How to Mic a Band - Pick-up and Polar Patterns

Last week we talked about a few different types of microphones that can be used to mic a band (How to Mic a Band - Types of Microphones). This week we are going to talk about pick-up and polar patterns in microphones.

Microphones are classified not only by the method of transduction but also by their pickup pattern. The pickup pattern is the way in which the element responds to sounds coming in from different directions, and there are several different standard patterns. (This is akin to the polar response of a loudspeaker… in reverse.)

Omnidirectional elements, as their name implies, pick up sound more-or-less equally from all directions.

One might think that omnidirectional microphones are never used in sound reinforcement, since they offer no protection from feedback. This is generally the case, but not entirely so. There is a myth that cardioids are better, but omnis have better low frequency response, and less susceptibility to breath noise ad wind noise. Because omnidirectional mics tend to have much smoother frequency response than directional mics, there are fewer peaks to trigger feedback, so sometimes a good omni is as useful (or more so) as a mediocre directional mic. Lavalier mics (mics worn on a lanyard around the neck, or clipped to a shirt) are often omnis. Omni mics are quite useful in recording, and virtually every studio owns at least a few of them.

The cardioid is unreservedly the most popular of all microphone pickup patterns. Note that the pattern is heart-shaped - hence the name "cardioid." As the figure clearly shows, the cardioid microphone is most sensitive to sounds coming in on the primary axis, and rejects sounds from the sides and rear of the microphone.

The directional qualities of the cardioid make it a natural choice for sound reinforcement, since they help in reducing feedback and increasing system gain. This effect is overrated, and omnidirectional mics are often a better choice for close work than is a cardioid. Cardioids tend to have more coloration when sound does not arrive on axis because their directional qualities vary in frequency.

Cardioids are quite common in recording, since they can be used to diminish unwanted sounds arriving from off-axis. Their frequency response is usually rougher than that of an omni and they are somewhat more sensitive to wind noise and breath popping.

The supercardioid is highly directional microphone element.

Note that, in contrast to the cardioid, the supercardioid does exhibit more of a rear pickup lobe, though small. It thus supplies far less rejection of sounds coming in directly from the rear than does the cardioid. The forward pickup lobe is far more concentrated and the supercardioid offers superior rejection of sounds coming in from the sides.

Supercardioids are used in special situations where greater side rejection is desired, but some rear pickup may be tolerated. Because of the concentration forward lobe, they also may "reach" farther than typical cardioid, and are sometimes used for pickup of distant sources.

Incidentally, the supercardioid is similar to, but not identical to another very directional microphone, the hypercardioid.

I hope this helps explain some of the basics on why some mics are used and hopefully you are thinking about situations where one type may work better than others.
Next week I'll be posting about types of speakers. Hit the subscribe button to make sure you get notified when it publishes.

©2009 Fred Russell Publishing, All Rights Reserved. This article can not be used without permission from the Author. To Contact the Author email curt@RockHouseMethod.com

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