Mastering Basics

The final stage of the production process can be critical.

By Rich Tozzoli

Mastering: It's an industry term that has long conjured up visions of guru-like professionals in super expensive rooms with esoteric audiophile speakers, performing black magic to help make finished tracks sound amazing. While the services of a great mastering engineer can never be marginalized, today's technology allowsmusicians and producers to optimize their finishedmixesmore than ever before.Whether you're preparing an MP3 for your website, uploading a rough mix to a client, or sending a demo out to a label, there are steps you can take to help give your tracks that extra sonic lift.

Start with a Good Mix
Mastering can make a good track sound great, but you generally can't turn a badsounding track into a good one just by mastering it. If you begin with a clipped 16- bit recording, you're cooking with bad ingredients.

The mix should be of the highest resolution possible (if digital) or should be printed to good analog tape. Fortunately, even moderately priced recording systems can record at 24-bit these days. As for sample rate, many pros think 44.1kHz is a better starting point than 48kHz if you're converting to CD quality. If you have the ability to record at 88.2kHz, 96kHz or above, go for it. Even MP3s will sound better if you record and mix at high resolution.

Back in the day, engineers only needed to concern themselves with stereo and mono mixes. Today, you may need to deliver two-channel mixes in both uncompressed and compressed formats, as well as discrete stems (tracks where the individual parts of a mix are kept separate—a common technique in video production). You may even be asked to generate something in surround sound— which itself comes in a variety of formats.

Don't print the final mix too "hot" by taking the audio to the limit. (And never ever go over that limit!) By leaving at least –3dB of headroom (up to –6dB is often recommended), you'll have a good foundation to work with later on. Getting an ideal output level is actually harder than it sounds. One of the problems of DAWs is that it's easy to clip (overload) the master bus— unpleasant sonic artifacts will result. If the summed tracks in your mix are making it distort, first try turning them all down by at least 1dB.

If you're afraid of sounding too digitally artificial, you can also send your mix out to an analog console, or use an analog summing mixer. Such products are available from Dangerous Music, Neve and SPL.

Although modern music tends to have a compressed sound, a good mix should retain dynamic range without distortion. Bob Katz's excellent book, Mastering Audio, the Art and Science, defines dynamic range as "the difference between the loudest and softest passages of the body of the music... The dynamic range of popular music is typically on 6-10dB, but for some musical forms it can be as little as a single dB." Without getting too technical, that single dB of headroom is a sticking point for many in our business— the dreaded "loudness war." However, if you "squash" your mix and remove all of its dynamic range, it may sound good (or just loud) in the short run, but will eventually fatigue the listener.

Pre-Mastering
Many engineers apply their own processing across the mix bus before printing a final, which is often referred to as "pre-mastering." Multi-platinum GRAMMY-winning producer/ engineer Bob Power has his own preferred gear for just such tasks. "It's usually a combination of the McDSP ML4000 Mastering Limiter, Sony Oxford Limiter— which is excellent, and a hardware analog limiter," he says. "The analog piece is the Pendulum Audio PL-2. It does the same thing as a software limiter but perhaps not quite as severely, keeping the depth and width of the mix."

You'll find a variety of high-quality software tools that can be used for pre-mastering. Products such as the Waves L3; TC Electronic's MD3 Stereo Mastering package; the Roger Nichols Digital (RND) Detailer; Massey's L2007 Mastering Limiter; and Universal Audio's Precision Limiter and Maximizer are just several of the products currently on the market. Note that Universal Audio also has a three-part tutorial DVD called Mastering with PC Workstations, for those who want to go deeper into the entire process.

Each software-based tool will have its pros and cons, which is why engineers such as Power often combine them with hardware. "With some software limiters, a lot of the front to rear depth disappears," he explains. "It happens because you're decreasing the dynamic range between the loud and soft things, so some of the finer detail moving back into the mix is going to disappear. I find my analog gear tends to keep more of that intact."

Just about any type of signal processing can be applied to your final mix, including dynamic compression and/or expansion, normalization, stereo enhancement, and equalization (EQ), which can save you when too much low-end bass information is overloading the mix buss. Any of the excellent EQ's available today can tame offending instruments such as electric and acoustic guitars, synth pads and even vocals. These often have information below 200Hz that may not always be necessary. By removing/filtering what you don't need, not only will you make your mix sound better, you'll have more space for other instruments to punch through. These same principles apply for the high frequencies as well.

Analyze This
One way to keep an eye on those frequencies and levels is to use an analysis plug in, such as Metric Halo's SpectraFoo or Waves PAZ analyzer.

RND Digital even has one you can download for free (RogerNicholsDigi tal .com) called the Inspector. It features a headroom indicator, clip checker, Master Alarm, Spectral Display, Balance and Peak/RMS meters. By using such tools, you'll really know what's happening inside that final mix before even printing it.

Surfing the Waveform
In addition to individual plug ins and hardware devices that integrate into your multitrack system, you'll find tools that specialize in mastering and editing. Waveform editors such as Steinberg's WaveLab 6 for Windows, and BIAS Peak Pro for Mac OSX, can handle final editing, mastering, noise reduction, CD burning, dithering and output of PQ Sub-codes, ISRC, CD-text and more—all in very precise detail. Another great software utility tool for Mac users is Snapper, from Audio Ease. Available as a 100-day free demo, Snapper can open over 50 sound file formats, and export to AIFF, WAV, or BWF. Even more useful, it can covert files into MP3 or M4A (an audio only extension of MPEG-4), while attaching them to an email—all in one click. You can even import an entire sequence of songs or a live show, make an individual selection, and send that out in a snap.

Pre-mastering and home editing are great if you're creating finals for media or the web, but if you're taking your work to a mastering engineer, don't over-process it beforehand. "If I'm preparing songs for mastering, I don't pre-master at all," noted Power. "With my more knowledgeable clients, I send them the raw mixes—they understand what the mastering engineer will do. For other people that just want to hear a song versus an album, I will usually 'bump it' up for them. But it's a really bad idea to do any sort premastering before you send it out for a [pro] mastering job."


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