The Truth About Panning Laws

Ignorance of the law is no excuse—in this case, panning laws

By Craig Anderton

The idea of panning seems pretty obvious, right? You turn a panpot (real or virtual) to place a sound somewhere in the stereo field. However, the end result depends not just on the stereo position, but also on whatever panning laws your DAW or hardware mixer follows.

These laws govern exactly what happens when a monaural sound moves from left to right in the stereo field, which can be different for different pieces of software. In fact, not knowing about panning laws can create some significant issues if you need to move a project from one host to another. Panning laws may even account for some of the online foolishness where people argue about one host sounding “punchier” or “wimpier” than another when they loaded the same project into different hosts. It’s the same project, right? So it should sound the same, right?

Well, not necessarily…keep reading.

ORIGINS OF PANNING LAWS

Panning laws originated in the days of analog mixers. If there was a linear gain increase in one channel and a linear gain decrease in the other channel to change the stereo position, at the center position the sum of the two channels sounded louder than if the signal was panned full left or full right.

To compensate for this, it became common to use a logarithmic gain change response to drop the signal by -3 dB RMS at the center. You could do this by using dual pots for panning with log/antilog tapers, but as those could be hard to find, you could do pretty much the same thing by adding tapering resistors to standard linear potentiometers. Thus, even though signals were being added together from the left and right channels, the apparent level was the same when centered because they had equal power.

But this “law” was not a standard. Some engineers preferred to drop the center level a bit more, either because they liked the signal to seem louder as it moved out of the main center zone, or because signals that “clumped up” around the center tended to “monoize” the signal. So, dropping their levels a little further created more of an illusion of stereo. And some of the people using analog consoles had their own little secret tweaks to change the panning characteristics.

PANNING MEETS THE DIGITAL AUDIO WORKSTATION

With virtual mixers we don’t have to worry about dual ganged panpots, and can create any panning characteristic we want. That’s a good thing, because it allows a high degree of flexibility. But it also adds a degree of chaos that we really didn’t need.

For example, Steinberg Cubase has five panning laws in the Project Setup dialog; you get there by going Project > Project Setup and choosing the Stereo Pan Law drop-down menu (Fig. 1).

Fig. 1: Cubase’s documentation states that the program’s default pan law is the classic -3 dB setting.

Setting the value to 0dB eliminates constant-power panning, and gives the old school, center-channel-louder effect. Since we tried so hard to get away from that, it’s not surprising that Cubase doesn’t defaults to it. You can also choose to drop the center by -4.5dB or -6dB if you want to hype up the extremes somewhat, and make the center a bit more demure. Fair enough; it’s nice to have options. However, note that if you use RME’s Hammerfall DSP audio hardware, you should set the card’s preferences to -3 dB.

Adobe Audition has two panning options. L/R Cut Logarithmic is the default, and pans to the left by reducing the right channel volume, and conversely, pans to the right by reducing the left channel volume. As the panning gets closer to hard left or right, the channel being panned to doesn’t increase past what its volume would be when centered. The Equal Power Sinusoidal option maintains constant power by amplifying hard pans to left or right by +3dB, which is conceptually similar to dropping the two channels by -3dB when the signal is centered.

Cakewalk SONAR takes the whole process further with six different panning options (Fig. 2), which means you can not only choose the panning law you want for SONAR, but the odds of being able to match another host’s panning law are very good. You can access these by going Preferences > Audio.

Fig. 2: SONAR lets you choose from six different pan laws.

In the descriptions below, “taper” refers to the curve of the gain and doesn’t have too radical an effect on the sound. The six options are:

• 0dB center, sin/cos taper, constant power. The signal level stays at 0dB when centered, and increases by +3dB when panned left or right. Although this is the default, I don’t recommend it because of the possibility of clipping if you pan a full-level signal off of center.
• 0dB center, square root taper, constant power. This is similar, but the gain change taper is different.
• -3 dB center, sin/cos taper, constant power. The signal level stays at 0dB when panned right or left, but drops by -3 dB in each channel when centered. This is the same as the Cubase default panning law.
• -3 dB center, square root taper, constant power. This is similar, but the gain change taper is different.
• -6 dB center, linear taper. The signal level stays at 0dB when panned left or right, but drops by -6 dB when centered. This is for those who like to hype up the sides a bit at the expense of the center.
• 0dB center, balance control. The signal level stays constant whether the signal is in the left channel, right channel, or set to the middle.

Fig. 3 shows what happens when  a mono signal of the same level feeds a fader pair, and each pair is subject to different panning laws. Note the difference in levels with the panpot panned to one side or centered. The tracks are in the same order as the descriptions in SONAR’s panning laws documentation and the listing in preferences. Although the sin/cos and square root versions may seem to produce the same results, the taper differs across the soundstage between the hard pans and center.

Fig. 3: How panning laws affect signal levels.

SO WHICH IS THE BEST LAW TO CHOOSE?

As laws go, this particular one is pretty unspecific. In fact, if you compare the three programs mentioned above, they all default to a different law! This can become a real problem when you move a project from one host sequencer to another—unless the selected panning laws match, look out. I often wonder if when some people say a particular host sounds “punchier” than another, the “punchy” one boosts the level when signals are panned hard left or right, while the “unpunchy” one uses the law that drops the level of the center instead.

For example, suppose you move a SONAR project to Cubase. It’s going to sound softer, because Cubase drops the center channel to compensate, while SONAR raises the left and right channels to compensate. Conversely, if you move a Cubase project to SONAR, you might have to deal with distortion issues because signals panned hard left and hard right will now be louder.

But where these laws really come into play is with surround, because here you’re talking about spatial changes among more than just two speakers. Bottom line: Be consistent in the panning law you use, and document it with the file if a project needs to be moved from one platform to another.

Personally, I go for the tried-and-true “-3dB down in the center” option. I designed analog mixers to have that response, and so I’m more than happy to continue the tradition within the various sequencer hosts. Also, this is one option that just about every host provides, whereas some of the more esoteric ones may not be supported by other hosts.

SO WHAT DOES IT ALL MEAN?

We can’t sign off without mentioning one more thing: The pan law you choose isn’t just a matter of convenience or compatibility, although I’ve stressed the importance of being compatible if you want to move a project from one host to another. The law you choose can make a difference in the overall sound of a mix.

This is less of an issue if you use mostly stereo tracks, as panning in that case is really more of a balance control. But for many of us, “multitrack” still means recording at least some mono tracks. I tend to record a mono source (voice, guitar, bass) in mono, unless it’s important to capture the room ambience – and even then, I’m more likely to capture the main sound in mono, and use a stereo pair of room mics (or stereo processing) that go to their own tracks. And if you pan that mono track, you’re going to have to deal with the panning laws...but at least now you know how not to break them.

Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.