4″ SB12NRX25-4 / Norex


  • Proprietary cone material with natural fibres made in-house
  • High damping Butyl rubber surround for non-resonant sound character
  • Vented pole piece for reduced compression
  • Vented cast aluminium chassis for optimum strength and low compression
  • CCAW voice coil for reduced moving mass
  • Long life silver lead wires
  • Non-conducting fibre glass coil former for minimum damping
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Additional information

Nominal Impedance

4 Ω

DC resistance

Re 3.1 Ω

Voice coil inductance

Le 0.14 mH

Effective piston area

Sd 50 cm2

Voice coil diameter

25.4 mm

Voice coil height

15 mm

Air gap height

5 mm

Linear coil travel (p-p)

10 mm

Magnetic flux density

0.84 T

Magnet weight

0.32 kg

Net Weight

0.76 kg

Free air resonance

Fs 55 Hz


(2.83 V / 1 m) 87.5 dB

Mechanical Q-factor

Qms 3.2

Electrical Q-factor

Qes 0.46

Total Q-factor

Qts 0.40

Moving mass incl. air

Mms 5.6 g

Force factor

Bl 3.6 Tm

Equivalent volume

VAS 5.6 liters


Cms 1.57 mm/N

Mechanical loss

Rms 0.6 kg/s

Rated power handling

* 30 W


* IEC 268-5, T/S parameters measured on drive units that are broken in.



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