Active Crossover.
I made a PCB that I use as a Stereo 2-way Butterworth 2nd order, Sallen Key topology, -12db/octave.
This can also be configured as 3rd order, 4th order Mono and 3-way 2nd order Mono .
This is version II, and in this version a gain >=1 can be fixed for every crossover stage.
Very good software for calculation of filter part values comes from TI, you just have to register and it is free to download.
It supports Butterworth and other filter types. It is called FilterPro and you can download from: http://www.ti.com/tool/filterpro
For my 2-way speakers I use a crossover frequency of 2300Hz so C1,C5=22nF, C2,C6=10nF, R1,R5=3,3K, R2,R6=6,2K and C3,C7=22nF, C4,C8=10nF, R3,R7=3K, R4,R8=6,8K
Gain for each stage: Left Low Gain = 1+R9/R10, Left Hi Gain
= 1+R11/R12
Right Low Gain = 1+R13/R14, Right Hi Gain = 1+R15/R16
I want a 6db gain for the low frequency because my woofers are less sensitive than may tweeters so R9,R10,R13,R14=2,7K R11,R15=short-circuited R12,R16=not connected
If this is the last stage like in my case 100Ohm resistors should be added in series to the output of the four op-amps mainly for short-circuit protection.
Second order filters have 180o phase difference so one of the loudspeakers either woofer or tweeter should be connected with reversed polarity.
The power supply is a symmetric ±16V regulated using the LM317, LM337 regulators.
This PCB can also be used to implement a:
2-way 3rd order -18db/octave MONO
2-way 4th order -24db/octave MONO
3-way 2nd order -12db/octave MONO
For 2nd order STEREO:
Connect pin 1 to 2 and pin 3 to 4 of JP1
Connect pin 1 to 2 and pin 3 to 4 of JP2
L_IN, R_IN are the is inputs of left, right channel
L_LOW, L_HI, R_LOW, R_HI are the outputs
For 4th order MONO:
Connect pin 1 to 2 and pin 3 to 4 of JP1 only
Connect L_HI to pin 1 of JP2
Connect L_LOW to pin 4 of JP2
L_IN is input, R_LOW, R_HI are low and hi outputs
For 3rd order MONO
Connect pin 1 to 2 and pin 3 to 4 of JP1 only
Connect L_HI to pin 1 of JP2
Connect L_LOW to pin 4 of JP2
Don’t connect C1, R3 and short-circuit R1, C3 using a small wire
L_IN is input, R_LOW, R_HI are low and hi outputs
Crossover PCB
