18 Sound 21LW1400
18 Sound 21LW1400: 21″ subwoofer driver with ferrite motor, 4″ voice coil and Fs 28 Hz – widely used in bass reflex, bandpass and horn enclosures.
Current · Last checked: 2026-09-28
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General data
Link to section “General data”- Type
- Subwoofer driver
- Nominal size
- 21″
- Nominal impedance
- 8 Ω Manufacturer
- Minimum impedance
- 6.4 Ω Manufacturer
- Sensitivity
- 99 dB 2.83 V / 1 m Manufacturer
- Frequency range
- 24 Hz – 2,000 Hz Manufacturer
- Voice coil Ø
- 100 mm Manufacturer
- Winding height
- not available
- Gap depth
- not available
- Flux density
- not available
- Magnet
- ferrite
- Weight
- 17 kg Manufacturer
- Baffle cut-out Ø
- 492 mm Manufacturer
- Overall diameter
- 545 mm Manufacturer
- Mounting depth
- 259 mm Manufacturer
- Displacement
- not available
- Recommended enclosure volume
- 300 – 300 L Manufacturer
Sensitivity is referenced to 2.83 V at 1 m, i.e. to 1 W only at exactly 8 Ω. The manufacturer does not state Cms; the value is left empty here.
The model number says 1400; the product page gives 1000 W as rated power handling. We use the product page value; dealer claims of “1400 W AES” do not come from the manufacturer.
What can this driver do?
Link to section “What can this driver do?”Simulation from the datasheet values above. The suggestions are calculated, not stated by the manufacturer.
The EBP is above 100 – by the rule of thumb, this points to a vented enclosure (bass reflex). This is based on an EBP of 116.7.
- Net volume
- 135 L
- Tuning frequency
- 48 Hz
- F3 (−3 dB)
- 46.8 Hz
- F6 (−6 dB)
- 42.2 Hz
- F10 (−10 dB)
- 37.3 Hz
- Sensitivity (2.83 V / 1 m)
- 99.6 dB
- Max. SPL at 46.8 Hz
- 126.6 dB
- Max. SPL at 93.6 Hz
- 130.1 dB
- Xmax limits below
- 38.5 Hz
- Ports
- 2 × 200 mm
- Port area for 17 m/s
- 664 cm²
- Max. port velocity
- 18 m/s
- Port length
- 45.7 cm
- at 1,000 W
- Maximum SPL (limited by Xmax)
- Power into 8 Ω (nominal impedance of the wiring).
- Flattest alignment: lowest F3 without the response rising more than 0.25 dB above the passband level or dropping more than 0.5 dB at 2 × F3.
- The 17 m/s limit (about 5 % of the speed of sound) is a common rule of thumb against port noise, not a standard. Rounded port ends allow higher values.
- Lumped-element Thiele/Small model, Half space, 1 m, chamber losses QL 7, Le as a plain inductance, no room influence. At high levels (heating, non-linear Bl and Cms) real results are lower.
Thiele-Small parameters
Link to section “Thiele-Small parameters”Small-signal parameters as stated by the manufacturer. They change with temperature and level.
Plausibility check
Link to section “Plausibility check”We recalculate dependent values from the datasheet. We flag deviations above 3 %.
| Check | Formula | Datasheet | Calculated | Result |
|---|---|---|---|---|
| Qts from Qes and Qms | Qts = Qes · Qms / (Qes + Qms) | 0.24 | 0.234 | consistent |
Power handling
Link to section “Power handling”- Continuous power (standard not stated)1,000 W
- Programme power1,600 W
18 Sound tests rated power handling for two hours with pink noise in the range Fs to 10 × Fs, free-air mounted, referenced to the minimum impedance. The manufacturer defines programme power as 3 dB above rated power handling – it is therefore a calculated figure, not a second measurement.
Build plans with this driver
Link to section “Build plans with this driver”Sources
Link to section “Sources”-
Tier A · primary source
18 Sound 21LW1400 (8 Ω) – Product page with Thiele-Small parameters
Eighteen Sound S.r.l. · accessed on 28 September 2026
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Tier A · primary source
Application Note – Single 21'' Band-Pass Subwoofer Kit (121BP_v2.pdf)
Eighteen Sound Srl · 23 September 2024 (Date from file metadata) · accessed on 13 September 2026