Etymotic Research-ER4SR
A reference earphone continuing the single BA tradition from the 1991 ER4, pursuing measurement accuracy. Its exceptional >35dB isolation, comparable to custom IEMs, and a precise soundstage from drivers matched within ±1dB, offer unique value. While cheaper alternatives exist for sound quality alone, as a unique choice combining both isolation and measurement accuracy, it delivers high cost-performance for professional use and in specific environments.
Overview
The Etymotic Research ER4SR represents the latest evolution of the ER4 series, which debuted in 1991 as the world’s first hi-fi earphone. The “SR” stands for Studio Reference, designed for use in recording studios with an extremely flat frequency response as its primary goal. Featuring a single balanced armature driver, it offers 20Hz-16kHz frequency response, 98-104dB sensitivity, and 45Ω impedance. Its most distinctive feature is the industry-leading 35-42dB passive noise isolation, achieved through deep insertion and proprietary triple-flange ear tips. The left and right drivers are matched within ±1dB across 100Hz-10kHz, demonstrating a strong commitment to measurement precision.
Scientific Validity
\[\Large \text{1.0}\]The ER4SR’s measurement data faithfully reflects its design philosophy. THD (Total Harmonic Distortion) ranges from 0.15-0.81%, which is excellent for a single BA driver. The frequency response follows the target curve well above 800Hz, while maintaining extremely flat characteristics below 800Hz before gently rolling off around 80Hz. Intentional boosts at 2.7kHz and 5kHz compensate for the ear canal effects from deep insertion. At 44mVrms to achieve 90dBSPL, it can be driven adequately by portable devices. The measured isolation performance of -39dB is exceptional, achieving this level without any active noise cancellation is particularly noteworthy.
Technology Level
\[\Large \text{0.9}\]The ER4SR demonstrates high technical completion, particularly excelling in quality control. Each unit includes an individual measurement certificate showing actual frequency response, sensitivity, and THD values. While the single BA driver configuration appears simple compared to modern multi-driver IEMs, it offers advantages in phase coherence and transient response excellence. However, the bandwidth limitations inherent to single drivers (particularly low-end extension and high-frequency resolution) cannot be denied. The cable is detachable with MMCX connectors, designed for long-term use. The housing durability is high, with many users reporting over 10 years of continuous use.
Cost-Performance
\[\Large \text{0.6}\]The cost-performance evaluation of the ER4SR varies greatly depending on which features are valued.
If focusing solely on pure sound quality (frequency response fidelity, low distortion), the 349 USD price is hard to justify when excellent, inexpensive products like the Moondrop CHU II (around 22 USD) exist.
However, the ER4SR’s true value lies in its combination of “>35dB passive isolation comparable to custom IEMs” and “reference-grade measurement accuracy.” While high-isolation products like the Shure SE215 (around 100 USD, up to -37dB) and Etymotic’s own ER2SE (around 100 USD) exist, they don’t undergo the same rigorous quality control (e.g., ±1dB channel matching).
If we define “equivalent function and performance” as both high isolation and measurement accuracy, the ER4SR becomes a unique product, and its cost-performance approaches 1.0. However, for many, “reference-grade accuracy” may be overkill. If “practically sufficient high isolation” is the only requirement, alternatives exist for around 100 USD, leading to a calculation of CP = 100 USD / 349 USD ≒ 0.29.
Here, we assign a score of 0.6, considering a middle ground and its reliability for professional use. The product’s value is determined not just by sound quality, but by what one will pay for the physical function of isolation.
Reliability & Support
\[\Large \text{0.8}\]Etymotic Research, founded in 1983, has an established reputation for product reliability. The ER4SR includes a 2-year warranty with comprehensive repair services available in the United States. Many users report over 10 years of use, with the simple single-driver configuration contributing to long-term reliability. Consumables like replacement ear tips and cables are continuously available, supporting a system designed for long-term use. However, support in international markets relies on distributors, which may not be as prompt as domestic U.S. service. Additionally, a certain number of users abandon use due to comfort issues with deep insertion, which should be recognized before purchase.
Rationality of Design Philosophy
\[\Large \text{0.9}\]The ER4SR’s design philosophy is based on an extremely rational approach that prioritizes measurable performance metrics. Excluding subjective elements like “musicality” or “tonality” and tuning purely based on measurement data is commendable. Achieving high isolation through deep insertion is a rational choice for maximum effectiveness through passive means. The single BA driver adoption can be interpreted as prioritizing phase characteristics while avoiding complex crossover circuits. However, considering modern DSP technology and multi-driver design advances, this could be seen as a somewhat conservative approach. Nevertheless, the consistent approach toward a clear design goal (studio reference) is highly evaluated.
Advice
The ER4SR remains valuable for specific applications, but careful consideration is needed for general listening purposes. When considering purchase, I strongly recommend finding an opportunity to experience the deep-insertion fit firsthand. Many users cannot adapt to this fit and abandon use.
For those prioritizing price-performance ratio, I recommend first trying lower-priced products like the Moondrop CHU II (22 USD) or CCA CRA (15 USD). These products offer sufficiently high basic sound quality performance, with the quality difference from the ER4SR not being as large as the price difference suggests.
The ER4SR truly shines in the following special situations: use in environments requiring extremely high isolation (aircraft, subways, etc.), studio monitoring work, or as a reference device for hearing tests. In these applications, the ER4SR’s characteristics provide value that is difficult to replace with other products.
Additionally, if you value trust in the Etymotic brand and durability lasting over 10 years, there’s room to consider it as a long-term investment. However, if seeking pure sound quality performance or cost-performance, I recommend considering other options.
(2025.7.7)