18SOUND 21LW1390
18SOUND (Eighteen Sound) 21LW1390 — 21" / 21 inch · Woofer · Subwoofer / Bass · Ferrite Magnet
4" voice coil · 8+8 Ω
Part no.: 42A-CHS-TT-18S-0003
18Sound 21LW1390: 21" ferrite subwoofer with dual voice coil 8+8 Ω
The 21LW1390 is a 21" woofer from 18Sound's LW series with a ferrite magnet and 4" voice coil – plus one feature that sets it apart from the other LW models: the voice coil is a dual voice coil rated 8+8 Ω. Two separate windings on one former, each with its own terminals, which you can wire in series, in parallel or to two amplifier channels.
Why build it this way? A dual voice coil makes the impedance configurable: in parallel, 8+8 Ω becomes a 4 Ω load that makes full use of an amplifier; in series you get double the impedance for multi-driver cabinets; wired separately, each coil runs from its own channel. For subwoofer cabinets with several 21" drivers, for bridged operation, or for systems where the total load on an amplifier needs to be hit exactly, that is a useful degree of freedom. The ferrite motor adds mass but is insensitive to temperature, and in large installation cabinets that is no drawback anyway.
Use and enclosure
A 21" driver makes the most of its cone area in the deep bass: at the same excursion it moves considerably more air than an 18", which reduces the excursion demand at low tunings. The 21LW1390 belongs in large bass reflex or bandpass cabinets for subwoofer duty, typically in sound reinforcement, club installations or as the basis of large home cinema subwoofers. The actual design depends on the Thiele-Small parameters; use the driver database at 42.audio to check them and the enclosure calculator to simulate volume and tuning.
When wiring, always connect both windings with the same polarity. If you run only one coil, usable power handling drops and the motor does not work as intended. As a subwoofer the 21LW1390 is crossed over low, with a high-pass below the tuning frequency to protect against over-excursion.
What to look out for
- 8+8 Ω dual voice coil: 4 Ω in parallel, double the impedance in series, or two channels
- Ferrite magnet – heavy, but insensitive to heat in continuous operation
- 4" voice coil with two windings, always connected with matching polarity
- 21" cone area: plan large cabinets, deep bass is its domain
Frequently asked questions
How do I wire the two voice coils of the 21LW1390?
In parallel for 4 Ω on one amplifier, in series for double the impedance, or each coil to its own channel. Make sure both windings have the same polarity, otherwise the coils work against each other.
What is a 21" subwoofer good for?
Deep bass at high level: large PA subwoofers, club installations, home cinema with plenty of room. The large cone area produces more SPL at the same excursion than smaller drivers, but demands corresponding cabinet volume.
Where do I find the parameters for enclosure design?
The 18Sound drivers are listed in the driver database at 42.audio, and the enclosure calculator handles the simulation of volume and tuning. For questions about wiring the dual voice coil, 42.audio can help directly.
18Sound 21LW1390: manufacturer, spellings and classification
18Sound, 18 Sound and Eighteensound all refer to the same manufacturer: Eighteen Sound S.r.l. of Reggio Emilia, Italy. The 21LW1390 is a 21-inch woofer with ferrite magnet from the LW series, available from 42.audio, 18Sound dealer in Germany, with datasheet and full specifications in the driver database.
At 42.audio you get the 18SOUND 21LW1390 with all key data in the driver database and the enclosure calculator. More drivers from this manufacturer: Atlas 18Sound.
Specifications
| Allgemein | |
|---|---|
| Manufacturer | 18SOUND |
| Category | Low Frequency |
| Series | LW |
| Magnet | Ferrite |
| Impedance (Ω) | 8+8 |
| Abmessungen & Korb | |
|---|---|
| Diameter | 21 |
| Voice coil (inch) | 4 |