Lightweight, robust cellulose-aramid fiber matrix woofer. The main speaker diaphragm of the XS-690ES is made from Sony's unique, lightweight, and durable cellulose material, formerly known as MICA-reinforced cellulose (MRC). The latest generation diaphragm blend has been further optimized alongside mechanical driver enhancements to achieve an even wider frequency response and a smoother, more natural sound profile. Optimal composition. By embedding it in a unique aramid fiber matrix, diaphragm resonance is eliminated, and distortion is minimized—not only in the low frequencies but also in the mid and high frequencies. The result is powerful, exceptionally clear sound across all frequencies—even at high volumes. Separated notch edge surround sound. The woofer's surround sound features another technology from Sony. Distinct curved notches improve vertical vibration symmetry, resulting in significantly less distortion and greater clarity. Five-part frame structure and dynamic air diffuser. The five-part frame design disperses resonance, while the integrated dynamic air diffuser ensures smooth cone movement, efficient air circulation, and cooling of the voice coil. Spider for progressive height positioning. Higher nominal power and optimized airflow are achieved through the acoustically optimized spider, which allows for faster and more precise damping of the speaker cone. Tweeter hits all high notes. A soft dome tweeter diaphragm is directly attached to the voice coil, compatible with High-Resolution Audio, and capable of reproducing ultra-high frequencies with a frequency range of up to 40 kHz.