Filter Separation Inspired By Moog
One of my favorite knobs on the Moog Voyager is the Spacing knob. What it does is quite simple: it sets different cutoff points for two filters that are placed on the left and right channel separately, so you’re detuning two separate hard-panned filters.
Here’s an excerpt from the manual to understand what it does exactly:
The Spacing control is used to determine the difference between the cutoff frequencies of the two filters in both dual lowpass mode and highpass/ lowpass mode.
In Dual Lowpass mode, the numbers on the legend around the knob refer to octaves. When the Spacing control is centered, the cutoff frequencies of the two filters are identical and the filter sounds like a classic Moog Filter. Setting the Spacing control to +1 in Dual Lowpass mode means that the right filter has a cutoff frequency equal to where the Cutoff knob is set, and the left frequency has a cutoff frequency that is one octave higher than the right filter. This means when the Cutoff control is swept, two resonant peaks are heard, giving the filter a unique quality.
I like to call this “panning deluxe”. Let’s replicate this in Logic Pro.
The quickest way to do this, one might think, is to use a simple Stereo Delay, like so:
The left channel remains untouched, and the right channel is filtered. Unfortunately, the filter is for both channels. The delay time starts at 10 milliseconds (it can’t be set to zero) and it can only be adjusted in increments of 10 milliseconds, and that’s rough, since I want to throw in some Haas Effect later. So this won’t do. Consider this setup, with far better control:
Audio 1 has no output, but sends to bus 1 and 2. Both busses have a Channel EQ inserted and are panned hard. Replace the Channel EQ with a filter plugin of your choice. We’ve got the buses coming back on stereo bus 3. I’ve inserted a Sample Delay for some optional Haas Effect and a Direction Mixer for some final “stereo” width control.
How many knobs to control this?
It would be cool to control the cutoff frequency for both channels with one knob, and control the separation with another, just like the Moog Voyager. But then the cutoff knob will override any change we’ve made to the filter separation. So, to keep things simple, I’d simply assign five knobs: one for each filter, one for each side of the Sample Delay and one for the Direction Mixer. That’s all easy to setup with Easy View, ⌘+L.
To illustrate, some examples. All sources are Apple Loops, converted into mono. You’ll hear the original first, then the version that’s been processed with varying degrees of filter separation, delay, and width. It’s best to listen on studio monitors or headphones. Have a great weekend.
And why not, a Clarinet:
Finally, a drumcomputer without Haas Effect, and no Milli Vanilli: