SM525CX

The Autotek SM525CX is a pair of 5.25-inch 2-way coaxial car speakers built to replace factory door and rear speakers with more output and better detail. Each speaker handles 125W RMS and 250W peak at 4 ohms, with 88dB sensitivity that works on head unit power and scales up when you add an amplifier.

A 1-inch Neo Mylar soft dome tweeter covers the top end with clarity and takes power without turning harsh. The Alpha-Cellulose poly cone produces musical midrange and mid-bass while staying light, and a passive Butterworth crossover with a 6dB internal network hands off at 4kHz so the transition between cone and tweeter stays coherent.

Durability is built into the parts you cannot see. The UV resistant rubber surround handles moisture and sun exposure, high temperature adhesive keeps the cone and surround bonded under high power, a pure copper voice coil on a Kapton former dissipates heat, and an epoxy infused natural fiber spider keeps flexibility with strength. The anti-resonant stamped steel basket keeps the frame quiet.

Grilles are included, which matters when the speakers mount in a location where feet, cargo or passengers can reach them. Mounting specs are a 4.48-inch cut-out, 6.26-inch outside diameter and 2.0-inch depth, a shallow enough profile for most door openings. Frequency response runs 60Hz to 20kHz. Use spade connectors or solder directly for the best connection.