This article will give you a quick overview on how to properly prepare your audio tracks for mastering process. The more you follow below suggestion, the better your masters will be.
Plug-ins on the Master Output
It’s best to mix without anything on the master output but if you are using plug-ins on the master output during mixing, then export two versions for mastering: One version with plug-ins enabled on the master output and one version with all plug-ins off. Make sure clipping does not occur in any of the versions. If the master output is clipping simply lower the master fader.
Having two mix versions gives us the choice in case you over- processed the master bus.
When we talk about clipping in this guide we are talking about digital clipping. Some people find analog clipping very useful and can give your mix some interesting twist on individual channels. However digital clipping is never pleasant or desirable and can cause serious problems down the line so it must be avoided at all times.
Headroom
Headroom is the amount of dB before your mix is clipping and the overload indicator lights up on your master channel. When your mix is clipping, simply lower the master fader until the highest peak is between -12 and -3 dBFS (Decibels relative to Full Scale)
Sound quality will not be affected when lowering the fader.
While mixing the amplifier’s “volume” knob is your friend and digital clipping is your enemy.
There is no reason to maximize the master level during mixdown.
Tips for Mixing
Phase and polarity
Check to see if recorded sounds are not too much out of phase. Common problems are synthesizer sounds with too much anti-phase and applying a fake stereo spreader. Check your mix in mono playback. If sounds almost or entirely disappear, fix it.
Most professional sequencers include a correlation meter to check for phase problems or you can use plug-ins for this. +1 means in phase (mono). -1 means out of phase.
Sub frequencies
Loud or unnecessary sub frequencies (below 40 Hz) in individual tracks can cause problems with the sound quality and the final level of the master. Make sure you low cut all tracks that do not contain meaningful sound in the sub frequencies (such as hi-hats, vocals etc). You can use a frequency analyzer for this.
Noise
Gate or mute individual channels or groups when they are not active. This is especially important in the quiet parts where it will be most audible.
Vocal levels
An uneven vocal is difficult to fix in the mastering process. Sometimes two compressors with a low ratio is better than one compressor with a high ratio. Even with correct vocal compression you often still need to do volume automation. Turn individual passages or words up or down until everything is smooth and clearly audible. Listening at a low level while adjusting makes it easier to hear differences.
Start/End
Export your mix at least one bar before it actually starts and include some extra bars at the end to ensure reverbs, delays, and instrument decays have faded out completely. This way we also know we have the entire audio file.
File Format
WAV or AIF is preferred. MP3’s are not suitable for mastering.
Stereo Format
Choose interleaved stereo and not split stereo when bouncing or exporting your mix.
If your sequencer does not give you a choice of stereo format then it is most likely using interleaved stereo. Interleaved stereo uses one single stereo file.
Bit Resolution
24bit!
16 bit files are only used whenever it is not possible to get a 24 bit file of the same mix. Check your DAW settings to export in 24 bit. 32 bit floating point is identical to that of the 24 bit fixed format, it just takes up more space, and is slower to data transfer.
Sample Rate
44.1 kHz or higher.
Only export in higher than 44.1 kHz if your project is actually recorded and processed at that rate. If your project contains different sample rates then do not convert sample rates.
Dithering and Noise Shaping
Do not use noise shaping or colored dither, e.g. UV22 or POW-r when exporting your mix for mastering.
The final bit reduction to 16 bit (audio CD format) is performed by us as the last step of the mastering process.
Normalizing:
Don't!
Normalizing just raises the signal level in an unnecessary way, and it will change the amount of headroom left in the mix. The final level of the mix will be optimized by us.
Listen to Your Mixdown
Sending a new mix will mean a new mastering so it’s important to listen to the exported file from the beginning to the end before sending. Make sure everything is playing correctly, that the beginning and end are intact, and that no artifacts or click sounds occur. It’s advised to do this a day after you have completed the mix, giving you a fresh ears and a fresh perspective.
Delivering Files on a CD
If you can’t or don’t want to upload you tracks thru the website you can burn your CD as a data CD. Do NOT make an audio CD. An audio CD will reduce your 24 bit files to 16 bit files.
Check that your burned data CD is readable on your own computer and that the data can be copied to your hard disk without errors. Doing this before sending the CD in the mail can save us both a lot of time.
Song Order and Other Notes
Let us know about wishes for the mastering. You can do this in the upload form. We will notice any problems and enhance the sound in the right places. If mastering can’t fix specific issues in your mix we will contact you to discuss the best route in solving it. If you have special wishes for pauses between tracks or bonus tracks then let us know in advance.
Evaluating Your Master
Listen to your master in the same places where you normally listen to your music: in your living room, in your studio, in your car, on your iPod or on your computer.
Use the same volume level as you normally do. If you like to play loud in the studio, then play your master loud. If you play at low levels in your living room then set the volume low. This will give you the best grounds for comparison. A well rounded mix and master will work at all levels.