Eighteensound 8 NMB 420 - 8 Ohm

The 8NMB420 neodymium transducer has been developed in response to a specific market
requirement for a 8" midbass driver that combines excellent linearity with good efficiency and high
power handling capabilities. 8NMB420 is primarily intended for use as a midbass driver in compact 2-
way or multiway reflex enclosures comprising line arrays. The parameters had been chosen to offer
significant low frequency output in vented enclosure with size starting from 20 lit. with a tuning
frequency around 60Hz. The low pass filter might be positioned as high as 2000-2500Hz. Multiple
8NMB420 units might be used: the compact size reflects in the capability to have precise attack time.
This characteristic makes it the ideal choice for stage monitoring and bass guitar amplification. The
extremely powerful external neodymium magnet assembly assures high flux concentration, low power
compression and excellent heat exchange. The levels of force factor and power handling are, as a
consequence, at the upper professional level with best power to weight ratio. The exclusive
dedicated double roll surround design offers enhanced linear travel and control, in order to
reproduce precisely low frequency. The curvilinear paper cone is formed using a unique wood pulp
composition designed to achieve the best possible rigidity and stiffness. The 50mm inside outside
aluminum voice coil employs Interleaved Sandwich Voice coil (ISV) technology. It is composed by a
high strength fiberglass former used to carry windings on both the outer and inner surfaces to
achieve a mass balanced coil. This results in an extremely linear motor assembly which, in
conjunction with the highly advanced design of the magnetic structure, provides a high force factor
or BL. The voice coil is cooled incorporating airways between the chassis back plate and the magnet
faceplate so that heated air is channeled away from the voice coil and gap and dissipated by the
chassis basket. Thanks to the increasing use during outdoor audio events, the ability to perform in
humid environments is a key feature of the 8NMB420. This is achieved trough a proprietary humidity
repellent cone treatment without a moving speaker mass increase.

Features
95 dB SPL 1W / 1m average sensitivity
51mm (2 in) Interleaved Sandwich Voice coil (ISV)
280 W AES power handling
External neodymium magnet assembly
Single Demodulating Ring (SDR) for lower distortion
Weather protected cone and plates for outdoor usage
Suitable for line arrays and compact two way Systems

Specifications
Nominal Diameter 200mm
Nominal Impedance 8Ohm
Minimum Impedance 4.9 Ohm
Nominal Power Handling1  280W
Continuous Power Handling2 400W
Sensitivity3 95.08 dB
Frequency Range 60-5500 Hz
Voice Coil Diameter 51 mm (2.0)

Thiele Small Parameters
Fs 61 Hz
Re 5.0 Ω
Qes 0.31
Qms 4.0
Qts 0.28
Vas 33.0 dm3 ( ft3)
Sd 230.0 cm2 (35.65 in2)
Xmax 5.8 mm
Mms 14.9 g
BL 10.0 Txm
Le 0.35 mH
EBP 196 Hz

Mounting and Shipping Info
Overall Diameter 210mm
Bolt Circle Diameter 195mm
Baffle Cutout Diameter 186mm 
Depth 99mm
Flange and Gasket Thickness 14mm
Net Weight 1.7kg
Shipping Weight 2.0kg
Shipping Box 235 x 235 x 150 mm (9,25 x 9,25 x 5,91 in) mm (in)