Panning and Stereo at Mixdown

We live in a stereo world. We hear our environment with our two ears, and our brains calculate the distance and direction of sound sources from the information they receive.
Pan pots change the relative amount of a mono signal being sent to the left and right speakers. Pan is short for 'panorama', and the pan pots let us simulate some of the aural cues that give us a sense of direction.

Bass-Heavy Sounds

Bass-heavy sounds and lead vocals need to be panned centrally so the load is shared equally between the two speakers. This creates an anchor point for the mix.

The 'Live' Effect

Panning is often used to approximate the way performers might be arranged on stage. This is known as creating a 'sound stage'.

How Wide?

Don't be tempted to pan stereo signals (pianos, drum overheads etc) hard left and right; psychoacoustically you'll end up with a 20 foot long instrument! Try panning ½ left and ½ right, or hard pan on one side and panned centrally on the other.

The Hard Instruments

Guitars, brass, keyboards and similar instruments can be panned to either side, as can backing vocals. It only takes a couple of instruments panned 'wide' to create an impressive sense of space.

Stereo Reverb and Stereo Positioning

Stereo reverb outputs are always panned hard left and right.
No matter where the original signal is panned, the reverb will come equally from both sides. This mimics what happens in real life.
This effect can 'dilute' the panning of the original signal, and replace it with a sense of stereo 'space'.

A pan pot splits a mono signal from the output of a fader and varies the level difference between the two signal. A balance control is used on stereo signals, and varies the relative levels between the two channels.
A pan pot feeds the mix bus using logarithmic curves.

Panning Law

Prevents a centrally panned signal from being too subjectively loud. Left unchecked, a centrally panned signal will be twice as loud in terms of sound power (3dB higher) than when the sound is hard panned. Some desk designers incorporate a -3dB drop in both L and R levels when panned centrally to avoid this. However, when these two (identical) levels are summed to mono there is a 6dB rise in voltage, so some desks incorporate a -6dB central pan attenuation. This works best for mono compatibility, but the 3dB attenuation is best for stereo reproduction. As a result of this confusion, many desks now use a compromise attenuation on each side of the signal of 4.5dB.

Psychoacoustically, we only need around 18dB difference in level between left and right to make it feel as though the signal has been panned hard left or right, but most desks provide full attenuation panning anyway.

Delay Panning

Introducing a time difference between the left and right signals mimics the interaural time difference (ITD). Insert a stereo Sample Delay on a mono track and delaying one side by anything up to 30ms (at a 44.1 kHz sample rate, 1ms = 44.1 samples). Stereo tracks are less effective. A stereo Sample Delay can also be placed on a bus, so that audio objects can send a percentage to be delay panned.
Remember to check out the result in mono for phase problems.

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