Flanger -&- Chorus
Audio Effects from modulating an Echo or Delay signal
How it Works
Let's start with a recording of you saying "Hello". When you play back the recording, the sound says "Hello".
If we now play back the original but add a delay of maybe 3 seconds to a copy, we get "Hello... Hello". It's an echo.
But if we play back the original but add a tiny delay of maybe 20 milliseconds to a copy, we get "Hello" but this would sound strangely hollow.
Chorus and Flanger effects are about adding a tiny delay to the original signal.
The graph shows an audio signal of a triangle wave. It's played at "A3" which is the "A note" just below "middle C". "A3" is pitched at 220Hz and so that graph represents 30ms (or 6.6 cycles).
Here is the same audio signal of triangle wave except it is delayed by 10ms (or 2.2 cycles).
The next 3 graphs show the result of adding the first two graphs together.
Here the delayed signal is 9ms.
The result of adding a delayed signal (to the original) causes interference. In this 9ms example, the interference happens to be constructive; resulting in a larger amplitude signal.
Here the delayed signal is 10ms.
The interference basically changes the waveform.
Here the delayed signal is 11ms.
Different delay amounts create different resultant waveforms. In this 11ms example, the interference happens to be destructive; resulting in a smaller amplitude signal.
Here is an animation of the 3 summed signals for 9ms, 10ms and 11ms.
By changing the delay times, we can create some "motion" to change the resultant waveform.
Controlling the Effect
We create the "motion" in Flangers and Chorus by modulating the delay time using a Low Frequency Oscillator (LFO). The parameters available for LFO are usually Frequency of oscillation and Modulation Amount. LFO Frequency is sometimes labelled as Rate or Speed. LFO Modulation Amount is sometimes labelled as Depth or Width.
We can mostly assume that the LFO will use a triangle-wave or a sine-wave.
The diagrams below shows parameters for Flanger and Chorus devices which are typical to Boss and Ibanez models.
Flangers have a Feedback parameter (sometimes labelled as Resonance or Regeneration or Enhance), which Choruses tend to not have. Feedback is when some of the delayed signal is added back to the input; creating a string of delayed copies; causing a whoosh-like effect.
Flangers and Choruses also tend to use different Delay Times. Delay Time is sometimes labelled as Manual or Effect. Flangers use very short delays which accentuates movement in the high tones; causing a "metallic whirl" effect. Chorus uses a longer delay time which accentuates movement in the mid tones; causing a shimmer-like effect.
Some devices have pre-set Delay Times (which you cannot change).
Parameter controls labelled as Effect-Level or Delay-Level determine the amount of delayed signal which is added to the original signal.
How it Sounds
As the delay time increases or decreases, the delayed copy creates interference which is changing over time. There are many descriptions of the sound of flanging or chorusing which mostly involve fluidity. It could be something from a "fluttery shimmer" to a "swirly breeze" or from a "twinkly ripple" to a "wave swell". An ethereal quality: You get the idea. Whatever imagery it evokes, there are several generalisations we can garner:-
When the LFO speed is slow, you can push up the Delay Level and/or the LFO width (and/or the Feedback). It will still sound acceptably subtle.
When the LFO speed is fast, you have to turn down the Delay Level and/or the LFO width (and/ or the Feedback). At fast speeds, the effect becomes very noticeable.
Most of the time, the LFO is sweeping up or down. This modulation effect is subtly pleasant. But at the "ends" of the sine-wave (or tri-wave), the delay-time "bounces back" to change direction. These "turning-points" create a noticeable whir-like sound. This is the "dead giveaway" that you are using a Chorus or Flanger. Too much of the whir will spoil the magic. The "sweep" is like swaying through water while the "whir" makes you a bit seasick... maybe.
Short delay times accentuate the high timbres; medium delay times accentuate the middle timbres, and; long delays accentuate the low timbres. Because Flangers have a Feedback control, short delay times are better suited for pleasant sound control. If you add Feedback to long delay times, you end up with something like Vibrato (and that is another story).
Guides and References
Guides : Delay times for Flanger & Chorus
Source \ Delay in ms Flanger ChorusWikipedia less than 20 ms not givenSweetwater 0.5 - 15 ms 20 - 50 msMusic Radar about 10 ms 25 ms and aboveSplice 1 - 5 ms 5 - 30 msPremier Guitar 0.5 - 10 ms not givenThese are only guides. Is it a Chorus or Flanger? In the end, it's really a question of what sound we are after. What device are we trying to emulate? Let's look at some popular Chorus & Flanger devices for a better idea of the "sound" we want.
Notable articles on Chorus and Flangers : from Reverb, Making Music, Premier Guitar, Presonus, Strymon, Mr Black, Wampler, Electro Harmonix, GearPage [1] & [2].
Specifications of popular devices:
Flanger : Delay times
0.0039 - 4 ms MXR Micro Flanger MX-1520.3 - 6.3 ms Boss BF-3 Bass In0.3 - 14.4 ms Boss BF-3 Guitar In0.4 - 3.2 ms Boss RBF-10 MicroRack Flanger0.4 - 14ms A/DA Flanger0.5 - 6.5 ms Boss BF-2B0.5 - 15 ms Roland SBF-325 Fl.mode0.5 - 16 ms (mid= 3ms) Boss BF-10.6 - 10 ms Moog MF-108M Fl.mode0.8 - 16 ms Ibanez FL-3051 - 12.8 ms Ibanez FL91 - 13 ms Boss BF-21 - 15 ms Tokai TFL-12.4 - 2.8 ms EHX Electric Mistress (Flanger)^2.5 - 12 ms Ibanez FL-3015 ms Ibanez AD-202 Fl.modeLFO range
0.025 - 5 Hz Roland SBF-3250.04 - 10 Hz A/DA Flanger0.05 - 10 Hz Boss BF-10.057 - 11 Hz Ibanez FL-3010.06 - 13 Hz Ibanez FL90.0625 - 10 Hz Boss BF-2B0.0625 - 10 Hz Boss RBF-10 Microrack Flanger0.08 - 8.8 Hz Ibanez FL-3050.1 - 8 Hz MXR Micro Chorus0.1 - 10 Hz Guyatone MC30.1 - 14 Hz Boss MicroRack Ensemble Chorus0.1 - 20 Hz Yamaha SPX900.25 - 1 Hz SR&D Rockman Stereo Chorus0.2 - 5.5 Hz MXR Micro Flanger0.25-1 Hz Scholz Rockman St. Ch./ Delay0.33 - 10 Hz Seymour Duncan Catalina* not verified^ depends on version. Delay estimated from CombFilter chart.From the above tables, we can guess at some typical settings:- Effect Type Delay Mod.Range Flanger High 0.5ms +4ms Flanger Low 2ms +4ms Chorus High 8ms +4ms Chorus Low 16ms +4ms
Chorus : Delay times
0.5 - 35 ms Boss RCE-10 MicroRack Ensemble Chorus0.9 - 6.4 ms Ibanez CS9 re-issue1 - 8 ms Guyatone MC31.2 - 12.8 ms Ibanez BC10 Bass Chorus3.2 - 8.5 ms Ibanez CS9 original4 ms Boss CE-300*5 - 15 ms Roland SBF-325 Ch.mode5 - 50 ms Moog MF-108M Ch.mode5.1 - 7.3 ms MXR Micro Chorus MX-1486 - 60 ms Seymour Duncan Catalina10 - 50 ms Ibanez AD-202 Ch.mode16 ms MXR M-134 St. Chorus20~24 / 40~44 ms Scholz Rockman Stereo Chorus20~24 / 50~54 ms Scholz Rockman St. Ch./ Delay
Links: Boss manuals, Manuals Lib, Effects Database, Tone Home, Rockman Fr, SynthManuals
Designing a dual 180° mod. Chorus & Flanger
This design takes inspiration from Roland SDD-320 Dimension D -&- Electro-Harmonix Electric Mistress (plus a bit from Tom Scholz Rockman Stereo Chorus). Only the best.
The Design : We will use one LFO but take two outputs which are 180° out-of-phase. These will modulate the two devices (1 Chorus & 1 Flanger). So the devices will be 180° out-of-phase; so when 1 device peaks, the other device will trough.
The dual 180° phase-locked Chorus & Flanger will be created within Propellerhead Reason 9.5 using the CF-101 Chorus/Flanger. The same principles apply if you're using another Digital Audi Workstation (DAW).
Roland's SDD-320 Dimension D is a studio Chorus device from 1979 and it only has 4 buttons to select your sound. So you could select [1] or [2] or [3] or [4], from softest effect to strongest. Why bother with knobs for twiddling when the sounds are already beautiful? Actually, you could also select combinations of [1 + 4], [2 + 4] and [3 + 4] too. The same Chorus design idea was later released as Boss Dimension C (in pedal form). The Dimension effects devices create dual Chorus by using a single LFO with 2 outputs at 90° phase-difference to modulate 2 delay devices.
-: using Propellerhead Reason 9.5 :-
Electro Harmonix's Electric Mistress is the "Holy Grail" in the Flanger/ Chorus world. Since the beginning of time (around 1976), the Electric Mistress has been consistently voted into the top "Best Flanger" and "Best Chorus" category. There are many devices which can switch between a Flanger OR a Chorus. But the Electric Mistress is a Flanger AND a Chorus.
For our design, we will use one LFO to modulate a Chorus and a Flanger but the modulations are phase inverted (ie phase difference of 180°).
Delay time for Flanger = 2.7ms {like E. Mistress}Delay time for Chorus = 17ms {close to Rockman}LFO rate = slow to mediumWe will be using the Reason CF-101 Chorus/ Flanger as the main device. We will use 2 x CF-101; one for Flanger and one for Chorus.
But first, let's get some idea of the delay times in milliseconds...
Propellerhead Reason CF-101 Chorus/ Flanger - in milliseconds:- CF - 0 1 2 3 4 5 6 7 9 11 13 15 ms - 0.16 0.31 0.47 0.63 0.78 0.94 1.09 1.25 1.56 1.88 2.19 2.5CF - 17 19 21 23 27 31 35 39 43 47 51 ms - 2.81 3.13 3.44 3.75 4.38 5.0 5.63 6.25 6.88 7.5 8.13
CF - 55 63 71 79 87 95 103 111 119 127 ms - 8.75 10.0 11.25 12.5 13.75 15.0 16.25 17.5 18.75 20.0
For our CF-101, we will be using Delay settings:-
● Flanger appx 2.7ms = 16
● Chorus appx 17ms = 110
For the phase offset LFO, we will use 4 Phase LFO by Spectral Scan.
Creating "Misty" - the dual 180° mod. Chorus & Flanger
Device List :-
● CF-101 Chorus/ Flanger x 2● 4 Phase LFO by Spectral Scan. This device can have 3 phase-offset outputs from 1 main LFO.Alternatively:-○ Elements DS-LFO by AirRaid Audio.Procedure to create our dual Chorus & Flanger device.
○ Insert two CF-101s.○ Insert the 4 Phase LFO.○ Rename the CF-101s: one as Chorus and one as Flanger.Wiring up 4 Phase LFO Modulation control.
○ 4 Phase LFO will modulate delay times of the Chorus & Flanger. By default, the phase of outputs 1, 2, 3 & 4 are already set at 0°, 90°, 180° & 270° respectively.- 4 Phase LFO 01 CV-out ->- Flanger Delay CV-in- 4 Phase LFO 03 CV-out ->- Chorus Delay CV-inWiring up "Misty" into Aux Effects #3.
○ (Master Section) FX 3 Send L ->- Flanger Left Input (CF-101)○ (Master Section) FX 3 Send R ->- Chorus Left Input (CF-101)○ (CF-101) Flanger Left Output ->- FX 3 Return L (Master Section)○ (CF-101) Chorus Left Output ->- FX 3 Return R (Master Section)4 Phase LFO set-up:-
○ Rate = 0.88 Hz○ Type = N (non-linear)○ Level = 25%○ 03 Level = 25%○ 03 Offset = 180 degreesFlanger [CF-101] set-up:-
○ Delay = 16○ Feedback = 35○ Rate = 0 / Sync = Off / Mod = 0○ Send Mode = OnChorus [CF-101] set-up:-
○ Delay = 110○ Feedback = 0○ Rate = 0 / Sync = Off / Mod = 0○ Send Mode = OnThat's it!
If you are using Elements DS LFO instead
○ LFO1: Freq = 0.88 Hz○ LFO1: Phase = 90○ Global: Amp = 20%In DS-LFO, only the Right CV-out is affected by Phase (LFO Left CV-out is not affected).Chorus -&- Flanger set-up:-
Rear: Delay CV (knob) = 64The Delay CV is adjusted to half (64) because the CV-output of DS-LFO is double that of the 4 Phase LFO.Using Reason's CF-101 -&- 4 Phase LFO dual 180° modulated delay:
Variations on Misty
I use "Misty", as an "always On" effect permanently on my AUX FX Send/ Return setup. But the settings for Misty are tailored to my taste:
○ The LFO uses a slow comfortable rate of 0.88 Hz.○ The Chorus uses an uncommonly long delay time of 17ms {close to SR&D Rockman}.○ The Flanger uses a medium delay time of 2.7ms {like E Mistress}It works well for me but you'd probably want to make adjustments to suit your own style of music. The LFO Rate and the Delay Times are the most obvious variations you can make.
If you want to use this more like SDD-320 Dimension D, then set both Delay devices to use the same Delay times. Use the "Checking Output Waveforms" diagram as your guide to delay times and modulation amount.
When the Phase offset is at 180°, the "sweeps" and "whirs" are in opposite directions to "balance the motion". Both delays are also on opposite ends of the stereo field. Put together, we get an ethereal shimmery effect. When both Delay times are the same, this effect becomes very "light" or subtle.
What happens if we use a different Phase offset? Using a different Phase offset between 90° to 180° (and back to 270°) actually still works well. The difference is how light or heavy we want that ethereal shimmery effect.
For example: if we set the Phase offset to 90° (or 270°), then when one device has a "whir", the other has a "sweep". The net effect is that the "sweeps" masks out the "whirs" and this squashes the "seasickness"; and you can still perceive the Chorus effect quite clearly.
If you want to make the effect more "analogue" (like a BBD), then you would want to filter the delayed signal. Basically the analogue circuits did not have pristine clear delayed signals. You can emulate this by boosting the middle frequencies [or by cutting the lows and highs] of the delayed signal.
Try out different settings!