The 15NPM is a truly unique full range woofer. We have designed cutting edge product, using the best available materials and highly optimized design for the best performance in its class. It delivers very high efficiency, (98 dB 1watt / 1 meter), incredibly linear frequency response characteristics with extended HF frequency response, high power handling capability, while generating ultra low harmonic distortion artifacts. The 15NPM uses a lightweight carbon fiber loaded cone assembly along with a high excursion triple roll constant geometry surround. This combination provides remarkable strength, high efficiency and a peak to peak linear excursion of 21mm. Magnetic Circuit The magnetic circuit sports two aluminum shorting rings, double air-gap front plate. The cooling system and the air flow has been designed using modern FEM techniques and further optimized to provide the highest levels of cooling efficiency. The magnetic circuit design is optimized to generate the minimum amount of flux modulation, providing exceptional stability..