Blumlein requires the use of two Bi-Directional Microphones placed at a 90º angle. Bi-Directional microphones capture the signal in front of them and behind so the room ambience plays a significant factor in the sound. Most microphones have a setting that looks like a figure “8” and can be switched easily into this mode. As you can see by the above image it takes a bit of setup to get the capsules of the microphones as close to one another as possible without having them touch. The next step is getting the 90º angle to face the sound source.
In this case the microphones were moderately close to the acoustic guitar player and the 90º angle was pointing at the highest fret of the guitar which was just past the sound hole. The outcome was a wide and clear signal that could accommodate most recordings for general acoustic guitar tracking. This worked well because the signal was within a small and somewhat quiet room. I found that the signal could be routed in stereo or mono and still work well in most mix situations.
2. One Large Diaphragm Condenser Close Mic
This placement used a single Large Diaphragm Condenser facing the area between the soundhole and the top of the fretboard. The microphone was switched into the Cardioid polar pattern setting to reduce any room ambience from behind the microphone. Cardioid focus the microphone to only retain signals from mostly in front of the microphone. This setting is much more narrow in comparison to a stereo configuration and would be perfect for double-tracking purposes where the player would strum two different performances of the same chord progression and pan them hard left and hard right. By nature the microphone is very sensitive and picks up much of the low end of the acoustic giving it a thick and chunky sound. This caveat makes it the perfect candidate for Acoustic Guitar driven music where the acoustic guitar upholds much of the harmony for track.