4″ SB12MNRX25-4 / Paper


  • Proprietary cone material with natural fibres made in-house
  • Shortened voice coil optimized for pure midrange reproduction
  • 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 3.2 Ω

Voice coil inductance

Le 0.14 mH

Effective piston area

Sd 50 cm2

Voice coil diameter

25.4 mm

Voice coil height

9.5 mm

Air gap height

5 mm

Linear coil travel (p-p)

4.5 mm

Magnetic flux density

0.9 T

Magnet weight

0.4 kg

Net Weight

0.85 kg

Free air resonance

Fs 58 Hz


(2.83 V / 1 m) 88.5 dB

Mechanical Q-factor

Qms 3.6

Electrical Q-factor

Qes 0.42

Total Q-factor

Qts 0.37

Moving mass incl. air

Mms 4.9 g

Force factor

Bl 3.7 Tm

Equivalent volume

VAS 5.5 liters


Cms 1.55 mm/N

Mechanical loss

Rms 0.5 kg/s

Rated power handling

50 W


IEC 268-5, high-pass Butterworth, 200 Hz, 12 dB/oct.



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