The default stereo panner distributes 2 inputs to 2 outputs. Its
behaviour is controlled by two parameters, width and position. The
default settings for the stereo panner are width=100%,
position=center (L=50%, R=50%). This panner assumes that the signals
you wish to distribute are either uncorrelated (that means totally
independent), or they contain a stereo image which is
mono-compatible
With the default values it is not possible to alter the position, since the width is already spread entirely across both outputs. To alter the position, you must first reduce the width.
The panner user interface consists of 3 elements, divided between the top and bottom half. Click and/or drag in the top half to control position; click and/or drag in the bottom half to control width (see below for details).
In the top half is the position indicator, which shows where the center of the stereo image is relative to the left and right edges. When this is the middle of the panner, the stereo image is centered between the left and right outputs. When it all the way to the left, the stereo image collapses to just the left speaker.
In the bottom half are two signal indicators, one marked "L" and the other "R". The distance between these two shows the width of the stereo image. If the width is reduced to zero, there will only be a single signal indicator marked "M" (for mono), and whose color will change to indicate the special state.
It is possible to invert the outputs (see below) so that whatever would have gone to the right channel goes to the left and vice versa. When this happens, the entire movable part of the panner changes color to indicate clearly that this is the case.
Although the implementation of the panner uses the "position" parameter, when the user interface displays it numerically, it shows a pair of numbers that will be familiar to most audio engineers.
| Position | L/R | English |
|---|---|---|
| 0 | L=50% R=50% | signal image is midway between left and right speakers |
| -1 | L=100% R=0% | signal image is entirely at the left speaker |
| 1 | L=0% R=100% | signal image is entirely at the right speaker |
One way to remember this sort of convention is that the middle of the USA is not Kansas, but "Los Angeles: 50% New York: 50%".
| Appearance | Settings |
|---|---|
| Width=100%, L=50 R=50 |
| Width=0%, L=50 R=50 |
| Width=-100%, Position = 0 (center) |
| Width=36%, L=44 R=56 |
| Width=0%, L=0 R=100 |
Mouse operations in the upper half of the panner adjust the position parameter, constrained by the current width setting.
Mouse operations in the lower half of the panner adjust the width parameter, constrained by the current position setting.
To change the position smoothly, press the right button and drag within the top half of the panner, then release. The position will be limited by the current width setting. Note: you do not need to grab the position indicator in order to drag
To change the width smoothly, press the right button and drag within the lower half of the panner, then release. The width will be limited by the current position setting.Note: you do not need to grab the L/R indicators in order to drag
When the pointer is within a stereo panner user interface, the following keybindings are available to operate on that panner:
When the pointer is within a stereo panner user interface, the scroll wheel may be used as follows:
Note that the stereo panner will introduce unwanted side effects on
material that includes a time difference between the channels, such
as AB, ORTF or NOS microphone recordings, or delay-panned mixes.
With such signals, when you reduce the with, you are summing two signals
with different delays, which will introduce comb filtering.
Let's take a look at what happens when you record a source at 45° to the
right side with an ORTF array (cardioids, spacing 17cm, opening angle
110°):
The time difference is 350 usecs or approximately 15 samples at 44k1. The
level difference due to the directivity of the microphones is about 7.5dB.
For testing, we apply a pink noise signal, which displays as a straight line in the analyser. To simulate an ORTF, we use Robin Gareus' stereo balance control LV2 to set the level difference and time delay. Ignore the Trim/Gain - its purpose is just to align the test signal with the 0dB line of the analyser.
Now for the interesting part: if we reduce the width of the signal to 50%, the time-delayed signals will be combined in the panner. Observe what happens to the frequency response:
Depending on your material and on how much you need to manipulate the width, the comb filter may be acceptable. Then again, it may not be. Listen carefully for artefacts if you manipulate unknown stereo signals - many orchestra sample libraries for example do contain time-delay components.