Core Principles of Live Sound and Mixing- Part 1- Signal Flow

One of the most important things to understand when doing live sound is signal flow. Signal flow is the path of the audio signal from its source to its output. In mixing, it’s how the sound gets from an instrument or input to the audio console and what path the signal takes through the console before finally coming out of the speakers.

Why do you need to understand signal flow?

Well for one, so you can properly connect all the various parts of your sound system.

Sound Systems are comprised of many different pieces of equipment, including but not limited to loudspeakers, crossovers, amplifiers, signal processors, audio consoles, microphones, DI boxes, sub-snakes, splitters, etc. There is a specific path the audio signal needs to take through this equipment for it to function properly.

Knowing signal flow allows you to correctly wire all these components together.

You need to patch the inputs on the stage to the snake, the snake to the consoles, the console to the system EQ and processors, the processors to the amplifiers, and finally the amplifiers to the speakers.

Along that path, you may find sub-snakes, devices inserted on channels in the console, and console outputs routed to things like monitor mixes. When you understand signal flow, you can easily visualize how all these pieces go together. Being able to visualize this helps in troubleshooting problems.

If you want to troubleshoot quickly and efficiently, a thorough understanding of signal flow is essential.

When something in the signal path fails or breaks down you will need to fix the problem as quickly as possible. Trust me, it’s going to happen this is live sound we’re talking about, gear fails all the time.

If you are mixing a live show and suddenly the vocal drops out of the PA, what do you do first? No- the correct answer is not -‘PANIC’. You remain calm and work through the signal path in a systematic and logical order.

Is the vocal microphone patched directly into the console? Is there anything inserted on that channel? What is the path from the vocal microphone to the console and from the channel in the console to the Stereo Mix? Knowing this signal path, you can quickly find the problem and remedy it.

While we are talking about the console, do you know how to mix on every console out there? Or are you terrified when faced with a console you’ve never used before?  Here’s a secret- if you understand signal flow, you’ll be able to mix on any audio console.

The vast assortment of audio consoles on the market today can be intimidating to a novice engineer. Fret not, even the most veteran engineers aren’t experts on every single one.

A thorough understanding of signal flow will allow you to be more comfortable when using a console you’ve never mixed on before. Here’s why- Signal flow through the audio console follows virtually the same path no matter which one you are using. The difference is where everything is located on the surface. Knowing where every single button and knob is on an Avid Profile isn’t going to do you any good when you have to mix on a Yamaha CL 3 or Midas Pro 2. You won’t be very useful if you can only mix on one particular console.

If you understand signal flow you’ll be able to get your head around a new console much faster.   Now learning all the different software platforms and filing systems is a topic for another blog, but when you fully grasp signal flow through the audio console, you’ll know exactly how to get from the input gain to the Master mix bus and everywhere in between.

Watch this video on Signal Flow

To achieve proper gain structure and gain staging you need to know signal flow.

Both are necessary for getting good sounds and the best performance from the sound system. Understanding signal flow through the console will allow you to achieve optimum gain of your inputs and maximum headroom. This is a necessary step in getting the best quality audio with minimal distortion and or noise.

Each component that the audio signal travels through in the channel strip of the console has the potential to add noise to the signal, and what you do to the signal in one component can affect the signal as it moves through its path.

To understand how each component in that path affects the signal, you need to know what the path (signal flow) is.

This is vital for achieving the results you are looking for.   

Where are you sending the signal? How is it getting from the pre-amp to the mix bus? Where are you adding or subtracting gain?

Are you sending the signal to an insert? Where is the insert in the signal path?

What’s the best way to run monitors from the FOH console?

If you’re pre-amp gain is set correctly but your signal level is too low at the fader, where are you losing gain?

If you are hearing mechanical feedback, would you know how to find it?

When should you use Groups instead of VCAs and VCAs instead of Groups?

How do you figure all of this out? I think you know the answer by now- UNDERSTAND SIGNAL FLOW.

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By: Michelle Sabolchick