The ER3XR is a single driver in-ear monitor (IEM) known for its high sensitivity. Its anodized aluminum shell is CNC machined to precise tolerances, resulting in a slim and lightweight design. The use of a single balanced armature (BA) driver in the ER3XR provides accurate audio reproduction without the complexity of crossovers, while the included user-replaceable cable adds to its convenience. Etymotic IEMs are widely recognized for their outstanding passive noise isolation, which can reduce outside noise by 35-42 dB depending on the eartips used and their depth of insertion. This level of isolation is higher compared to most custom IEMs that provide around 25-28dB attenuation and foam earplugs that provide up to 32dB reduction. The ER3XR is an ideal choice for audiophiles and budget-conscious consumers who are looking for easy-to-drive IEMs that provide enhanced bass compared to the neutral ER3SE. Both ER3 models, the ER3SE and ER3XR, use the same high-sensitivity, low-impedance balanced armature (BA) driver, meaning no amplifier is required. The main difference between the two models is their tuning, with the ER3SE having a flat frequency response while the ER3XR offers an emphasized bass that adds 1-2dB to the mid-bass and 3-4dB to the sub-bass. The ER3SE is suitable for audio creators and musicians who want precise and neutral audio reproduction, as well as for prosumers who prefer to hear their music as it was recorded. On the other hand, the ER3XR is favored by those who want to enjoy the extra bass in their music while maintaining balance. Etymotic's target frequency response graph aims for a "perceptibly flat" frequency response. This requires accounting for the resonance inside the average ear canal and the need for higher SPL in the 2-5k region (lower treble) to compensate. The resulting "hump" in the frequency response graph helps ensure that the eardrums perceive a flat frequency response for all frequencies.