I ask for -6dB peaks, 24-bit resolution, no processing at all in the master bus, and if applicable, ten seconds or more of "silence" at the beginning and end in case I need to take a noiseprint for noise reduction.
 
However, it's important to note that -6dB doesn't guarantee there wasn't internal clipping or limiting within the mix itself. I sometimes get flat-lined material - it just flatlines to -6dB instead of 0.1dB.

Craig, That is interesting.  I have not sent anyone tracks yet and was just inquiring, but Sweetwater specifically asked for 16-bit.
 
They also asked for the songs in CD order, which seemed odd to me.  I may rearrange after mastering.

If you sent them a bunch of songs for a cd, it's probably because it helps for smoothing the changes from track to track for a more balanced level throughout the cd.

I am also a bit surprised that they are insisting on 16 bit files. That seems a bit odd to me. If you have done all the recording and mixing in 24 bit then the best way is to master is do all the mastering in 24 bit as well and dither down to 16 bit usually in the limiter (eg ala PSP Xenon. I also see that PSP have released a special dither plugin which also looks very interesting.)
 
So how are you going to turn the 24 bit files down to 16 bit. You need to think that through.
 
Song order I can agree with because sometimes you may have to tweak the volume of a track that is sandwiched between two tracks and if that is changed for any reason then it may not need that gain adjustment after all.
 
Sweetwater in not in the business of mastering (sorry) they are in the retail business. Maybe you should reconsider a different mastering option.
 
Leaving that amount of headroom is the correct approach for sure. In Craig's case if I received a flat lined file that only peaked -6dB I would send it back and tell to remove what ever it was that was flat lining it in the first place. It means that some silly person has heavily limited the music somewhere and that is a form of mastering.
 
 
 
 
 
 
 

To reiterate (I love spell check) what Jeff said, 16 bit isn't good for mastering, as you would have to dither. You cannot (should not) dither before mastering. Dithering is done at the very end.
 
 
CJ

drewfx1
I'm always baffled by this "leave room" argument.
 
Do mastering engineers not request/use/understand floating point? Or do they, and this is supposed to be some sort of social engineering?

Most people who mix don't test for (or are even necessarily aware of) inter-sample distortion.

Jeff Evans
I am also a bit surprised that they are insisting on 16 bit files. That seems a bit odd to me. If you have done all the recording and mixing in 24 bit then the best way is to master is do all the mastering in 24 bit as well and dither down to 16 bit usually in the limiter (eg ala PSP Xenon. I also see that PSP have released a special dither plugin which also looks very interesting.)

 
Agreed. I'd rather that the mastering engineer do the dithering.

Leaving that amount of headroom is the correct approach for sure. In Craig's case if I received a flat lined file that only peaked -6dB I would send it back and tell to remove what ever it was that was flat lining it in the first place. It means that some silly person has heavily limited the music somewhere and that is a form of mastering.

 
You are welcome to use the term "faux mastering" free of charge
 
You'll appreciate this, Jeff: I once received a mix that was flat-lined due not to limiting, but clipping. So I sent it back and asked the person to give me a version that was down -6dB. So I got the same clipped version, but the peaks were at -6dB. Eventually we got it sorted out. It was worth it, I liked his music.

drewfx1
I'm always baffled by this "leave room" argument.
 
Do mastering engineers not request/use/understand floating point? Or do they, and this is supposed to be some sort of social engineering?

Quite right! If they just requested 32-bit files then levels wouldn't really matter. But while some will gladly accept any format you want to send them, others will be specific, perhaps asking for 24-bit files. I always assumed it was because they were using a PT HD system.
 
In this case they asked for 16-bit files, which while not the norm isn't entirely unheard of. They probably specified 44.1 as well. Perhaps it's like buying unfinished furniture: you save money by doing some of the labor yourself.

Egads... It seems very counter-intuitive that with the flaming that goes on about bit depth, sample rates, etc., that someone would then send the unfinished (but damn near done) product to someone else for "finishing" in significantly lower formats. That just makes me even more confused as to "what is the point?" Isn't that akin to taking a beautiful painting to be framed and having the framer say "no, no... you need to first sand that painting smooth... then we will frame it for you!"
 

bitflipper
Perhaps it's like buying unfinished furniture: you save money by doing some of the labor yourself.

I think I will head down this recommended path... even failing miserably as I learn, I will at least learn as I go... and I do have all of the tools, I just don't know how to use them well (yet).

peak at - 0.1 is fine for mastering. anything under zero. the headroom is determined more by the RMS. Usually pre-mastered mixes are round -19 - -20.0 RMS with the peak just under zero. That leaves the mastering engineer about 6 - 7 dbs of headroom to raise via multiband and/or brick wall limiter. (L2 threshold at -6 with peak at -0.2 with 16 bit dithering) This would result in a RMS of -13, a good CD volume.