The flat frequency response of the ER2SE will appeal to sound professionals and audiophiles alike. The ER2SE shells are made of anodized aluminum, CNC machined with extremely tight tolerances. Using a single dynamic driver allows for a very accurate IEM without the added complexity of crossovers, and helps keep the aluminum body small and slim. Included is a user-replaceable cable. The ER2SE offers Etymotic’s renowned passive isolation, providing 35-42 dB attenuation. Both ER2 models, the ER2SE and ER2XR, use the same low-impedance dynamic drivers. The difference between the 2 models is the tuning of the lower (bass) frequencies. The “Studio Edition” ER2SE is tuned to have a flat frequency response. The “eXtended Response” ER2XR is tuned to have an emphasized bass, adding 1-2dB to the mid-bass and 3-4dB to the sub-bass. ER2SE is a great choice for audio creators and musicians on a budget, who require a precise and neutral sound reproduction. ER2SE is also the IEM of choice for consumers who prefer to listen to their music exactly the way it was recorded. Ideal for sound engineers audiophiles who are looking for in-ear monitors that are easy to drive while offering accurate audio reproduction. Accurate Earphone Reproduction When tuning in-ear monitors to accurately reproduce a recording of a live performance, our goal is for the sound hitting the eardrums to be identical to that at the original performance. To achieve this, the acoustic properties of the ear must be factored in. The acoustic resonance and horn effects of the ear change a flat audio signal entering the open ear into sound with a (2700 Hz) high-frequency boost, which is the same response heard at the eardrum in a typical ear. That is the reason for the “hump” in the frequency response graph, which assures the eardrums perceive a perfectly flat frequency response for all frequencies.