Headroom and Dynamic Range

The two most important areas in audio recording and mixing are Dynamic Range and Headroom. Your entire mix should be governed by these two critical factors. The ear/brain combination needs ample dynamic range in music to maintain interest.

Headroom

Headroom is the difference between an audio tracks peak level (when the meter is displaying its highest value) and 0 level (ceiling) on the output meter. Let me give you a simple analogy I always use to explain headroom to my students. You are 6 feet tall and you enter a room that is 10 feet high. You have 4 feet of headroom. I know it’s simplistic but it works for me.

Dynamic Range

In digital audio we are concerned with two values: the noise floor which is the lowest or quietest value, and the ceiling which is 0. This difference between the noise floor and ceiling is what we refer to as dynamic range. In layman’s terms think of this as being the difference between the quietest and loudest part of an audio signal.

Bit depth

Let us now look at the afforded dynamic range available in your DAW:

Using the old ballpark calculation of 6dB/bit we can ascertain that a 16 bit system will have a dynamic range of 96dB whereas a 24 bit system can accommodate a range of 144dB. These are not absolute figures and you will invariably find that the range is actually compromised and the figures are less than quoted. In a typical 24 bit system a 120dB range is more accurate, but this is not gospel and is dependent on a number of factors. As far as we are concerned we only care about the extended headroom and wider dynamic range.

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.

In the video I explain what dynamic range, headroom and summing are.