and phase irregularities and other colourations to the sound.  Coupled with the weakening Australian dollar, chasing high sound quality using multi BA based earphones is getting expensive.


Recently my Westone 4's died, so I went on a search for replacements.  I tried a lot of the new multi BA options.  They are making progress in sound however IMO are still quite compromised in sound quality versus full sized earphones.  I also tried some of the new extremely expensive dynamic in ears (I won't mention names).  They had some nice qualities but again have substantial coloration to the sound mostly due to uneven frequency response and ringing distortions.  I am always happy to see new research and development in dynamic in ears but I don't fancy spending big money on (still) flawed products.


Now to my review:

I think my demo of the HifiMan RE-400 was one of the fastest purchasing decisions I have made.  Compared to the other in ears I was testing, they just sounded so "right" with a flat midrange and such natural timbres!  I have had other similarly quick demos but those mostly involve me ripping headphones off my head because of how badly coloured they are, but that is another story.  RE-400's were clearly the most faithful earphones I had heard that day regardless of price (I had listened some earphones costing 20x the price of RE-400!)


Anyway I think it is customary to break reviews down into sections, maybe BASS, MIDS, TREBLE etc. so I might do the same:


BASS:  Flat.  Not elevated or rolled.  Just flat down to 20 Hz like a planar.  Tight.  Not boomy.  Detailed.  Acoustic.  Fast.  A little shy when not driven with enough power.  Excellent.


MIDS:  No peaks or dips.  Clear.  Perfect timbre.  Fast and clean.  Resolving - this is not the same kind of (overly) airy sense of resolution you get with BA earphones, and subjectively there is not as much finer microdetail as some of the multi BA solutions, but the overall faithfulness of timbre is higher and resolution is hardly lacking*.  *Actually I think part of the subjective impression of resolution might be down to the frequency balance which I will discuss that later.


TREBLE:  Good timbre, moderately good extension.  I can still make out all the cymbals and acoustic instruments all sound remarkably lifelike.  There is some lack of air due to rolloff in the high treble.  Mid treble also needs some boosting with EQ.  I added +6dB centered at 6kHz and +10dB centered at 16kHz, however you may find different adjustments more to your taste.


I use these earphones with my Sony ZX2 DAP, which from experience may be slightly lacking the power to make the bass wake up but, interestingly the RE-400 are not holding back this high end DAP. The RE-400 will improve with better gear such as Chord's Mojo, or even some other higher powered DAPs.  The RE-400s are incredibly transparent and revealing.  Colourations in source components or amplifiers are laid bare.  They are not harsh (though there is some very slight sibilance splash).  Yes it makes sense to use this (USD) $100 earphone with high end portable gear like Chord Mojo, Sony ZX2, Astell & Kern AK240 etc.


I mostly listen to classical and jazz, however I still listen to some heavy metal.  With classical and jazz the technical prowess of these earphones is hard to beat at any price.  For heavy metal, the technical ability and truthfulness is usually also good, however poorly recorded material will sound however it sounds.  I can just back off the treble EQ to compensate if the recording is too harsh for high volume listening.  When playing acoustic music you want to be able to appreciate the full performance in all it's nuance and dynamics.  Timbres are very convincing.


Anyway I could continue to waffle about the technical ability of this earphone, however at the end of the day it will be up to the listener and his gear, music and tastes to determine if they like this earphone or not.  I almost overlooked these earphones, firstly because of the price (I think many others do as well), but secondly because I was not aware of just how good they are regardless of lack of hype.  I am sure that the few listeners with good ears who have discovered these gems are happy that their performance is not widely hyped.  It's a small miracle that this level of sound quality can be found for so little money, especially considering the general trend in the market towards more costly designs.  I recommend for everyone to try these earphones, especially audiophiles who value neutral, transparent, and low distortion sound.  Do NOT make the mistake to overlook these earphones because of the low price.

HiFiMAN RE-400

The RE-400 Waterline by HiFiMAN is a premium quality, high-performance In-Ear Monitor (IEM) that sets the standard for others to follow. Featuring advanced ergonomics for superb fit, and premium materials such as Titanium Diapharagm, Neodymium magnet and OFC Copper cabling, RE-400 represents best-in-class performance and comfort.

Model Name/TypeMPNEAN/UPC
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