Latency is, in the most simple terms, the time it takes from a sound go from the source to the output. A sound goes into the system. The system then converts it to digital, routes it around, does some math to it, and then spits it out. Latency is that middle stage. How long does it take to do all the stuff we do to a signal before we hear it again.
Most church techs know that the lower latency is, the better. This tech tip will look at the impact of latency on performers and the whole system and how we can be aware that it is affecting performances.
While we can’t generally hear the effects of latency until they are around 15-30 milliseconds (ms), performers can begin to feel them at around 5-10ms. At 7ms, latency starts to mess with our ability to play or sing on top of or behind the beat. Sound starts to feel sluggish at 10ms. These are generalities, of course. A study presented to the Audio Engineering Society called “The Effects of Latency on Live Sound Monitoring” found that each instrument has different tolerances for latency. They also found that performers were more forgiving of latency when using floor wedges over in-ear monitors.
With an analog system, it’s not really a problem. Analog sound travels through components at or near the speed of light with an effective latency of 0. Adding digital components to the mix is what makes latency. There is a “cost” in time for every conversion a sound undergoes to and from the digital realm and for every process applied to that sound. As we rely on more and more digital gear, all those components stack up and start to be problematic.
What we want to be aware of is the total system latency, as well as how each performer contributes to it. Latency is one of those things that most devices will publish in their specs so it’s good to look into the gear you have to get some exact numbers, but there are some generic guidelines we can use.
Every time your signal gets converted from analog to digital you can expect 1 to 1.5ms of latency. That’s the processing time of the Analog to Digital Converters (ADC) and the Digital to Analog Converters (DAC). Below is a chart of some common system elements that add latency.
Digital Mixer: 1.5 to 3ms
Wireless Microphone: 2.5 to 5ms
Wireless In-Ear Monitors: 2.5 to 5ms
Digital Effect Pedal: 2 to 3ms
Amp Modeler: 2 to 3ms
So how does this translate into issues with performance?
Let’s look first at a singer. If a singer is using a wireless microphone and a wireless in-ear monitor system, you can have latency of up to 13ms when it all adds up. Since a vocalist will hear their voice through their sinus cavities and bones, they might be able to notice that their monitored signal arrives just slightly later than their sung notes. We’re still under 15ms so it’s probably not too noticeable, but a sensitive singer might complain that their monitor sounds muddy or smeared. For singers who might be reporting these kinds of “symptoms”, try switching to a wired microphone and see if that helps.
Guitar players represent one of the biggest potential latency offenders on the stage. This is because their own signal chain can add to their latency before it gets to the system. Digital effect pedals and digital amps all add latency. And while that Strymon Timeline delay by itself is not going to give you problems, the Timeline, plus a Strymon BigSky or Eventide Space, plus an Eventide H9, peppered with a bit of TC Electronics Sub N Up Octaver could be tricky. With three digital pedals alone you are starting to get to the place you can feel it. Then add the mixer and wireless monitors and you can be pushing 18-20ms, definitely in that range of feeling it and most performers will start to hear it too.
If you're a church sound guy discussing latency with a guitar player it’s helpful to know the overall delay in the sound system, not just in the pedal board. It will help you decide when to go analog vs. digital. How many digital pedals will your signal traverse? Why does it feel better to plug directly into an amplifier? If you use an amp modeler or a multi-effects unit, you only have to convert from digital to analog one time so your latency can be reduced.
On to drummers. Most drummers are pretty free from latency issues. Some sensitive drummers might feel some impact when using a wireless monitor system. With 3ms-5ms on the wireless system and 3-5ms on the console, they might feel the effects. Consider using a headphone amplifier if this is the case to bring that down.
This is a fairly limited view of a much broader topic. Your digital network, personal monitor systems, and outboard gear can add to latency too. What's important to understand is how this will impact each performer and then be able to take steps to limit the effects on their performance.
