Differing lengths of mic cable onstage - how much effect on timing?

[James Lehmann]

Guys,

Do you give consideration to differing lengths of mic cables onstage?

SCENARIO

I'm running 8 lines into a 15m Stagebox and then back to my pre-amps.

For my mic cables I could use:

2 x 5m
4 x 10m
2 x 20m

or would I be better trying to use:

8 x 10m

in order to avoid having to line the tracks up in the DAW later.

Or is a difference of 15m negligable?

My application is very much recording as opposed to live.

Thanks for the advice.

[rumleymusic]

Or is a difference of 15m negligable?

Very. An audio wavelength is a short thing in the air, it is very, very long when passing through a cable. You can have several hundred feet difference between two cables with out any problem.

[d_fu]

"typical high-end cables/wires to propagate audio signals in the range of 50% - 70% the speed of light"

Fast enough...?

[klaukholm]

The speed of the electrons is not relevant, the speed we are talking about is that of electromagnetic waves, which is what determines the transfer time of digital and analogue signals over cable.
This is slower than light in a vacuum (c), but at the same time it is no different than the speed of light as both are electromagnetic waves.
In other words, don't worry

The speed the electrons move is effected by shielding etc and travels faster in an unshielded copper wire, than in a shielded one. typical coax cable is about 2/3 of c, while unshielded copper approaches c (95% give or take)
This does not effect the speed of the signal (see above)

[Petrus]

If the length difference is over 3000m, you might get 3 dB level differences in 40 kHz signals. For audible frequences the cable length difference would have to be twice that (6 km = almost 4 miles).

[klaukholm]

The OP was asking about timing/latency of cables, not signal-loss.

[James Lehmann]

Thanks guys.

CONCLUSION: use whatever length of cables is convenient to rig onstage - the sorts of time differences we are talking about are entirely negligable.

Next question - when you talk about 'lining up all the drum tracks' for example - what are you referring to? Is this dealing with the time difference that the sound arrives at the various mics, ie through air, and thus much slower than through cable?

I think I know this - I just want to be 100% sure.

[klaukholm]

James, sound travels about a foot per millisecond
(varies with humidity, and elevation and high/low pressure weather, but 1'/ms works for me)
In an orchestra setting this would mean that the sound from back players 30 ft back from the main mics (line of sight) arrives 30ms earlier in the spot than in the mains.

Hope that helps

[7rojo7]

overheads and room mics are the farthest from the source, lining up drums means delaying the other mics to arrive at the same time as the sound arrives at the over heads (if one likes to be really picky). before digital if you had sync head outs, you could play the overheads and/or room mics and delay them (an oscilloscope helps, or out of phase proof) always a little dangerous, but it's a sound. now it's a snap.
with bigger setups, ensembles orchestras (I always ping the setup with a ciak (2 pieces of something hard and flat plywood etc... drumsticks work)
sometimes the delays sound nice
depends upon the critical distance mostly
I love recording, playing with time and space

[Petrus]

Originally Posted by klaukholm

The OP was asking about timing/latency of cables, not signal-loss.

Sorry, what I meant was time difference, with one cable 3000m longer than others, you might get 3 dB dip in 40 kHz signal when you mix them. If your stereo cables are mismatched by 6 km, somebody just might hear a quarter wavelength difference at 20 kHz.

Few hundred meters do not matter anything, few meters even less.