3-way 4th Order Active Crossovers for Car Audio

These crossovers are meant to be used with my amps in my car audio system. They derive +/-15V power from an extra winding on the car amp's power supply transformer. Aside from their power source they are general purpose crossovers. Note that the low frequency output is DC coupled from the input - you can only do this if you have an input source and op-amps which create negligible offset (or it's OK if your amp is AC coupled). I designed my filters to have a 4th order Butterworth characteristic with crossover points at 100Hz and 3kHz. All of my filter resistors and capacitors are mounted on DIP headers for easy removal to change the crossover frequencies. The current component values I'm using are as follows:

Filter

R1

R2

C1

C2

3kHz HP Stage 1

4.87k

5.76k

10nF

10nF

3kHz HP Stage 2

2.05k

13.7k

10nF

10nF

3kHz LP Stage 1

8.87k

31.6k

10nF

1nF

3kHz LP Stage 2

3.92k

10.2k

10nF

6.8nF

100Hz HP Stage 1

14.7k

17.4k

100nF

100nF

100Hz HP Stage 2

6.04k

41.2k

100nF

100nF

100Hz LP Stage 1

7.87k

21.5k

150nF

100nF

100Hz LP Stage 2

26.7k

95.3k

100nF

100nF

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