NuForce HEM4 Reference Class Hi-Res In-Ear Headphones with Dual Balanced Armature Drivers

General Information

The High Resolution certified HEM series set a new standard for accuracy, speed and comfort. Designed for music lovers and professionals, these innovative in-ear headphones offer budding artists, home recording musicians and DJs incredible audio reproduction. Combining the latest balanced armature driver technology with advanced crossover design, the HEM series reveal a wider frequency range for the ultimate listening experience.

Latest reviews


Headphoneus Supremus
Pros: Ergonomic fit and build, excellent treble clarity, extension on both treble and bass, textured sound
Cons: Lack of bass presence, can be very lean and thin sounding with certain types of music, cold and analytical signature
Nuforce HEM4 – impressions and comparison with HEM2
After listening to the HEM2s recently courtesy of the Nuforce Massdrop, I managed to pick up a pair of the next model in their HEM series (the HEM4) as part of a trade to see how this compared, and whether the additional BA being used would make a significant difference to the sound. For clarity, as the only difference to the retail packages for the HEM series is the number of drivers in the shells themselves, a large portion of the below is lifted directly from my review of the HEM2 as the package, design and accessory load-out it identical. Feel free to skip to the sound impressions if you have read my previous review - this impression is written as a comparison piece to the previous review, so it may help if you read them both. To be clear, I have no affiliation to Nuforce, so the views expressed are 100% my own with only my own (questionable) judgement and listening bias having a bearing on the final verdict.
About me: newly minted audiophile, late 30s, long time music fan and aspiring to be a reasonably inept drummer. Listen to at least 2 hours of music a day on my commute to work – prefer IEMs for out and about, and a large pair of headphones when I have the house to myself and a glass in my hand. Recently started converting my library to FLAC and 320kbps MP3, and do most of my other listening through Spotify or Tidal HiFi. I am a fan of rock, acoustic (apart from folk) and sarcasm. Oh yeah, and a small amount of electronica. Not a basshead, but I do love a sound with some body to it. My ideal tuning for most IEMs and headphones tends towards a musical and slightly dark presentation, although I am not treble sensitive in general. Please take all views expressed below with a pinch of salt – all my reviews are a work in progress based on my own perceptions and personal preferences, and your own ears may tell you a different story.
Tech specs (from the Nuforce website)
Frequency response: 18Hz - 40KHz
Sensitivity: 124dB +/- 3dB
Cable: 1.38m
Impedance: 38 Ohm
Maximum input power: 2mW
Maximum input sound level: 124dB

The HEM series all share a similar packaging design and accessory load-out, and while the HEM4 is slightly further up the price range than the HEM2 at an RRP of $299, it is still an impressive set of goodies to include with an IEM in this bracket. The outer packaging carries a nice glossy picture of the headphones overlaid on a matte background, with all the usual technical info and schematics you would expect, including the ubiquitous “Hi-Res Audio” logo. Inside the cardboard insert is a black presentation box that is held closed with a magnet and opens book-style to reveal the contents. All very understated and classy. The actual contents of the package keep up the theme: one large transparent waterproof case with foam padding inside (including a moulded foam insert holding the IEMs), and another smaller semi-hard zippered case which fits inside that containing the selection of tips (both silicon and Comply in various sizes), two detachable 2-pin cables, a cleaning tool and nice gold plated stereo adapter. The waterproof casing is reminiscent of various Otterbox cases used by other brands, and has (just) enough room to fit a DAP inside, which gives it comfortably enough to house the IEMs and a few selected accessories. The zipper case is also a nice size, being slightly thinner and longer than the average case churned out with IEMs at this price point, making it very pocket friendly. The accessories are well thought out and very plentiful, with nice touches such as the addition of an “audiophile” silver coated copper cable (braided, of course) to complement the standard rubberised cable with in-line microphone.
Build quality and ergonomics
The HEM4 comes in a metallic blue colouring, with a small teardrop design which hugs the inner contours of the ear very well. There is an almost industrial design motif with the shells due to the acoustic modelling that Nuforce have done on the internals, with the outer shell holding multiple ridges which make it reminiscent of the world’s smallest bicycle crash-helmet. The shells themselves are made of Lexan, a light polycarbonate used to make bulletproof glass – while I haven’t broken out the in-laws shotgun to test out if they would survive a trip to the front lines, there is definitely a sense that despite the lack of weight, these are not a fragile piece of kit. Another useful property of Lexan is the fact that it apparently resonates at a frequency higher than the human ear is capable of hearing, meaning it should reduce unwanted sonic interference inside the driver housing from shell vibration. In terms of fit, the light weight allied to the small teardrop size of the enclosures make these IEMs extremely comfortable to wear for extended periods, practically disappearing into the side of your head once settled. The nozzle of the IEM is also worthy of mention, as this is one of the thinnest and longest nozzles I have seen on an IEM, taking Comply T-100 tips. Nuforce claim that this is done to aid the tuning and delivery of the sound – in practice, this doesn’t seem to have an effect on wearing comfort for me as I have large ear canals, but might be a plus point for wearers who normally struggle with wide-bore earphones. Due to my cavern sized ears, I found that the best fit and isolation was achieved with the enclosed Comply tips, but there are a few mods that have already been suggested on the forums to fit larger bore eartips onto the casing, so that shouldn’t be a problem if you wish to go “off piste” with your tip selection. The bore size is compatible with Westone tips used in their W and UM series IEMs if you have any handy and are looking for a deeper insertion. The IEMs are designed to be worn over-ear, but due to the use of heatshrink rather than memory wire on the main braided cable, they can if needed be worn “down” as well. With reference to the cables, they are both light and pliable, with the braided cable exhibiting no major memory recall and minimal microphonics – I haven’t used the microphone cable yet so can’t really comment on that. The overall build quality also extends to the connectors, where the right-angled Nuforce connectors are finished in a sturdy metal shell with just the right size to tuck in nicely underneath a mobile phone or DAP audio slot. In fact, the only element of the whole package that doesn’t scream “come see how good I look” in true Ron Burgundy fashion is the heat shrink tubing acting as the cable splitter, and the smaller sliding piece of tubing acting as the cable cinch. The splitter is functional at least, but the cinch on my cable is loose enough to slide over the splitter and down towards the connector without any problems at all – a strange choice considering the high level of finish on all the other elements of the package (the cables even come with their own mini-cable tidies made out of Velcro). It doesn’t detract in a major way, but just leaves the impression that there are some beautifully designed splitters sitting in the Nuforce factory somewhere gathering dust because someone forgot to add them to the production line.
Sound quality
Test gear:
LG G Flex 2 (via Neutron Player)
iBasso DX90 (with Cayin C5)
Sansa Clip+ (Rockboxed)
Microsoft Surface Pro 2 (straight from the output jack)
Main test tracks (mainly 320kbps MP3 or FLAC/Tidal HiFi):
Nathaniel Rateliff & The Night Sweats – S.O.B. / Wasting Time
Blackberry Smoke – The Whipporwill (album)
Slash – Shadow Life / Bad Rain (my reference tracks for bass impact and attack, guitar “crunch”)
Slash & Beth Hart – Mother Maria (vocal tone)
Richie Kotzen – Come On Free (bass tone)
Elvis – various
Leon Bridges – Coming Home (album)
Daft Punk – Random Access Memories (album)
Sigma - various
Rudimental – various
Rodrigo y Gabriela – various
Mavis Staples – Livin’ On A High Note
Don Broco – Automatic
Foy Vance – The Wild Swan
General impressions on the sound signature (and comparison to the HEM2)
On first impression, the HEM4 has a lean and clear sound, with good texture to the notes and good extension at both ends of the frequency spectrum. The range is noticeably bigger than the HEM2, but due to this “widening” of the sound spectrum, the body of the presentation sounds much leaner as a result, with little of the warmth to the lower and midranges that made the HEM2 so inviting. To compare the two would be like comparing the warm and slightly stuffy summer’s day of the HEM2 to the brilliant sunshine of a cold winter’s day of the HEM4, with accompanying frost on the floor. As a presentation, the HEM4 is markedly different from the HEM2, and provides a much leaner and more neutral overall tone to the song being played, with a wider and clearer presentation and sharper focus on the detail at the expense of the “feel” in some cases. To see how much extra bass the HEM2 produces, I plugged both IEMs into a Brainwawz AP001 amp I use for travelling as it has two output jacks – I listened to the same song from the same source with one bud from each set of IEMs in my ears, and was actually fairly surprised at the results. Without being able to volume match the two, I was surprised to hear a similar amount of bass being output by both the 2 and the 4, and the two IEMs sounded a lot closer in signature with only a noticeable “bump” in extension and resolution audible in the 4, leaving the 2 sounding a bit warmer and fuzzier to my ears. Taking the buds out and doing a traditional A/B comparison, my brain immediately switched back to the impression that the HEM4 is a leaner sound with less bass – this was hardly a scientific test so take my conclusions at face value, but I wonder if the more balanced and extended sound being produced by the 4 makes it appear “stretched” in comparison to the 2, leading to the brain hearing the bass in comparison to the other frequencies and giving the impression of a thinner sound. In any case, conventional A/B left me thinking that the HEM2 is a warmer and more “musical” IEM with slightly less definition and a smaller stage and range. Technically, the HEM4 is a more capable IEM, but falls on the cold side of neutral so lacks the warmth to really hammer home its technical advantages, losing some of the soul of the music to that glorious winter’s day.
The highs on the HEM4 are probably the probably the strongest part of the overall sound, with good clarity and very good extension, reaching up into the higher registers without sounding too sharp or strained. High guitars and soprano voices come through strongly, with the dual-BA setup pumping out a crisp and engaging high range. Cymbal crashes are still a little on the subdued side rather than splashy, but sound natural and decay realistically. The definition of the high notes leaves a good sense of micro-detail behind, with single guitar strums carrying all the associated noises with them through the earpieces like the harmonics as the strings are scuffed and other studio noise that usually makes its home in the high rafters. The presentation is notably sharper and airier than the HEM2, but the tuning still steers clear of sibilance, so it merely leaves the impression of a more “complete” and emphasised frequency range at the top end of the scale compared to the more warm and rolled off take given by the HEM2.
The mid range on the HEM4 is quite textured, with guitar notes and vocals both showing their rougher edges and rasps behind the smoother elements emphasised in a more warm tuning. The sound is lean and defined, with the lack of weight behind the notes serving to emphasise the detail and texture in the delivery. The speed of the BA drivers is apparent here, with fast guitar pieces from Rodrigo y Gabriela and Slash both translating excellently, the analytical nature of the sound allowing the listener to track each note through the passages with ease. There is an element of bite and definition to the mid-range that does give a nice edge and pace to most rock music, but this is counterbalanced by the lack of substance to the notes, leaving more meaty passages of music feeling a little anaemic in comparison to the warmer and thicker sound offered by the HEM2. The flat nature of the tuning shows again here, with the mids feeling somewhere between neutral to slightly recessed. That being said, acoustic guitars sound excellent through these IEMs, with the precision-tuned thinness of the sound presenting the strumming of Jack Johnson or Justin Nozuka with an almost crystal clarity and detail. Another point to note about the midrange is the overall cohesion of the sound – with a dual BA setup in the HEM4, the midrange is usually where the two drivers would overlap, but the “Linear-phase” crossover implemented in the HEM series manages to keep the two drivers together admirably, with no apparent “join” audible as the drivers exchange duties.
Bass presentation on the HEM4 is fast, accurate and well extended, with decent dip into sub-bass territory before trailing out of audibility. Unfortunately for those who like a neutral or heavier dose of bass, there just isn’t very much of it compared to the rest of the frequency spectrum, leaving the overall impression of a very lean and surgical sound. For acoustic music this works quite well, with the light low end freeing up more air for the mids and highs to shine, but for EDM and more driving rock songs, this can leave the sound feeling a little thin and lifeless compared to the more full-blooded HEM2. Running my favourite bass test tracks through their paces, the lack of substance is obvious – on “Bad Rain”, the emphasis is on the sound of the strings rasping as they vibrate, not the underlying bass note itself. Similarly with the Sister Hazel track I normally use, the usually liquid bassline pours into your ears like water rather than chocolate, with a thinness and lack of substance that leaves the song feeling a little under-done. In contrast, the fast jazz-style double bass used by Foy Vance on his album “The Wild Swan” benefit greatly from the speed and agility of the driver, with the plucked tones ripping along at speed. The greater sub-bass presence than the HEM2 also makes itself felt on some tracks, with “Burden” by Foy Vance benefitting from the quiet presence of the sub-tones to the bass line underpinning the track as opposed to the HEM2’s beefier but less extended take on the same song. Tom be fair, the longer I have listened to these IEMs, the more the bass tonality can be adjusted to, but on first listen these are strictly for people who err on the thin side of neutral as a favourite preference.
Soundstage feels reasonable, and is slightly wider that its sibling the HEM2 – there is a decent stage width inside your head, with more width than height, but the music never leans too far outside what you perceive to be the inside of your skull. The imaging is good, and again shows a noticeable (if small) upgrade from the HEM2 due to the increased clarity, with instruments clearing spacing themselves out and playing further from the centre of the stage where needed. Presentation is still more 2D than 3D, but there the additional precision and cooler tone help to give a more precise feel. Separation is good, with the dual-BA setup handling multi-instrument passages with ease.
Due to the size of my ear canals, I have mainly been using the accompanying Comply foam tips, which provide an excellent seal and therefore excellent isolation. The shape of the shell inserts quite well to block the opening of the ear, and the lack of venting in the shell casing due to the all-BA design does help to keep external noise out. These are easily good enough to block out most external travelling noises or family arguments, so wear with care if you actually need to hear what is going on around you. As mentioned previously, I have tried Westone foams on these, and they also provide an excellent fit and better isolation due to their deeper insertion.
The HEM4 have a higher resistance than the HEM2, but still aren’t difficult to drive well off a mobile phone or DAP. As with the HEM2, adding my Cayin C5 to the mix does bring a little perceived precision (and the higher resistance allows them to be driven harder if required) – much like the HEM2, amping brings nothing radical to the table though, so these are easily in the “standalone” bracket for mobile use.
Comparisons (in similar price bracket)
FLC 8S – Another recent listening acquisition, the FLC 8S play in a similar price bracket to the HEM4, but come with a myriad of tuning options due to their unique interchangeable filters and plugs. For comparison purposes, I have used the most commonly quoted filter setup on the FLC thread for these IEMs of red/grey/gold. The FLC is a hybrid (with both dynamic and BA drivers), so you would expect the bass on offer to be more substantial than the HEM4, and this does prove to be the case. Where the HEM is lean and accurate, the FLC offers considerably more presence while not sacrificing the precision. Lower range extension is similar on both, with the additional bass volume on offer with the FLC adding some body to the sound compared to the HEM. Midrange is won by the FLC, with the liquid mids offering as much detail but more musicality and a slightly thicker sound. Highs sound a little more emphasised on the HEM, with a greater extension but less overall weight. In terms of build and comfort, the HEM edges it for ergonomics, and is a more elegant build than the utilitarian plastic of the FLC. Overall, the FLC offers a more musical and substantial sound with this filter configuration, and is superior to the HEM in enough categories to make it a good option in the same price bracket if you are looking for an IEM with more flexibility and a warmer and less analytical sound.
Lear NS-U1 Natrosound – this is a dual-dynamic setup rather than a dual-BA, but plays in a roughly similar price bracket so I have included it for reference. The tonality of the NS-U! in either mode (normal or in “Natrosound”) is markedly warmer and bassier than the HEM4, with a wider soundstage and more extreme separation of the individual instruments in the default mode. In terms of highs, the HEM4 wins on clarity and extension, but for mids and bass, the NS-U1 provides a more pleasing and dynamic sound to my ears. In terms of soundstage, the NS-U1 can feel a little bit laterally stretched sometimes when not playing in Natrosound mode, whereas the HEM4 presents a smaller but more cohesive stage for the listener. In terms of ergonomics and comfort, this is a slam dunk for the HEM4 – the small coffee bean shape of the 4 looking almost lost when paired against the golf ball sized shells of the NS-U1 and the accompanying stems, which are almost as long as the 3.5mm jack.
Overall conclusion
Despite my 3.5 star ratiung, the HEM4 are not a “bad” IEM, with a clear and detailed presentation and a great sense of texture and tonality that offers some beautiful listening moments. Unfortunately for me, the overall lean and cold impression they leave on me is just too far away from my own idea of musical perfection for my brain to truly enjoy these in the same way as their warmer baby brother the HEM2. Listened to in isolation, these are a good example of what a quick, clinical dual-BA setup is capable of, but when compared to other IEMs in my recent listening experience like the Cardas A8, the sound is a bit too cold and neutral for my tastes. As mentioned in the initial sound impressions paragraph, when directly A/B’s using my Brainwavz amp/splitter the actual volume in the lower end seems roughly similar to the HEM2, but something about the overall combination leaves a feeling of thinness that I just can’t shake (guess that's the subjective nature of sound for you). As with the HEM2, the accessory package that comes with these IEMs is still possibly the most impressive and well thought out I have seen in any in-ear product at this price, and ergonomically and aesthetically, they are a thing of beauty. To summarise, if you like your music cold, clinical and as lean as a marathon runner, these will be a great match. For those who like the design and accessories but looking for a warmer sound, consider one of the other HEM models in the series.


There are no comments to display.