XM Above ExcellenceSpawned from Â«the first of the five â€“ X2CÂ» we created the XM, a subwoofer sharing many of the ideas from the X2C, but scaled down to a 4â€³ voice coil.With the same SAFT* design basket on the 15â€³, airflow is optimized for best possible cooling and increase in the SPL.All drivers also inherited the OCAF* motor design that allows for both longer excursion and minimizes heat and distortion. In 2016 we introduced the V2 of the XM. Where the V1 was efficient and brutal, the V2 goes beyond the extreme for a 4â€³ voice coil design. We even added the option of a 21â€³, whereas the 15â€³ and 18â€³ are also available in both dual 1 and dual 2 ohm.The new tall wind voice coils has increased xmax by 30%, not to mention the benefits of a more efficient power handling as well. To transfer the power to the coil, we still use the 4 Ga push terminals with heavy duty quad multi-layer high strand count tinsels. On the XM15â€³, these are even mounted to a ~12â€³ 100% Nomex spider, whereas the XM18 settles for 10â€³ which is far better than the norm.Semi-pressed, fiber blend cones coupled with high roll surrounds and dual stitching ensures stability at high excursion. This new blend has also made the cones lighter, but strength is now superior compared to ordinary cones. As a little bling, we highlighted the B2 logo on all 2016 subwoofersPlease note, this listing is for a Dual 2 ohm subwoofer.