The following circuit diagrams shows detail electrical schematic for a 22W into 4 Ohm power amplifier, car subwoofer driver. This device is intended to be connected to an existing car stereo amplifier, adding the often required extra "punch" to the music by driving a subwoofer. The power amplifier used is a good and cheap BTL (Bridge Tied Load) 13 pin IC made by Philips (now NXP Semiconductors) requiring a very low parts count and capable of delivering about 22W into a 4 Ohm load at the standard car battery voltage of 14.4V.
This device consists of following parts: Log Potentiometer, Dual gang Linear Potentiometer, 1/4W Resistors, 25V Electrolytic Capacitors, 63V Polyester Capacitors, LED, 100mA NPN Transistors, Dual BIFET Op-Amp, 24 W BTL car radio power amplifier, RCA audio input sockets and 4 Ohm Woofer or two 8 Ohm Woofers wired in parallel.
Find more information about Circuit Diagram for Car Subwoofer Driver here – source: www.RedCircuts.com