Three and Four Mic Methods

Three and four microphone techniques are generally an extension of the other methods already discussed, therefore, most of the characteristics, advantages and dis-advantages apply. The most successful means to employ three and four mic techniques is to setup a primary pair of microphones and a secondary or accent pair of mics. These secondary mics should be used to augment the sonic character of the primary pair.

A center channel omni-directional mic used with a 90 degree x-y pair of hypercardioid mics will produce a recording that is more open, with a more natural and extended bottom two octaves. This third microphone should be in the same vertical plane as the primary pair, this reduces time and phase differences between mics and allows for better high frequency response (out of phase = dull ). If great care is not taken with mic placement a noticeable degradation at high frequencies occurs, producing a dull, transient poor sound. The level of this third microphone should be about 9 to 20 db below the primary pair. If a phase monitor oscilloscope is used a rearward spacing of the third microphone yielding an in phase time delay of 15 to 20 microseconds can produce very good results. This third, delayed microphone , has the effect of opening up the soundstage allowing for better delineation of vertical spacial information.

Using Four microphone techniques it is much more difficult to achieve desirable results. The time and phase differences become significant and should be restricted to capturing reverberant or audience information. This second pair of microphones should be between 12 and 24 db down from the primary pair or a phase monitor oscilloscope should be used. Using four directional microphones, as two stereo pairs, on a single stand generally degrades the sound so much as to render this technique unusable for stereo ambient recordings.