What is a pan law?

Pan law in plain English

A pan knob places a mono sound between two speakers by playing it louder in one than the other. Hard left, the left speaker plays it at full level and the right is silent. Turn the knob to the middle and both speakers play it, which makes the sound seem to come from a point halfway between them, called the phantom centre.

Two speakers playing the same thing are louder than one. If the pan knob left both at full level in the middle, every sound would jump up in volume as you centred it and fall back as you moved it out. The pan law is the correction: at the centre it turns both speakers down by a fixed amount, and between the centre and the edges it follows a curve that the law also defines.

That fixed amount is the number in the name. A −3 dB pan law plays a centred sound 3 dB down in each speaker, and a −6 dB law plays it 6 dB down. Counted this way, every law agrees at the edges, where one speaker is at full level and the other is silent, so what changes from law to law is what happens on the way across.

For the bigger picture of how two channels combine, and what goes wrong when they cancel, start with what phase is. This page stays on the levels.

Why does a centred sound get louder?

It depends on how the two copies add up, and they add up differently in a room and in a mono sum.

When the two signals are added electrically, as they are in a mono sum, they are perfectly in step and their levels add like numbers. Two copies at full level make a wave twice as tall, which is 6 dB louder. To get back to where one speaker on its own started, each copy has to come down by 6 dB, to half its level.

Through two speakers into a room the copies reach your ears at slightly different times, from different directions and with reflections off the walls mixed in, so for most of the frequency range it’s their power that adds up. Two equal sounds adding by power come out 3 dB louder than one, and the fix for that is 3 dB down in each speaker. Very low frequencies have wavelengths long enough that the two speakers stay in step at your ears, so down there the result sits nearer the 6 dB end.

So there are two right answers, and that’s why more than one pan law exists. −3 dB keeps a sound’s loudness constant in stereo and −6 dB keeps it constant in mono; the other common laws sit between them, apart from 0 dB, which corrects for neither.

The common pan laws

The figures below are for a mono sound panned dead centre, compared with the same sound panned hard to one side. The lab draws each law’s full curve when you pick it.

0 dB

No correction at all. At the centre both speakers play the sound at full level, and as you pan away from a speaker, only that speaker fades. A centred sound comes out 3 dB louder than a hard-panned one through speakers and 6 dB louder in mono. Its one advantage is that a centred track plays at exactly the level its fader shows, but it makes panning change the balance of a mix more than any other law.

−3 dB, equal power

Each speaker gets the cosine or the sine of the pan angle, where hard left is 0° and hard right is 90°. At the centre both are cos 45°, which is 0.707, or −3 dB. The squares of the two levels always add up to one, which means the total power coming out of the speakers never changes, so a sound keeps the same loudness wherever you put it in stereo. That’s why −3 dB is the usual default, and why you’ll also see it called equal power, constant power or sine/cosine panning.

The cost shows up in mono. 0.707 plus 0.707 is 1.414, so a centred sound is 3 dB louder in the mono sum than a hard-panned one.

−4.5 dB

A compromise between the two. Its curve sits halfway between the equal power and linear curves in decibels, so each speaker is at about 0.59 at the centre. In stereo a centred sound comes out 1.5 dB quieter than a hard-panned one, and in mono 1.5 dB louder. You trade a small error in both places for a large error in one of them.

−6 dB, linear

Each speaker’s level falls in a straight line from 1 to 0 as you pan away from it, so at the centre both sit at 0.5. The two levels always add up to one, which keeps the mono sum the same at every pan position, and that’s where its other name, the constant amplitude law, comes from. In stereo, though, a centred sound comes out 3 dB quieter than a hard-panned one, so a sound you sweep across the speakers seems to sink as it passes the middle.

−2.5 dB and compensated laws

−2.5 dB is a touch less than equal power. Older versions of Pro Tools used it, and current ones still offer it as a Pan Depth option. Centred sounds come out about 0.5 dB louder than hard-panned ones in stereo and 3.5 dB louder in mono, so it behaves almost exactly like −3 dB.

A compensated law, like the “−3 dB compensated” option in Logic Pro, uses the same curve as its plain version with everything raised to put the centre back at 0 dB. A centred sound plays at the level its fader says, and a hard-panned one comes out 3 dB above it. The tracks sit against each other exactly as they would with the plain −3 dB law, so it changes your fader positions without changing the mix.

Pan laws in stereo and in mono

Each row is a law. The last two columns show how loud a centred sound is compared with the same sound panned hard to one side, first through two speakers and then in a mono sum.

Read down the last two columns and they always differ by 3 dB. No pan law can make a sound hold its level in stereo and in mono at once, because a room adds the speakers by power and a mono sum adds them by amplitude. Choosing a law means choosing which of the two to get right.

Reading the lab

The lab plays every sound in mono, because a pan law is about placing a single mono signal between two speakers. Pick a law along the top and move the Pan knob, or press Sweep and the sound travels from hard left to hard right and back every six seconds at an even speed. Sweeping is the quickest way to hear what a law does.

The big screen draws the law. Pan position runs along the bottom, and the teal and pink lines are how loud the left and right speakers play the sound at each position. The ivory line is the total through two speakers and the amber line is the total in mono, both measured against the same sound panned hard to one side, and whichever of the two you’re listening to is drawn solid. The lab measured these lines by stepping a constant signal through its own panner, the same one you hear.

The goniometer under it plots left against right. A mono sound always draws a single straight line, and panning tilts it: straight up is the centre, and the two diagonals are hard left and hard right. Next to it, the bar screen shows all four laws at your current pan position, so you can see how far apart they are at any point. The panel on the right gives the levels of the loop itself, measured through your settings.

Press Mono, or M on the keyboard, to hear both speakers added together the way a single speaker would play them. You can use your own sound too. Upload a file or record eight seconds with the Record button, and it plays through the lab in place of the vocal without leaving your device.

Which pan law should I use?

Use your DAW’s default, which is −3 dB or close to it in most of them, and settle it before you start mixing. −3 dB is right for the way most people hear a mix, through two speakers or headphones. The parts that come up in mono are the centred ones, usually the vocal, kick, snare and bass, and most mixes can afford to have those a little louder on a phone speaker.

The exception is music that will mostly be heard in mono, like a jingle meant for phone speakers or a mix for a mono PA. There, −4.5 or −6 dB stops hard-panned parts dropping back when the mix folds down.

Whichever you pick, staying on it counts for more than the choice. You balance a mix by ear, so any law sounds right while you’re working. Trouble only starts when the law changes underneath a finished balance and every panned track moves against every centred one.

Where to find the pan law in your DAW

Most DAWs keep the pan law in the project or session settings instead of on the mixer, because it applies to every channel at once. Logic Pro has a Pan Law menu in the project’s audio settings with 0 dB, −3 dB and −3 dB compensated. Cubase and Nuendo have Stereo Pan Law in Project Setup, with 0, −3, −4.5 and −6 dB and Equal Power, which is Cubase’s default. Pro Tools calls it Pan Depth, in Session Setup, with −2.5, −3, −4.5 and −6 dB.

If you can’t find the setting, measure it. Put a sine tone on a mono track, pan it hard left and note the level on the left meter, then centre it and read the left meter again. The difference is your DAW’s pan law.

Panning a stereo track

Everything above is about mono tracks, where one signal gets shared between two speakers. A stereo track already has its own left and right channels, and in most DAWs its pan knob is a balance control. Turn it left and the right channel gets quieter while the left stays at full level. Nothing crosses from one speaker to the other, so a hi-hat on the right of a stereo drum loop gets quieter as you pan left without ever moving.

To move a stereo track properly, use a stereo panner or a dual pan mode, which places each channel separately. Logic’s Stereo Pan mode, the two pan controls Pro Tools gives a stereo track and Ableton Live’s Split Stereo Pan mode all work this way. Narrowing the track with a width control and then panning it also works, and the stereo width lesson covers that side of it.

How to choose and check a pan law

1. Check the setting before you mixOpen the project settings and see which law the session uses. If you’re going to change it, do it now, while nothing is balanced yet.
2. Leave it alone from then onChanging it later shifts every panned track against every centred one by 3 dB or more.
3. Balance the mix by earSet levels with the panning in place. A sound in its final position at the level that sounds right is right, whatever the law.
4. Check it in monoFold the master to mono and listen to the hard-panned parts. With −3 dB they drop back about 3 dB against the centre, and if a guitar or keyboard part disappears, bring it in from the edge a little.
5. Keep the law when you move a sessionIf you open the project in another DAW, set the same law there first, or bounce stems and rebuild from those.

Common pan law mistakes

Changing the law mid-mix

It looks like a harmless setting, but switching from −3 to 0 dB lifts every centred track by 3 dB against the hard-panned ones. The vocal comes forward and the guitars sink behind it.

Blaming the pan law for a mono problem

A pan law only moves levels, by a few decibels. If a part gets thin, hollow or vanishes in mono, look for a phase problem instead: a stereo widener, a short delay between the sides or a polarity flip. The mono compatibility lesson goes through those.

Expecting a stereo track to pan like a mono one

On a balance control the far channel just gets quieter. If you pan a stereo synth left and its right-hand notes fade out without moving across, switch the track to a stereo or dual panner.

Forgetting the law when you automate a pan

A moving pan shows the law more than any fixed position does. With −3 dB an auto-pan holds its level in stereo and pulses by 3 dB in mono each time it passes the middle; with −6 dB it stays level in mono and dips in stereo. Check automated pans both ways.

Train your ears

The quiz under the lab sweeps a sound across the speakers with a hidden pan law, sometimes in stereo and sometimes in mono, and asks whether the level rises, falls or holds as it passes the centre. Some rounds use pink noise, which makes the change easiest to hear. Eight rounds take about three minutes, and your best score stays in your browser.

Questions people ask

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