คำอธิบาย

Features
Non-resonant diaphragm design for minimum high frequency break-up
Copper cap for reduced voice coil inductance and minimum phase shift
Compact low distortion neodymium motor system
Non-resonant rear chamber with optimized damping for improved dynamics
CCAW voice coil for low moving mass
Long life silver lead wires
Low resonance frequency
 
Specs
Nominal Impedance 4 Ω
DC resistance, Re 3.1 Ω
Voice coil inductance, Le 0.04 mH
Effective piston area, Sd 4.6 cm2
Voice coil diameter 20.4 mm
Voice coil height 1.5 mm
Air gap height 2.0 mm
Linear coil travel (p-p) 0.5 mm
Moving mass incl. air, Mms 0.25 g
Free air resonance, Fs 850 Hz
Sensitivity (2.83V/1m) 89.5 dB
Mechanical Q-factor, Qms 2.71
Electrical Q-factor, Qes 2.45
Total Q-factor, Qts 1.28
Force factor, Bl 1.3 Tm
Rated power handling* 40 W
Magnetic flux density 0.9 T
Magnet weight 0.01 kg
Net weight 0.06 kg
* IEC 268-5, high-pass Butterworth, 2600 Hz, 12 dB/oct.
 
https://sbacoustics.com/product/sb21rdcn-c000-4/