18SOUND 21NLW9601
18SOUND (Eighteen Sound) 21NLW9601 — 21" / 21 inch · High-Performance Woofer · Subwoofer / Bass · Neodymium
5.35" voice coil · 8 Ω
Part no.: 42A-CHS-TT-18S-0033
Documents
18SOUND 21NLW9601 — 21" · Woofer
1800 W AES · 98 dB Sensitivity · Frequency range 25 Hz – 2000 Hz
Technical data
- Diameter: 21 "
- Voice coil: 5.3 "
- Power handling: 1800 W AES
- Sensitivity: 98 dB
- Impedance: 8 Ω
- Magnet: Neo
- Weight: 13.5 kg
- Mounting depth: 250 mm
- Frequency range: 25 – 2000 Hz
Datasheet (PDF) · Manufacturer page
Series: NLW · Part no.: 42A-CHS-TT-18S-0033
18Sound 21NLW9601: 21" neodymium subwoofer with BL 43 Tm and 5.3" voice coil
A force factor of 43 Tm is the figure that defines the 21NLW9601 from 18Sound's NLW series. The neodymium motor with 5.3" voice coil (18Sound: 5.35") pulls the cone with enough force for a very low electrical Q: Qes 0.31, Qts 0.29, despite 0.408 kg of moving mass. Power handling 1800 W, sensitivity 98 dB, nominal impedance 8 Ω with Re 5.9 Ω.
The Vas of 175 l is small for a 21", fs sits at 37 Hz, Xmax at 14 mm. This combination – strong motor, small Vas, high mass – is typical of subwoofers meant to produce very high levels from compact reflex boxes with DSP equalisation, rather than playing deep passively in huge volumes. At 13.5 kg and 250 mm mounting depth it stays manageable.
Use and enclosure
An EBP of 119 points towards bass reflex. The classic approximation formulas give a guideline of around 75 l tuned to 47 Hz with f3 near 54 Hz – an unusually small volume for a 21" driver. In practice a driver like this usually goes into a larger box with lower tuning and the response is linearised by DSP; the high power handling and strong motor are there for exactly that. Sealed would give about 35 l at fc 90 Hz. The enclosure calculator at 42.audio helps balance volume, tuning and excursion demand; the operating range starts at 25 Hz.
Le of 3.1 mH is comparatively high, which limits the usable range at the top – irrelevant for a subwoofer with a low crossover. At 8 Ω, two drivers can run in parallel at 4 Ω.
What to look out for
- BL 43 Tm, Qts 0.29: strong motor, compact reflex boxes with DSP
- 5.3" voice coil, 1800 W, 98 dB at 8 Ω
- Xmax 14 mm, Mms 0.408 kg
- Le 3.1 mH – low crossover, pure subwoofer use
- 13.5 kg, mounting depth 250 mm
Frequently asked questions
How does the 21NLW9601 compare with the B&C 21SW152?
The 21SW152 is listed in the database at fs 32 Hz, Qts 0.3 and 200 l Vas, the 21NLW9601 at fs 37 Hz, Qts 0.29 and 175 l. Both are drivers for compact, equalised high-output subwoofers; the 18Sound has the slightly smaller Vas.
Why is the bass reflex guideline so small?
Because the classic alignments derived from Qts 0.29 and Vas 175 l produce a small volume with high tuning. Practical subwoofers with this driver are larger and tuned lower, then equalised with DSP – the strong motor allows that.
Which amplifier suits it?
An amplifier around 1800 W at 8 Ω with a limiter; two drivers in parallel at 4 Ω is common practice. A high-pass below the tuning frequency protects against over-excursion at 14 mm Xmax.
At 42.audio you get the 18SOUND 21NLW9601 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 impedance | 8 Ω |
|---|---|
| Resonance frequency fs | 37 Hz |
| Total Q Qts | 0.29 |
| Electrical Q Qes | 0.31 |
| Mechanical Q Qms | 5.5 |
| Equivalent volume Vas | 175.0 l |
| Moving mass Mms | 408.0 g |
| Cone area Sd | 1,662 cm² |
| Linear excursion Xmax | 14 mm |
| Force factor BL | 43 Tm |
| DC resistance Re | 5.9 Ω |
| Voice coil inductance Le | 3.1 mH |
Enclosure suggestion
The EBP of 119 suggests a bass-reflex enclosure. EBP = fs / Qes = 37 / 0.31
Sealed (Qtc 0.707)
- Enclosure volume Vb
- 35.4 l
- System resonance Fc
- 90 Hz
- Cut-off frequency F3
- 90 Hz
Bass reflex (QB3 after Small)recommended
- Enclosure volume Vb
- 58.9 l
- Tuning frequency Fb
- 52 Hz
- Cut-off frequency F3
- 60 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 %.
- B&C Speakers 21SW152fs 32 Hz · Qts 0.3 · Vas 200 l · in the database
- B&C Speakers 21DS115fs 34 Hz · Qts 0.27 · Vas 204 l · in the database
- SB Audience NERO-21SW1100Dfs 32 Hz · Qts 0.34 · Vas 312.6 l · in the database
- B&C Speakers 21SW115fs 33 Hz · Qts 0.36 · Vas 278 l · in the database
- B&C Speakers 21IPALfs 37 Hz · Qts 0.21 · Vas 155 l · in the database
- FaitalPRO 21XL3000fs 32 Hz · Qts 0.22 · Vas 223.5 l · in the database
Specifications
| Allgemein | |
|---|---|
| Manufacturer | 18SOUND |
| Category | Low Frequency |
| Series | NLW |
| Magnet | Neo |
| Impedance (Ω) | 8 |
| Power handling (W) | 1800 |
| Sensitivity (dB) | 98 |
| Frequency from (Hz) | 25 |
| Frequency to (Hz) | 2000 |
| Abmessungen & Korb | |
|---|---|
| Diameter | 21 |
| Voice coil (inch) | 5.3 |
| Mounting depth (mm) | 250 |
| Weight (kg) | 13.5 |
| Thiele-Small-Parameter | |
|---|---|
| Re (Ω) | 5.9 |
| Le (mH) | 3.1 |
| Fs (Hz) | 37 |
| Qms | 5.5 |
| Qes | 0.31 |
| Qts | 0.29 |
| Vas (l) | 175 |
| Xmax (mm) | 14 |
| BL (Tm) | 43 |
| Mms (kg) | 0.408 |
| Sd (m²) | 0.1662 |