The 21NLW9001 is an ultra low frequency 21 inch neodymium high performance transducer. The transducer is the evolution of the 21NLW9000 subwoofer, and has been optimized for direct radiation and bandpass subwoofer cabinet designs. For optimum results recommended amplifier should be able to deliver 3600 Watt program power without clipping. At the heart of the updated design stays the improved double silicon spider based on DSS technology, letting the 21NLW9001 being able to control the moving mass with high linearity, showing an exceptional stability of mechanical parameter values in the long term. The transducer design features include a high performance large displacement suspension system for improved cone control at very high level of SPL matching. Eighteen Sound engineers have obtained the best possible results with today's available materials in terms of clean and undistorted LF reproduction at a ultra high SPL, with the lowest possible power compression figure. The state-of-the-art 5,3" diameter ISV copper voice coil is an inside-outside split winding, four layers design, enabling the 21NLW9001 to handle up to 3600W program power. Bl force factor, as well as all other electro-dynamic parameters, are linear within the working range. The high excursion design (70mm before damage, ±14mm linear Xmax) makes the The 21NLW9001 capable of amazing SPL in direct radiation enclosures and its motor has been developed after intense FEA and fluidodynamics simulation and testing, focusing on dissipating the heat generated by the powerful 5.3" coil. Special attention was given to the optimization of air flow into the gap without introducing audible noise. A special low density material air diffractor placed into the backplate acts as a cooling system, increasing the power handling capability and lowering the power compression figure. The low distortion and sound quality are further improved by an aluminum demodulating ring (SDR technology) that flatten impedance and phase with a constant power transfer. The carbon fiber reinforced, straight ribbed cone shows a proprietary resin treatment for extra pulp strength and water repellent properties. A special coating applied to both the top and back plates makes the transducer far more resistant to the corrosive effects of salts and oxidization.