When compared to 208 Sigma, ES has larger and stronger dual magnet structure (BL 14.8), new hyperbolic paraboloidic cone made of banana fiber, new rubber surround which was designed with Finite Element Analysis and impressive weight for 10 inch unit; almost 11 kilos.
Driver is designed for rear-loaded horns. They are priced much higher (about $355) than predecesor Sigma( $140). At this moment only Japanese diyers have chance to work with 208 ES driver. Based on the experience with older drivers, 208 ES should perform even better than Sigma, which is very musical unit. Can't wait to hear ES!

For more info check FE208ES.pdf. You must have japenese font pack to see it.