Working too quietly vs working too loud
When you work too quietly:
You don’t hear painful high-end stuff as being painful, so you don’t deal with it appropriately, and your mix ends up having painful high-end stuff (screechy vocals, guitars that take the top of your head off, too much high end on the drum kit, etc).
You can generally end up with too much low end and too much high end on individual sounds and/or your entire mix; our ears prioritize midrange sounds at lower loudnesses, for reasons of saber-toothed tigers.
Your drums may not have the low-end punch they should have; our chest can be better than our ears at telling us when the drums are hitting, but this only happens when you’re listening fairly loud.
When you work too loud for too long:
You may tuck the vocal too much.
You may overly de-emphasize the low and high end, both on individual sounds and on your mix in general.
You might not compress the master bus enough; your eardrums do their own compression when you listen loudly, and so you think there’s more compression than there is!
You may end up with a dull or midrange-y mix, because the high end seems too aggressive and so you keep EQing it down.
The Goldilocks solution: work loudly, but fairly quickly, to get your initial EQs and balances — and then work more quietly, frequently adjusting both your listening volume and the speakers you’re using.
When I’m working on a mix, I tend to start very loud on my big speakers with the subwoofer for the first 30-45 minutes — this helps me get the low end bumping appropriately.
Then I turn way down and alternate between the NS-10s and the Auratone for a while — this helps me do finer-detail EQing, and make sure that the bumping I was enjoying in the first phase wasn’t just the subwoofer hitting me in the chest.
Then I work back and forth between all my speakers, at a variety of loudnesses — different details stand out in different listening situations.
Just right — jamie