problem
Headroom is about clean margin, not making the mix artificially quiet.
Mastering headroom means leaving enough unclipped peak margin for final EQ, compression, limiting, and delivery conversion. It is not a magic number that improves sound by itself.
A mix peaking around -6 dBFS can be fine, but a clean mix peaking higher can also be workable if nothing is clipped or over-processed.
The bigger problem is sending a mix that already clips, has hidden limiter pumping, or was made loud only to impress during approval.
If a limiter is part of the sound, print a limited reference and an unlimited version so the mastering decision is clear.
Check sample peak, true peak, and integrated loudness on the final mix print. Confirm there are no accidental overs at the output.
Meter Core helps keep final mix delivery honest by showing whether headroom, loudness, and peak margin are actually under control.