Active subwoofer filter circuit based on TL072 Opamp is designed for use with Power amplifier with good parameters (narrow frequency response). The transition band of the filter is between about 10Hz (bottom) and 80Hz. + -12v symmetrical Zenerli regulated... Electronics Projects, TL072 Active subwoofer filter 80 Hz-250 Hz "audio control circuits, " Date 2020/04/02