Fostex FF125WK 120mm 8 Ohm Full Range driver

Fostex FF125WK 120mm 8 Ohm Full Range driver

FF-WK series are full-range speaker units ideally and exclusively designed for a bass-reflex enclosure. The previous FF series speaker units construction has thoroughly been redesigned on the FF-WK series.

With a new addition of a 10-cm diameter speaker unit to the product range, new technologies such as a double-layer paper cone, a ridgedome shape aluminum alloy center cap and a pocket neckdamper have been employed for high-quality sound. Even with these new technologies, FF-WK series inherits the previous FF series' bright and realistic sound character and achieve a powerful low sound and uncharacterized high-frequency sound reproduction.

Double-layer cone / up-roll edge using a new material

A double-layer cone paper consists of two layers. One is a basic layer and the other is a surface layer. In the FF-WK series, a long-fibered (low freeness) wooden pulp is used for the basic layer, which has high rigidity realized by the large volume structure and appropriate internal loss. For the surface layer, the bincho charcoal powder is blended with a short-fibered (high freeness) kenaf, which allows to accelerate the propagation speed on the cone paper surface.

The up-roll edge shape realizes a long stroke. A polycarbonate series material which has opposite physicalities of high loss and high Young’s modulus is specially blended with urethane foam.

The color tone of FF-WK series cone paper is created by the bincho charcoal and no dye is used. Due to this fact, there is a case that the color tone slightly differs from each other.

Ridge-dome shape aluminum alloy center cap / Mechanical 2-way construction

A ridge-dome shape center cap made of aluminum alloy is employed. Dispersing and deadening a resonance occurred at a specific frequency with this cap helps to ease an unnecessary sound coloration at high  requency range. Also direct coupling with the voice coil bobbin expands the high frequency response.

3-point gluing / Pocket neck damper

3-point gluing which glues the cone paper, damper and the voice coil at one point is employed on the FF-WK series. Increasing the strength of the cone neck section realizes an improved high frequency  response. Employing the pocket shape at the damper neck section has realized the 3-point gluing even with the usage of junction cable.

Faston 205 gold coating connection terminal

In order to minimize the sound variation, the Faston 205 gold coating connection terminal is employed as a speaker terminal.


  • Power Handling: 50 Watt
  • Impedance: 8 Ohm
  • Frequency from: 67Hz
  • Max. Frequency: 22kHz
  • Sound pressure: 89dB


  • Overall dimensions: 120mm
  • Baffle cutout: 104mm
  • Depth (Total): 61.3mm
  • Frame Material: Steel plate
  • Membrane Type: Cone
  • Membrane Material: Kenaf Fibre
  • Voice coil Ø: 25mm
  • Magnet-weight: 388g
  • Magnet-inductance: 5.596T


  • Resonance fs: 67Hz
  • Mechanical Q Qms: 5.091
  • Electrical Q Qes: 0.464
  • Total Q Qts: 0.42
  • Equivalent Air-Volume Vas: 7.265 Liter
  • DC-Resistance Re: 6.7 Ohm
  • Coil Inductance Le: 0.044 mH
  • Mech. Compliance Cms: 1.153 mm/N
  • Moving Mass Mms: 5g
  • Max. Excursion +/- Xmax: 1.65mm
  • BL Product Bl: 5.596 N/A
  • Membrane Ø Md: 92
  • Membrane Area Sd: 66cm²
  • Sound pressure dB: 89 SPL
  • Efficiency Nref: 0.451%

PRICE (1 off)
£67.23 +vat +p&p

Big Picture
PDF datasheet

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