Alesis 4 - Stereo Flange Effect Explained

Chapter 3 – Overview of Effects
36 MidiVerb 4 Reference Manual
Stereo Flange
First used in the 1960s, “flanging” was achieved by the use of two tape recorders that
would record and play back the same program in synchronization. By slowing down
one tape machine, and then letting it catch up with the other, different phase
cancellations would occur at different frequencies. Since the slowing down of the
tape machines was done by hand pressure against the flanges of the tape supply
reels, the term “flanging” came into being.
Flanging is similar to chorusing , but modulates the delayed signal over a much
shorter delay range (typically 0-12 ms). This produces a “jet airplane”-like sound.
The flange modulation sweep can be triggered by the audio input (either the left or
right input, or both), in order to sync up with the rhythm of your playing. You can
adjust the attack and release threshold of this audio triggering function.
In the case of the Stereo Flange, the signal is split into three parts with a dry signal
and a separate Delay section for both left and right channels with one channel
flanging up while the other channel flanges down. Once again, this causes the effect
to become more pronounced and dramatic.
When flanging was done using two tape machines, it was possible for one to be
behind the other, catch up and then go past the other. This is called passing “through
zero”. The “zero” point is when both signals were in perfect synchronization. Since
the MidiVerb 4 is digitally simulating the flanging effect, it normally cannot provide
the through zero effect. Instead, it delays the effected signal to a point, then brings it
back to the zero point, and repeats this over and over. The “Thru0” parameter found
in the MidiVerb 4’s flanging effects lets you create the appearance of the effected
signal passing through the zero point. It does this by actually delaying the uneffected
signal by as mush as 12 milliseconds (an amount virtually undetectable to the human
ear). This allows the wet signal to move “behind” the dry signal as it cycles.