Here’s what those levels are adjusting:
16Hz – 60Hz = SUB BASS This is the super low-end that can be felt physically by your body on a good subwoofer/sub-bass system. Sounds with these frequencies are the most powerful ones, and they will take up a lot of room in the mix. Use this range to fatten up your kick drums or sub-bass patches. Too much volume in this range makes your mix sound «muddy.»
