Eighteen Sound 21iD
Subwoofer
21″ / 533 mm
Nominal diameter
38 Hz
Resonance
0.23
Q factor
96 dB
Sensitivity
± 14 mm
Linear excursion
3600 W
Program Power
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Sensitivity (1w, 1m, infinite baffle)
SPL1W
96.2
dB
Frequency response
29 - 1600
Hz
Thiele & Small parameters
Resonance frequency (free air)
fS
38.0
Hz
Mechanical quality factor
QMS
5.60
Electrical quality factor
QES
0.24
Total quality factor
QTS
0.23
Large signal parameters
Maximum linear excursion
xmax
14.0
mm
Air volume displaced at xmax
VD
2324
cm³
Power handling
P
1800
W
Program power
Pmax
3600
W
Voice Coil
Nominal impedance
Z
2
Ω
DC resistance
RE
1.3
Ω
Inductance (1kHz)
LE
1.08
mH
VC Diameter
135
mm
Winding material
Copper
Magnet
Force factor
Bl
25.2
N/A
Motor constant
Bl/√RE
22.1
N/√W
Material
Neodymium
Diaphragm
Effective diameter
460
mm
Effective area
SD
1660
cm²
Moving mass
MMS
489
g
Moving mass (without air load)
MMD
441.5
g
Material
Water,UV repellent
Suspensions
Stiffness
KMS
27.78
N/mm
Compliance
CMS
36
µm/N
Equivalent volume to the compliance
VAS
143
L
Mechanical resistance
RMS
20.85
N·s/m
Dimensions
Nominal diameter
21
″
533
mm
Overall diameter
545
mm
Baffle cutout diameter
492
mm
Overall depth
250
mm
Flange thickness
18
mm
Mounting depth
232
mm
Volume occupied by the driver (estimated)
9.2
L
Net weight
13.6
kg
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fS
37 Hz
SD
1680 cm²
37 - 1000 Hz
QTS
0.21
xmax
22.0 mm
SPL1W
97 dB
Bl/√RE
23
Pmax
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fS
36 Hz
SD
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30 - 1000 Hz
QTS
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SPL1W
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fS
30 Hz
SD
1210 cm²
30 - 500 Hz
QTS
0.20
xmax
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SPL1W
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Bl/√RE
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3400 W