Those are good questions where there are no definite answers, neither can I set "rules" for that.
cpsmusic wrote: ↑Sun Jul 26, 2020 01:41 CEST
1. Do we need to be concerned with the mono compatibility of the final mix? If so, how important is it?
Even though we're mostly listening to stereo these days (headphones being the biggest value from various stats), one should always keep mono compatibility in mind.
While we do not specify a "device target", watching from a tablet, seeing an ad at a cinema, having a kitchen radio, listening to music while in the car... if you go a bit too wild with stereo placement, the listening experience would suffer. Kick Drums and Bass should ideally always be in center at bar minimum (orchestra being different, of course). We also don't know if one of the Mix Challenge mixes will be negotiated (in the future) to be put on to tape or vinyl, here a good mono compatibility is important.
cpsmusic wrote: ↑Sun Jul 26, 2020 01:41 CEST
2. I've noticed that most pro mix engineers will have a limiter on their mix bus that they use for referencing what the mastered mix will roughly sound like. They switch it on from time to time to check that the mix balance will still sound ok after mastering. I know that Mix Challenge competition is for mixing and that there are loudness specs, however is this something we should consider? Something I've found when experimenting with this is that a mix that behaves well when limiting is applied is different to one that is only mixed.
To me, that is a workflow question.
The Mix(ing) Challenge allows "summing bus treatment", as long it is considered to be "artistic" and not to for the purpose "make things louder". Summing bus compression is definitely not a new concept, and both Rock and Electronic productions can definitely benefit from that. But it shouldn't turn into a bigger deal.
To me, mastering is (and always has been for me) just adding "final touches" - as in, cleaning up some rogue frequencies, giving a slight enhancements (like: making the track a bit wider, keeping the lowend in check), setting proper fades, setting up the final format/medium for release, etc. The "Limiting" is then only for setting the absolute maximum. Mastering" back in the days was really just that - "fairy dust" and "safety mechanics" prior to a mass release.
If you use a "Limiter" to only clip away rogue transients - that is one thing. But if you push things... maybe you should look into properly A/Bing your edits. Example: your mix is in -16LUFS, but you run it through a mastering array and the output suddenly reaches -8LUFS. Pull down this "mastered track" by same same value you've pushed (in this case, 8LU), A/B to the "unprocessed" material. If you hear things that could be improved in the mix, do so. If it sounds worse at the same loudness - you went too far.
A track should be able to stand on it's own, no matter the perceived loudness. A "mastering limiter/array" (dynamic compression) will always influence that - compact things even more, make it more "In your face" and then sound subjectively better (louder = richer, fatter, better).
The Mix(ing) Challenge tries to teach you how to just focus on the song, how you can portray a certain feel. I can guarantee you that overly squashed material will usually always sound worse.
Which brings me to this good old Youtube video from 2006 (or rather the 2016 re-release), giving you a no-nonsense demonstration on "brickwalling and it's negative side-effects" in less than 1:30min (well... 2:30min if you watch the following Youtube video from start to finish). I think this should help answer your question.
"The Loudness War" - by Matt Mayfield Music, originally released October 2006, enhanced re-release for a Change.org petition in March 2016 (notice: broadcasting stations already adapted Loudness Normalization for about 4 years at this point, while streaming services were still uncertain regarding deciding on a unified value)