The Mahogany wood now undergoes a new proprietary curing process that enhances its natural tone properties. Wood, being a product of nature, is subject to variations in density and other properties. Our curing process ensures consistency of the signature Grado sound. Rhodium, the most expensive precious metal on earth, is employed in The e Series headphones to prevent corrosion on connectors, and unwanted graininess in your music. Our new driver cone geometry tracks frequencies with unequaled precision, and the coil has been fine-tuned for symmetry throughout the full range. One thing we didn't change is the traditional appearance that Grado fans cherish. The open-back form factor of our headphones produces a cleaner, more authentic sonic experience.