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Fostex FE103En Fullrange Speaker Driver Transducer
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Fostex FE103En Fullrange Speaker Driver Transducer

The new Fostex FE103En speaker driver replaces the Fostex FE103E. The Fostex FE103En is a 100 mm (3.9") diameter fullrange speaker driver. The cone is made of banana plant fiber and light-weight. A new treated cloth surround is used. The 80 mm diamter ferrite magnet weighs almost 195 grams. The FE103En can be used in a wide variety of enclosures ranging from simple bass reflex, Transmission Line, Quarter Wavelength, Back Loaded Horn and also with open baffles. The full-range speaker driver is capable of an extended frequency response from about 90Hz to 15kHz. In some large enclosures about 50-60Hz in room bass response is possible with this little speaker.

Fostex FE103En Full-range Speaker Driver

Photograph 1: Fostex FE103En Fullrange Speaker Driver

The FE103En drivers came neatly packaged in a cardboard box which indicated the speakers are Made in China. Inside the box is a foam gasket, four wood screws with washers and a datasheet with the driver specifications and speaker enclosure plans.

Fostex FE103En Fullrange Speaker Driver Box Contents

Photograph 2: Fostex FE103En Fullrange Speaker Driver Box Contents

The frame of the FE103En is made using stamped steel. The lightweight stamped steel frame is prone to "ring" and efforts to "damp" and deaden the frame will improver performance. There are a number of modifications for this driver ans some of them are shown on the modifications and tweaks page for the Fostex FE103En fullrange speaker driver.

Fostex FE103En Fullrange Speaker Driver - Motor and Frame

Photograph 3: Fostex FE103En Fullrange Speaker Driver - Motor and Frame

Thiele/Small (T/S) Parameters - Fostex FE103En Driver

We have measured the Thiele/Small Parameters of the Fostex FE103En drivers using the Dayton Audio Woofer Tester 3 (WT3). The T/S testing results and the parameters noted on the datasheet are summarized in Table 1. The measured T/S parameters do not match very closely with those published by the manufacturer. The measurements were made at about 21 degrees Celsius.

Table 1: Thiele/Small (T/S) Parameters - Fostex FE103En Fullrange Driver

 Parameter  Fostex Driver 1 Driver 2
Fs 83 Hz 95.5 Hz 102.3 Hz
Vas 5.95 L 3.56 L 3.31 L
Qts 0.33 0.45 0.47
Qes 0.377 0.53 0.55
Qms 2.75 3.31 3.27
Re 7.5 Ohms  7.40 Ohms   7.57 Ohms 
Le  0.0398 mH  0.19 mH 0.21 mH
SPL 89 dB 89.5 dB 90 dB

Notes:
  - Le measured with Sencore LC75.
  - SPL estimated with Radio Shack 33-2050 SPL Meter.
  - Remaining measurements with Dayton Audio Woofer Tester 3 (WT3).

Fostex FE103En Frequency Response and Impedance

Figure 1: Fostex FE103En Frequency Response and Impedance (from Datasheet)

Figure 2 shows the impedance sweep produced with the WT3

Fostex FE103En Measured Impedance

Figure 2: Fostex FE103En Measured Impedance

Datasheet - Fostex FE103En

Fostex FE103En Recommended Bass Reflex Type Enclosure

Below is the Fostex Recommended Standard Bass Reflex Type Enclosure for the FE103En. The speaker box plan is from the Fostex FE103En datasheet.

Fostex FE103En Recommended Bass Reflex Enclosure

Fostex FE103En Recommended Bass Reflex Type Enclosure

Enclosure Plans and Projects Links - Fostex FE103En