Direction Mixer

You can use the Direction Mixer to decode middle and side audio recordings or to spread the stereo base of a left/right recording and determine its pan position.

The Direction Mixer works with any type of stereo recording, regardless of the miking technique used. For information about XY, AB, and MS recordings, see Getting to Know Stereo Miking Techniques.

Figure. Direction Mixer window.
  • Input buttons: Click the LR button if the input signal is a standard left/right signal, and click the MS button if the signal is middle and side encoded.
  • Spread slider and field: Determines the spread of the stereo base in LR input signals. Determines the level of the side signal in MS input signals. See Using the Direction Mixer’s Spread Parameter.
  • Direction knob and field: Determines the pan position for the middle—the center of the stereo base—of the recorded stereo signal. See Using the Direction Mixer’s Direction Parameter.

Using the Direction Mixer’s Spread Parameter

The Direction Mixer’s Spread parameter behavior changes when fed LR or MS signals. These differences are outlined below.

When working with LR signals, the following applies to the Direction Mixer’s Spread parameter:

  • At a neutral value of 1, the left side of the signal is positioned precisely to the left and the right side precisely to the right. As you decrease the Spread value, the two sides move toward the center of the stereo image.

  • A value of 0 produces a summed mono signal—both sides of the input signal are routed to the two outputs at the same level. At values greater than 1, the stereo base is extended out to an imaginary point beyond the spatial limits of the speakers.

The following applies when working with MS signals:

  • Values of 1 or higher increase the level of the side signal, making it louder than the middle signal.

  • At a value of 2, you hear only the side signal.

Using the Direction Mixer’s Direction Parameter

When Direction is set to a value of 0, the midpoint of the stereo base in a stereo recording is perfectly centered within the mix.

The following applies when working with LR signals:

  • At 90°, the center of the stereo base is panned hard left.

  • At -90°, the center of the stereo base is panned hard right.

  • Higher values move the center of the stereo base back toward the center of the stereo mix, but this also has the effect of swapping the stereo sides of the recording. For example, at values of 180° or -180°, the center of the stereo base is dead center in the mix, but the left and right sides of the recording are swapped.

The following applies when working with MS signals:

  • At 90°, the middle signal is panned hard left.

  • At -90°, the middle signal is panned hard right.

  • Higher values move the middle signal back toward the center of the stereo mix, but this also has the effect of swapping the side signals of the recording. For example, at values of 180° or -180°, the middle signal is dead center in the mix, but the left and right sides of the side signal are swapped.

Getting to Know Stereo Miking Techniques

There are three commonly used stereo miking variants used in recording: AB, XY, and MS. A stereo recording, put simply, is one that contains two channel signals.

AB and XY recordings both record left and right channel signals, but the middle signal is the result of combining both channels.

MS recordings record a real middle signal, but the left and right channels need to be decoded from the side signal, which is the sum of both left and right channel signals.

Understanding AB Miking

In an AB recording, two microphones—commonly omnidirectional, but any polarity can be used—are equally spaced from the center and pointed directly at the sound source. Spacing between microphones is extremely important for the overall stereo width and perceived positioning of instruments within the stereo field.

The AB technique is commonly used for recording one section of an orchestra, such as the string section, or perhaps a small group of vocalists. It is also useful for recording piano or acoustic guitar.

AB is not well suited to recording a full orchestra or group as it tends to smear the stereo imaging/positioning of off-center instruments. It is also unsuitable for mixing down to mono, as you run the risk of phase cancelations between channels.

Understanding XY Miking

In an XY recording, two directional microphones are symmetrically angled, from the center of the stereo field. The microphone on the right is aimed at a point between the left side and the center of the sound source. The microphone on the left is aimed at a point between the right side and the center of the sound source. This results in a 45° to 60° off-axis recording on each channel (or 90° to 120° between channels).

XY recordings tend to be balanced in both channels, with good positional information being encoded. They are commonly used for drum recording. XY recording is also suitable for larger ensembles and many individual instruments.

Typically, XY recordings have a narrower sound field than AB recordings, so they can lack a sense of perceived width when played back. XY recordings can be mixed down to mono.

Understanding MS Miking

To make a Middle Side (MS) recording, two microphones are positioned as closely together as possible—usually on a stand or hung from the studio ceiling. One is a cardioid (or omnidirectional) microphone that directly faces the sound source you want to record—in a straight alignment. The other is a bidirectional microphone, with its axes pointing to the left and right of the sound source at 90° angles. The cardioid microphone records the middle signal to one side of a stereo recording. The bidirectional microphone records the side signal to the other side of a stereo recording. MS recordings made in this way can be decoded by the Direction Mixer.

When MS recordings are played back, the side signal is used twice:

  • As recorded

  • Panned hard left and phase reversed, panned hard right

MS is ideal for all situations where you need to retain absolute mono compatibility. The advantage of MS recordings over XY recordings is that the stereo middle is positioned on the main recording direction (on-axis) of the cardioid microphone. This means that slight fluctuations in frequency response that occur off the on-axis—as is the case with every microphone—are less troublesome, because the recording always retains mono compatibility.