Recording snake latency for tracking

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Brightside

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I'm looking to buy a 30 or 50 metre balanced recording snake & was wondering about the latency this could introduce.

Obviously, it wont be a problem if I'm recording say a live gig or orchestral performance but what if I'm tracking a drummer with monitoring back to him on headphones?
That's a long distance & I was wondering if any of you guys have any experience with this kind of length & whether it would cause a noticable/problematic latency problem.

I'm guessing it will cause a lot of latency (too much to work with) but I'm just looking for confirmation of this.

Scott
 
As I understand it, a signal will travel 50meters in .0000000167 sec. Is your band THAT tight??
 
Wow, that's good news. I wish drummers were that tight though! Maybe not, they'd sound like a machine.
I guess my PC latency is the biggest issue then.
Thanks
Scott
 
I actually did some research on this today and it looks like the worst case would be about .00000021 sec. Anyone with a better figure [no jokes, please] may feel free to correct me. Latency doesn't arise from the length of the signal path (unless you're maybe sending it through an uplink to a satellite and back), but from the speed or lack of it in your digital processing chain. The idea is that it takes some amount of time for the computer to process the data we're using to record, and that amount can vary from "hardly any" all the way to "too much."
 
Just a thought, the figure will double as the signal has got to get back down the cable again to the headphones. Not that it matters, not at that speed anyway!
Have you had any experience of recording/monitoring this way? I'm not doubting your calculations in any way but, you know, sometimes things don't work out how they should from theory.
Scott
 
Since the signal propagation is almost instantaneous, there's no noticeable delay. I routinely overdub using a mic or instrument through a 20' cable to the mixer, which feeds a 20' cable that crosses the room overhead to the headphone amp, while the musician synchs up with a playback coming from a sound card via fiberoptics back to the mixer, then through the 20' cable to the headphone amp. There is no discernible delay. Here's a quote from John Dunlavy, a well-known audio engineer:

"When electrons are induced to flow as a current along a conductor, they move in the direction of the "positive polarity", where a 'shortage' of electrons exists, much as air tries to fill a vacuum. As a 'current', electrons attempt to travel in a more-or-less straight line, parallel to one another along the axis of the wire. Although the velocity of individual electrons is typically only a very small fraction of the speed of light in a vacuum (and sometimes as slow as sound in air), their flow as a current induces the formation of both electric and magnetic fields (at right angles to each other) which surround the wire and travel along it at velocities closely approaching the speed of light (about 186,000 miles per second). And, it is this 'electro-magnetic field', working in unison with the current, not individual electrons (as many believe), that actually transports the 'signal power' along a wire, at 'near light speeds'."

Unlike computer "latency", there's no processing going on in the wires or interconnects (the mixer is treated as an interconnect in this example); all that's happening is that you are energizing a circuit. Think of it as turning on a light switch: you can't distinguish the time delay between when you turn the switch on and when the lamp starts to shine, except for the very short time it takes the filament in the lamp to heat up enough to radiate light. A change at the originating end (the audio) is almost instantly heard at the other end of the circuit.

Hope this helps.
 
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What's the formula you used to figure that number out then? My physics has gone a little rusty.
 
That's great, thanks man. Very interesting & full explanation. The light switch/filament example is a very good way of thinking about the signal and the 'latency' inherent in the light bulb (or digital processor!).
I'll bide my time, but one day I'm going to be able spring someone with the question 'When does sound travel at the speed of light?' :D
Good stuff, thanks again.
Scott
 
noisedude said:
What's the formula you used to figure that number out then? My physics has gone a little rusty.
Click to expand...

The first figure is 50 m / 300,000 km/s (speed of light) = .0000000167 sec. The second figure is probably based on a slower speed of light due to the medium of copper wire rather than a vacuum, but I don't know that value.

Brightside, latency generally has to be at least 2 msec (.002 sec) to be noticeable. That means that the round trip through the cable would have to be around 600 km, or 300 km one-way, for any noticeable latency.
 
What's the formula you used...

Sorry, I missed your question, noisedude, but mshilarious answered it. The second figure I offered was computed by figuring propagation at 80% of the speed of light. (Graffiti seen at Princeton in the '50's: "e=mc2. Show your work.")
 
Brightside said:
That's great, thanks man. Very interesting & full explanation. The light switch/filament example is a very good way of thinking about the signal and the 'latency' inherent in the light bulb (or digital processor!).
I'll bide my time, but one day I'm going to be able spring someone with the question 'When does sound travel at the speed of light?' :D
Good stuff, thanks again.
Scott
Click to expand...


And they will laugh at you because an audio signal in a wire is not sound.
 
Ok I thought it was that too but I baulked at why it involved the speed of light .. ?
 
why it involved the speed of light .. ?

Because it does: the speed of light is just a specific instance of the principle that electromagnetic propagation radiates at a finite (and, as far as I know, standard) speed. There's nothing esoteric about it, it's just the way it works. Light happens to be in one range of frequencies, electricity and audio signals happen to be in others. It's kind of a hard thing to comprehend in one sense (any frequency from DC to infinity radiating at the same speed?) but's it's simple in another: the same rules apply to everybody. Another way of looking at is that it's not a case of everything having to be speeded up to the speed of light: rather, it's that phenomena travel at the same constant speed everywhere. Some of these phenomena are light waves, and others are the drum licks racing down your XLR cable to the headphone amp. And, be grateful: what a hassle if it wasn't this simple!
 
And they will laugh at you because an audio signal in a wire is not sound.
Click to expand...

Yeah, just a wee joke guys. Technical issues aside, to the layman it could appear that sound is traveling at the speed of light (approximately!). The sound is, of course, not sound, but an electrical signal whizzing through the cable. ;)
Scott
 
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