Crossover FX (3-Band)

Thought folks on here might find use in this processor rack I put together: https://patchstorage.com/crossover-fx-3-band/

This rack fx takes incoming audio and splits it into 3 streams based upon user defined frequencies (low/mid/high). The 3 streams are then run through fx layers (add your own fx) and then mixed together.

The low and high streams are created via low/high pass filters. The middle stream is created by adding the phase inverted low/high streams to the full incoming audio (e.g. noise cancelling).

Inspired by a 3 band fx AUv3 I missed greatly working inside Drambo.


Comments

  • The user and all related content has been deleted.
  • edited June 2020

    This is the first time I’ve built a brickwall filter, and my understanding is that you run multiple lower order filters in series. But maybe there is a different way? I wanted the filter cutoffs for high and low to be extremely steep so that any one frequency would be going to only one fx (as I generate the middle band from the inverse of the low+high spectrum content)

  • Have you considered the phase effect of these high-order filters? Every order of the filter results in 45˚ phase shift at the cutoff frequency, and phase shift builds up gradually, over a decade or more, so it is significant well inside the passband. So, a 4th order filter will have 180˚phase at cutoff, and significant phase shift approaching cutoff. This will affect your attempt to get a mid band by subtracting the filter outputs from the source signal. Some frequencies outside the mid may be reinforced, not removed.

  • Oh wow, I didn’t know that! I didn’t do anything to deal with the phasing. I think the number of filters I used would even out the 45 degrees, but it’s not evenly distributed across the spectrum? How do you deal with that?

    I wasn’t noticing much audible/spectrum visualizer difference between the spectrum separated and unprocessed signal, but I haven’t used it that heavily.

  • @uncleDave Are you sure the digital filters in Drambo do phase? I am definitely naive on this but I do know that some digital fiters can have a linear phase.

  • @quartzite does the right thing obviously.

    Chaining filters will indeed not only allow for higher steepness/roll-off but also offer more choices in filter sounds, like an LP24 followed by an LP12 to get two resonance peaks.

    Who cares about phase as long as you have working ears? 😉

  • @rs2000 Only when you're adding/subtracting signals, since they may reinforce or cancel at cetain frequencies. No problem for the ears, unless you're hearing from two sources, like misphased speakers.

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