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?