Do-It-Yourself Mastering

Feb 1, 2007 12:00 PM, By Michael Cooper

           

Mastering is essentially the art of applying signal processing to finished mixes in order to enhance them or correct perceived problems, sequencing the processed tracks in the desired order for playback, and exporting the resulting file in the correct format for delivery to the replication plant for mass production. Although mastering is a highly specialized process, so many affordable mastering-oriented products have been introduced to the market over the past several years that almost anyone can now master their own recording project. However, can doesn't always mean should.

Many engineers look to mastering as a solution for fixing a mix that has problems they can hear but can't quite figure out. For example, they might feel their mix lacks punch or is fatiguing to listen to but don't know how to make it sound otherwise. In this case, indiscriminately piling on additional processing during the mastering stage won't solve anything and could, in fact, make the finished masters sound a lot worse. Here it makes a lot of sense to hire a great mastering engineer to add fresh ears and skill sets to the project.

If, on the other hand, your mix has problems that you can readily identify and know how to fix, it makes more sense to remix than it does to try to correct a bad mix in the mastering stage. Because processing applied during mastering typically affects all elements of a mix, correcting one thing might make another thing sound worse. For instance, boosting EQ in the mastering stage to make a dull-sounding snare drum sound brighter might make vocals too sibilant or the cymbals sound harsh. (There are other ways to fix such a problem, which I'll discuss later.) In this case, it would be best to remix the song and apply needed EQ only to the snare drum track before mastering the project.

All that said, mastering can work miracles on poorly wrought material that cannot be remixed for some reason, such as when the multitrack master is lost or damaged or exists only in an obsolete format for which there is no playback mechanism. In that case, the 2-track mix may be all that is available to work with, and mastering is the only recourse to improve the program.

Mastering yields the best results when used to make great mixes sound even better. It can also make a program flow better from beginning to end by lending more consistent spectral balance and dynamics to all the mixes on a project so that no jarring changes occur (unless intended) from song to song. Also implicit in the mastering process is preparation of the premaster (the file or disc used for replication), which involves sequencing of songs (with gaps and track offsets), documentation (including CD-Text), preparation of reference discs (for auditioning and final approval), and delivery of the master in an error-free format that the replication house can handle.

In this article, I'll discuss what's involved in mastering your own stereo project for CD release. I'll begin with a brief overview of requirements for accurate room response and monitoring setup. Then I'll dive into how to optimize your work flow and evaluate what types of processing may be needed for your program material. Along the way, I'll give a small sampling of some of the mastering products currently on the market. We'll finish with a discussion of preparation of the premaster.

The main focus will be on do-it-yourself projects and not on running a commercial mastering studio. (See the sidebar “Do unto Others” for a brief overview of things to consider when mastering other people's projects.) For the sake of simplicity, I'll talk about mastering an album project inside a DAW, but most of what I'll discuss also applies to other mastering scenarios.

Go to Your Room

It is absolutely vital that your mastering work be performed in a room that has highly accurate frequency, phase, and reverb responses. Trying to master your project in an inaccurate room makes as much sense as doing color photo touch-ups while wearing tinted sunglasses. Likewise, unless your monitoring setup is flat and can accurately reproduce the entire audible frequency spectrum, how can you confidently decide which frequencies need adjusting on your program? If you can't truly hear what is going on with your source material, you're just shooting in the dark.

While a full-blown examination of room acoustics, control room equalization, and monitoring setups is way beyond the scope of this article, a few points bear mentioning here. (For an in-depth look at tuning your control room, see “Truth or Consequences” in the November 2001 issue of EM, available online at www.emusician.com.) First, learn what room modes (those narrow peaks or dips in frequency response) your room exhibits and keep them in mind while mastering. Before boosting or cutting EQ at or near any room-mode frequencies, listen to the same program from a position in the room where those same modes are not being reinforced to determine if corrective EQ is really needed. Mastering can be effectively performed in a room that has only minor imperfections in response if you know what those imperfections are and compensate for them.

Room tone is another matter. You should make sure the RT60 (essentially the reverb decay time) is not skewed in any one frequency band in your room. Otherwise, you may end up cutting bass frequencies, for example, simply because your room reverberates longer in that band than elsewhere throughout the spectrum and not because there is excess bottom end in your mix.

Get with the Program

You should have at least two pairs of monitors on which to evaluate the program. One pair should be full range (extending at least down to 35 Hz or so) or be paired with a subwoofer to extend bass response. The second pair should ideally be band limited (that is, bass deficient) to provide you with an idea of how the finished product will sound when played back on small consumer systems.

Full-range monitors suitable for use in mastering are too numerous to list here. But strangely, there are relatively few high-quality band-limited models on the market, so I can make some recommendations: the Yamaha HS50M and NS-10M Studio (the latter model is discontinued) and the Avant Electronics Avantone MixCubes are the best I've heard for this purpose. Most other tiny close-field monitors I've auditioned attempt to sound like a big speaker in a small box and have way too much bass response to serve as a proxy for small consumer-playback systems (not to mention that their bass response usually becomes highly inaccurate when placed on workstation shelves or a console meter bridge).

Both pairs of monitors (full range and consumer proxy) and the subwoofer should be wired to a switch box (or patched to separate control-room outputs on your mixer) so that you can select playback on either pair — alternately with and without the subwoofer engaged — at the push of one or two buttons. Depending on the capabilities of your gear, you may need to wire up a custom setup to allow simultaneous playback on one pair of satellites and sub. By switching among different playback references while working, you'll be able to tell if your mastering changes will sound good across a variety of audiophile and low-end consumer-playback systems.

Equally important to having high-quality monitors is knowing their inherent frequency limits (bass and high-frequency rolloffs). For example, I know my NS-10M Studio monitors don't reproduce bass frequencies below 60 Hz very well. If I hear boomy bass guitar frequencies on my full-range monitors but the boominess disappears when I switch to my NS-10M Studios, I know the problematic frequencies lie below 60 Hz. And if I listen to playback on my subwoofer only (with satellites muted) and a boomy acoustic guitar track completely disappears, I know the boomy frequencies lie above the 110 Hz high-frequency cutoff of my sub.

During your mastering sessions, you'll occasionally and very briefly want to check your work at a loud volume to make sure extreme low and high frequencies are in proper balance with the rest of the spectrum. (Compared with the midrange band, the human ear is less sensitive to the extreme frequency ranges at low listening levels.) But avoid listening fatigue by resisting the urge to listen at loud levels for more than just a few minutes spread out over each day. And as the day progresses, take more frequent breaks to rest your ears and gain a fresh perspective.

Drag-and-Drop

At the beginning of the mastering session, your first task is to import all your mixes into your digital audio workstation (unless they are on tape, in which case any desired analog processing should be applied before you bring those tracks into your DAW). This is usually accomplished by simply dragging-and-dropping each file into the appropriate folder or window in your DAW and, from there, into a blank track. If at all possible, you should be working with 24-bit files for your mixes.

After importing all the audio files for an album project, I will listen through virtually the entire project and make notes for each song as to what types of signal processing may be needed to correct problems or further enhance what's already good. (I'll discuss what some of those treatments might be in a bit.) This gives me a plan of attack for each song while my ears are their very freshest. It also reveals at a glance whether the same problems repeatedly crop up in most or all of the mixes. For example, I often hear unnecessary boosts or cuts in the same bass band for every song when a project was mixed in an inaccurate control room. In such a situation, the engineer compensated for a problem with their mixes that simply didn't exist, and part of the mastering process is to undo that equalization and restore spectral balance.

As I'm listening through and evaluating the project's mastering needs, I'll place markers at the beginning of each song. That will later allow me to quickly jump from songs for which I've already rendered signal processing and level changes to the one I'm currently working on, to check for consistency or artistic compatibility of spectral balance, dynamic range, and so on.

I will also place markers where at least one significant peak for each song occurs. This allows me to make comparisons between songs at those points to ensure that no song is much louder or softer, or more dynamic or compressed, than the others in the finished product. More >>>

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