Pre-masters at -6dBTP: myth
You don’t need to ensure your pre-master peaks at -6dB; this is an internet myth.
Why not? Because, in a simple technical sense, audio formats such as WAV and AIFF are Linear PCM; which means that as long as they aren’t clipping (and haven’t been dithered) it makes no difference how loud you export the file; the gain can be adjusted afterwards with no consequences.
Here’s an example:
(Apologies for the amateur video: I make music, not movies)
This video demonstrates that no matter what level a Linear PCM file is exported at, the gain can be adjusted without any issues: as long as the master channel wasn’t clipping, and the file hasn’t been dithered.
Of course, this means that there’s also no harm in sending off your files to mastering at -6dBTP; in theory. In practice, though, many people will simply put a limiter, maximizer or clipper on the master channel before they send it off. This is almost always a bad thing to do, which will cause artefacts, and also reduce dynamic range and perceived loudness.
However…
Perhaps somewhat controversially, personally I don’t believe it’s always bad to export a pre-master with a limiter on - although it almost always is. The exception to the rule is when the limiter, or maximizer, or clipper has been a part of the mixing process and forms a crucial part of the sound.
If you’re in agreeance, you might be one of the artists who use these tools to create grit, power and glue, most commonly in aggressive dance music. But proceed with caution, and turn the limiter off to carefully compare whether it actually contributes something musical, or just makes it sound louder. Consider sending a limited and unlimited version to mastering; there’s no harm in that.
In other words, don’t just put a limiter on at the end, but if it’s a genuinely irreplaceable part of the sound that you’ve worked hard to create, then keep it on and send both a limited and ‘clean’ version to mastering.
(P.S. What is dither? Here is the best demonstration I have encountered.)
