Rutcho's Audio Page dedicated to Hi-End Audio Systems Fullrange Speakers Tube Amplifiers

Ruitcho's page dedicated to hi-end audio Blackswift Audio Logo

Fostex FE-103 En

Pair of Fostex FE-103 E/n 4 inch Fullrange Drivers

FE-103 is a Fostex driver with a long history. FE-103En is one of the latest versions with the typical performance of the FE series. 

This is the manufacturer's brochure  Link To Fostex FE-108 Sigma Manufacturer's Datasheet

My Measurements

Driver Properties Thiele - Small Parameters
Chassis material Stamped Steel   Parameter Measured Datasheet
Membrane material Banana Pulp Paper Fs 93Hz 83 Hz
Magnet System Ferrite Re 7.3 Ω 7.5 Ω
Surround Cloth Qms 3.2 2.75
Voice Coil Diameter 20 mm Qes 0.45 0.38
Nominal Impedance 8 Ω Qts 0.39 0.33
Sensitivity 89 dB/W/m   Vas 3.4 ltr 5.95 ltr
Rated Power 5W Le 0.21 mH 0.04 mH

SPL Responce of Fostex FE-103 En at 1m on axis and 15 30 deg off axis

Frequency response at 1m with 2.83 V input RED - on axis, BLUE - 15 º off axis, GREEN - 30 º off axis

Second, Third and Fourth Harmonic of Fostex FE-103 En in 18 ltr sealed box

The second, third and fourth harmonic curves measured at 2.83V input RMS.

Burst decay Responce of Fostex FE-103 En at 1m in 18 ltr sealed box

Burst decay response, measured at 1m on axis

The impedance of Fostex FE-103 En in 18 ltr seled box

The impedance curve in 18 ltr sealed box


This driver has a typical T/S parameters for a bassreflex applications. It can be used as an extended midrange speaker in two or three way systems with a great success

Arrow up icon To The Top Arrow up icon