The ESB 4.165 is a high-performance mid-woofer from the 4000 Series, designed to deliver clear and impactful sound in custom car audio installations. It handles an RMS power of 150 W with a peak capacity of 300 W, while its sensitivity of 92.5 dB ensures efficient energy conversion into audible volume across a frequency range from 50 Hz to 6000 Hz. Its construction focuses on rigidity and durability, featuring a die cast aluminum alloy basket and a cone made from long-fiber, unbleached pulp with a specialized external treatment for better stability. The soft nitrile rubber surround is UV-resistant to prevent degradation over time, while the internal motor utilizes a Y35 ferrite magnet optimized via FEA simulation and a large aluminum copper-clad vented voice coil. Precision is further ensured by the CNC-machined and cold forged ultra-low carbon alloy steel pole piece and plate. With a mounting diameter of 143 mm and a depth of 67 mm, this 4 Ohm driver fits into most standard 6.5-inch locations. It comes with a deluxe stainless-steel protective grille, making it a reliable choice for audiophiles who want to build a robust front stage in their vehicle without sacrificing technical precision.