18TLW3000 uses Eighteen Sound proprietary Tetracoil technology, where two different, axially separated magnetic gaps and two inside-outside 4" diameter voice coils are  wound on the same former and suspended evenly in the two magnetic gaps.
The Tetracoil design key advantages are:

1. a symmetric flux density versus displacement behavior, that minimizes the even distortion products;
2. a very symmetric and flat inductance curve;
3. the equivalent voice coil diameter of a 4" Tetracoil speaker is greater than 6". Consequently heat dissipation occurs over a larger surface area, driving AES power handling up to 1800 W.

18TLW3000 design features include a large displacement suspension system which, in conjunction with a fiberglass reinforced, straight ribbed cone allows an ultra-linear piston action and provides full mechanical control across the entire working range.
In order to furtherly increase power handling and reduce power compression figure, a low density material air diffractor is placed into the backplate venting hole acting as a cooling system, increasing power handling capability and lowering the power compression figure.
18TLW3000 is able to perform properly under inclement weather conditions: the exclusive cone treatment improves pulp strength and gives water repellent properties to both sides of the membrane. In addition, magnetic structure metal plates coating is far more resistant than standard zinc coating to the corrosive effects of salts and oxidization.

Features

• 3600 W program power handling
• 100 mm (4 in) Tetracoil dual voice coil, equivalent to a single coil diameter larger than 152 mm (> 6 in)
• Ultra linear suspension behavior for excellent sound clarity
• Symmetric flux density and inductance behaviour
• Low noise forced air cooling design
• Water repellent cone and epoxy coated plates for outdoor use
• Suitable for vented, horn loaded and bandpass subwoofer design

Specification

GENERAL SPECIFICATIONS

• Nominal Diameter:460 mm (18 in)
• Rated Impedance:8 Ohm
• AES Power:1800 W
• Program Power:3600 W
• Peak Power:10000 W
• Sensitivity:95 dB
• Frequency Range:30 - 2000 Hz
• Power Compression @-10dB:0,6 dB
• Power Compression @-3dB:2,0 dB
• Power Compression @Full Power:3,4 dB
• Max Recomm. Frequency:150 Hz
• Recomm. Enclosure Volume:100 ÷ 350 lt. (3,53 ÷ 12,36 cuft)
• Minimum Impedance:5,7 Ohm at 25°C
• Max Peak To Peak Excursion:45 mm (1.77 in)
• Voice Coil Diameter:100 mm (4 in)
• Voice Coil Equiv. Diameter:> 152 mm (> 6 in)
• Voice Coil Winding Material:copper
• Suspension:Triple roll, Polycotton
• Cone:Curvilinear fiberglass loaded cellulose

THIELE SMALL PARAMETERS

• Fs:33 Hz
• Re:4,6 Ohm
• Sd:0,1225 sq. mt. (189,88 sq. in.)
• Qms:13,00
• Qes:0,42
• Qts:0,41
• Vas:185 lt. (6.53 cuft)
• Mms:266 gr. (0,59 lb)
• BL:24,5 Tm
• Linear Mathematical Xmax:± 12 mm (± 0,47 in)
• Le (1kHz):1,80 mH
• Ref. Efficiency 1W@1m (half space):94,0 dB

MOUNTING INFORMATION

• Overall diameter:462 mm (18,18 in)
• N. of mounting holes and bolt:8
• Mounting holes diameter:8,5 mm (0,33 in)
• Bolt circle diameter:438-440 mm (17,24-17,32 in)
• Front mount baffle cutout ø:425 mm (16.73 in)
• Rear mount baffle cutout ø:414 mm (16,30 in)
• Total depth:275 mm (10,83 in)
• Flange and gasket thickness:24 mm (0.94 in)
• Net weight:13,2 kg (29.10 lb)
• Shipping weight:14,6 kg (32,18 lb)
• CardBoard Packaging dimensions:482 x 482 x 257 mm (19 x 19 x 10,1 in)