SAC Plugin Latency Question

Discussions about the use and operation of SAC (Software Audio Console)

Re: SAC Plugin Latency Question

Postby Gil Navarro » Sat May 30, 2015 11:56 am

In the analog world, if I take a lead voc and insert a comp, I wonder how much latency that introduces? I suspect more than .1 ms.
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Re: SAC Plugin Latency Question

Postby RBIngraham » Sat May 30, 2015 12:13 pm

No, I doubt it. Assuming all the process is fully analog gear. There are obviously very tiny amounts of latency in very long cable runs. But really for all practical purposes, analog has no latency. Now, lets be realistic of course even before the big switch to primarily digital consoles there were several digital components typically. Effect processors, speaker processing and probably some dynamics processors that were digital devices under the hood.
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Re: SAC Plugin Latency Question

Postby jlepore » Sun May 31, 2015 2:12 am

Well, it depends on how long your interconnect cables are between your analog gear.

At 20km you would be up to 1ms of delay (you can only put it 10km away if you only want 1ms for the entire return path).
So - 6 miles away is your limit if you want to keep the audio latency under a ms - of course adjustments may take a bit longer depending on traffic... :mrgreen:
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Re: SAC Plugin Latency Question

Postby BrentEvans » Sun May 31, 2015 9:45 am

Interesting math that brings, though. .6 of a mile would be .1ms, which is 3000 ft... that's not an unheard of amount of cable in larger venues. It would be pretty easy in a stadium setting that starts on one side, takes two different signal paths to a broadcast truck on the other side, and gets mixed at the broadcast truck... but that's an extreme example.

Also, on larger distributed digital systems, you can have different latencies at different entry/exit points to the system. It's not normally a problem with proper design, but it CAN be a problem.

The moral of the story is simple... even small amounts of latency can have an effect on audio frequencies if the latent signal is mixed with the non-latent signal. In real life, this typically isn't a problem, as either the digital processing or the analog cabling is all roughly the same length.
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Re: SAC Plugin Latency Question

Postby jlepore » Sun May 31, 2015 7:34 pm

Since the question was about inserting an analog compressor, I figured that would be a bit excessive for an insert cable.
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Re: SAC Plugin Latency Question

Postby BrentEvans » Mon Jun 01, 2015 2:37 pm

Very true, but it's tangentially related and this is an internet forum...
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Re: SAC Plugin Latency Question

Postby IraSeigel » Tue Jun 02, 2015 10:57 pm

I think I remember reading some time ago that the typical listener can't distinguish less than 20ms of delay.

But for the couple ms you're discussing here, I can't see what difference it makes, unless you're recording sounds separately in an anechoic chamber, 1 source and 1 mic at a time. Any other scenario will have lots of intrinsic delay and phasing.
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Re: SAC Plugin Latency Question

Postby RBIngraham » Wed Jun 03, 2015 8:37 am

IraSeigel wrote:I think I remember reading some time ago that the typical listener can't distinguish less than 20ms of delay.

But for the couple ms you're discussing here, I can't see what difference it makes, unless you're recording sounds separately in an anechoic chamber, 1 source and 1 mic at a time. Any other scenario will have lots of intrinsic delay and phasing.


I really wish whenever people would make blanket statements like these they would put in the proper qualifiers. Yes I would agree that you need at least 15ms (I say 15 rather than 20, as I can perceive that most days, if you're doing an A and B comparison anyway) before most humans can perceive the time shift. But that is really only the case if your'e talking about sound coming out of two separate speakers or two separate sources (think actors mouth and speaker here). If you want to test this out, take a mono source, play it out of your studio monitors at home and delay the signal in one of the two monitors. You will hear the image shift left or right. Typically when I'm at home in a controlled environment I can start to perceive that image shift around 12ms or so, depending on the source material, speaker placement and the phase of the moon. ;) It's the Haas effect in action.

Change the situation to a singer and their monitors, particularly with In Ear Monitors on and it won't take 20ms for them to hear what sounds like comb filtering, but it's combining in their heads. They hear the natural voice, the transmission through the bones in their skull and the monitors all combining. I'm not a voice performer so I have never bothered to experiment on myself in these kinds of situations. But I can tell you that if I combine a dry source with a delay source and listen in headphones or In Ear Monitors, it takes a lot less than 20ms for me to actually hear the phase cancellation happening. I'm talking about purposely combining a non processed and processed signal in some manner here. If you're smart and careful obviously most days you're not going to do that except for things like time based effects (i.e. reverb or delays) in which case you want that because it's part of the effect.

Of course having said all that, I remember sitting in on a session in the Live Sound Reinforcement workshop (used to be hosted by Syn Aud Con and Live Sound Mag) where Dave Robb was demonstrating this, using the exact example above, two speakers, using a time delay in one channel to "pan" a signal. I was blown away by how many in the room said they could not perceive the shift in image at all. Even some that were right in the middle of the listening area like myself. It was very obvious to me. Just shows how many "cloth ear'd" there are running around in the herd. :o
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Re: SAC Plugin Latency Question

Postby Butch » Wed Jun 03, 2015 9:17 am

I was working a show Friday with small studio monitors at FOH instead of can's and I delayed them and could tell the sound moving with just a couple ms of delay (nice dead room) sometimes in bad rooms 25 ms does not make much difference

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Re: SAC Plugin Latency Question

Postby RBIngraham » Wed Jun 03, 2015 9:29 am

Butch wrote:I was working a show Friday with small studio monitors at FOH instead of can's and I delayed them and could tell the sound moving with just a couple ms of delay (nice dead room) sometimes in bad rooms 25 ms does not make much difference

Butch


I assume you're talking about delaying the FOH monitors back to your mains?
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