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October 6, 2020 / consort3

Chebychev crossover

I have been designing some exotic filter crossovers, but what about a “simple” Chebychev crossover? I found the circuit in Leaches filter potpourri pages 30 and 31 referenced in my page Xmax problems. I chose the 0.3dB ripple as being a compromise between flatness and slope. I then tweaked the frequency offset to give a smooth phase slope for the combined signal, a reversed tweeter third order design. R1-3 are non-standard values but are 2 39k resistors in parallel. Similarly C2 is 2 10nF in parallel.

chebyX1

chebyX

Adding C7 and R7 makes the filter elliptic and gives better out of band rejection. R1-3 become 18.5k and can be 18k +510R in series.

chebyel1

chebyel

How about making C7 larger and R7 smaller? This would bring the nulls further together and make the slopes steeper. The side lobes get bigger but are still 30dB down. R1-3 can be 12k in series with 5.6k

chebel2chebel2b

The above crossover is a 3kHz one. Make R1-3 21k (22k parallel with 470k) and C4-6 6.8n for a 2.5kHz crossover and R1-3 25.4k (27k parallel with 430k) with C4-6 8.2n for a 2kHz one. For the RS52 metal dome R1-3 are 8.4k and C4-6 are 2.7n for a 6.3k crossover. The latest batch of the RS52 has a problem according to Jon Marsh

http://www.htguide.com/forum/showthread.php?33490-Driver-Evaluations-for-a-new-project/page10

Final tweak is to add zeros by adding R8-11 which deepens the notches, but may be of academic interest only.

final

How the additions changes the response, green traces are with R8-11 added.

2zvs1z

With deeper notches

final1

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