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Topic: Delay and Predelay Question

  1. #1

    Delay and Predelay Question


    I am wondering what to do with different instruments in regards to delay and predelay.

    If the listener sits say 15 m away from the first violins and 25 m away from the horns ... and 5 m behind the horns there is the backwall of the room ...

    Listener <- 15 m -> Violins <- 10 m -> Horns <- 5 m -> Backwall

    then the dry violin signal should be delayed for 50 ms (for 15 m) and the dry horn signal for 83 ms (for 25 m). So far so good.

    But since the sound is traveling from the horns to the backwall and from there to the front the wet sound needs 117 ms (for 35 m). The violin wet sound needs 150 ms (for 45 m).

    For rendering purposes we could subtract 50 ms from all numbers. Also we assume that the dry signal of the horns is delayed and then given to a send effect reverb. Then we come to:

    Violins dry: Delay = 0 ms
    Violins wet: Predelay = 100 ms
    Horns dry: Delay = 33 ms
    Horns wet: Predelay = 67 ms

    In conclusion the instruments farer away from the listener should have a bigger delay but a smaller predelay.

    Yes - No - Maybe?

    All your strings belong to me!

  2. #2

    Re: Delay and Predelay Question

    Is this a "good point"? I don't know, but I am willing to try it.


  3. #3

    Re: Delay and Predelay Question


    I tried it.
    Combined groups, see Garritan layout"

    woodwinds (left and right) --> predelay 130
    brass (left and right) --> predelay 100
    percussion in the middle --> predelay 80
    violas in the middle --> predelay 150
    celli and violins 2 combined in one distance --> predelay 160
    contrabass and violins 1 combined in one distance --> predelay 170

    Without taking into account the corners, I ended up with a fairly straight forward approach and input that into the mastering of my new piece.
    I don't have any reverb plugin where I can set the delay, only the predelay, so it was more guessing than calculation.

    The result was good, but not noticeable different from the "classic approach" taking just one reverb for the whole orchestra.

    But the theory behind it is good. By the way... isn't this somehow almost the surround effect?


  4. #4

    Re: Delay and Predelay Question

    Hannes and others,

    I spent two full days on this subject. I designed myself a concert hall from some photos I have of the interior of the Anton Phillips Hall in The Hague and estimated the various distances from the stage to the seats.

    Mixed together with the Panning Instructions from Glenn Rudolph (tutorial) I applied those to my Piano Concerto (part1). I had to look in very dark corners finding those books with mathematical formulas for audio and found some very useful ones (including math for geometrics).

    I placed the instruments as in the Garritan manual and applied the first 36 degrees table for panning. Together with the distances I ended up with different times for pre-delay, delay, decay, dB's over a certain distance.

    It was very complicated and at the end I had to do some guessing [estimated guesses].

    Every instrument got his own reverb characteristics, depending on the angle and panning [from the listeners point of view]. The result: not convincing in respect to some Convolution Reverbs I have. And let me tell you that in the end I applied the simple SIR reverb and had a better result than the previous exercises.

    Conclusion: with the limited equipment we [mostly] have - and with the given software - it is no use doing it the complicated way [unless we have very expensive hardware equipment and a "real life recording" with the best gear.

    During this whole "thing" I came upon a thought. Sometimes CD's come out with "life recordings" and they sound very well. I once attended such a concert and saw all the mics hanging over the various instrument groups. And that is NOT where the audience is sitting. So there is always a difference in perception of the sound - the hall or the stage. How do you take that into a calculation of the artificial reverb, and which one?


  5. #5

    Re: Delay and Predelay Question


    I have worked out a very simple solution with three distances and use ConvoBoy for it. Since I do not have Wizooverb or Altiverb this is by far my best sounding setup up to now.

    Also I am always happy if I understand what I am doing. Delivering all of the thinking to program developers can be dangerous .

    The basic idea is that the horns should not have a big predelay since they are more or less sitting close to the back wall. I still think that this principle is valid. But since I seem to be the only one that cares about it ... I'll leave it like that. No problem for me because it works here.

    All your strings belong to me!

  6. #6

    Re: Delay and Predelay Question

    I sometimes use a multi-position impulse set with Perfect Space convolution reverb (included with Sonar PE). In one case I used the six different stage positions on six different busses, and routed the orchestral sections through those. I went through the trouble of mixing some of the signals through more than one buss if the instrument group sat near two different positions. It was a lot of work, and six instances of the reverb was asking a lot of my PC. The results were pretty convincing, but I now limit myself to three instances, and it's just about as good to my ear.
    - Jamie Kowalski

    All Hands Music - Kowalski on the web
    The Ear Is Always Correct - Writings on composition

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