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18SOUND 6NMB420

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18SOUND (Eighteen Sound) 6NMB420 — 6" / 6 inch · Midrange without Bass (Mid) · Midrange · Neodymium
1.77" voice coil · 8 Ω
Part no.: 42A-CHS-MT-18S-0031

165.00 € 165.0 EUR 165.00 €

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18SOUND 6NMB420 — 6" · Midrange Driver

200 W AES · 100 dB Sensitivity · Frequency range 200 Hz – 7000 Hz

Technical data

  • Diameter: 6 "
  • Voice coil: 1.75 "
  • Power handling: 200 W AES
  • Sensitivity: 100 dB
  • Impedance: 8 Ω
  • Magnet: Neo
  • Weight: 1.25 kg
  • Mounting depth: 73 mm
  • Frequency range: 200 – 7000 Hz

Datasheet (PDF) · Manufacturer page

Series: NMB · Part no.: 42A-CHS-MT-18S-0031

18Sound 6NMB420: 6" neodymium midrange with 100 dB and 0.1 mH inductance

A voice coil inductance of 0.1 mH is the most striking figure on the 6NMB420 from the NMB series by 18Sound (Eighteen Sound): it means the impedance stays almost flat across the whole operating range of 200 Hz to 7,000 Hz and the top end is not held back by the coil. Add 100 dB sensitivity, 200 W AES on a 1.75" voice coil and a neodymium motor that keeps the 6" driver at 1.25 kg.

The cone has a moving mass of only 8.5 g, the motor delivers BL 9 Tm. With Fs 110 Hz, Qts 0.33 and Vas 6.1 l the 6NMB420 is slightly less tightly damped than other midranges in the series, which gives it forgiving behavior in sealed chambers. Xmax is 3 mm, mounting depth 73 mm – a pure midrange for three-way cabinets, line arrays and columns, not a driver for lower mids.

Use and enclosure

The 6NMB420 belongs in a sealed midrange chamber, for which the guideline suggests about 1.7 l with a system resonance of 236 Hz. Larger chambers lower the resonance and create distance to the lower crossover point, which should sit well above 200 Hz. A vented chamber (guideline 3.8 l, tuned to 125 Hz, f3 around 135 Hz) is possible but offers no practical advantage for a midrange; the EBP of 289 argues for midrange or horn use. If you combine several drivers in a column, the 16 Ω version provides the right impedance for parallel wiring. The enclosure calculator on 42.audio shows how the chamber volume affects the system resonance.

At the top the range ends at 7,000 Hz; the hand-over to a dome, ribbon or 1" compression driver sensibly sits well below that. At 100 dB the driver is louder than most woofers and gets level-matched in the DSP or crossover.

What to look out for

  • 8 Ω (Re 5.3 Ω) or 16 Ω: choose the impedance by the number of drivers run in parallel.
  • Le 0.1 mH: flat impedance up to 7,000 Hz, a passive crossover works without impedance correction.
  • Xmax 3 mm: high-pass well above 200 Hz, no operation in the lower mids.
  • 1.25 kg and 73 mm mounting depth: light and shallow for arrays and columns.
  • 100 dB sensitivity: plan for level matching to the woofer.

Frequently asked questions

Is the 6NMB420 suitable for a two-way box?

No. The operating range starts at 200 Hz, Fs is 110 Hz and Xmax 3 mm – it lacks the substance for lower mids. As a midrange in three-way cabinets or in arrays with subwoofers underneath, however, it is right in its element.

What separates the 6NMB420 from the 6NMB900?

Both are pure 6" midranges rated at 200 W AES. The 6NMB900 is tuned very similarly with Fs 100 Hz, Qts 0.34 and Vas 6.65 l, but is offered in 16 Ω and therefore has lower sensitivity for the same voltage. Both are in the 42.audio shop.

How much amplifier power is needed?

Very little. With 100 dB sensitivity and a band restricted to the midrange, the driver needs only a fraction of the power of the low-frequency section. The 200 W AES are the thermal ceiling of the voice coil.

At 42.audio you get the 18SOUND 6NMB420 with datasheet PDF, all key data in the driver database and the enclosure calculator. More drivers from this manufacturer: Atlas 18Sound.

Thiele-Small parameters

Nominal impedance8 Ω
Resonance frequency fs110 Hz
Total Q Qts0.33
Electrical Q Qes0.38
Mechanical Q Qms2.7
Equivalent volume Vas6.1 l
Moving mass Mms8.5 g
Cone area Sd130 cm²
Linear excursion Xmax3 mm
Force factor BL9 Tm
DC resistance Re5.3 Ω
Voice coil inductance Le0.1 mH

Comparable drivers

Same size, same type, Qts within ±30 %.

Specifications

Allgemein
Manufacturer 18SOUND
Category Mid Frequency
Series NMB
Magnet Neo
Impedance (Ω) 8
Power handling (W) 200
Sensitivity (dB) 100
Frequency from (Hz) 200
Frequency to (Hz) 7000
Abmessungen & Korb
Diameter 6
Voice coil (inch) 1.75
Mounting depth (mm) 73
Weight (kg) 1.25
Thiele-Small-Parameter
Re (Ω) 5.3
Le (mH) 0.1
Fs (Hz) 110
Qms 2.7
Qes 0.38
Qts 0.33
Vas (l) 6.1
Xmax (mm) 3
BL (Tm) 9
Mms (kg) 0.0085
Sd (m²) 0.013