Patented by Dan Dugan in 1976, automix is an essential audio tool for conference PA engineers. This is because automix is probably the only really effective way to control multiple open mics during a live discussion. However, automix can also have a positive effect on your conference video or livestream’s audio quality. Read on to find out why you should have automix available for your next conference livestreaming or filming session.
Increasingly, events such as conferences and training seminars feature Q&A panel sessions. These can involve anything from 3 to 6, or more individuals, each requiring their own mic for good audio production. Conversation among panelists and between the panel and audience inquisitors is, hopefully, fairly dynamic and naturally unpredictable. While this makes for an engaging conference feature, without automix, it would be a nightmare for audio engineers.
Find out more about effective conference sound.
Conference Q&As are an unpredictable mixing environment.
Q&A sessions are, by their nature, very unpredictable. If you’re responsible for sound, you have no way of knowing who will speak next and how long for. Nor can you predict how loud they’ll be while they’re speaking. On top of that, a fellow panel member or an adjudicator might need to interject at any point. No matter how carefully you try to follow the flow of the conversation, there is no way to respond effectively.
Ideally, each panelist should have their own mic.
So why not just leave all the mics open?
An obvious answer to the issue of handling multiple mics is to do nothing. You could simply set the levels on each mic and leave them all open. Each person speaks when required and everyone hears them loud and clear. While this sounds like a perfect solution there are potentially significant problems:
Noise.
Every open mic captures unwanted sound, including room ambience (echo) and incidental noise like coughing and off-mic conversation. If you have multiple open mics, they will simply compound this effect. Obviously, over a PA system, this can also contribute to feedback problems. However, when you’re filming or capturing audio for a livestream, noise is your biggest problem.
Dangerous dynamics.
Q&A sessions are inherently dynamic and several people briefly speaking at once is common. This unpredictable increase in gain through your system could result in clipping (distortion). Allowing enough headroom to avoid this is problematic for live production work. Leaving excessive headroom inevitably results in noise from the electronics in your signal chain. While traditional audio dynamics processing can help to some degree, setting this for speech is notoriously problematic.
Why not control mics Manually?
As we’ve seen, attempting to ride faders or to solo individual mics as a conversation unfolds is simply impractical. While fine in theory, in practice the inability for an engineer to predict the flow of a conversation would render this approach inherently prone to error.
You could try one of the solutions whereby panelists control their own mics to manage the situation. A whole range of switched ‘conference’ mics are available which allow panelists to activate and deactivate their own microphone. However, in practice, user error often disrupts the flow of a discussion significantly.
So, how can automix control your Q&A audio?
Automix responds to changes in the input level of individual mics within a group. When the input level of one mic increases, a sidechain process reduces the gain of the other mics. This happens instantly to all intents and purposes. In other words, when you start speaking into a particular mic, all of the other mics are attenuated or ‘ducked’.
Because mics are ducked rather than muted, panelist interjections remain audible, and conversation can flow naturally. Accidental muting is no longer a problem. Crucially, automix responds dynamically to restrict noise levels and to keep these normalised. This means that you don’t get the noticeable changes in background noise that would result from muting.
In addition to giving one of your mics priority, the overall level of your mic group is normalised. Therefore, if several people speak at once, the resulting output volume is limited automatically to compensate. This means that you can leave all of your mics open as they, effectively, self-regulate.
How do I get automix?
You will find that most modern digital mixers incorporate their own version of the original Dugan Automix. You will find this kind of system on units like the MR18 from Midas, for example. This particular automix function is very easy to set up and highly effective. The same system is also available on sister mixers like the XR18 from Behringer.
If you need greater portability, you will also find automix on devices such as the Sound Devices Mix-Pre series.
The Midas MR18 has an effective, easy to use automix function.
On the job with automix and conference audio.
Depending upon the size of the event, you may simply feed already mixed audio straight to your camera/camera switcher. For example, at larger events, with a hired PA and sound engineer, chances are that you will capture your audio from their mixer. In this case, they will be taking care of mics and audio mixing so you have little to worry about.
However, if you are working on a smaller event, chances are that you’ll be capturing audio yourself, so things could be the other way around. In other words, you’ll be feeding a simple in-house PA from your audio mixer. Certainly, most of the smaller conferences and so on that I have filmed or streamed at hotels and the like would fit this description. Very few of them, in my experience, supply more than a couple of mics. For this reason, I carry a case of mics and a small mixer with an automix function. This means that, if needed, I can easily mic up a Q&A panel or similar. Having automix also means that I can manage a dozen mics or more while I’m also operating video equipment.
For those who are getting into the world of event filming and live streaming, making sure that your choice of mixer includes an automix function is a wise move!
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