[Cliff Hughes]

In an outside environment with no hard surfaces there is no delay, but you will find hi passing at 120-160 Hz should give you more of the right sort of feel. If you were walking between hard surfaces say in a street with walls both sides, you are looking for a combination of delay and a bit of phasing when the reflected sounds come back and collide.

Personally I think it s debatable how much you need you have to judge yourself.