ER•4PT earphones, intended for sound engineers and audiophiles in constant motion, comes equipped with extra accessories and adapters. ER•4PT earphones can be used with portable devices without an additional amplifier—or converted to the ER•4S response with the included P-to-S cable. Compared to the ER•4S, the ER•4PT has 10 dB greater output at high frequencies and 13 dB greater output at low frequencies. The higher sensitivity and enhanced bass of the ER•4PT have made it the most popular earphone in the series. Included with every pair of ER•4PT earphones is an industry-exclusive channel-matching compliance graph, signed by the Etymotic engineer who precision matched and custom tuned the balanced-armature drivers.
ER•4S earphones were designed to compensate for the high frequency emphasis in all CD recordings, in order to provide accurate sound reproduction. Performing musicians often use them as in-ear monitors because the response of the ER•4S matches the response of most typical monitor loudspeakers. The high accuracy and exceptional sound isolation of the ER•4S have made these earphones popular with musicians, recording engineers and audiophiles. ER•4S earphones can be used with a headphone amplifier when using low power portable devices.
ER•4B earphones are for the binaural recording enthusiast. The ER•4B is an ideal earphone for use with material that has not been equalized for loudspeaker playback. It was developed from the ER-1 earphone that is referenced to a flat diffuse field and used primarily for speech reception research, where the goal is to produce the same frequency response at the eardrum as would be produced in the live situation.
Accurate Earphone ReproductionFor earphones to have 100% accuracy, a recording of a live performance must produce exactly the same sound at the eardrum as 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.