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Fostex FE-168 Σ

Pair of Fostex FE-168 Sigma 4 inch Fullrange Drivers

FE-168 Σ is the middle model of the legendary Sigma series. It looks exactly like the FE-208 Σ, but the size is 6".

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

My Measurements

Driver Properties Thiele - Small Parameters
Chassis material Vacuum Molded Aluminum Alloy   Parameter Measured Datasheet
Membrane material Banana Pulp Paper Fs 66 Hz 60 Hz
Magnet System Ferrite Re 7.5 Ω 7.6 Ω
Surround Cloth Qms 4.10 4.53
Voice Coil Diameter 26 mm Qes 0.42 0.40
Nominal Impedance 8 Ω Qts 0.38 0.37
Sensitivity 94 dB/W/m   Vas 17.3 ltr 15.27 ltr
Rated Power 27W Le 0.34 mH N/A

                                       
SPL Responce of Fostex FE-168 Sigma 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


SPL Responce of Fostex FE-168 Sigma at 1m on axis and 15 30 deg off axis

Frequency response at 1m with 2.83 V input from 0 º to 90 º off axis with a step of 10 º, normalized at 1/3 octave.


Second, Third and Fourth Harmonic of Fostex FE-168 Sigma in 18 ltr sealed box

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



Burst decay Responce of Fostex FE-168 Sigma at 1m in 18 ltr sealed box

Burst decay response, measured at 1m on axis


The impedance of Fostex FE-168 Sigma in 18 ltr seled box

The impedance curve in 18 ltr sealed box


Conclusion

This driver differs from the other models of the series by its T/S parameters, which make it suitable for bassreflex constructions, open baffle or a top range driver in a multiway systems. It keeps the well balanced and uncolored sound signature of the "Sigmas".

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