The ER4SR is Etymotic’s reference hi-fidelity ear monitor for those who demand the highest reproduction accuracy. The ER4SR’s right and left channels are matched to an industry-leading tolerance of 1 dB across frequencies from 100 Hz to 10 kHz..

The ER4SR is the highest performing single-driver in-ear monitor. The IEM housing is made from anodized aluminum, CNC machined with extremely tight tolerances. Using a single Balanced Armature (BA) driver allows for highly accurate IEMs without the complexity of crossovers, and helps maintain the aluminum body's small and sleek size. The included high-quality, user-replaceable cable is reinforced and twisted to increase durability and longevity.

Etymotic earphones are recognized worldwide for their class-leading passive isolation, providing 35-42 dB attenuation (depending on the earplugs used and insertion depth). In comparison, most custom earphones provide about 25-28 dB attenuation, while foam earplugs can reach up to 32 dB. The ER4XR is a must-have for sound engineers and consumers who demand the most accurate in-ear monitors.

The target frequency response graph of Etymotic depicts a "perceived flat" frequency response. Our goal is to achieve a flat frequency response curve when the sound notes reach the eardrum. To achieve this, we must consider the average resonance within the ear canal, as IEMs bypass the structure of the outer ear. As a result, a higher SPL is required in the 2-5k range (lower treble) to compensate for the mentioned resonance. This is the reason for the "hump" in this range.

The target curve used by Etymotic for fine-tuning IEMs slightly differs from the Harmon preference curve. We developed it in-house more than 20 years ago, leveraging our expertise in human hearing and our acoustic research.

When tuning in-ear monitors to accurately reproduce a recording of a live performance, our goal is for the sound reaching the eardrum to match the sound of the original performance. To achieve this, the acoustic properties of the ear must be considered. The acoustic resonance of the ear and horn effects transform a flat sound signal entering the open ear into a sound with a high-frequency boost (2700 Hz), which is the same response we hear at the eardrum in a typical ear. This is the reason for the "bump" seen on the frequency response graph below, ensuring that the eardrum perceives a perfectly flat frequency response across all frequencies.

Every ER4SR and ER4XR device comes with a channel matching compliance graph.