+ The default stereo panner distributes two inputs to two outputs. Its + behaviour is controlled by two parameters, width and + position. The + default settings for the stereo panner are width=100% and + position=center. + This stereo panner assumes that the signals + you wish to distribute are either uncorrelated (i.e. totally + independent), or that they contain a stereo image which is + mono-compatible, such as a co-incident microphone recording, or a + sound stage that has been created with pan pots.* +
+
+
++ The panner user interface consists of three 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). +
-The stereo panner distributes 2 inputs to 2 outputs. Its behaviour is
-controlled by two parameters, width
-and position (the latter could also be referred to as
-"direction", or "azimuth" without loss of accuracy).
+ 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), 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. +
+ +
-The default settings for the stereo panner
-are width=100%, position=center. With these
-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.
+ 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 +
+ 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 +
+ 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 +
+ 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. + 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 +
+ 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. + 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: +
+Let's take a closer look at what happens when you record a source at 45° to the +right side with an ORTF stereo microphone array and then manipulate the width. +
++For testing, we apply a pink noise signal to both inputs of an Ardour stereo +bus with the stereo panner, and feed the bus output to a two-channel analyser. +Since pink noise contains equal energy per octave, the expected readout is a +straight line, which would indicate that our signal chain does not color the +sound: +
+
++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. +
++Recall that an ORTF microphone pair consists of two cardioids spaced 17 cm +apart, with an opening angle of 110°. +For a far source at 45° to the right, the time difference between the capsules +is 350 μs or approximately 15 samples at 44.1 kHz. The level difference +due to the directivity of the microphones is about 7.5 dB (indicated by the +distance between the blue and red lines in 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 of the left and right outputs: +
+
++You may argue that all spaced microphone recordings will undergo comb +filtering later, when the two channels recombine in the air between the speakers. +Perceptually however, there is a huge of difference: our hearing system is +very good at eliminating comb filters in the real world, where their component +signals are spatially separated. But once you combine them +inside your signal chain, this spatial separation is lost and the brain will +no longer be able to sort out the timbral mess. As usual, you +get to keep the pieces. +
+