RCF LF21N551 21" Low Frequency Woofer w/ 5.3" Voice Coil

The new Dual forced design provide an excellent heat dissipation and lower power compression. Special air-forced ventilations are provided for voice coil, magnet assembly and basket. The combination of carbon fibre loaded cone assembly, large triple roll surround, double silicon spider provides to the LF21N551 remarkable strength and best control under large excursion conditions.

A fully optimised T-pole design generate the minimum amount of flux modulation offering a peak to peak excursion of 72 mm. The waterproof body cone treatment and polycotton surround ensure a durable performance in every application.

• 5.3 - inch Inside/Outside copper voice coil
• 4000 Watt continuous program power handling
• 97 dB Sensitivity
• 30 Hz - 1 kHz Frequency range
• Dual-forced air ventilation for minimum power compression
• Dual spider designed with silicon based damping control
• BL of 39 Txm to provide a faster and accurate low frequency

General specifications
Cone Design: Curved
Dual-force air ventilation: Yes
Effective piston diameter: 470 mm / 18.5 inch
Frequency range: 30 - 1000 Hz
Kind of layers: inside/outside
Magnets: Neodymium
Max. Excursion Before Damage: 72 mm / 2.83 inch
Minimim Impedance: 7 ohm
Nominal Diameter: 21 inch / 533 mm
Number of layers: 2
Power handling capacity: 2000 W
Program Power: 4000 W
Rated Impedance: 8 ohm
Sensitivity: 97 dB
Spider: Dual with silicon based damping control
Surround Design: Triple roll
Surround Material: Polycotton
Top Plate Thickness: 18 mm / 0.71 inch
Voice Coil Diameter: 5.3 inch / 135 mm
Voice Coil Material: Copper
Voice Coil Winding Material: 39 mm / 1.54 inch

Mounting Information
Bolt circle diameter: 527 mm / 20.75 inch
Bolt hole diameter: 7 mm / 0.28 inch
Front mount baffle cut-out: 512 mm / 20.16 inch
Overall diameter: 547 mm / 21.54 inches
Rear mount baffle cut-out: 512 mm / 20.16 inch
Volume occupied by the driver: 7.2 liters / 0.28 ft3

Size
Diameter: 547 mm / 21.54 inches
Height: 260 mm / 10.24 inches
Weight: 14 kg / 30.86 lbs

Standard compliance
CE marking: Yes

Thiele - small parameters
BL factor (BL): 39.00 T x m
DC resistance (Re): 5.20 ohm
Effective moving mass (Mms): 434 gr
Effettive piston area (Sd): 0.17 m2
Electrical factor (Qes): 0.35 Qes
Equivalent Cas air loaded (Vas): 200 liters
Half-space efficency (Eff): 2.40%
Max. linear excursion (Xmax): 15 mm
Mechanical factor: 6.20 Qms
Resonance frequency (Fs): 35 Hz
Total factor: 0.33 Qts
Voice coil inductance @ 1kHz (Le1k): 3.20 mH

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