A good look at digital mastering, by Max Read
What Is Mastering?
Once recorded and mixed, there is one more very important stage that can make a dramatic difference to the sound of your tracks - mastering.
Mastering involves a combination of different processes on the raw mix to achieve a variety of effects. Different kinds of music require different approaches; for example an unplugged acoustic song would sound very nasty with the kind of mastering used for a rock song. The end result can then be optimised for CD duplication.
Until recently, mastering was the exclusive trade of posh studios with hundreds of thousands of pounds worth of highly sophisticated equipment. Now, the power of a modern PC enables high quality digital mastering to be done on a much lower budget.
A mastering session involves listening to each track individually and fine tuning the mix, paying attention to the amount of bass, overall presence, dynamics and perceived volume. Sometimes it may be necessary to 'fix a mix', for example if the vocals are too quiet it is sometimes possible to pick them out with a bit of added eq. at just the right notch. Good mastering is the "icing on the cake" for any track.
A good mastering will add clarity, depth, 'air' and also perceived volume to a mix. Whereas a bad mastering may just add a lot of volume and distortion!
It is important to note that the skills and experience of a mastering engineer working in a purpose-built room with calibrated equipment is by far preferable.
Too Much Limiting
The most critical aspect of mastering is to get the program material to the right volume (average R.M.S. level to be precise, with 0dB being the maximum level). An increase in RMS level can be achieved by using compression/limiting - the more compression, the louder the track sounds but the less dynamic range it has. Increased compression/limiting is potentially damaging to the program material, resulting in a distorted, crowded, unnatural sound.
"Clients must be informed that they can't get something for nothing; a hotter record means lower sound quality!" - Bob Katz - legendary Mastering engineer.
There are no rules about how loud a CD should be. In fact, the average level of CDs has been edging up year after year since their inception and a kind of 'Loudest CD Contest' has emerged. The chart below says it all:
* chart courtesy of Bob Katz' great article
"I listened to all the CDs submitted to NARAS for consideration in the 'Best Engineered Non-Classical' Grammy category. We listened to about 3 to 4 cuts [from the 267 albums submitted]. Every single CD was squashed to death with no dynamic range...the Finalizers and plug-ins were cranked to 'eleven' so that their CD would be the loudest... Not one...attempted to take advantage of the dynamic range or cleanliness of digital recording." - Roger Nichols - Grammy winning engineer for Steely Dan, Beach Boys and more - Jan. 2002 Eq Magazine
So, what is the best level to aim for? Well, for most 'pop' music with drums, somewhere between -10 and -14 is a good place to be.
"Note that there is a point of diminishing returns above about -14 dBFS. Dynamic inversion begins to occur and the program material usually stops sounding louder because it loses clarity and transient response." - Bob Katz
What Does This All Mean To Us?
At The Lodge we try to make sure that the client is made aware of the above issues at mastering time. The bottom line is that - however tempting - it is not a good idea to try and make your CD the loudest that was ever made.
What is a CD ROM Master?
It’s a DATA CD that can be read on a PC or Mac that usually contains .WAV files. The studio will usually provide you with a CD ROM Master if you intend to copy the tracks to a PC then create your own copies.
A CD ROM contains error correction so you know that your files will be glitch free if you copy them from a CD ROM.
An audio CD may contain small errors which you don’t hear (unless they are big scratches) because your CD player uses error concealment to smooth them over. When you 'rip' a CD these errors are not always corrected.
What is a Red Book Master?
It’s just a standard Audio CD that you can play in any standard CD player.
A standard CD-Audio (Compact Disc Digital Audio) has a maximum capacity of 79 minutes. This standard was established by Philips and Sony in what is known as the 'Red Book'.
The most important thing is that your Master disc should be burned in what's called 'Disc At Once Mode' (DAO) (Not Track At Once or Session At Once), which may happen if u use Media Player for example. It should also be burned at a speed lower than the maximum speed that the burner can manage.
What is a Glass Master?
A Glass Master is used in CD replication to make proper CDs like the ones you buy in shops. The data from your Red Book Master is transferred to a photo-sensitive layer on a glass disc. A photo-chemical process then etches the glass to create a mask. The Glass Master is then used in the replication machine and can be re-used to run off future copies.