Zero Latency Audio Is A Myth - Don't Believe The Hype
In the third instalment of the Indiana Jones series of movies, The Last Crusade, Jones and his father, played by the late Sean Connery, are in search of the Holy Grail, in this case, it’s the cup of Christ. In the final showdown between Indy, his father, and the Nazi treasure hunter, they are presented with a multitude of cups. One of these cups is the one from which Christ drank and therefore if anyone drinks from it they will receive healing. The Nazi chooses the wrong cup and soon pays for it with his life.
Why tell this story? In many ways, some of us have the same journey with audio interfaces. We think there’s a ‘holy grail’ audio interface, so we spend time researching, testing and buying, often with disappointing results. Thankfully, unlike the treasure hunter, we don’t pay with our lives.
The other thing the movie and our quest for zero-latency monitoring have in common is this; they are both a myth!
The term ‘zero latency’ is nothing more than a marketing slogan, dreamed up by someone to try and get you to buy their audio interface. There’s close to zero, but when it comes to zero, there’s no such thing.
You Can’t Defy Science
If you’ve ever been to a large concert, particularly at a festival, then you will have seen towers of speakers some way back from the stage in the audience. They are often called delay towers, this is because a small amount of delay is added to them before output takes place, so that the audio leaving them is in sync with the audio coming from the speakers on the main stage, sometimes a few hundred meters away.
The speed of sound is 343 meters per second, it’s actually variable depending on what it is travelling through, temperature, and other factors. However, for now, let’s stick to the basic 343 meters per second. That means we don’t hear sound instantly. To give it more context, the time it takes for sound to reach you in 1 metre is about 3ms in air. So if you have anything, such as a guitar cab, a metre away, then it has a latency of about 3ms in the real world.
Or take something as simple as an acoustic guitar sitting on your lap. Given the height of the average person, that’s about a third of a meter away from the ear, making the latency about 1ms.
Humans Use Audio Latency For Good
We often regard audio latency as the enemy and something we need to remove altogether. However, the human body uses latency all the time to get auditory cues. Science Daily has an excellent article How we hear distance: Echoes are essential for humans to perceive how far away a sound is, to explain how our ears use sound to map environments;
“Reverberation is usually considered a bad thing," detrimental to hearing clearly, says Kuwada. "But it is necessary and beneficial in order to recognize distance." You can read the entire article here.
So, whilst we often consider audio latency to be a bad thing, it’s an important part of how we perceive our environment. We get used to the tiny delays taking place in everyday life and use it to our advantage.
Computers Made Things Worse
In the good old days of analogue recording, the tiny amount of latency taking place between the mic and the speakers or headphones, was almost imperceivable. The instrument or voice went into the microphone, into the desk, and out again - the delay was no greater than had we been sat next to the source. In some cases with a closely mic’d instrument playing through headphones, actually better.
When computers arrived in the studio it changed everything, mostly for the good, but sometimes for the bad. When audio enters a DAW via an audio interface, the computer has to process the data. Depending on the audio driver, the DAW, the complexity of the session, the plugins used in the recording chain, and the CPU power of the computer, this can add a significant amount of delay to the sound you hear when monitoring via the DAW.
However, while there’s a lot of fuss made about tracking latency, it’s not always an issue.
A typical software mixer used with an audio interface
Low Latency Solutions
There are several solutions to deal with latency introduced when tracking;
Old School Mixer
A lot of people have recognised the issue of latency via a DAW when tracking, for some, it’s not just the delay, it’s also the comb filtering effect that takes place when related sounds with differing latencies are heard together. To deal with this they monitor via a hardware mixer, this means latency doesn’t matter. In a large studio that’s not a problem when you have tons of channels to work with, but even at home, you can buy a small mixer for less than a couple of hundred dollars to use for monitoring when recording. If you want to push the boat out then there are products like the SSL SiX, which are ideal for something like this, offering SSL EQ, compression and more in a very small footprint.
Software Mixer
Most audio interface manufacturers offer some kind of software monitoring solution for this very purpose. The software allows you to monitor your audio pre-DAW and means that, like a hardware mixer, the latency is almost non-existent. Depending on the manufacturer these solutions vary in complexity, some brands like RME and Metric Halo even offer the ability to use effects like reverb and delay on the monitor mix.
However, it is worth nothing that even software mixers can add latency. For example, the UAD Apollo system can add latency, especially when adding certain plugins. There’s a helpful chart created by UA’s Matt Hepworth that shows the latency added depending on the plugin used.
Turn The Knob
Some audio interfaces offer the option to turn a hardware knob on the interface that routes the signal coming into the hardware directly to the headphones. Early interfaces like the original DigiDesign Mbox offered this feature, and you can find it today on interfaces like the Focusrite Scarlett range.
DSP Solutions
When it comes to low latency then the most suitable solution for many is to use DSP hardware. This is where the audio interface takes the CPU load off the computer and uses its own processing. Pro Tools HD/HDX is the industry standard in this regard, offering a latency of 0.7ms. However, it’s worth noting that Avid say this about that number; “Latency calculated using a 96 kHz sample rate with a 64-sample buffer. Tests run using Pro Tools | HDX and Pro Tools | HD Native with Pro Tools | HD I/O, and Pro Tools | HD Accel with 192 I/O. In many cases, people aren’t recording at 96 kHz, but at 48/44.1 kHz, in this case, the latency figure goes up.
More recently, hybrid solutions have become available from brands like Avid, PreSonus, and Universal Audio, claiming to give people the best of both worlds.
Tolerable Latency
Whilst the concept of Zero Latency is a myth, tolerable latency is what matters.
Trying to debate latency as an absolute is pointless, what matters is how much latency you can live with when tracking audio. Some people can live with pretty high latency, in some cases up to 5ms when tracking, others think that number is absurd and impossible to work with. These numbers, viewed without reference to the real world can appear more significant than they possibly are. To compare the latency you are considering against the distance you would have to be from a sound source to produce equivalent latency is good way to judge what these numbers mean. 5ms latency is about the same as playing a guitar with the amp a few metres away. Is that unacceptable latency?
There are plenty of solutions on offer to help each of us find a workable solution when tracking. It’s worth trying them out and finding out which one works for you.