Circuit MC33074 (Operational Amplifiers) and PT2351 (Subwoofer Crossover Low Pass Filter) based on 55Hz and 65Hz 75Hz 85Hz 95hz 6 Step Switchgear 105Hz stage material can be selected by changing the values ​​you can use different frequency Bass Subwoofer... Electronics Projects, Gradual Subwoofer Bass Filter Circuit "audio control circuits, " Date 2014/06/21