[sdiy] Mathematics of flanging

BrightBoy jdec at mindspring.com
Sat Mar 5 23:21:56 CET 2022

Sorry, meant to say Electronic Musician (EM) magazine.
There are a couple of issues available from these pages:
-----Original Message-----
From: BrightBoy 
Sent: Mar 5, 2022 5:19 PM
Subject: Re: [sdiy] Mathematics of flanging
Precursor to Electronic Magazine run by Craig Anderton.

-----Original Message-----
From: grant musictechnologiesgroup.com 
Sent: Mar 5, 2022 4:49 PM
To: Pete Hartman , Michael E Caloroso 
Cc: synth-diy mailing list 
Subject: Re: [sdiy] Mathematics of flanging
What the heck is Device Magazine? Sounds interesting of course.
------ Original Message ------
From: "Pete Hartman via Synth-diy" 
To: "Michael E Caloroso" 
Cc: "synth-diy mailing list" 
Sent: 3/5/2022 1:29:35 PM
Subject: Re: [sdiy] Mathematics of flanging
Thanks for that Michael.

I've tweaked the image so that the contrast is a bit more readable, I figured I'm not the only one whose vision needed such assistance, so here it is :)


On Sat, Mar 5, 2022 at 12:57 PM Michael E Caloroso via Synth-diy  wrote:
The key to extreme flanging sounds is inversion in place of the summing node.  Many delay units do not include inversion.  The inversion produces a radically different frequency response.
But a real "jet flanging" effect - same as the classic technique using analog tape players - needs a minimum of TWO delay elements.  The concept of the flanging effect heard by a listener in a fixed position relative to a jet airplane in motion was laid out in Electronotes #56 pg 12, so I attempted to implement it with my Korg SDD-3300, a very flexible triple digital delay.  See attached.
The result was flanging but the effect was mild.  In Device Magazine volume 1:10:79 pg 10, Stephen St Croix - inventor of the CCD-based Marshall Time Modulator effect processor - lays out the crucial criteria for effective jet flanging effects.
Digital delays aren't ideal because you can't get deep enough modulation, the modulation LFO in digital domain is often too discrete at low sweep rates, and you need ~0.3ms delay (few digital delays offer short delay times).  BBDs aren't ideal because the amplitude of the direct and delayed signals must be matched within 0.1dB for widest notch bandwidth in the comb filter effect.  Also the bandwidth of delayed output must be as wide as possible for deepest nulls in the comb filter effect.  The deep nulls and wide bandwidth of the notches result in more extreme flanging effects.
Granted, from the Electronotes concept the two delays will need some filtering to emulate the two delay paths between listener and jet airplane, especially the reflected path.  Also the Electronotes concept does not take into account other indirect reflections.
The Marshall unit used CCD based delay elements to meet these criteria - dual independent delays, smooth/deep LFO modulation, wide bandwidth, and precise output matching.  CCD and BBD elements are bucket related, but operate differently.  Each sample charges the storage capacitor of each BBD element, while each sample DRAINS the charge of an initially fully charged CCD element.  CCDs are also much quieter.
Effect connoisseurs report that the Marshall Time Modulator delivers the best "jet flanging" effect.

On Sat, Mar 5, 2022 at 1:36 AM Lanterman, Aaron D via Synth-diy  wrote:
I just put together a lecture on that, if you’re into that kind of thing: 
Aaron Lanterman, Prof. of ECE, Georgia Tech
My blog on Education and Innovation: https://edupocalypsenow.wordpress.com
My blog on Electronics and Programming: https://lantertronics.blogspot.com
My YouTube channel on Electronics and Programming: https://www.youtube.com/c/lantertronics

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