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