Polar Pickup Patterns

The best way to visualise a microphone’s polar diagram (pickup pattern) is to think of the pattern representing a view from above the capsule, which is on the horizontal axis, and its centre is bisected by the vertical axis.

Remember that the position of the capsule in a microphone is usually in a ‘side on’ e.g. Beyer Dynamic MC 704 or ‘end on’ e.g. Shure SM57 configuration so you need to establish where the capsule is first to visualise the polar pattern. see fig 1 below .

Polar diagrams are usually shown as idealised or simplified shapes, however if you look at the actual plots provided by the manufacturers you will see that the plots are more ragged and not as perfect as the smooth lines of the classic diagrams.

The classic polar diagrams are usually shown at one frequency e.g. 10khz but an actual plot of a microphone will typically show a range of frequencies, in all but the Omni microphone's case the lower frequencies will appear to be very different than their idealised shape would suggest, this is because the lower the frequencies get the more omnidirectional the pickup pattern becomes.

An extra windshield is recommended should you decide to use one for close up vocal work. Its light weight means that it responds readily to high frequencies and fast transients in the sound.

The pickup pattern of ribbon microphones is always ‘figure of eight’ which makes them useful for ignoring sound sources to their sides. They make good audience microphones since they can be put next to the P.A. speakers which they wont ‘hear’ very well but the audience’s laughter and applause will be recorded well.

Omni polar response microphone pick up pattern

Omni Pickup Pattern

This pattern exhibits a uniform frequency response at all frequencies from all directions so these mic’s are not very good at rejecting unwanted sounds (unless you put a physical object that soaks up sound between the microphone and the unwanted sound source).

However they have a very natural sound, free of ‘out of phase’ artefacts that you can get when using several microphones e.g. many cardioid mic’s around a drum kit.

Hypercardioid polar response microphone pick up pattern

Figure of Eight Patterns

This pattern has very good rejection of all frequencies at its sides and it can be used with an omni or cardioid microphone when recording stereo sound in a Mid-Side configuration. This is because the response from the back of the microphone is 180 degrees out of phase with respect to the front and of the same magnitude.

It is this ability to detect phase difference i.e. the fraction of a second it takes for a sound to be ‘heard’ by the left and then the right side (when the sound source is to the left of the listener), and vice versa, that makes the figure of eight microphone essential for M-S recording. (see stereo recording)

cardioid polar response microphone pick up pattern

Cardioid Pattern

This pattern has a heart shaped pickup pattern providing good response at the front, less at the sides and very little at the rear, it is more prone to having some ‘out of phase’ artefacts since it is the result of an omni and a figure of eight capsule being added together - the small differences in time it takes for a sound to reach each capsule can lead to cancellations or additions at different frequencies.

Often in dynamic cardioid mic's the same effect is achieved acoustically within the microphone where there is only one capsule.

Hypercardioid Pickup Pattern

This pattern resembles the cardioid pattern but is thinner and longer i.e. more sensitive at the front but it also has a small lobe at the back so you should be careful using such a mic in a system where foldback speakers are being used, with cardioid mic’s you put a foldback speaker at the back of the mic’ (180 degrees from the front central axis) where it is least sensitive and with a hypercardioid mic you put it at about 160 degrees or 200 degrees.

An omni capsule and a figure of eight capsule together in one microphone can be electronically combined to produce all pickup patterns, there are small trade-offs in accuracy however, so to get the most ideal frequency response you should use a dedicated microphone for the pattern you require.

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