The Delay Spectrum

por Rafa

Hi! This is Rafa Monteiro, from Montpellier, France. This is an assignment for lesson for week 5 of “Introduction To Music Production” at Coursera.org. Today, I would like to talk to you about the delay spectrum.

All delay effects work on the recorded signal following the very same principle: by creating and applying copies of an original signal over and over again, with a delay between them.

Older delay gear would literally make a copy of a recorded tape.

These effects are important because they allow us to recreate the sensation of the space in which the sound was recorded or was intended to sound. The sensation of ambience of a small room, a big theater or even an open field can be recreated by proper use of delay effects.

You might ask: “well then, why don’t we just capture the sound of the space in which the sound was recorded in the first place and make things simple?”.

The reason is related to the notion of the good take: it’s impossible to change or fix a distorted or poor take, and the same applies to ambience. A take with recorded ambience will be stuck with that sound, and it’s hard to manipulate it without making it sound unnatural. If that’s the sound you are after, fine. But if you are not, it might be best to record with the least ambience possible and apply them later with the delay effects.

There is a trick, however: depending on the time of the delay, the acoustic result changes drastically. They may sound as completely different effects. In fact, many devices sold in the market have different names, more suited to express the acoustic result of the applied effect. Choruses, Envelop Filters, Phasers, Flangers and so on. However, in essence, all they do is work on the signal by manipulating copies of the delayed signal.

Know what you are using

Delays can be separated into three categories. Both can be fixed delays, with the periodic repetition set on a fixed time value, or variable delays.

  •  Short delays (usually <10 ms): a copied signal delayed up to (usually) under 10 milliseconds won’t be perceived as a delayed sound. This is a very interesting phenomena, in which the repeated sound won’t sound like an echo
    Instead, the short delays will influence the sensation of pitch, due to phase cancellation between the two signals. The acoustic result is called “Comb Filtering”, named after the shape of a comb that the signal gets, with all those peaks and notches from phase canceling of the harmonics.
    Phasers, Flangers and Choruses are effects based on those short delays, with the first two being fixed and the last being variable.
  • Medium delays (usually between 10 and 50 ms): as the time of the delay increases, the acoustic result stop being perceived as a difference in pitch and timbre and starts being perceived as the sound of ambience.
    Do you know that bathroom echo, in which people love to sing while taking a bath? It’s made of those medium delays of sound.
    Delays that fall in this category (they are usually called Reverbs) emulate the acoustic reflection of the sound in different ambiences and surfaces, since the sound of space is dependent on these short reflections of sound. They manipulate the number and intensity of those short delays to create the sound of small rooms, big concert halls, churches, stadiums, etc.
  • Long delays (usually over 50 ms): these delays stop being perceived as ambience and, start being perceived as discrete repetitions of a sound. They work like the “mountain echo”, in which a given sound will be perceived more than once, without changing timbre (like the small delays) or ambience (like medium ones)
    Usually, plugins and equipments in the market labeled “Delay” – analog delay, digital delay, and so forth –  will refer specifically to this category of delay. But we know that delay is much more than a simple echo, and we shouldn’t be confused.

It’s very important to understand how these three categories of delay work, since they are very different manifestations of the very same effect. Even simple delay plugins, with small adjustment in settings, can turn from a Reverb into a Flanger or Phaser. It’s a dramatic change that will surely be problematic if we do not understand what is going on.

On the other side, good knowledge in delay will allow us to take more from our equipment an even saves us from purchasing unnecessary stuff or overload our DAWS with plugins, since many delay can be configured to produce different effects.

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