Empire Ears ESR MK-II IEM Review


A New Standard in Detail and Resolution

Is there a doctor in the house? In fact, with the new ESR MK-II in-ear monitor from Empire Ears, there's a surgeon. When it comes to precision, the ESR was and is the detail king of the Empire Ears lineup, delivering a surgical-like consistency for recording and mixing engineers.

The ESR, or Empire Studio Reference, is part of Empire Ears' EP (Empire Professional) series of IEMs. Here's what Empire Ears has to say about the MK-II: 

  • More controlled bass

  • More "reference" sounding

  • Wider soundstage

  • Absolutely ludicrous resolution 

The more notable update to the second generation of this IEM was the addition of two electrostatic drivers, bringing the total driver count to five. This gives a huge boost in treble extension and detail retrieval. The ESR MK-II also features a boost in frequency response and a lower impedance rating. 

The ESR is marketed toward sound techs on films, recording and mixing engineers, and front-of-house engineers, but IEM-loving audiophiles for whom truth and reference are king will certainly want to give the ESR MK-II a look. 

Let's think about what mixing and mastering engineers do: They combine all of the elements of a recorded piece of music into a marketable version, balancing the myriad parts to achieve the intended effect. To do so, they need to hear the music as accurately and true-to-life as possible. This is what a studio monitor is for.

Materials, Quality & Comfort

The ESR MK-II has a cool-looking brushed silver faceplate with a bit of a holographic quality. A winged Empire Ears logo in silver sits in the center of this striking design. It's a design step up from the original, which featured a simple Empire Ears "EE" logo on a black background.

The cable is the Alpha-IV bespoke 26AWG UP-OCC copper Litz cable with multi-size stranding. The cable features a durable, overmolded .78 2-pin connector offered with either a 3.5mm right angle or 2.5mm balanced termination.

The shells are similar to other Empire Ears models, with a rounded triangular shape and a short nozzle. With the proper ear tips (for me, the size medium Final Audio Type E ear tips), the nozzles fit comfortably in my ear canal with no issue. I listened to the ESR MK-II for several hours at a time on multiple occasions with no discomfort. As always, Empire Ears' craftsmanship and attention to detail are evident on the IEMs, with no obvious flaws, glue, misalignments, or what have you.

Driver Technology

EIVEC| Credit: Empire Ears

The original ESR featured three balanced proprietary balanced armatures (one bass, one mid, and one high). For the MK-II, Empire added two electrostatic drivers -- for ultra highs -- giving this IEM a huge boost in treble extension and detail retrieval. The ESR MK-II boasts a frequency response rating of 10Hz-100kHz. This substantial treble extension -- well beyond the upper limit of what the human ear can hear -- lends a sense of airiness, spaciousness, and realism to music.

The two driver types in the IEM are controlled by the latest iteration of Empire's proprietary synX crossover network. Empire describes synX as a supercharged crossover design that designates more individual audio bands per driver than any other crossover technology currently in existence. Each iteration of Empire Ears' snyX crossover system is designed to maximize performance from every single driver type. In the ESR MK-II, a four-way crossover is used to bring harmony to the use of these two driver types. 

Empire Ears own EIVEC (Empire Intelligent Variable Electrostatic Control) technology is used to keep the electrostatic drivers from dominating the BA's. Electrostatic drivers have an amazing frequency range and top-notch resolution, but they do not traditionally play well with other driver types, with a tendency to drown out their dynamic and balanced armature counterparts. A single bespoke transformer unites the two separate electrostats via EIVEC, eliminating any signs of phase incoherence and distortion. Empire's proprietary EIVEC technology essentially "tames" the electrostatic drivers, allowing them to shine to their greatest potential.

The ESR MK-II's low impedance of 3.9 Ohms @ 1 kHz (down from 19.3 Ohms on the original) makes it easy to drive, including from your phone or a great portable DAP (digital audio player) like the Sony NW-WM1Z. With a sensitivity rating of 111dB @ 1kHz, 1mW, I wanted to pair the ESR with a headphone amplifier/DAC (digital-to-analog converter) that would be good for high-sensitivity IEMs, which require a very low output impedance and a quiet power supply. A common issue with home-based gear is the power supply can interject hiss in the signal path of a high-sensitivity IEM.

For my review, I chose the Roon-certified Element X by Matrix Audio music streamer/server/DAC/headphone amp. If you're looking for an all-in-one desktop solution that is also excellent with high-sensitivity IEMs, I would strongly recommend the incredibly quiet Element X.



  • Drivers: 3 balanced armatures
  • Frequency response: 10 Hz-40kHz
  • Impedance: 19.3 Ohms
  • Sensitivity: 112 dB


  • Drivers: 3 balanced armatures, 2 electrostats
  • Frequency response: 10hZ-100kHz
  • Impedance: 3.0 Ohms
  • Sensitivity: 111 dB

Sound Impressions

The ESR MK-II is the first IEM I have listened to from Empire's EP series. Comparatively speaking, it has a flat sound signature -- as it should for being a studio monitor. I think what surprised me right away was how flat did not equate with sterile or boring. The sound was exceptionally clear and lifelike, with an insane level of detail retrieval. Little sounds -- a cymbal hit, an intake of breath, layers of vocal harmonies -- stood out with amazing precision and clarity without feeling overbearing. In other words, I perceived these details but didn't feel like they overshadowed the main elements of songs.

"Every decision made in the recording, mixing, and mastering process relies on the truth, and that's explicitly what the Empire Studio Reference (ESR) MK-II delivers: Pure, neutral and unadulterated sound reproduction with unrivaled detail retrieval."

Empire Ears

I perceived the sound to be balanced, with no frequency boosted above any other. Bass is polite and controlled, textured and punchy. It's not super-deep or rumbly, but there is no dynamic driver, so this is to be expected. And you wouldn't want a bass-heavy IEM for pro use, anyway. Treble is smooth and pretty without crossing into brightness. And while I wouldn't call this a mid-forward IEM, vocals had a presence. Male and female vocals alike sound very real, as if I am right there in the studio listening to tracks being laid down.

I was especially pleased with the imaging on the ESR MK-II. These IEMs gave me a real sense of where the various instruments and vocalists were positioned. You could contrast this with a sense of a compressed soundstage whereby the music comes to you as more of an amorphous unit rather than individual elements in 3-D space. Now, if you're spending over $1,000 for a headphone or IEM, you'd expect imaging to be solid. I'm just saying that it was something that particularly impressed me with the ESR.

Speaking of soundstage, I didn't have the widest feeling with the ESR, nor would I except to in an IEM. Empire does tout the soundstage on its IEMs, though. I'm not saying it's lacking, but I don't feel utterly enveloped by the music, either. It's more intimate than it is wide.

Something to note about the ESR MK-II -- which is something I'd expect with a more reference-sounding headphone or IEM -- is that less-than-ideal recordings will sound, well, less than ideal. Similarly, bright recordings may sound overly bright. For example, I listened to a track that has an ongoing amount of what I think is a ride cymbal, which creates an almost hazy effect to the recording. A warmer headphone might gloss over this, but the ESR MK-II put it on display. It's not a horrible sound, but it definitely stood out.

For a brighter recording, I listened to the Beatles' Rubber Soul. The first track, "Drive My Car," sounded a little forward for my taste, but at the same time, the cowbell was so sharp and "in my face" that I actually kind of enjoyed it. Backing vocals on "You Won't See Me" were so crisp and clear that I would be hard-pressed to even call them backing vocals. And this is where the ESR MK-II shines as it rightly should: resolution and clarity.

Dragon Cable Recommendation

When you're making a significant investment in an IEM or headphone, you want to consider your cable. A high-quality, well-made cable will help you squeeze every ounce of performance out of your high-end audio gear. The right cable will add another layer of clarity to your music and help your headphones or IEMs "breathe." Dragon Cables use only the best materials, because we know that materials matter.

For a mixing and mastering professional, detail and clarity are king. To support that, we recommend pairing the ESR MK-II with a Silver Dragon IEM cable. UP-OCC silver strands in the Silver Dragon will open up the soundstage and lend light, air, and definition to your music. The Silver Dragon will add top-end sizzle and find "lost" mids and highs. It's a great choice for those who love to -- or, by nature of their work, have to -- hear ALL the detail in their music.

That being said, if you'd like to add some fullness and body to the ESR for more casual listening, you'd do well with a Black Dragon IEM cable. Copper conductors in the Black Dragon will give you a more musical sound with a bump in the bass while silver conductors will support an open, airy, detail-oriented sound. We call it our "do it all" cable.

The Verdict

  • Great for (genres): Rock, EDM, blues, folk
I'm not a music professional, but from what I understand about the desirable attributes of a studio monitor, the ESR MK-II is a strong contender. It has a neutral, balanced, slightly mid-forward, slightly warm-sounding signature with incredible resolution, clarity, and tonal quality. I've not listened to the original ESR, but from what I've been told, the MK-II is more "reference-sounding." I definitely perceived a high degree of detail and bass articulation, which I will assume to be a notch (or several) up from the original. But I don't think the ESR's appeal is limited to professionals. If you're looking for an audiophile-quality IEM with tons of detail and a lively, realistic (but not "fun" or bass-heavy) sound, the ESR may be a good choice for you. When you take into account build quality and aesthetics, the ESR MK-II is a solid pick at $1,099 ($1,299 custom).

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Review Video

Empire Ears ESR MKII In-Ear Monitors Review


Frequency Range: 10Hz - 100kHz

Impedance: 3.9 Ohms @ 1kHz

Sensitivity: 111dB @ 1kHz, 1mW

EIVEC (Empire Intelligent Variable Electrostatic Control Technology)

A.R.C. Resonance Mitigation Technology

5 Proprietary Drivers, Hybrid Design

3 Proprietary Balanced Drivers - 1 Low, 1 Mid, 1 High

2 Premium Electrostatic Drivers - 1 High, 1 Super-High

4-Way synX Crossover Network

Bespoke Alpha IV UPOCC Copper Litz Cable