Reverb_D delay clarification

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- April 16, 2020 at 4:39 pm #115868
  
  eventidesurf
  Participant
  
  Hello everyone,
  
  I have a few questions on Reverb_D:
  
  How do the delays work? Example:
  
  L R L R
  
  10 20 30 40
  
  Is that absolute, or is 30 actually 30+10, and 40, 40+20?
  
  If absolute, then on Italos ‘plate’:
  
  75.7 83.1 90.3 93.9 94.3 78.6 108.8 114.0 157.2 134.2 141.9 123.1
  
  Could also be:
  
  75.7 78.6 90.3 83.1 94.3 93.9 108.8 114.0 141.9 123.1 157.2 134.2
  
  Note: I just sorted L/R channels.
  
  Also,
  
  Does the first delay matter? Can it be set to 0 and use ‘predelay’ to shift delays over? Is it customary to use something over 5, 10, 15?
  
  Any tips to simulate plates, halls, rooms, etc? Note: I know diffusion has a lot to do with that.
- April 16, 2020 at 4:46 pm #154607
  
  DGillespie
  Moderator
  Eventide Staff
  
  Hi eventidesurf,
  
  The Reverb_D module uses what is often called a Feedback Delay Network (FDN) structure. In this structure the delays aren't left and right, but they're all in parallel with a large feedback matrix which controls how they're fed back. If you're interested in a good introduction to FDNs you can check out Julius O Smith's page on the topic (https://ccrma.stanford.edu/~jos/pasp/FDN_Reverberation.html)
  
  So the delays aren't really left and right, and because of the matrix the order does matter. You can obviously sort the delays that way, and the reverb will probably sound similar, but different.
  
  A full reverb would usually be built by adding a multitap delay module, like multitap or easytaps to simulate early reflections, followed by some diffusors, like the diffusor module, then a Reverb_D, then maybe some EQs for the output. Setting the delays lengths and feedback values tends to be a dark art, and honestly my approach is usually just to fiddle with it until it sounds good.
- April 16, 2020 at 4:47 pm #154608
  
  DGillespie
  Moderator
  Eventide Staff
  
  You can also look at the existing Reverb programs in the H9000 and look at what was done for a primer.
- April 16, 2020 at 6:27 pm #154610
  
  eventidesurf
  Participant
  
  DGillespie wrote:
  
  Hi eventidesurf,
  
  The Reverb_D module uses what is often called a Feedback Delay Network (FDN) structure. In this structure the delays aren’t left and right, but they’re all in parallel with a large feedback matrix which controls how they’re fed back. If you’re interested in a good introduction to FDNs you can check out Julius O Smith’s page on the topic (https://ccrma.stanford.edu/~jos/pasp/FDN_Reverberation.html)
  
  So the delays aren’t really left and right, and because of the matrix the order does matter. You can obviously sort the delays that way, and the reverb will probably sound similar, but different.
  
  A full reverb would usually be built by adding a multitap delay module, like multitap or easytaps to simulate early reflections, followed by some diffusors, like the diffusor module, then a Reverb_D, then maybe some EQs for the output. Setting the delays lengths and feedback values tends to be a dark art, and honestly my approach is usually just to fiddle with it until it sounds good.
  
  I was afraid it was going to be more complicated. Italo’s plate and chamber seem to be a bit vibey, even if I reduce the first delay down to 15 and shift the rest of the delays down evenly, then increase rsize to compensate. If you use more consistent delays, such as one of the other presets from Italo (I’m using H8000FW btw):
  
  15.0 22.0 30.0 39.0 50.0 60.0 78.0 90.0 120.0 135.0 158.0 166.0
  
  The reverb sounds smoother, but somewhat less dimensional, less bloom.
  
  I’m using stereo taps to simulate ERs. Unfortunately the other modules were buggy when I tried them. I do use an EQ also. Thanks for the link!
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