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FOSTEX FE127E FULLRANGE DRIVER

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The Fostex FE127E is a 120 mm (4.7") full-range driver. The driver is well built and like most Fostex units, it sounds excellent. The FE127E has been used in a wide variety of enclosures including sealed, bass reflex, Transmission Line and Quarter Wavelength enclosures. I had a lot of success with this driver in a Sealed Bipole Speaker Enclosure. This full-range driver is capable of frequency response from about 70Hz to 20kHz, but note the limited Xmax. The cone is made of banana plant's fiber and this it is very light and the driver is fast. It is magnetically shielded for use near television or CRT monitor. The drivers main flaw is a little bit of shout, which some have managed to address through modifications.

Fostex FE127E Full-range Driver
Photograph 01: Fostex FE127E Fullrange Driver

The frame is stamped steel so it should be damped with ductseal. See the Radio Shack 40-1197 (FE103) for a good example of how to damp the driver frame using ductseal. Also, take a look at this thread for FE127E modifications.

Fostex FE127E T/S Measurements

I have measured the Thiele/Small Parameters of the Fostex FE127E drivers manually (using a signal generator and mulit-meter) as well using the Dayton Audio Woofer Tester 3 (WT3). The results shown below are the average of four drivers which were very closely matched. As you can see, the parameters measured do not match very closely with those published by the manufacturer. The table below shows a comparison of the measured results. The measurements were made at about 22 degrees Celcius.

 Parameter   Manufacturer   SG + DMM1  WT32
Fs 70.4 Hz 87.1 Hz 92.9 Hz
Vas 9.9 L -- 7.4 L
Qts 0.43 0.66 0.68
Qes 0.50 0.74 0.77
Qms 3.33 6.11 5.81
Re 6.5 Ohms 7.0 Ohms  7.1 Ohms 
Le n/a 0.17 mH 0.16 mH
SPL 91 dB ~90.5 dB 90.9 dB

T/S Parameters - Fostex FE127E Driver

Notes:
  1 - Average of 4 drivers using Signal Generator and Digital Multi-Meter (SPL from SPL Meter)
  2 - Average of 4 drivers using Dayton Audio Woofer Tester 3

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