Stereo Microphone Techniques.
A majority of the recording scenarios in capturing piano, be it solo, with small ensemble, or large ensemble will have a basis in stereo microphone techniques. This is relevant to those considering portable recorders as they come with mics already set in a pattern, so when you choose a portable recorder consider the stereo pattern as well. As a basic starter setup, you will have either: a portable recorder with preset stereo pattern(s), or a pair of microphones which you place into a stereo pattern.
When using the patterns below, position according to the capsules, not the microphone housing.
AB, spaced pair.
Microphone capsules kept parallel to each other and spaced. Good for picking up the room, and hearing the space. If you are in a good acoustic and want to capture that in the recording, it is a consideration. You could make a very wide stereo image, if you so desire, though it may sound unnatural. Using omni mics here allows one to take advantage of their low-end frequency response. Issues with phase cancellation in mono.
XY, coincident pair.
Directional microphone capsules placed close to one another, typically one above the other, between 90 to 135 degrees relative to each other. Good directional image, less defined sense of space. Will not sound as wide as compared to AB spaced pair. Directional microphones loose low-end frequency response at longer distances. There are no issues with phase cancellation and excellent mono compatibility.
Near coincident pairs.
They combine characteristics of AB and XY spacing.
ORTF, near coincident.
Two directional microphones, capsules 17 cm apart, angled at 110 degrees. Wider than XY
DIN, near coincident.
Two directional microphones, capsules 20 cm apart, angled at 90 degrees.
NOS, near coincident.
Two directional microphones, capsules 30 cm apart, angled at 90 degrees.
Blumlein, coincident pair.
Position like XY, but uses microphones with bi-directional (figure 8 ) pattern. The directional image of XY with the sense of hearing the room behind the mics. No issues with phase cancellation and excellent mono compatibility.
Mid-side.
One small diaphragm condenser, cardioid or omni, plus one large diaphragm condenser bi-directional (figure 8 ). Figure 8 mic is placed at a 90 degree angle to the instrument to capture the side. The other mic is placed above or below the figure 8 and pointed directly at the instrument, the mid. The relative difference in amplitude of the mid and side determines the stereo width. The differentiating feature of mid-side is the ability to adjust the stereo width after recording.