Headroom. (The amount in dB above the peak of the audio)
I’m sure you’ve all heard about the rule of thumb regarding leaving ~6dB of headroom for the mastering engineer. This isn’t bad advice but i’m going to break this one down for you as there is a lot of confusion as to why.
Technically, the amount of headroom that a mastering engineer NEEDS is ZERO, as long as it’s not clipping (Any number above 0 on the Stereo Out channel in Logic).
Example, if I receive a mix-down for mastering, the very first thing I will do is make a gain movement to where I want it to be prior to processing.
However, what really matters, and what this is massively confused with is…
Mastering engineers can only work with the information that’s given to them. If you send a mix that had a hard limiter on the mix bus, reducing the dynamic range by 8 dB for example, that’s 8dB that the mastering engineer will never see. That’s information you have shaved off the top of the dynamic range of your audio prior to sending to mastering. By doing this, the mastering engineer’s job is 8dB harder or closer to impossible.
Let me paint you another picture. If you use a limiter and reduce the dynamics to 10dB (very low for a whole song) but it has ‘headroom’ because you simply turned it down post-limiting, then that completely misses the point.
So, is 6dB good advise? Yes! Why? Because it makes you think about your levels before submitting, and it’s headroom for the headroom. Meaning, that if I say to you “-6dB headroom please” and your meters miss something that went 3dB beyond, there is still another 3dB of headroom above that unforeseen peak. It’s just ultra precautionary as to not break up the customer journey by asking them to go back and rebounce etc.
Basically, headroom isn’t really the problem, dynamic range is. Just make sure you aren’t using a limiter on the mix bus before you bounce down and send off for mastering.
1dB of headroom but full dynamic range (no limiter)
6dB of headroom but heavily squashed dynamics (limiter on mix bus)
6dB of headroom, full dynamic range, and no clipping (no limiter on mix bus, peak level under 0)
To summarise, the message is that the peak of the information is the peak of the information. Meaning there is nothing but emptiness above that, so there is nothing to be gained or to be lost either way. The mastering engineer will give themselves the headroom they need via a simple gain movement at the beginning of their chain. However, the dynamic range of the information is the most important variable. It’s no good sending a 24 bit mix with 6dB of headroom if the dynamic range of the material is only at 4dB because it was pushed into the ceiling of a limiter. Headroom or no headroom, that will be quite the task for the engineer. In that case, they will likely ask for a re-print minus the limiter.
If you are still unsure, please feel free to submit your mix to me for a free review.