Cheap car subwoofer filter circuits

This car subwoofer circuit set Suitable for use with a great car audio system. Since this circuit is designed to operate with a 12 volt DC power. But if you put it to use with a home stereo, It do not have any rules.
This subwoofer circuit set is designed to has a cut off frequencies of 200 Hz. If you are not satisfied, you can change the C6, C7, C8, new, follow the table below.

Cut off frequency piont
60 Hz
100 Hz

How it works
The left cannel input signal is entered pass through capacitors C1, C3 are the output Signal to the original circuit. (Or rear left in the car). And the right cannel input signal is entered to C2, C4 to the original circuit. (Or rear right in the car).
Two resistors R1 and R2 will be mixer audio signal the left channel and the right channel both together. Then next wire connects to C5. This capacitor is also know as the coupling capacitor to inverting input of M5218A (IC1a).


The VR1 serves as a set of IC1a gain with much or less as you want.
The output signal is entered pass through the low pass filter circuit that consists of R5, R6, R7, R8, C6, C7, C8 and IC1b Which will allow low frequencies under 100 Hz passed away only.
And the output from pin 1 of IC1b is entered to pass through R9, C9 on to the power amplifier circuit that be designed for driver only the subwoofer loud speaker
We use the LM7812 IC2 as 12V dc fixed regulator for this circuit so can use the voltage supply range 12Vdc to 24Vdc as we want.
The diode D1 is protector connection voltage supply that wrote terminal that it can damage the IC1.


The detail of parts

IC1: M5218A or 4558
IC2: LM7812 IC-regulator 12V
R1, R2, R3: 47K, Resistor 1/4W 1%
R4, R5, R6, R7, R10: 10K, Resistor 1/4W 1%
R8: 20K, Resistor 1/4W 1%
R9: 100 ohms, Resistor 1/4W 1%
C1, C2, C3, C4, C5: 4.7uF 63V see text
C6: 0.33uF 63V see text
C7: 0.27uF 50V see text
C8: 0.027uF 50V see text
C9, C10: 10uF 16V see text
C11: 0.1uF 63V see text
C12: 100uF 16V Electrolytic Capacitors
C13: 100uF 25V Electrolytic Capacitors

This circuit requires enough power supply. Do you have this one? If you do not have it. Look:Learn Many Power supply circuits

How to build

Equipment as circuit whole, can be placed on the PCB as shown in Figure 2. Then we can connect the voltage to the circuit. For immediate use.
This circuit is designed to the highest quality. When we use a capacitor is best, such as type of Metalize Polyester, Poly Carbonate etc., so the price is quite high.
But if you want a cheap and acceptable sound quality is slightly lower.
It may be use a capacitor electrolytic C1, C2, C3, C4 and C5 was. And for C7, C8 It replaced with normal mylar capacitor. Thus helping you save a lot.

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