Can someone explain -18 db mixing?

Do you recommend doing the -18 group trim with plugins on or off the individual channels? Reason im trying to keep things at that level is that a great write up on this -18dbFS = 0dbVU matter mentioned to try keep your master input at -18dbFS as well as the output.
 
I trim audio on tracks, apply plugins, make right balance between tracks, send them to a group. trim group to 0 VU, apply plugins and so on.
 
for you guys on reaper, I just wanna say I use JS: Utility/Volume for this and it works great.
 
Quick Question.
What are most people doing when sample replacing.

Example
I've tracked the kit snare peaking at - db ish (-18rms) yada yada. Then i insert drumagog on the snare and say drop a Slate sample in. That puppy is not sitting at -12 to - 6db its bangin'. I know i could lower its level many ways I just was curious to standard procedure. Also with pro tools 10 now having CLIP Gain is this playing a part in anyones gain staging.

Thanks Everyone.
 
Damn iam dissapointed, i was thinking about settings all faders about -18db and start mixing (about a year) and now all is explained. But i still not understand it fully :D i need that to try in practice :D so if i record di signal at 0dB max it is good or not?
 
For the 100th time...

Don't record around digital zero, because there is no safe zone if you aim for peaks at ~0 dBFS. If you do that, you will most certainly get clipped signals.
The whole point with this virtual headroom is to try and 'recreate' the headroom that analog desks have (most of them have around 20dBUs above 'analog' zero, which is 0dBVU, so that's why you hear this 'record with average levels around -20dBFS' sentence a lot).

The analog zero (0 dBVU) and the Digital zero (0 dBFS) are not the same, and that is where a lot of people are confused. If you go above zero in the analog world, you will not clip your signal (because as I said, most of them have around 20dB reserve above the analog zero), while if you go above zero in the digital world you will get your signal up to the point where it will clip, which in the digital realm is very bad. There is nothing above the digital zero, only pure clipping. Avoid that at all costs.

Don't record to ~0dBFS, there's simply no good reason to do so.
 
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for you guys on reaper, I just wanna say I use JS: Utility/Volume for this and it works great.

Dude, clean up your chain.

Preferences> Appearance> Media> "adjust media item volume by dragging: ITEM VOLUME KNOB"

Now you have a handy trim built-in to your tracks in the media bay, without the clutter of extra plugs in your chain.

For everyone else: Get a VU meter. Get an RMS meter. USE THEM BOTH.
 
For presonus studio one you can switch meter on master to Kxx. I think it solves the problem ;) cause after properly setting volumes on i think k20 to about zero i get from -6 to -12 on rms :)
 
Quick Question.
What are most people doing when sample replacing.

Example
I've tracked the kit snare peaking at - db ish (-18rms) yada yada. Then i insert drumagog on the snare and say drop a Slate sample in. That puppy is not sitting at -12 to - 6db its bangin'. I know i could lower its level many ways I just was curious to standard procedure. Also with pro tools 10 now having CLIP Gain is this playing a part in anyones gain staging.

Thanks Everyone.