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18SOUND 21NTLW5000

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18SOUND (Eighteen Sound) 21NTLW5000 — 21" / 21 inch · Super-Performance Woofer · Subwoofer / Bass · Neodymium · Dual-Gap
2x4.5" voice coil · 8 Ω
Part no.: 42A-CHS-TT-18S-0032

775.00 € 775.0 EUR 775.00 €

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  • Frequency to (Hz)
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18SOUND 21NTLW5000 — 21" · Woofer

1800 W AES · 97 dB Sensitivity · Frequency range 30 Hz – 1800 Hz

Technical data

  • Diameter: 21 "
  • Voice coil: 4.5 "
  • Power handling: 1800 W AES
  • Sensitivity: 97 dB
  • Impedance: 8 Ω
  • Magnet: Neo
  • Weight: 12.5 kg
  • Mounting depth: 320 mm
  • Frequency range: 30 – 1800 Hz

Datasheet (PDF) · Manufacturer page

Series: NTLW · Part no.: 42A-CHS-TT-18S-0032

18Sound 21NTLW5000: 21" neodymium subwoofer with dual-gap motor, 1800 W AES and 17.5 mm Xmax

The 21NTLW5000 is the 21" woofer of 18Sound's NTLW range, built for subwoofers that have to go deep and loud in large-scale sound reinforcement. The heart of the driver is a dual-gap neodymium motor: two 4.5" voice coils work in two separate magnetic gaps, spreading motor force and thermal load across more coil area than a single coil could offer. The figures reflect that: 1800 W AES power handling, a BL of 32 Tm and 17.5 mm of linear excursion moving 372 g of cone assembly.

Within the 21" class the 21NTLW5000 sits, with Fs 31 Hz, Qts 0.36 and Vas 270 l, as a classic bass-reflex woofer that does not depend on extreme cabinet volume. Its 97 dB sensitivity is what you would expect from 1662 cm² of cone area driven by a motor of this strength. At 12.5 kg the neodymium design stays in a weight range a 21" ferrite driver cannot reach, which matters for touring subwoofers loaded with two drivers per box.

Use and enclosure

The Thiele-Small parameters point to a bass-reflex volume of around 216 l tuned to 33 Hz with an f3 near 34 Hz as a guide value. An EBP of 82 means a sealed box also works: roughly 95 l for a cut-off around 61 Hz, which can be an option for a sealed cardioid array or a compact bass cabinet with equalisation. Port length and excursion control are best worked out with the enclosure calculator at 42.audio.

The usable range spans 30 to 1800 Hz; in practice you will cross over well below the upper limit, as is normal in subwoofer duty. With Le at 1.6 mH the impedance rises towards higher frequencies, irrelevant for a subwoofer but worth noting if you ever run it higher up in a full-range box.

What to look out for

  • 8 Ω nominal, Re 5.3 Ω: size the amplifier for 1800 W AES into 8 Ω and use a limiter.
  • Mounting depth 320 mm: check cabinet depth and port routing against the motor early on.
  • Two 4.5" voice coils in a dual gap: strong thermal reserves, but keep the cabinet ventilated.
  • Xmax 17.5 mm: with the reflex tuning at 33 Hz, protect excursion below fb with a high-pass filter.
  • 12.5 kg thanks to neodymium, a real advantage for a 21" driver on tour.

Frequently asked questions

Which enclosure suits the 21NTLW5000?

Bass reflex at around 216 l tuned to 33 Hz is the obvious guide value, sealed it is roughly 95 l. Both figures come from the classic approximation formulas and should be verified in the enclosure calculator with port and excursion plots.

How does the 21NTLW5000 differ from the 21NLW5300?

The 21NLW5300 has a slightly tighter motor at Qts 0.32 and a larger Vas of 325 l, so it tends to ask for more volume. The 21NTLW5000 relies on the dual-gap motor with two 4.5" coils and sits at Qts 0.36 and Vas 270 l.

What amplifier makes sense?

A power amplifier that delivers 1800 W into 8 Ω cleanly, plus a limiter and a high-pass filter below the tuning frequency. If you run two drivers in parallel per cabinet, make sure the amplifier is rated for 4 Ω loads.

At 42.audio you get the 18SOUND 21NTLW5000 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 fs31 Hz
Total Q Qts0.36
Electrical Q Qes0.38
Mechanical Q Qms5.2
Equivalent volume Vas270.0 l
Moving mass Mms372.0 g
Cone area Sd1,662 cm²
Linear excursion Xmax17.5 mm
Force factor BL32 Tm
DC resistance Re5.3 Ω
Voice coil inductance Le1.6 mH

Enclosure suggestion

The EBP of 82 is in the intermediate range — either works; sealed plays tighter, bass reflex deeper and louder. EBP = fs / Qes = 31 / 0.38

Sealed (Qtc 0.707)

Enclosure volume Vb
94.5 l
System resonance Fc
61 Hz
Cut-off frequency F3
61 Hz

Bass reflex (QB3 after Small)

Enclosure volume Vb
185.4 l
Tuning frequency Fb
35 Hz
Cut-off frequency F3
37 Hz

Vb is the required net internal volume, Fb the tuning frequency of the reflex port and F3 the frequency at which the level has dropped by 3 dB. Calculated approximation after Small. A starting point for simulation, not a finished build plan.

Comparable drivers

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

Specifications

Allgemein
Manufacturer 18SOUND
Category Low Frequency
Series NTLW
Magnet Neo
Impedance (Ω) 8
Power handling (W) 1800
Sensitivity (dB) 97
Frequency from (Hz) 30
Frequency to (Hz) 1800
Abmessungen & Korb
Diameter 21
Voice coil (inch) 4.5
Mounting depth (mm) 320
Weight (kg) 12.5
Thiele-Small-Parameter
Re (Ω) 5.3
Le (mH) 1.6
Fs (Hz) 31
Qms 5.2
Qes 0.38
Qts 0.36
Vas (l) 270
Xmax (mm) 17.5
BL (Tm) 32
Mms (kg) 0.372
Sd (m²) 0.1662