What’s Going On Here?

It’s not easy being a mastering engineer these days. It sounds so simple – a little assembly editing, a little EQ, some compression, just tweaking clients’ tapes so they sound really good over REALLY good monitors in a REALLY GOOD room. Sounds like a lotta fun to me.

But there are clouds in paradise. In my last piece on mastering (October, 1998 issue of Recording) I mentioned a friendly little game played by clients called The “Make My Record LOUDEST Of All!” Game.” In this highly competitive blood sport, clients beg, threaten, cajole and extort the mastering engineer to get him/her to make their particular mixes sound louder than any other CD on the planet. They often bring in their favorite LOUD CDs and say, “Beat this!” Lotta fun, especially when you’ve got a stack of unpaid bills.

Now, this game is based on the assumption that the CD that is louder will sound better to consumers. We’ll consider that idea below. It also assumes that such louderness will translate into better record sales. Such assumptions are central to the process, but first we’ve got to consider the physics of the problem.

In digital audio, the loudest level without distortion we can have is 0 dB Full Scale (FS). Because there are no other bits available above this level, we encounter clipping instantly, and often that clipping is brutally offensive and violent. If we take a 0 dBFS sine wave and amplify it by, say, 60 dB, it will become a 1 kHz. square wave, with a level of +3 dBFS. We cannot reproduce a sine wave above 0 dBFS. Period.

With digital audio, then, the game has changed. We no longer have a safe and sane analog output level specification that has any correlation to perceived loudness, but rather a digital clipping specification: 0 dBFS, which is detected by a peak meter that gives no indication of perceived loudness and which lacks correlation to any VU or RMS sort of amplitude measurement (which does correlate well with perceived loudness). Interestingly, digital console manufacturers have acknowledged and standardized this, so that engineering practice has evolved into pushing the peak levels right up to 0 dBFS and treating that level as a “nominal overload level.” “Hot” mixes may cruise along at levels as loud as +22 dBu (10 volts RMS, 30 volts peak-to-peak)! To drive the point home even further, manufacturers have replaced the VU meter and its RMS-based brothers with a “peak” meter, which indicates ONLY the peak levels. Such levels are usually 6 to 20 dB hotter than VU levels, except for steady state tones, and there is no reasonable correlation between them, or with what we hear. In a nutshell, we’re now obsessing about peak levels instead of good levels, and ignoring our perceived loudness levels into the bargain.

Is Louder Really Better?

In my October article, I wrote, “One of the primary goals of mastering, as driven by client preference, is to make the CD as LOUD as possible. . . . The louder of two otherwise identical recordings will be preferred by end-users. The engineer that can most effectively push the level right up near 0 dBFS wins!”

I got some irate mail about this paragraph, and, frankly, I think the criticism is somewhat justified. While my statements reflect industry practice in a general way, they do not take into account the basic nature of the problem, and they make some unfounded assumptions. So, let’s go a little further with this subject.

What Does The Research Say?

Interestingly, I don’t personally know of any study that rigorously shows that a louder version of a recording is preferred to a softer one, but nonetheless any subjective test that doesn’t have precisely controlled levels will be regarded with suspicion as unreliable. I’ve casually assumed that someone did the research, probably years ago, and that that is why the practice is ingrained in all of us who do subjective testing.

Therefore, I suggest that it is safe for you to assume such a preference in listeners. I may actually test the assumption some day, especially if I can’t find any supporting research and can get someone to hire me to do the study. At the same time, my studio experience has been that, when comparing two otherwise identical versions of a recording, louder is better, within a range of normal listening levels. There is considerable psychological and neurological justification for such a principle, including increased intelligibility, emotional intensity and the adrenaline stimulation that are all caused by increased sound levels. However, such a phenomenon exists only as a function of the DIFFERENCE between two amplitude levels. A recording that is constantly loud defeats this effect, and usually ends up being tiring, irritating and generally unpleasant.

When we’re mixing, and compress a track and then compare between compressed and bypass, if the apparent loudness goes up when the compressor is engaged, we often get the mistaken impression the sound has “more energy, more punch,” when really, it's simply, well, louder! As soon as we adjust the compressor's gain so it has the same subjective loudness as the bypassed signal, we are often seriously surprised to hear that the compressor isn't doing anything good to the sound. Worse, we find it may be doing some really bad things. I’ve been bagged by this little mistake at least a zillion times!

Similarly, mastering engineers may use compressors to help the sound of a "flabby" or weak recording. But when such compression derives its impact primarily from increased loudness, we lose. The quality of the sound, including such essential musical and technical attributes as clarity, transient response and stereo separation, often goes down when too much compression is applied.

Are There Any Solutions?

How can we deal with this problem? This is where the whole thing enters the twilight zone. Except for one particular playback modality, the car, the whole problem shouldn’t exist! It shouldn’t matter whose recording is loudest (at least within limits), because the actual loudness of a recording in playback is under the direct control of the listener, and the limits of that loudness are not a function of 0 dBFS, but of the listener’s loudspeaker/amplifier system and listening environment! If the music is a little soft, the listener can simply TURN IT UP! It’s that simple!

The limits to this are (1) laziness, and (2) troubled environments, cars in particular. Laziness has been dealt with, sort of, with the general implementation of remote controls that have level adjustment on them. Cars are tougher, because of their extremely limited dynamic range. We’ll discuss that in a moment.