Peter Ostry said:
where do the 4 additional samples come from?
I could quite likely be spouting nonsense here, but could the headphone transducers themselves cause a slight latency?
They do, I see what you mean. Solenoids in the phones bend a metal diaphragm which moves the air. 15 mm later the air bends the microphone's diaphragm. We get an electrial/mechanical and a mechanical/electrical conversion that were not included in the calculation above. I doubt that the masses of the diaphragms and the "reaction time" of the air cause a delay in the order of samples but they must add a little latency. We cannot explore this microcosmos with a DAW, we would need to go to the lab.
... delays caused by converters, software etc. ... "musical" delays ... I think it is important to seperate the two.
Very true and that is why I find Pete's headphone measurement better for the common headphone monitoring situation. Normally we say,
"get your technical adjustments correct and deal with the other things separately" but in this case we have no chance to correct something somewhere else. Analog driven headphones and an analog recording path are the shortest and fastest signal flow we can construct.
Well, for best accuracy we should split the recording signal for monitoring hence avoiding the interface. I play best with a splitted signal while others don't care about 40 ms. I don't even feel that, I just hear it afterwards. With a (timing-wise) lousy player like me you have no other chance than either split the recording signal or let it run as it goes and give me a negative delay afterwards. Although, the latter is not optimal because mentally not locked to the time I don't only delay but also float a bit.
Whatever we do, the target is to write the recorded signal to the correct position in the track. I think everything should be done to reach this target even if the method looks strange. When my studio is up and running again I will certainly try Pete's method. Would not be the first time that something in the opposite direction than the technical brain suggests works better.
Wouldn't it be good if Logic had a default but bigger recording latency and let us adjust this delay for each track, positive and negative? Those who don't care could simply ignore it, for others it would be a valuable tool for finetuning. But whom do I tell that, John Pitcairn requested it many years ago and just a few people listened (
http://www.opuslocus.com/logic/record_offset.php - scroll fully down to the paragraph "A better suggestion").
I wonder at what actual number of ms anything actually matters, or becomes "unrealistic"
Unrealistic or not depends on the music and on the musical and emotional perception of the listener. Playing out of time can add an attractive feeling if it fits in the context. But what to do with the normal looseness, what is artistic, what is accepted and what is wrong?
Our brain is used to a certain delay in a particular situation and a different delay introduced by technical equipment irritates us. Therefore anything above 0 ms matters. But this is only the technical part. The trick is to imitate what a musician would hear under natural circumstances. This is not trivial and not taught in any school.
Look at a couple of live situationa:
(A) Playing in a band and trying to play in time with a drummer who is maybe 30 feet away ... and reflections of the drums from the back of the room.
Following Mark's suggestion we can talk about technical and musical delays. The musical delay is natural and any musician can handle it. Unnatural reflections and technic-based delays disturb the feeling. A drummer 30 feet away feels quite normal, he has a natural delay. But the reflection from his back wall is not natural, this is a technical delay. You are lucky if the wall is at the right distance to produce a natural reverb. Otherwise you get all kinds of weird soundwave modulations.
Such modulations are often accepted and part of a live performance. But in recording, if we shift the time by latency, the problem gets worse. A recording musician does not automatically imagine a huge stage. With the phones directly at his ears he notices just the time difference without any reason for it. Maybe he adapts to that, maybe not.
(B) playing in orchestra watching the beat from a conductor ...
Has this to do with latency? The conductor tries to give all players the same feeling. He stands in a position where the music sounds pretty bad but it is the only position where he can hear all of them with their natural delay. Ok, in this regard it has to do with latency. But only for the conductor. For the musicians he is not an optical metronome but tries to move the hearts and breath of all of them to let them sound like one big instrument.
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