In-Ear Monitors for the Studio

New options for critical and on-the-go listening
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Although we pick our studio monitors based on their ability to reveal imperfections in our recordings, when it comes to critical listening away from our console or workstation, we rarely put much thought into what we choose, grabbing whatever earbuds we have close at hand. This is where having access to a trustworthy set of in-ear monitors (IEMs) can be helpful.

Once, seen as solely the province of performers and audiophiles, a quality pair of IEMs can be just as revealing while mitigating the influence of the listening environment. For anyone that uses a laptop as a portable extension of their studio, or for those who simply want to take notes on a project while in transit, numerous resolution-minded IEMs are available for critical listening while making sure stray frequencies don’t creep in uninvited.

The top-of-the-line models, whether universal-fit or custom-molded, sit in a Venn diagram of imaging, musicality, and accuracy. Some products lean a little more in one direction or the other, but the best of them use their technical accomplishments to dispel hype and help engineers hear important details.

The following are my impressions of recent standouts among this type of IEM, keeping in mind the three elements I mentioned earlier—imaging (Campfire Audio Andromeda), musicality (HiFiMan RE2000 and Ultimate Ears 18+ Pro) and accuracy (InEar ProPhile 8 and Westone ES80). The goal of this article is to help you determine a baseline for finding products that fit your style of working.


Fig. 1

Fig. 1

Ken Ball, founder of boutique earphone manufacturer Campfire Audio, has a long history of getting sound into people’s heads. Ball launched his original company, ALO (Audio Line Out), to make handcrafted cables, as well as portable and desktop headphone amplifiers. Campfire is the logical extension of that, giving him control over the final stage of performance. The Andromeda ($1,099), Campfire’s co-flagship in-ear monitor, shows Ball’s command of immediacy, efficiency and capacity (Figure 1).

Both ALO and Campfire share the same workshop in Portland, Oregon, where the team prototypes universal-fit IEMs that feature atypical materials and uncommon configurations. Everything is painstakingly machined; there are no off-the-shelf components. One thing the company’s IEMs have in common, however, is nomenclature: Each model is named after a constellation. Couple that with the company brand name, Campfire, suggesting an intimate gathering, and you get a glimpse into Ball’s intention: to bring the listener closer to the original musical experience.

The Andromeda stands out for its beveled industrial design and anodized evergreen-shrub finish. But once you put it through its paces, the Andromeda immediately reveals why it is distinctive beyond the physical aesthetics.

The Andromeda features five balanced-armature drivers, tiny arrays that use magnetic flux to fluctuate a plate which, in turn, manipulates a stiff diaphragm to produce sound. Arranged as dual-low/single-mid/dual-high drivers put through a single crossover network, they provide a 10Hz to 28kHz frequency response (with 115dB sensitivity) that, when properly utilized, holds its own even against monitors with higher driver counts and price tags. This model even comes with a detachable silver-plated-copper Litz cable, making it an even more impressive value.

As with any highly calibrated personal monitoring system, there are no inline controls or other circuitry that could introduce artifacts. But what is lost in the connectivity and convenience is gained in focus when you audition 24-bit, 96kHz audio.

The bass response has a reach not typically associated with balanced armatures, emphasizing rumble without coming across as distended. Depth is as pronounced as width on recordings that require it. The midrange is nicely integrated, coalescing around gradients without getting granular.

But it is in the top end that the Andromeda truly flashes its high-fidelity credentials. A spoutless armature design, where the high-frequency drivers are fed into an acoustic resonator chamber in the nozzle, avoids any reduction of treble common to a traditional tube-and-damper system. This blending leads to an iridescent effect. Pneumatic transients show off the leading edge of notes, extending into rarified territory with audible and genuine decay.

Sometimes a balanced sound is described as one where nothing is unduly forward. In the case of the Andromeda, the sound is balanced because everything stands out simultaneously, but always as intended. Parts that are bassy are bassy, and parts that are brassy are brassy. The soundstage extends on every axis.

With its sensitivity and an impedance of 12 ohms, the Andromeda is revealing with any source, but also of any source. The Andromeda can handle PCM and DSD playback with aplomb, though it can also reveal hiss from the playback device, and tonal weight can shift based on a device’s output impedance.

Fig. 2

Fig. 2

In these cases, a quick, cheap fix is the iFi iEMatch ($49), a dongle that, in the simplest terms, lets you select an impedance of 1 or 2.5 ohms while at the same time, lowering noise, increasing headroom, and stabilizing factors that possibly subvert levels, skew balance, and suppress dynamic range (Figure 2). There is the potential that some perceived air could be lost at the top end, but while purity of signal is typically preferred, sometimes it is worth it to recalibrate control measures in order to lower the noise floor as much as possible.

Fig. 3

Fig. 3

Like a control room’s acoustic treatment, the tip you select will play a part in any IEM’s performance, as well (Figure 3). Silicone tips can bring out treble, whereas foam may attenuate it. A narrow bore compared to a wide bore also moves the needle between bright detail and more broad resonance. Try different materials, shapes, and sizes (with this and every universal IEM) to get your ear’s best match, because you want to maximize the Andromeda’s exemplary spatial expression.


Fig. 4

Fig. 4

Founded in New York City and now headquartered in China, HiFiMan was started by Dr. Fang Bian in 2007. The company’s three primary product lines were quickly established: planar magnetic headphones, high-resolution digital audio players, and earphones. The headphones, in particular, saw a flurry of activity with multiple iterations released at price points from a few hundred to multiple thousands of dollars. The earphones were always more modest, running $50 to $200 and designed for more casual listening. That is, until 2017, when HiFiMan introduced the $699 RE800 and $2,000 RE2000, which sonically and fiscally cemented itself as a proper flagship model (Figure 4).

It must also be mentioned that the RE2000’s housing is partially constructed from 24K gold-plated brass. But that is not what justifies its price. What makes the RE2000 a standout and worthy investment is that it is a single dynamic driver-based, universal-fit earphone that is impactful without affectations.

Dynamic drivers—those tiny transducers that pack a loudspeaker’s voice coil and diaphragm into your ear—have long been looked down upon because of a market flooded with inexpensive, overly warm-sounding models. The RE2000, however, has all the positive attributes of a moving coil—engagement, coherence, and the ability to push serious air when called for—without being a basshead’s monitor.

According to company literature, the reason behind the RE2000’s clarity and distortion control is the custom application of various patterned compounds to the 9.2mm driver’s surface, negating unwanted vibrations and frequency alterations. The proprietary nano coatings seem to work because the RE2000 produces a 5Hz to 20kHz frequency response (with 103dB sensitivity, 60-ohm impedance) that manages slam and precision, the equivalent of a well-tuned 2.1 speaker system. The imaging is immersive rather than holographic, radiating more than sizzling, but it never feels cluttered.

Both in physical build and sonic density, the RE2000 is a presence in your ear. The actual ear-phone is medium to large, not the most ergonomic but not uncomfortable if you have at least an average-sized concha. How it sits (and to some extent how it sounds) will depend partially on which tips are used. Seated correctly and driven from a clean source, however, the RE2000 is controlled but never reserved and transitions between genres effortlessly.

The bass is undeniably tipped a few decibels above flat, but it isn’t forward or intrusive; it just assures that an emotional foundation is never absent. The sub-bass has an analog irresistibility, while mid-bass attacks without edge. Whereas some dynamic drivers exhibit a slower, more diffuse pulse compared to balanced armatures, the RE2000 maintains their definition, and decay is smooth.

Midrange is lightly sweetened; textured but not put under a microscope. It’s tactile, sloping forward just a touch but with nothing carved out. Visceral and sumptuous. The treble response does exhibit a couple small peaks, allowing full articulation of notes and directional cues without drawing the borders too severely. There is occasional brightness but any sibilance is authentic, never exaggerated. Overall, it has just the slightest bit of a “smiley,” u-shaped frequency curve, which is only pronounced if a source is overtly tipped and offering a top and bottom extension that benefits EDM/modern pop production.

Fig. 5

Fig. 5

Though efficient enough to run out of any player, the RE2000 does scale nicely when fed increased resolution and amplification. For example, the iFi nano iDSD Black Label ($200) is a portable battery- and USB-powered DAC/amp that won’t take much out of your wallet or take up much of your pocket (Figure 5). Capable of converting any file format/bit rate—and compatible with desktops and laptops, iOS and Android—the nano iDSD Black Label has an open, but not clinical sound. Producing a few hundred milliwatts for most monitors, it urges tracks forward without pressuring them, and the IEM-optimized 3.5mm jack reduces noise, distortion, and crosstalk, while increasing dynamic range and useable volume (tempered with a smidgen more warmth). It is a convenient upgrade bringing format compatibility and quickening rhythmic authority, with the ability to transition from sensitive in-ears on the road to more demanding headphones when appropriate.

Helping drive the RE2000 at its most resolving is a pleasingly springy silver-coated, crystalline copper wire. The wire is detachable and adapters are provided if you care to experiment with how different materials sculpt the tone. Also, some people (including HiFiMan) would argue that a dynamic driver won’t show its best without extensive burn in, so leave those pink-noise loops and sine sweeps running overnight if you are so inclined. Able to be lush without getting flushed, the RE2000 is best used to test a track’s overall body and fluidity.

18+ PRO

Fig. 6

Fig. 6

Ultimate Ears (or UE as the company is commonly branded) launched in the mid-’90s to a nascent market. While in-ear monitors had been around since the ’80s, touring musicians still depended primarily on wedges for monitoring the proportion and pace of everyone onstage. Contributing to the practical use of balanced armature arrays in isolating, custom-molded enclosures, UE played an important role in making in-ear monitors the new live-sound normal. This legacy is important in context when taking into consideration the company’s newest custom model: While some monitors are merely a presentation, the UE 18+Pro (priced from $1,500) is a performance (Figure 6).

In 2010, UE introduced the Reference Monitor, a collaboration with Capitol Studios resulting in a benchmark IEM for engineers seeking a perceived flat response. In 2015, UE refined the Reference Monitor with proprietary low/mid/high True Tone Drivers and rebranded it the Reference Remastered ($999). These drivers, featuring extended treble response and midrange presence, reinforce the Reference Remastered as a nearfield-monitor equivalent for unsympathetic environments. Doubled in the 18+ Pro, however, the same drivers allow more latitude for room presence and richness.

Configured in a four-way crossover triple-bore system, the six drivers deliver 5Hz-22kHz (with 100dB sensitivity; 37.5-ohm impedance) for a sonic signature that is balanced, though not dead neutral. The focus is on natural timbre; on being linear without being gaunt. There is a fleshiness, an ensemble presence to the sound that is at home plugged into a belt pack, but equally adept at critical listening. Each note can be heard clearly without the need to contrast it against an antiseptic stage. (That tangibility is assisted by the -26-dB isolation from exterior sounds afforded with custom IEMs).

While its siblings show low-end punch and decay with more focus around the mid-bass, the 18+ Pro adds a little seismic shimmy without giving up speed or bleeding into the midrange. Again, they are not flat, but there is a fluid transition throughout the band, with the upper bass adding warmth without bloat. In the mids, the 18+ Pro is particularly emotive, presenting male and female vocals energetically and without favoritism. If the mic could use a little less intimacy, or a better pop filter, it will show with these IEMs.

Treble exhibits crisp, but never jagged edges. It’s an airy, rather than austere, production. There are no spikes nor attempts at artificial excitement. If anything, the lower treble takes somewhat of a backseat, exhibiting the non-fatiguing heritage of a stage monitor. However, a lack of harshness is not the same as a lack of detail. Each note’s attack is clearly delineated, and transients honestly portray a live tracking session. It doesn’t display the sparkliest, most soaring top end, and is more forgiving than some monitors, but it plays its part in presenting a wide, uncongested soundstage.

Aiding this cohesion is the “sound engine,” which uses channels to blend lows and mids parallel to highs until all converge in the hollowed tip of the shell, available in two form factors. If opting for customs, UE has advanced the use of digital ear scanning and 3-D printing to make more exacting, expedited products (though not all audiologists offer digital support so old-fashioned silicone goo impressions might be required). The company also offers the 18+ Pro as part of its universal ToGo series, which doesn’t require impressions and retains resale value, but does fall prey to the tonal coloration of tip shapes, materials, and seating. Various cable options provide further aesthetic and sonic customization.


A bad mix can be a brutal, unflattering thing, and a pair of studio monitors shouldn’t be considered right if they don’t fully showcase that ugliness. In the world of universal in-ears, the InEar ProPhile 8 ($1,445) offers that unflinching feedback, anchored on the mids but unfolding to meet a track’s needs throughout the 10Hz to 20kHz range (with 120dB sensitivity; 34-ohm impedance).

InEar, a German company, made its transatlantic reputation with the StageDriver series. The line, originally developed for musicians, based its housing from more than 500 digitally captured ear impressions as a means of achieving a widely compatible, uncommonly comfortable fit. Internally, the StageDriver series topped off at four balanced armatures, a number doubled in the aptly named, tight sounding ProPhile 8.

Increasing the drivers (arranged as sub/mid/mid-high/high pairs in a 4-way crossover) did not come at the expense of contours, however. Nor did the doubling introduce any uneven frequencies. With appropriate tips that allow for a deep, solid seal, the ProPhile 8 locks tightly in the concha, narrowing the gap with custom fit (an even more compact “S” housing for smaller ears has entered limited distribution).

Fig. 7

Fig. 7

The black matte, logo-free shell of this inaugural “Studio Reference Signature” in-ear (which ships in an equally spartan box) belies the Pro-Phile’s transparency (Figure 7). It is a neutral, but never dry tuning with a soundstage that is neither too intimate nor too ample. It is intended to sit in the sweet spot, spreading a track’s parts in front of you to bob or jab like phantom meters.

Bass is just a ripple north of neutral, with a density to it (leaning slightly more to mid-than sub-bass) that doesn’t detract from its speed. It’s a dynamic approach to near-flat.

Mids express all the raw emotion, and wrinkles, of what’s been recorded. Male and female vocals have the same weighty presence. Crunching guitar can take full frame without losing each note’s outline.

Treble is perhaps the least projected of the frequency ranges, offering agile but not hyperactive detailing. Reverb trails evaporate naturally. It’s correct, with no veil, yet never piercing.

Above all else, the ProPhile 8 exhibits continuity, with no frequencies hollowed or hobbled by circuitry or choice. That centering brings to mind the Etymotic Research ER4, an IEM introduced in 1991 that spawned a line that continues to set the accuracy-isolation benchmark at the $350 price point. Etymotic’s trademark single BA driver is particularly suited for boring down into the midrange, while the ProPhile 8 widens far more to the fringes without exhibiting crossover dips or shelving.

But it also offers versatility, owing to the fact that there are two recessed switches located in the cymbal part of the housing that offer independent control over a +3dB bass boost and a +2dB treble boost. Together, these can offer a side glance into a more V-shaped consumer-portable response, or the bass boost can favor modern pop, while just the treble boost can heighten orchestral pieces. It’s not quite four different pieces of gear folded into one, but it does add value by giving a nondestructive “remix” option outside of the box.

The ProPhile won’t suddenly take the shape of a floor-standing speaker, or the boom of a subwoofer. The bass switch merely adds some low-end loudness, and the treble switch some contrasting pressure. The subtle boosts don’t aggravate imperfections so much as more clearly illustrate them. The overall signature remains one of exacting reproduction of even the most complex layering.


Fig. 8

Fig. 8

Plenty of in-ear monitors exhibit physicality, but more often than not they are sonically titled toward either a brawny mass or wiry frame. But when it comes to an aural physique that’s equally about potency and definition, look to Westone Laboratories’ latest custom, the ES80 (starting from $1,899). The flagship of the “Elite Series,” the ES80 is the equivalent of lean, well-trained muscle that can operate with intense pacing without confusing volume for strength (Figure 8).

Westone, based in Colorado since 1959, has decades of experience in hearing aids, hearing protection, military communications earpieces and musicians’ monitors (including pioneering work with balanced armature drivers and some intertwined history with UE, among other brands). These sectors, combined, inform facets of the ES80, including ergonomics, isolation and tonal foundations.

Led by brothers Karl and Kris Cartwright, the music division of Westone offers multiple families of monitors: the UM Series for efficient stage performance, W Series for personal listening, and the Elite Series for the most critical, purpose-driven monitoring. The ES80 follows the release of the W80 ($1,499) and shares its DNA of eight proprietary balanced armature drivers (dual-bass/dual-mid/quad-high with a 3-way crossover). However, as explained by Kris Cartwright, the W80 is optimized for the playback of mastered material, while the ES80 is an uncolored signal chain for untreated stems (whether from the soundboard or a studio console).

The W80 showed that bountiful sound could be squeezed into a small package. The ES80, while trim for a custom IEM, isn’t as shockingly economical in form as the W80, but it is even more expressive—no easy feat as the W80 was already an immensely organic monitor.

Bass is lush without being enhanced. When called for, a deep well of sub-bass can be drawn from the ES80’s 5Hz to 22kHz frequency response (with sensitivity of 111 dB; 80 ohms impedance, making amplification beneficial but not essential). However, it never feels stocky thanks to limber mid-bass and the grooming of any overzealous upper bass. Percussive fundamentals retain character and composure. Moving up the range, neither lower nor upper-mids lack intent or polish. Sometimes neutral can err on the rangy side, but the ES80 is nuance-enriched sinew. Each contraction and palpitation is precise.

Even though you can chart every harmonic tracer, treble never spits hot. It’s a top end that treasures realism over an analytical etching of each note. Separation excels and edges fray where the performances dictate; you can hear a vocalist’s sigh or a guitar’s strings settling as lower treble lifts in line with the bass. But it’s clarity with some charity; a warm source will thicken the sound, a cold one brighten it, but nothing nudges sparkle into spiky.

Helping the ES80 plumb a faithful and responsive rendition of a track in any environment is the build, which features a durable cold-pour acrylic earpiece coupled with a signature Flex Canal made from body-temperature reactive material. This means the nozzle, once naturally warmed in the ear, offers heightened comfort and seal for longer sessions.

And if you want to add a little more force and flesh to the tone, Westone accompanies its signature, pliant Epic cable with an additional, more rigidly braided ALO Ref8 silver-plated copper and OCC copper wire ($299, if purchased separately). The Ref8’s clarified tone (or the personality of any third-party MMCX cable you swap in) adds different aspect ratios to the ES80’s wide, black background.

Visit for additional coverage of innovative personal monitoring technologies, including Audeze’s miniaturized planar magnetic LCDi4; the Shure KSE1500, a singular electrostatic in-ear system; and both proprietary balanced armature and hybrid BA-dynamic driver models from Empire Ears.