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July 12, 2020 / consort3

Equal capacitor 3rd order active Xover

I came across the equal C 3rd order low pass filter on Uwe Beis’ excellent website and combined it with an equal C high pass filter to achieve this desirable circuit. It uses more  resistors than the minimum design but is  nonetheless desirable. The tweeter should be reversed polarity.

equalcap2

equalcap

Freq kHz R1 R7 R6 R8 R2 R3
3.3 6.2k 12k 15k 16k 15k 4.3k
3.1 6.8k 13k 16k 18k 16k 4.7k
2.8 7.5k 15k 18k 20k 18k 5.1k
2.5 8.2k 16k 20k 22k 20k 5.6k
2.3 9.1k 18k 22k 24k 22k 6.2k
2.1 10k 20k 24k 27k 24k 6.8k
1.9 11k 22k 27k 30k 27k 7.5k

Having got nice results with a 2 way crossover, I thought I would try a 3 way design with the following results. With the mid inverted, I got a similar “handlebar” response to my active Duelund. Crossover frequencies are 780 and 3070 Hz

3w3o1

3w3o2

The ripple of the combined output was slightly too much so I reduced it by moving the attenuator and offsetting the mid frequencies

3w3o4

3w3o3

To get a narrower band midrange you make the capacitors closer together in value and tweak the attenuator (R21). This crossover has frequencies of 1.22k and 3.02k

narrowmid
narrowmid1

For crossover frequencies of 429 and 3.7kHz you need the following

R18 30K, R16 27K, R17 7.5K, R21 1K, R1 10K, R7 20K, R6 24K, R8 15K, R2 13K, R3 3.9K, R11 5.6K, R13 11K, R12 13K, C5,6,7,9,10,11 22N  C1,2,3,4,8,12 4.7N

For crossover frequencies of 468 and 4.5kHz you need the following

R18 27K, R16 24K, R17 6.8K, R21 1K, R1 9.1K, R7 18K, R6 22K, R8 15K, R2 13K, R3 3.9K, R11 5.6K, R13 11K, R12 13K, C5,6,7,9,10,11 22N  C1,2,3,4,8,12 3.9N

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