Dayton Audio Sig150-4 5.25? Signature Series Woofer 60W Driver 4 Ohm The Dayton Audio Signature Series was designed to give DIY speaker designers access to the pinnacle of speaker technology at the value expected from Dayton Audio. Featuring an open aluminum cast frame, anodized aluminum cone and a polyimide former, these drivers can provide extended range with incredibly low distortion. After hours of painstaking engineering and testing with meticulous attention to detail, we at Dayton Audio deem this driver line worthy of the endorsement of even the most critical audiophile. Extensive Klippel LMP and LSI testing to optimize Bl symmetry and parameters Indexed cone/surround junction for smooth transition/frequency response Polyimide formers and aluminum shorting sleeve for improved inductance, damping, and frequency response One piece concave black anodized aluminum cone Vented former and elevated spider for improved air flow Open aluminum cast frame for improved heat dissipation Countersunk stainless steel magnet badging for long time aesthetics