18 Sound 21NLW4000 speaker, 8 ohm, 21 inch

94 dB SPL 1W / 1m average sensitivity
100 mm (4") Interleaved Sandwich Voice coil (ISV)
3200 Watt program power handling
Composite reinforced straight ribbed cone
Optimized high grade neodymium magnet assembly
Recommended for subwoofer usage in compact vented or bandpass enclosures

The 21NLW4000 is a 21" (533 mm) extended low frequency loudspeaker, designed for use in vented or bandpass enclosure. The loudspeaker is designed to withstand high power levels without damage while providing clean and undistorted LF reproduction at a very high SPL. For optimum results we recommend amplifiers able to deliver 3200 Watt program power. The 21NLW4000 features a unique motor featuring a high grade neodymium magnet assembly in a structure optimized for thermal and magnetic efficiency. 21NLW4000 features include a large displacement suspension system which, in conjunction with a composite reinforced, straight ribbed cone, allows an ultra-linear piston action and provides full mechanical control across the entire working range. The 100mm (4 in) state-of-the-art voice-coil utilizing Interleaved Sandwich Voice coil (ISV) technology, provides high levels of thermal stability and durability. The ISV technology achieves a balanced linear motor unit exerting an exceptionally high force factor.

General Specifications
Nominal Diameter 533mm (21 in)
Rated Impedance 8 Ohm
AES Power 1500W
Program Power 3200 W
Sensitivity 94 dB
Frequency Range 30-1800Hz
Power Compression @-10dB 0,62 dB
Power Compression @-3dB 2,18 dB
Power Compression @Full Power 3,57 dB
Max Recomm. Frequency 150Hz
Recomm. Enclosure Volume 120-300 lt (4.24 - 10.60 cuft)
Minimum Impedance 6 Ohm at 25°C
Max Peak To Peak Excursion 70 mm (2.76 in)
Voice Coil Diameter 100 mm (4 in)
Voice Coil Winding Material Copper wire
Suspension Triple-roll, Polycotton
Cone Complex Composite

Thiele Small Parameters
Fs 29 Hz
Re 4,9 Ohm
Sd 0,166 sq. mt. (257,30 sq. in.)
Qms 22.0
Qes 0,38
Qts 0,37
Vas 315 lt. (11,13 cuft)
Mms 376 gr. (0,83 lb)
BL 30,0 Tm
Linear Mathematical Xmax ± 15 mm (± 0,59 in)
Le (1kHz) 2,80 mH
Ref. Efficiency 1W@1m (half space) 2%

Mounting information
Overall diameter 545 mm (21.46 in)
N. of mounting holes and bolt 8
Mounting holes diameter 8,5 mm (0,33 in)
Bolt circle diameter 520 mm (20.47 in)
Front mount baffle cutout ø 492 mm (19,37 in)
Rear mount baffle cutout ø 490 mm (19,29 in)
Total depth 245 mm (9,64 in)
Flange and gasket thickness 18 mm (0,7 in)
Net weight 11,6 kg (25.5 lb)
Shipping weight 13,1 Kg (28,8 lb)