The Sonion-Powered Full Metal IEM The EPZ 550 offers a highly resolving and natural listening experience. Engineered with a powerful four-Sonion array and a single Knowles tweeter, it delivers deeply textured bass, remarkably sweet vocals, and pristine high-frequency extension. Core Features A Sonion Acoustic Core: Four dedicated Sonion armatures deliver a deeply textured bass and remarkably sweet, transparent vocals. A single Knowles tweeter completes the signature with pristine high-frequency extension. Five-Axis CNC Metal Chassis: Moving beyond traditional resin, the 550 features our first all-metal acoustic chamber. This high-rigidity structure effectively suppresses unwanted resonance, resulting in an exceptionally dark and pure sonic background. Flawless Frequency Control: We integrated a rigorous three-way electronic and physical crossover network. Enhanced by authentic Knowles acoustic dampers, this system guarantees perfect phase alignment and seamless transitions across the entire frequency spectrum. Optimized Acoustic Airflow: A newly engineered rear cavity intake system deepens bass response while alleviating inner-ear pressure. Paired with a highly compact footprint, the 550 offers uncompromising comfort for extended listening sessions. Premium 6N OCC Silver-Plated Cable: The included four-core monocrystalline copper cable ensures minimal signal loss. Terminated with a 4.4mm balanced plug, it maximizes the transparency and natural tone of the earphones right out of the box.