Template:Directional Microphones

Principles

Use a directional microphone. Hypercardioid is better than cardioid, which is better than omnidirectional. All sound waves impinging on the microphone from a direction other than the intended signal is "noise" and will lower the threshold of feedback.

Directional microphones "collect" less sound from directions other than what they're supposed to amplify (the voice, or an instrument) and hence are less likely to feed back.

In addition, most directional microphones have a strong behavior called proximity effect. This is the strong buildup of bass and low-mid response as the source (say the voice) to microphone distance decreases. For microphones intended to sound natural when the voice is very close -- say one of a number of popular stage vocal microphones -- what this means is that low-to-middle frequencies from sources at a distance, including loudspeakers being used to amplify the voice, are largely rejected by the microphone. This is a real plus in terms of avoiding microphone feedback.

Conversely, an omnidirectional microphone (equal sensitivity to sound coming from any direction) has no proximity effect. This is an advantage often in the studio where the engineer wants consistent tone regardless of distance. But it's a disadvantage on stage in terms of feedback. An omnidirectional mic collects more sound that's not the target, and because it has no proximity effect is more susceptible to feedback at low-to-mid frequencies than a directional mic.

Omnidirectional and Unidirectional Microphones

There are two basic types of microphone — omnidirectional and unidirectional

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Omnidirectional Microphone

Omnidirectional mic. It is sensitive to sounds from all directions.

It's unlikely you will use an omnidirectional microphone in a live performance setting. You will pick up too much ambient noise from the room, the audience, and the loudspeakers (leading to feedback).

Use omnidirectional microphones when the sound source could be anywhere around the microphone. This picks up a lot of room ambiance, which sometimes is the goal. Direct and ambient sound can be adjusted by moving the microphone closer to or further from the sound source.

Unidirectional Microphone

Unidirectional microphones are sensitive to sound coming from only one direction. Examples:

• a vocalist singing directly on axis directly into the microphone
• a guitar amplifier with the microphone aimed directly at the speaker cone

All of the following types are unidirectional

Cardioid

The most common type of unidirectional microphone is called a “cardioid” because its pickup pattern is heart-shaped. It picks up most sound from the front of the microphone and some from the sides.

Although you will get better gain-before-feedback from a cardioid microphone than an omnidirectional microphone, you will get better gain-before-feedback from a supercardioid or hypercardioid microphone (see next section).

Examples of common cardioid microphones (good to great microphones but not necessarily the best for gain-before-feedback with Bose L1 systems)

• Sennheiser e 835, e 935, MD 935
• Shure SM 58, SM 57, Beta 87C

Supercardioid / Hypercardioid

Supercardioid or hypercardioid microphones offer even greater sound isolation through narrower pickup patterns.

Examples of common supercardioid/hypercardioid microphones

• Audix OM 5, OM 3b, OM 6, OM 7, VX 5
• EV N/D 767A
• Neumann KMS 105
• Sennheiser e 845, e 865, e 945, e 965, MD 441, MD 945,
• Shure Beta 58A, Beta 87A