ER•4B (Binaural) earphones may be preferred by those who want to hear the slight high-frequency boost which is standard practice in CD and vinyl recordings (5 dB at 10 kHz). ER-4B earphones were originally designed to provide an eardrum-pressure frequency response closely mimicking that of the open ear in a diffuse sound field, making them ideal for any material that has not been equalized for loudspeaker playback, such as properly equalized binaural recordings. Many early listeners found the 4B earphones a bit bright, which led to the introduction of the ER-4S.

ER•4S (Stereo) 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•4P (Portable) earphones can be used with portable CD, MP3, DVD and other players without requiring an additional amplifier. As compared to the ER•4S, the ER•4P 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•4P have made it the most popular earphone for most uses.

ER•4B	ER•4S	ER•4P	ER•4 Feature Comparison
•	•	•	Lightweight and portable
•	•	•	High accuracy
•	•	•	Noise isolation (35-42 dB)
		•	Enhanced bass response

Effective Response of ER•4 Earphones