Wednesday, April 27, 2011

What is a Mixer?

This is a fairly generic term and how you define it will depend heavily on the context you are in – so let’s give it some context. Since this is a blog written by meeting planners, we’ll be looking at defining “mixer” in that light. But, even within the context of meetings and conferences, there is still more than one definition of “mixer” that could apply.

If you were to ask this question during a conference, most people will probably respond with one definition right off the bat: an event, often held in the evening, at which people gather for networking, informal discussions, or just to meet new people. Nearly every meeting planner, though, has also had to become familiar with another kind of mixer that is critical to the success of our meetings – and it is a specific piece of audio-visual technology that anyone with technical experience in a theater will instantly be familiar with… a mixer.

Whenever you order more than one microphone, the audio-visual department (or company) will almost always include a mixer. Why? What is so important about this device that they add one when all you need or want are the microphones?

Well, the short (and not-so-helpful) answer usually given is that you cannot have multiple microphones in a room without a mixer, but that still doesn’t really answer the question of what it does or why you need one so let’s break it down a bit further…

A microphone takes sound and converts it to an electronic signal, which is then sent to a speaker for conversion back into sound, which an audience can then hear. The electronic signal can be sent through a cable (wire) or wirelessly. If you only have one microphone, you usually don’t need anything further to make the system work - the microphone connects directly to the speaker. However, speakers can only convert one signal into sound at a time. So how does a single speaker unit handle multiple inputs and know which input to use? Through the intervention of a mixer. A mixer takes those multiple inputs, manages the signals, and then sends one signal out to the speaker, allowing the audience to seamlessly listen to multiple microphones effectively at the same time. A mixer also allows you to manipulate the signal strength of each input, raising it or dropping it (even down to zero) as needed for your final output.

So what size of a mixer do you need for your meeting? The answer is determined by how many sources, or inputs, you have. You need one channel for each input and every microphone (whether wired or wireless) or audio source counts as an input. So, if you have three microphones, you will need at least a 4-channel mixer. Why not a 3-channel mixer? Well, they don’t exist. Mixers come in a variety of sizes; each one is double the size of the one before it. So – 4, 8, 16, 32, 64, and 128-channel sizes are your choices. There are, I’m sure, mixers out there larger than a 128-channel mixer but I have yet to see one myself and I have never had a need, at any of my events, for more than 128 channels.

What happens if you have, say, 20 inputs from microphones, videos, and so forth – but don’t have a single mixer large enough to handle them all at once? The solution in this case is to concatenate, or “chain together”, two or more smaller mixers to get enough channels to cover your needs. For example, to get 20 channels, I might combine two 16-channel mixers together or pair a 16-channel mixer with an 8-channel mixer. When chaining mixers, you take the output from one mixer and feed it into one of the channels on another mixer – this means that combining an 8 and a 16-channel mixer together gives you a total of 23 channels available for your various inputs. Chaining mixers is a good work-around if you don’t have a mixer with sufficient channels to handle all of you inputs, but it is possible to run into some signal degradation issues if you link too many mixers together, so be careful with this approach. As always with AV issues, be sure to talk with your AV tech about any questions, concerns, or problems you have with the technology and how it relates to your event – they are there to help you.

Though technology stuff can get kind of boring for many people, I hope this brief overview on mixers has shown you how this single piece of AV equipment, while not often asked for (though often provided), is actually a crucial piece in making sure that your presenters sound good and that the audience can hear them clearly. Now, whether the audience is paying attention or not is another question entirely…

~ Karl Baur, CMP • Project Director, RDL enterprises