ValhallaShimmer Tips and Tricks: Using Diffusion instead of predelay

A number of users have asked why there is no pre-delay parameter in ValhallaShimmer. I decided to exclude a predelay parameter, partly due to the desire to keep the UI as simple as possible, but mainly because I feel that the Diffusion parameter can be used to serve a similar function: to create a sense of separation between the source signal and the reverbed signal.

Here’s a quick tutorial in adjusting Diffusion to create the proper separation/blending between dry and wet signals:

  • Create the desired reverb “size” and decay, through the use of ReverbMode, Size, Diffusion, and Feedback, as described in an earlier tips and tricks entry.
  • Gradually back down on the value of Diffusion. Remember that a value of 0.9 and above will result in a fast attack for the reverb envelope, while a Diffusion value of 0.5-0.618 will result in the reverb fading in very slowly. Setting the value somewhere in between will create an attack that isn’t instantaneous, and that will sit behind the dry signal in a way that is similar to how predelay is often used in reverbs.
  • Listen to the decay after adjusting Diffusion. If it is shorter than desired, turn up Feedback to get the desired decay rate. You can also adjust Size, but this will also affect the fade-in rate.

About the author:

Sean Costello is the "algorithmic reverb plugin wizard" [citation needed] at Valhalla DSP.

Comments (2)

  1. Very useful information. So is there no pre-delay under the hood either then (i.e. pre-delay is 0)? Or is there a fixed or variable pre-delay, perhaps varying with the diffusion parameter, but which is invisible to the user?

    1. No predelay under the hood. The perception of pre-delay in Shimmer will be entirely dependent on the diffusion parameter.

      Shimmer can be viewed as a “diffuse delay line” (or 2 diffuse delay lines, with different delays for left and right). With diffusion set at zero, all frequencies take the same amount of time to go through the delay, and it SOUNDS like a delay. As you turn up the diffusion, some frequencies start making it through quicker than others. This allows the attack to build, and also makes it sound like sounds starts at a faster onset than a pure delay. With high diffusion settings, there is an audible dry signal that is the first thing that you hear.

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