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SB Acoustics SB12NRXF25-4 Norex Midwoofer

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The SB Acoustics SB12NRXF25-4 is a 4 inch 4 ohm midwoofer featuring a Norex cone with a foam surround and a rigid aluminium chassis. Norex is a proprietary paper based material comprised of wood pulp and selected natural fibres blended for an optimally strong but lightweight cone that, combined with the foam surround, gives excellent midrange extension with resolution and detail. This unit can be used as a fine midrange drive unit.

Also available in 8 ohms: SB12NRXF25-8.

Key Features:

  • Proprietary cone material with natural fibres made in-house.
  • Foam surround for maximum transparency and midrange resolution.
  • Vented cast aluminium chassis for optimum strength and low compression.
  • Vented pole piece for reduced compression.
  • CCAW voice coil for reduced moving mass.
  • Non-conducting fibre glass coil former for minimum damping.
  • Long life silver lead wires.
  • Faraday shorting ring in motor system for reduced distortion.

Basic parameters:

Resonant frequency (fs) 61 Hz Nominal impedance (Zn) 4 Ω
Mechanical  Q factor (Qms) 5.3
DC resistance (Re) 3.1 Ω
Electrical Q factor (Qes) 0.53
Max power handling 30 W
Total Q factor (Qts) 0.48
Sensitivity (2.83V/1m)
Equivalent volume (Vas) 4.1L Chassis diameter

Here's the full datasheet:

.pdf link