The ER4XR is Etymotic's in-ear monitor for those who demand the highest reproduction accuracy in the mid and high frequency ranges but prefer the presence of tastefully added bass.

The ER4XR right and left channels are matched with industry-leading 1 dB accuracy across frequencies from 100 Hz to 10 kHz.

The ER4XR is the highest performing, single-driver in-ear monitor. The IEM housing is made from anodized aluminum, machined with CNC to extremely tight tolerances. Using a single Balanced Armature (BA) driver enables an exceptionally accurate IEM without the complexity of crossovers, and helps maintain the small and sleek size of the aluminum body. The included high-quality, user-replaceable cable is reinforced and braided to increase durability and longevity.

Etymotic earphones are globally recognized for their leading passive isolation in their category, providing 35-42 dB of attenuation (depending on the earplugs used and the insertion depth). By comparison, most custom earphones provide about 25-28 dB of attenuation, while foam earplugs can reach up to 32 dB. The ER4XR is a must-have for audiophiles and consumers seeking highly accurate ear monitors with added bass for a more "entertaining" sound.

Etymotic's target frequency response graph represents a "perceptibly 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 outer ear structure. As a result, higher SPL is needed in the 2-5k range (lower treble) to compensate for the mentioned resonance. This is the reason for the "bump" in this range.

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

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

Each ER4SR and ER4XR device includes a channel matching compliance graph.