ER•4 Technical Specifications

Frequency response: 50-10 kHz ± 2 dB; 20-16 kHz ±4 dB
Acoustic polarity: + electrical = + acoustic
Transducer type: balanced armature
1 kHz sensitivity (ER•4B/ER•4S): 108 dB SPL for a 0.79 V input
                                                                (90 dB @ 0.1 V; 100 dB @ 1mW)
1 kHz sensitivity (ER•4P): 108 dB SPL for a 0.2 V input
                                                  (102 dB @ 0.1 V; 106 dB @ 1mW)
Impedance (ER•4B/ER•4S): 100 Ohms nominal
Impedance (ER•4P): 27 Ohms nominal
Maximum output: 122 dB SPL
Maximum continuous input (ER•4B/ER•4S): 3.0 Vrms
Maximum continuous input (ER•4P): .75 Vrms
Weight: less than 1 oz.

MicroPro Frequency Response (measured at eardrum)

The ER-4S earphone has an equalized high frequency response. Most stereo recordings have been equalized, electronically or by choice of microphone type and placement, to sound good with mainstream "good" loudspeakers in typical living rooms. Several studies have been conducted dealing with the subject of loudspeaker response as affected by the listening room. The figure to the right shows the frequency response of loudspeakers considered to be "flat" in five studies. Even a loudspeaker with a perfectly flat power output exhibited a room response 4-10 dB down at 10 kHz, relative to the midband. The ER-4S has been designed with a gradual roll off in the high frequencies similar to that of the curve labeled MCK, which represents a compromise choice. The ER-4S is well suited for all types of stereo recording reproduction.

Loudspeaker Room-Equalized Response Five Recommendations