Subwoofer filter LM 741

Description for Subwoofer filter LM 741:

     If you like I want some more bass in your stereo, you can switch a subwoofer there. This is a speaker that only reflects the bass. Below is a circuit to ensure that the subwoofer gets really only the bass. 

This circuit is used between the signal source (mixer, CD player) and the amplifier. It is an active filter, better than passive filters which are generally mounted behind the amplifier. The circuit is mono because the bass for both channels are equal. The human ear can not yet determine the direction of this bass. 

The first 741 is used as a mixer amplifier. The gain is adjustable with P1. Then, the signal is applied to a second of the order Butterworth-filter. C A(C1 + C2) and C B (C3) can be calculate using the following formulas: where F k , the crossover frequency (the frequency at which filter stops the transmission of sound), pi = 3.1416, R = R3 = R4, F k in Hertz, and C. F. As shown, the filter is now set at 240 Hz. , the supply voltage must be symmetrical, + and - 12-15 V. A suitable diet is the Symmetric mini power supply . If you would like a better sound would have you two 741's replaced by an NE5532. The picture for the layout to be printed at 150DPI (= + / - 33x33mm).

Circuit Diagram:

subwoofer filter lm741 circuit diagram

Part-list:

• R1, R2 = 47 k
• R3, R4 = 4.7 K?
• R5, R6 = 100 Ω
• P1 = 47 k logarithmically
• C1-C3 = 100 nF
• IC1, IC2 = LM 741

Layout and PCB:

Subwoofer filter LM741 layout and pcb

Datasheet for LM741 and NE5532:
LM741 Operational Amplifier - Download
NE5532 Operational Amplifier - Download