The 18LW1251 is the updated version of the 18LW1250, an 18 inch (460 mm) high performance extended low frequency transducer. It has been designed for use as a low bass or sub-woofer component, in either a reflex, bandpass or horn loaded configuration, in high power loudspeaker systems. The 18LW1251 design has evolved from extensive research carried out at our own R&D and Engineering facilities. It provides clean, undistorted low frequency reproduction at very high levels and is able to withstand high power without damage. The transducer design features include a large displacement suspension system which in conjunction with a high quality cone and the Eighteen Sound Double Silicon Spider (DSS), assure a very linear piston action and provide full control across the entire working range. This is further improved by a inside outside copper voice coil, based on our Interleaved Sandwich Voice coil (ISV) technology. This provides high levels of thermal stability and durability. The ISV technology is based on a high strength fiberglas former with half the coil wound on the outside and half on the inside, bonded together using unique high temperature resin adhesives. The result is a balanced linear motor exerting a very high force factor. Excellent heat dissipation is derived from a basket design which incorporates air channels between the basket and the magnetic top plate. In addition, eight air vents in the back plate, aligned with the voice coil, force the air into the lower part of the gap. Maximum flux density in the gap is assured by the special top and back plate design, resulting in a high BL factor. Due to the increasing use of audio systems at outdoor events, the ability to perform in adverse weather conditions or in areas of high humidity is a key feature of the 18LW1251. This has been achieved using exclusive cone treatment and magnetic plate processes which increase resistance to corrosion and render the cone water repellent.