Microphone Polar Pattern Explained Using a Clock Dial

FAQ #4247 Updated September 15, 2017

Question:

I just do not understand the polar pattern of a mic and how angles are used in the polar pattern. Can you offer a simple explanation?

Answer:

The KSM9 microphone will be used as an example because it is available with four different polar patterns.

The Shure KSM9 and the KSM9HS are fraternal twins - nearly identical, but not quite.

The KSM9 is selectable for a cardioid pattern or a supercardioid pattern. The pattern is chosen using a toggle switch hidden under the mic grille.

The KSM9HS is selectable for a hypercardioid pattern or a subcardioid pattern, again chosen using a toggle switch hidden under the mic grille.

Before reading farther, let's discuss on-axis, off-axis, and angles:
On-axis means sound approaches the mic directly from the front.
Off-axis means sound approaches the mic from the side or from the rear.

Imagine a clock face with the mic grille pointed at 12 o'clock on the dial:
12:00 o'clock = 0 degrees (on-axis)
3:00 and 9:00 o'clock = 90 degrees off-axis
3:30 and 9:30 o'clock = 110 degrees off-axis
4:00 and 8:00 o'clock = 120 degrees off-axis
6:00 o'clock = 180 degrees off-axis

Image

Now, back to the KSM9 with its cardioid or supercardioid pattern:

Cardioid: -6dB at 90 degrees off-axis; > -25 dB at 180 degrees off axis.
Sound that approaches the KSM9 from 3 o'clock or 9 o'clock is heard 6 dB softer than sound that approaches from 12 o'clock. Sound that approaches from 6 o'clock is heard 25 dB (at minimum) softer than sound that approaches from 12 o'clock.

Supercardioid: -9 dB at 90 degrees off-axis; > -25 dB at 120 degrees off axis.
Sound that approaches the KSM9 from 3 o'clock or 9 o'clock is heard 9 dB softer than sound that approaches from 12 o'clock. Sound that approaches from 4 o'clock or 8 o'clock is heard 25 dB (at minimum) softer than sound that approaches from 12 o'clock.

And now the KSM9HS with its hypercardioid or subcardioid pattern:

Subcardioid: - 3dB at 90 degrees off-axis; >-10 dB at 180 degrees off axis.
Sound that approaches the KSM9HS from 3 o'clock or 9 o'clock is heard 3 dB softer than sound that approaches from 12 o'clock. Sound that approaches from 6 o'clock is heard 10 dB (at minimum) softer than sound that approaches from 12 o'clock.

Hypercardioid: -12 dB at 90 degrees off-axis; > -25 dB at 110 degrees off axis.
Sound that approaches the KSM9HS from 3 o'clock or 9 o'clock is heard 12 dB softer than sound that approaches from 12 o'clock. Sound that approaches from 3:30 o'clock or 8:30 o'clock is heard 25 dB (at minimum) softer than sound that approaches from 12 o'clock.

To summarize:

Off-axis rejection at 90 degrees (3 o'clock or 9 o'clock):
Subcardioid: -3 dB
Cardioid: -6 dB
Supercardioid: -9 dB
Hypercardioid: -12 dB

Angle of maximum rejection:
Subcardioid: 180 degrees (6 o'clock)
Cardioid: 180 degrees (6 o'clock)
Supercardioid: 120 degrees (4 o'clock or 8 o'clock)
Hypercardioid: 110 degrees (3:30 o'clock or 8:30 o'clock)

Though the term "directional" is often applied to microphones, the better term is "rejectional." The KSM9 does not enhance sound that approaches on-axis; instead it rejects sound that approaches off-axis. It is this off-axis rejection that makes the KMS9 appear to favor sounds approaching from on-axis.

Attachments

Find an Answer

Related Product Types

Microphones

Contact Information

Telephone: (800) 516-2525

Fax: (847) 600-8686

Additional Support

Ask a Question