Microphone Techniques

Written by: HeadSnack

The microphone is the instrument of the vocalist. An experienced singer will manipulate the mic based on how loud they are singing and how close they are to the mic. When close they can sing relatively softly for a deep, rich tone. This is known as the Proximity Effect which states that there is an increase in bass as the sound source gets closer to the microphone. Experienced vocalists will increase their volume as they move further from the mic. Although their voice seems to be getting louder, its really just a greater intensity and the listener is not deafened by the words.

The Proximity Effect can be eliminated by moving the microphone further away or using a low cut filter to reduce low frequency sensitivity. It can also be used to get a full sound with a source that would otherwise offer very little low end such as a whispering voice.

Plosives: When singing close, be careful about plosives, the popping sound that happens on words beginning with B or P. A pop filter can aid in filtering out plosives from speech but also aid in recording wind instruments such as flutes. Pop Filters can be either of mesh or metal material. While both materials help eliminate sibilance, metal is preferred. Metal pop filters are more durable so they will not degrade or sag over time. In addition, they can be easily cleaned whereas mesh filters accumulate saliva and odors without the ability to sanitize them.

Off-Axis Coloration is related to the placement of the sound source and the microphone’s polar pattern. As the sound source is moved further from the mic’s direct pickup pattern, the frequency response changes the sound captured from bright to darker.

Stereo Recording Techniques

The Three to One Rule (3:1) is used in stereo recording and prevents the pickup of one microphone from interfering with the pickup of the other mic. It states that two microphones need to be spaced three times as far apart from one another as they are from the source they are capturing sound from.

Phase Cancellation: When two wave forms with the same frequency, shape, and peak amplitude are in phase, the newly combined wave form will have the same frequency, phase, and shape but will double in amplitude. This is usually what you want when you’re double tracking vocals or instruments. The sound is thickened and has more impact.

However, a common problem occurs when you record the same sound source with more than one microphone. If the cycles of the waveforms are lined up opposite of each other, phase cancellation can occur which results in them cancelling each other out.

A/B (Spaced Pair): Two cardioid or omni-directional microphones are spaced there to ten feet apart from each other and panned with a left/right configuration. The distance of the mics depends on the physical size of the sound source. It is one of the simplest stereo miking techniques and provides a very wide field of sound. However, phase cancellation can occur due to the distance between the microphones and the time when sound arrives at each.

XY (Coincident Pair): Two cardioid microphones of the same type and manufacturer are placed as close together as possible (at a 90 degree angle), often with the grills touching. The pair is placed with the center of the two mics facing directly at the source, panned left and right. This eliminates phase cancellation problems encountered with the Spaced Pair technique. The sound is very focused in the center and mono compatibility is excellent.

ORTF (French Broadcasting Organization & NOS (Dutch Broadcasting Foundation) (Near-Coincident Pair): Two cardioid microphones of the same type and manufacturer are placed within 12 inches of each other facing outward at an angle between 90 (NOS) or 110 (ORTF) degrees, depending on the size of the sound source. The tails of the mics are almost touching and the center of the two mics directly faces the sound source, panned left and right. This technique nearly eliminates phase cancellation problems encountered with A/B but the stereo separation may be limited if the sound source is extremely wide.

Blumlein: The Blumlein technique is similar to X/Y, but the angle between the two mics are offset by 90 degrees and both mics are Figure 8. They are oriented so that their pickup patterns create an “X” with the tops of their heads almost touching. One mic is then turned so its facing north and south, with the other facing east and west. This allows for more ambient sounds to be picked up, creating a more realistic sonic image.

Mid-Side (MS): The Mid Side technique uses two different microphones with two different polar patterns. One mic is Figure 8, the other is a Cardioid. The Cardioid mic faces the source and the Figure 8 faces to the left and right of the source. Even though the Figure 8 captures sounds on both sides, it sends a mono signal which needs to be converted to stereo. This is achieved by copying the recorded track from the Figure 8 mic to another track, leaving two identical tracks. The second track is then phase reversed (many DAW plugins have a switch for inverting phase). The next step is to pan both of the Figure 8 tracks to the center, bring one fader up to 0, and then bring the other fader up until the sound cancels and you hear nothing. Now pan them hard left and right and bring up the cardioid mic. As you adjust the level of the cardioid you’ll hear a widening or narrowing of the stereo field.

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