RCF LF21X451 - 4000W 21-inch Ceramic Low-Frequency Driver with 4.5-inch Voice Coil and 8-Ohm Impedance in Black Finish

The RCF LF21X451 is a high-performance 21-inch ceramic low-frequency driver that sets new standards for power handling, efficiency, and low distortion in subwoofer applications. Designed after years of R&D, this transducer features a blend of advanced technologies, ensuring an incredibly linear frequency response and the highest power handling capabilities among comparable drivers. With a robust ceramic magnet structure and a 4.5-inch fiberglass voice coil, the LF21X451 delivers a frequency range from 28 Hz to 1000 Hz, making it perfect for producing deep, clean bass in professional audio systems.

At the heart of the LF21X451 is a fibre-loaded cone assembly paired with a high-excursion triple-roll surround, providing remarkable strength and stability even under extreme conditions. This driver offers a peak-to-peak excursion of 54 mm, allowing it to handle the most demanding low-frequency signals without distortion or power loss. The dual-forced hyper-venting system ensures optimal ventilation of the voice coil, reducing power compression and improving overall efficiency during extended use at high output levels. These features make the LF21X451 an exceptional choice for large-scale sound reinforcement systems that demand both accuracy and power.

With a continuous power handling of 4000W and a sensitivity of 97 dB, the LF21X451 excels in both high-output performance and low distortion. Its advanced construction, including a double spider system with silicon-based damping control, ensures stability and durability, even during high-excursion operations. The driver's impressive BL factor of 30.5 T x m contributes to faster and more accurate low-frequency response, making it an ideal choice for subwoofer applications that require both precision and power.

Features

• 4000W continuous program power handling for high-output subwoofer performance
• 4.5-inch fiberglass voice coil with inside/outside windings for efficient power handling
• 97 dB sensitivity for effective sound reproduction in demanding environments
• 28 Hz to 1000 Hz frequency range for deep and accurate low-frequency response
• Peak-to-peak excursion of 54 mm for exceptional low-frequency extension
• Dual-forced hyper-venting system for efficient voice coil cooling and reduced power compression
• Triple-roll polycotton surround for enhanced durability and control during large excursions
• BL factor of 30.5 T x m for faster and more accurate low-frequency response
• Ceramic magnet structure for high power-to-weight ratio and improved efficiency
• Dual spider system with silicon-based damping control for superior stability
• Resonance frequency of 28 Hz and maximum linear excursion of 14 mm for deep bass reproduction
• CE compliant for safety and reliability in professional installations

Specifications

General Specifications

• Nominal Diameter: 21 inch / 533 mm
• Rated Impedance: 8 ohm
• Program Power (watt): 4000 W
• Power handling capacity: 2000 W
• Sensitivity: 97.0 dB
• Frequency range: 28 - 1000 Hz
• Effective piston diameter: 470 mm / 18.5 inch
• Max. Excursion Before Damage: 54 mm / 2.13 inch
• Minimum Impedance (ohm): 6.7 ohm
• Voice Coil Diameter: 4.5 inch / 114 mm
• Voice Coil Winding Material: Copper
• Voice Coil Length: 34 mm / 1.34 inch
• Number of layers: 2
• Kind of layers: inside/outside
• Top Plate Thickness: 15 mm / 0.59 inch
• Cone Design: Curved
• Surround Material: Polycotton
• Surround Design: Triple roll
• Magnets: Ceramic
• Dual-force air ventilation: Yes
• Spider: 03

Thiele (small parameters)

• Resonance frequency (Fs): 28 Hz
• DC resistance (Re) (ohm): 5.40 ohm
• Mechanical factor: 6.90 Qms
• Electrical factor: 0.39 Qes
• Total factor: 0.37 Qts
• Bl factor (Bl) (T x m): 30.50 T x m
• Effective moving mass (Mms): 355.0 g
• Equivalent Cas air loaded (Vas): 385.0 liters
• Effective piston area (Sd): 0.170 m2
• Max. linear excursion (Xmax): 14 mm
• Voice coil inductance @ 1kHz (Le1k): 2.90 mH
• Half-space efficency (Eff): 2.20%

Mounting Information

• Overall diameter: 547 mm / 21.54 inches
• 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
• Rear mount baffle cut-out: 512 mm / 20.16 inch
• Volume occupied by the driver: 6.5 liters / 0.26 ft3

Standard Compliance

• Safety agency: CE compliant

Size/Weight

• Height: 9.65 inches
• Diameter: 21.54 inches
• Weight: 34.17 lbs

Shipping Information

• Package Height: 11.18 inches
• Package Width: 22.99 inches
• Package Depth: 23.78 inches
• Package Weight: 40.79 lbs