Harvey Gerst
New member
I'm gonna break this into sections and then post the basics first, then talk about how and when to use them.
Coincident stereo mic techniques.
In the late 1920's and early 1930's, Alan Blumlein (in Britain) and RCA were both working on recording techniques, using only a small number of recording channels for reproduction over a pair of loudspeakers.
The technique developed by Alan Blumlein consisted of a pair of microphones with figure 8 patterns, mounted close together,with the front lobe of one mic pointing 45 degrees to the left, and the front lobe of the other pointing 45 degrees to the right (Figure 2.). Although it provided excellent stereo imagining, sounds coming from the rear are also picked up and when reproduced over a pair of loudspeakers, these sounds were also mixed into the speakers. This results in a sound which is too reveberant for many people.
"Purists" who liked the simplicity and accuracy of the Blumlein technique modified it in order to remove this problem. By replacing the figure 8 microphones with cardioids and changing the angle between them to include the desired soundstage, it is possible to use the cardioid mic's lack of rear response to reduce the rear reveberant sounds. This results in a much more acceptable, if less accurate sound image. Typically, the angle between the mics should not be more than about 135 degrees, or less than 90. This technique is the popular "X/Y" stereo recording system. (Figure 1.)
Mid-Side (M-S) techniques use a figure 8 mic, sideways to the sound source, and a cardioid mic facing the source (Figure 3.). By inverting the signal from the real lobe of the figure 8 mic and using a matrix network, it is possible to adjust the width of the sound stage to almost any size.
Coincident stereo mic techniques.
In the late 1920's and early 1930's, Alan Blumlein (in Britain) and RCA were both working on recording techniques, using only a small number of recording channels for reproduction over a pair of loudspeakers.
The technique developed by Alan Blumlein consisted of a pair of microphones with figure 8 patterns, mounted close together,with the front lobe of one mic pointing 45 degrees to the left, and the front lobe of the other pointing 45 degrees to the right (Figure 2.). Although it provided excellent stereo imagining, sounds coming from the rear are also picked up and when reproduced over a pair of loudspeakers, these sounds were also mixed into the speakers. This results in a sound which is too reveberant for many people.
"Purists" who liked the simplicity and accuracy of the Blumlein technique modified it in order to remove this problem. By replacing the figure 8 microphones with cardioids and changing the angle between them to include the desired soundstage, it is possible to use the cardioid mic's lack of rear response to reduce the rear reveberant sounds. This results in a much more acceptable, if less accurate sound image. Typically, the angle between the mics should not be more than about 135 degrees, or less than 90. This technique is the popular "X/Y" stereo recording system. (Figure 1.)
Mid-Side (M-S) techniques use a figure 8 mic, sideways to the sound source, and a cardioid mic facing the source (Figure 3.). By inverting the signal from the real lobe of the figure 8 mic and using a matrix network, it is possible to adjust the width of the sound stage to almost any size.
I'm interested because the humidity level in our room is often 80%, and in addition to various channels on our Mackie going out, pickups rusting, and the overall smell of freshly reincarnated mildew, the mics might be "rusting" as well.
I've been recording some acoustic guitar (fingerstyle) and I tried what I think might be sort of M/S micing. I have a Soundelux U97 (Figure-8) and a KM184 into a Great River MP2. I point the U97 sideways a bit to the left of the soundhole (~8" out), and 
