Summing Audio

What is Summing, how to control summed levels, using sine waves for calibrating gains in your projects.

Gain Staging



One of the biggest problems facing producers, all producers, is that of summing. A clear explanation is needed to understand what happens to audio in a mix project when summed and I hope that I have provided that both with the description below and the supplied video tutorial.

Summing

When identical frequencies that exist in two different layers (channels) are combined, you invariably get a gain boost at those frequencies.
If you take two sine waves of the same frequency and amplitude, and sum them you will get a gain increase of 6dB (example below).

The waveform on the top is at ‑9 dB, and when duplicated and summed into a new single mono file we get a value of ‑3 dB. This is important information to take on board and nail into your brain: you can imagine what happens when you have a mix with a huge number of channels all summing and clipping the output simply because shared frequencies are always summed at the output.

Summing sines in a DAW project is the best approach in explaining how summing takes place with audio in any environment. I run through the pros and cons of understanding gain management in your mixes using 3 sine waveforms and summing them across the channels.

Topics covered in this video are:

  • What is a Sine wave
  • Why use Sines for Summing
  • Summing – what is it and why does it happen
  • Compensatory Headroom
  • Dynamic Range
  • Level boosts
  • Best Summing avoidance Practices