Etymotic ER4XR Review: Professional-Grade Reference Audio

Disclaimer: I received this product in exchange for my honest review. The Metalverse is an independent website, and all opinions expressed are our own with no monetary incentive. We thank the team at Jackrabbit Media and Etymotic for giving us this opportunity.

Etymotic

The name "Etymotic" derives from the Greek words meaning "true to the ear," perfectly encapsulating the company's philosophy since its founding in 1983. Dr. Mead Killion established Etymotic Research with a clear mission: design products that accurately assess hearing, improve the lives of those with hearing loss, protect hearing health, and enhance the listening experience for musicians and music lovers worldwide.

Etymotic's credentials in the audio world are unimpeachable. The company was one of the first to invent insert earphones (a.k.a in-ears) in 1984, pioneering the use of balanced armature receivers for audio applications. These tiny, efficient drivers were originally developed for hearing aids but proved ideal for in-ear monitors when implemented correctly. In 1991, Etymotic released the ER-4, the world's first noise-isolating high-fidelity in-ear earphone. This groundbreaking product became the foundation for the entire in-ear monitor category as we know it today—every IEM on the market owes something to Etymotic's original design.

Etymotic has also generated over 100 patents in hearing science, acoustics, and audio technology. Their products are used by audiologists for diagnostic testing, by musicians for hearing protection and monitoring, and by audio enthusiasts seeking reference-quality sound.

The ER4XR

The Etymotic ER4 comes in 2 models: the ER4SR (studio reference) or ER4XR (extended response), which features a "tastefully added bass presence". Released in 2016 as an update to the legendary ER-4 line, both models are created with the goal of creating the highest possible accuracy in sound reproduction.

The fundamental difference between the two models lies in their bass tuning. The ER4SR delivers ruler-flat frequency response across the entire spectrum—exactly what studio engineers and mixing professionals demand for critical listening work. The ER4XR takes that same foundation and adds a carefully calibrated bass boost, creating what Etymotic calls "extended response." This makes the XR variant more forgiving of different musical genres and more enjoyable for casual listening without sacrificing the midrange and treble accuracy that defines the ER4 series.

At the heart of both models lies a single custom balanced armature driver. In an era where multi-driver configurations dominate the market—with manufacturers adding 4, 6, 8, or even 12+ drivers into IEM shells—Etymotic's single-driver approach might seem quaint or underpowered. However, this design philosophy offers distinct advantages. Single-driver designs eliminate the need for complex crossover networks that can introduce phase issues, distortion, and coloration. Every frequency comes from the same source, ensuring perfect coherence across the entire frequency spectrum.

Each driver is precisely measured and calibrated, then matched with its pair to ensure channel balance within an industry-leading 1dB specification from 100Hz to 10kHz. This level of matching is exceptional—most manufacturers consider 2-3dB acceptable. Every unit ships with a signed performance certificate documenting the actual measured performance of that specific pair, demonstrating Etymotic's commitment to quality control.

Packaging

The ER4XR has nice packaging, giving an unboxing experience that is similar to even higher priced IEMs. A nicely designed sleeve slides to reveal the main box that contains all of the included accessories.

What's In The Box:

• 1 x ERX4 IEMs
• Detachable 5ft Cable
• Eartips: 4 Dual Flange (S, M, L, XL) 2 Triple Flange (Standard, L) 2 Foam (Standard)
• 1 x Soft Case, 1 x Medium-Hard Case
• Shirt Clip
• 1 x Filter Removal Tool and Replacement Filters
• 1 x Performance Certificate
• 1 x Etymotic Sticker

Cable

The detachable cable features a hybrid rubberized and threaded design. The cable terminates in a right-angled gold-plated 3.5mm stereo plug. The MMCX connectors allow cable replacement, crucial given that cables are typically the first component to fail on any earphone. However, Etymotic's implementation includes a small raised bump on the connector that fits into a corresponding recess on the earphone housing. This ensures optimal connection and prevents rotation, but it also means some third-party MMCX cables won't fit properly. The included cable is high-quality, but users seeking upgrades should verify compatibility.

Eartips

The included ear tips should have an ideal fit for everyone. Multiple sizes of both dual-flange and triple-flange silicone tips accommodate different ear canal sizes. Foam tips provide an alternative fitting option, that offers more isolation, but may affect sound slightly. I found that the triple-flanges were slightly uncomfortable for my ears, and the dual flange was a more comfortable fit.

Build Quality and Design

The ER4XR's design prioritizes performance and durability over aesthetics. The slim cylindrical aluminum housings measure just a few millimeters in diameter, small enough to disappear deep into the ear canal. The ER4's shell looks different than most modern IEM's but it's a functional necessity for Etymotic's deep-insertion fit philosophy, which positions the sound outlet much closer to the eardrum than conventional IEMs.

The aluminum construction provides exceptional durability. These earbuds feel lightweight but also very sturdy. The metal housings can withstand the rigors of daily use, stage performance, or travel without developing the cracks and stress points common in plastic designs. The finish resists scratches and wear, maintaining a professional appearance even after years of use.

Sound Quality

Sound Signature

The overall sound signature of the ER4XR is neutral and flat. Sound comes across with technical precision and a crisp level of detail. This is a reference IEM that creates an accurate representation of music as it was designed, with little to no coloration.

Bass Response

The ER4XR's bass presentation represents Etymotic's attempt to satisfy listeners who found the ER4SR's low end too lean while maintaining its reference-quality accuracy. The result is a bass response that sits in an interesting middle ground—not neutral by audiophile standards, but certainly not emphasized by the standards of modern tunings.

The overall bass quantity comes across as "light" in comparison with most earphones. Still, its bass quality is very good, with no bleeding or muddiness, and a certain clinical precision to its presentation.

Mids

The midrange is more upfront than the bass on the ER4XR; it is presented with a lively and accurate sound. Vocals come across clean and life-like while instruments reveal excellent texture and separation.

The tonal balance leans very slightly toward the warmer side of neutral, which many listeners find musical and engaging without sacrificing detail or accuracy. There's no obvious coloration, no nasality, and no shouty upper midrange peaks. The consistency across different volume levels is excellent—the tonal balance doesn't shift as you adjust volume, unlike some IEMs that become thin at low volumes or harsh at high levels.

Treble

The treble extension reaches well into the upper frequencies, providing adequate air and sparkle. Detail retrieval in the treble is excellent, particularly considering the price point. The treble is crisp and smooth, revealing detail and good brightness. Sibilants aren't too sharp, but they also aren't particularly tamed–some sibilants may be slightly harsh, although I wouldn't say the ER4XR is overall too bright.

The treble doesn't display the metallic tinge or artificial brightness common in poorly-tuned IEMs. Instead, it maintains a natural character that complements the rest of the frequency range.

Technical Performance

Timbre on the ER4XR is very convincing. Acoustic instruments sound real, with natural resonances and harmonic structures intact. String instruments maintain their woody character. Brass instruments have appropriate metallic bite without harshness. Vocals sound human rather than processed or artificial.

The soundstage represents one area where the ER4XR shows its limitations. The presentation is notably intimate and lacks the expansiveness of some IEMs with multiple drivers. The soundstage comes across as more flat and personal.

Imaging is quite good for a closed, deeply-inserted IEM. Center-panned elements sit firmly in place. Left-right positioning maintains accuracy. The imaging is more than adequate and provides noticeable separation and positioning between instruments. Despite the intimate-leaning soundstage, the ER4XR keeps individual elements distinct and separated. In dense, complex mixes with multiple simultaneous instruments and vocals, you can follow individual threads without them blending in. This separation comes from the excellent detail retrieval and low distortion rather than artificial emphasis of different frequency ranges.

Comfort and Isolation

The Etymotic deep-insertion fit philosophy represents the most polarizing aspect of the ER4XR. These IEMs are designed to sit much deeper in your ear canal than conventional in-ear monitors—the triple-flange tips can extend 10-15mm into the canal, far past where most IEMs stop. This deep insertion serves crucial functions for sound quality and isolation, but some people find this to be mildly uncomfortable.

Fortunately, Etymotic provides a few different tip options for ideal comfort. The triple flanges did not fit comfortably in my ear, and I couldn't get a good seal, so I opted instead for the included double flange, which felt much more natural and similar to a typical ear tip while still keeping a deep fit. Once you find the ideal ear tip for your comfort, the ER4XR actually has above-average comfort; they are very lightweight, low-profile, and don't cause fatigue like many larger IEMs.

Thanks to the deep insertion, the ER4-series provides incredible isolation that can range from 35-42dB, much above the average universal and custom IEM isolation level. This level of isolation also means there is virtually no sound leakage from these.

Comparisons

Shure SE215 ($109)

The SE215 uses a single dynamic driver rather than the ER4XR's balanced armature. This driver choice results in significantly more emphasized bass with greater impact and warmth. The SE215 delivers a fun, V-shaped sound signature that appeals to mainstream listeners and works well across popular genres. The bass has more quantity and visceral impact than the ER4XR, though it sacrifices some of the detail, texture, and control that the Etymotic provides.

Though both offer high isolation, the ER4XR provides a higher isolation and a more reference-based, accurate sound that is more suited for professional use. Both IEM's are well-known for live music use, but the ER4XR provides a more accurate mix and isolation, which is generally better if your budget allows.

Final Verdict

The Etymotic ER4XR succeeds brilliantly at its primary mission: delivering reference-quality sound from a single balanced armature driver at a price accessible to serious music listeners. At approximately $310, these IEMs provide performance that rivals models costing hundreds more, particularly in midrange accuracy, treble, and timbre.

The sound quality represents the ER4XR's greatest achievement and the reason these IEMs have maintained their reputation for nearly a decade since their 2016 release. The clarity, detail, and transparency across all frequencies reveal musical nuances that disappear on lesser IEMs.

The ER4XR is a staple for musicians, studio professionals, and anyone who wants a highly accurate reference-level sound. At $310, Etymotic delivers a technical IEM with excellent build quality and offers industry-leading professional sound quality.

Technical Specifications

• Driver Type: Single balanced armature
• Frequency Response: 20Hz – 16kHz
• Impedance: 27Ω @ 1kHz
• Sensitivity: 98dB SPL @ 1mW
• Maximum Output: 122dB SPL
• Channel Matching: ±1dB from 100Hz to 10kHz
• Cable Connection: Detachable MMCX with Etymotic bump
• Termination: 3.5mm gold-plated stereo plug, right-angled
• Noise Isolation: 35-42dB (depending on tip selection and insertion depth)
• Weight: Approximately 13 grams (earphones only, without cable)