FOSTEX UP-103

Commentary

10 cm cone type full range speaker unit of UP series aiming at natural sound with little distortion.

SM (Synthetic Material) cone is used for the diaphragm.
The SM cone is a composite molding cone newly developed by FOSTEX Co., Ltd. as a cone paper which also has the necessary condition as a vibration plate. In general normal cone paper, internal loss decreases greatly when rigidity is increased, and on the contrary, rigidity tends to decrease extremely when internal loss is sufficiently increased. However, in the composite molding cone, pulp material with sufficient rigidity and special material with large internal loss are used. By finishing by a special method different from the conventional cone paper molding method, strain is reduced and more ideal characteristics are realized.

The center of the cone paper is equipped with a high frequency radiator, which is made of metal material molded into a dome shape with an optimum radius of curvature. This radiator operates in the frequency band of 10 kHz or higher, greatly improving the directional characteristics and realizing natural high frequency reproduction.
A part of UP series uses titanium material for this radiator (I didn't know which unit it was.)

The voice coil uses an edgewise coil made of aluminum ribbon with a large diameter and narrow winding width.
This voice coil has undergone a special heat-resistant treatment to withstand temperatures up to 230 ° C.

The magnetic circuits use doughnut type ferrite magnets with larger magnet sizes than the conventional FE-SR series.

Die-cast frame is used for the frame.

Model Rating

Method	Cone type full range unit
Aperture	10cm(4")
Impedance	8 Ω
Lowest resonance frequency (fo)	75 Hz ± 11 Hz
Playback frequency band	Fo ~ 20 kHz
Output sound pressure level	87dB/W/m 88dB/W/m (listed in 1976 catalog)
Input	20W (Music Power)
Air gap magnetic flux density	10,000gauss
Total flux	70,000maxwell
Effective vibration radius (a)	4.0cm
Equivalent mass of the vibration system (mo)	3.5g
Q (Qo) of the speaker	0.5
Magnet weight	369g
Gross weight	1.5kg