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Discussion Starter · #1 ·
Good day, all
I'd like to build a set of all-pass filters to change the shape of the subwoofer phase curve in my car audio application in order to get it to align more closely with the mid-range drivers. Based on testing and modeling of the all-pass filters in REW, I've come up with three all-pass filters to apply:
1) fc=30 Hz, Q=6
2) fc=63 Hz, Q=3.6
3) fc=95 Hz, Q=2.3

To avoid the two single op amp all-pass filters for various reasons, leave the two op amp MFBP and Fliege circuits. The MFBP all-pass filter is a 1-2BP arrangement with an inverting BP section followed by a summing amplifier that multiplies the BP output by 2 and sums it with the input. It takes two op amps, one for the BP and one for the summing.
If I use the MFBP configuration for these three filter sections, is there any way to combine them such that they all use the same summing amplifier stage? Does it really matter which order I arrange the filters in the circuit?
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