When you create a new Mixbus track (or bus), you have the option to make the track either mono or stereo.

What is the difference between mono and stereo?

A stereo signal is typically recorded with 2 (or more) microphones such that a single sound (like a drum) is captured with both microphones; but because of their separate locations, each microphone will record the sound with slightly different timing & reflections. It is this difference (similar to the difference detected by our 2 separate ears) that causes stereo recordings to have additional width & depth beyond simple mono left/right “panning”.

In this document we will always use the word stereo in italics, if we mean a true recorded-in-stereo signal. Otherwise we will use the term stereo or “stereo” (in quotes) to indicate 2-channel audio with left and right sides.

2-channel audio is not necessarily stereo

Mixbus is designed to support 2-channel playback throughout. If you feed a true stereo signal into Mixbus, then Mixbus (by default) will maintain the _stereo_-ness of that recording throughout the signal flow.

You can also take multiple mono signals, and “pan” them to the 2 channels (left and right) by adjusting the level of each channel. This is sometimes called “pan-pot stereo” or even more commonly just “stereo”. But this is not strictly a stereo signal.

2-channel files are not necessarily stereo

You might receive a file that has 2 channels (“stereo”) but in fact it does not represent a stereo signal.

For example, you might have a 2-channel file recorded with a handheld recorder. The first channel is the host interviewer, and the second channel is the guest. In this case, the file has 2 channels but the information is not stereo and should not be treated as such.

Some other examples might be:

  • a vocal track is provided in a “stereo” file. The singer is louder in the left side. But it’s the same (mono) signal in both tracks, just panned slightly left.
  • a snare-drum track might be provided in the upper (head) and lower (snare) mics, but this is not a stereo signal.
  • a kick-drum might be provided with “inner” and “outer” (sound hole) mics, but this is not a stereo signal.

In Mixbus, what is the difference between a mono and stereo CHANNEL (i.e. TRACK)?

Mono channels/tracks

Mono channels use a panner – this means that the mono signal is sent to the right and left channels simultaneously, and then one side or the other is attenuated to make the sound appear farther to the left or right of the stereo field.

Stereo channels/tracks

Because stereo is a special case, Mixbus’s stereo channels operate differently. A stereo channel uses a balance knob instead of a pan knob. A balance knob preserves the left channel in the left speaker, and the right channel to the right speaker. Then one side or the other is attenuated to “balance” the signal to the left or right. But the left signal is never mixed into the right side, or vice versa. This preserves the stereo phase information in the signal.

When you mix a combination of mono-panned and stereo signals into a stereo mixbus, then the mixbus applies a “balance” control as well, and this maintains the phase relationship of the stereo signals throughout the mix.

Mixbus also treats stereo signals differently in the channel’s compressor: it is important that the compressor’s gain-reduction works on both left and right sides equally. This prevents the stereo image from shifting left or right when the signal is compressed. Mixbus’s stereo channelstrip compressor does this correctly. This is another reason that, when you have a true stereo signal, you should assign it a stereo channelstrip. Similarly, if 2 channels are together in a file but not really “stereo”, then you should create 2 mono strips instead of a stereo one.

How do I resolve the problem if I’m given tracks/files that don’t match my needs?

The easiest way to solve your mono/stereo questions is to resolve it during file “import”.

When you import a file, in the import dialog, there is a “mapping” pulldown menu which allows you to either:

a) select “one track per channel” to split selected stereo files into mono tracks.
b) select “one track per file” to import stereo files as stereo tracks.
c) select “sequence files” to import all the selected files into one track, sequentially.
d) select “merge files” to combine 2 mono files of identical length into a stereo track. ( this option ONLY appears when 2 files of identical length are selected ).

How do I convert a mono signal to stereo?

Strictly speaking, a mono signal cannot be converted to stereo. It wasn’t recorded with stereo phase information from a spaced pair of microphones.

However there are several ways to make the mono signal occupy both channels in a left/right “stereo” mix:

  • Every mono channelstrip has a “pan” knob that allows you to pan the signal left or right.
  • Insert a plugin that changes the channel’s signal from mono to stereo. Normally Mixbus uses only the “left” side of a plugin, if you insert a stereo plugin on a mono channel. But you can right-click on a plugin and choose “pin connections”, “add output” to split the channel into stereo for a mono-in, stereo-out plugin.
  • Assign the channel to a stereo mixbus, and apply an effect that enhances the left/right panning, such as a reverb, haas delay, auto-panner, chorus or doubling plugin.

How do I convert a stereo signal to a mono signal?

Generally speaking, if you have a true stereo signal, you shouldn’t just sum the 2 channels together and make a “mono” signal. The different time/phase relationship between the left and right sides will cause frequency cancellations and other artifacts.

If you have a truly stereo signal, it is rarely necessary or desired that you would want to make it mono. One exception might be the case where the stereo mic selection/location was poorly chosen. In this case, perhaps the best solution is to use only the “left” side, or the “right” … whichever sounds better for your needs.

If you have a stereo signal and you feel you must make it mono, some solutions might be:

  • Assign the stereo track to a mixbus, and use the mixbus’s width control to make the signal “mono”. ( this mono-summing happens at the top of the channelstrip, before any plugins )
  • Insert a plugin that provides a stereo-width control. (optionally: right-click on the plugin and choose “pin connections” if you want the plugin to have a single (mono) output)

How do I convert a stereo track to 2 mono tracks?

If you are “importing” a track to mix, the best way is to make this decision during the import operation. Select the option “one track per channel”, and your stereo file will be split into 2 mono tracks which you can manipulate separately.

If you have recorded a stereo track, and later want to split it into 2 mono tracks, you should first ask yourself why you did this recording in stereo, at all :)

Mixbus provides a Lua script which can split a stereo track into 2 mono tracks. The stereo track’s Playlist (including all edits) will be split into left and right components, and assigned to 2 new tracks. Each track has the same processing applied as the source track. To access the script, click Window->Scripting->Actions->Stereo To Mono->Run

How do I convert 2 mono tracks to a stereo track?

If you’ve read the prior information on this page, you might understand why converting 2 mono track to “stereo” is not as easy as it sounds. Consider the case where each of the mono channels has slightly different plugins, EQ, edits, and other details. We can’t trivially convert 2 mono tracks into a single stereo track.

The only sensible way to convert 2 mono tracks into stereo is to solo the 2 tracks, export the mix to stereo, and re-import the resulting file as a stereo track. (then de-activate or remove the original mono tracks) We might make a convenience function that does this automatically in the future.

In many cases, you don’t want to convert the tracks to stereo at all; instead you should consider making a “group” for the 2 tracks. This will “tie the tracks together” so that selections, fader levels, colors, and other parameters will be changed together, as if they were a single track. But you’ll still have individual panning, plugins, EQ’s and such. Since you can’t “really” make 2 mono signals into stereo anyway, this is usually the best choice.


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