Can you help me understand Polar Patterns

[Paul Cascio]

Thanks in advance. Mostly what I dodn't understand is what the polar pattern drawing refers to.

If I've got a cylindrical mic, lets use the or AT 4053A, a Hypercardiod, mounted on top of my camera. My camera is level and parralel to the floor. Is the sound pickuped from in front of (where this mic is pointing to in this case), and in back of the mic in this horizontal plane? Or is it the vertical plane.

Does the center of a polar drawing always refer to this same plane?

Are there pictures anywhere that illustrate this?

[Doug Lange]

It's both. The polar patterns are 2-D diagrams of a 3-D reality. A simple example of how the pattern may appear in reality is to place an inflated balloon on the end of your AT 4053a. If you push the mic into the balloon just a little, it will closely represent the polar pattern of the AT 4053a at 1k, albeit without the small rear lobe.

If we could add balloons into the same space as the first ballooon with each balloon representing a given frequency, then we would have a complete representation of a mic's pickup pattern.

www.neumann.com has a better graphic for polar patterns but it is still only 2-D.

[Bill Ravens]

the polar pattern refers to the horizontal plane when a shotgun mic is horizontal. Zero degrees is dead ahead, or where the axis of the mic is pointed. Therefore, 180 degrees is directly behind the mic. So, for example, you would expect zero pickup when the microphone screen is blocked by the body of the microphone.

On the other hand, the polar pattern is referenced to the vertical plane with some ribbon microphones. The reason for this is because of the pickup element, ribbon vs. condenser element, and its orientation with respect to the body of the microphone.

Proper positioning of a ribbon microphone (ball headed microphones) requires the mic body be held perpendicular to the source, while for a cylindrical condenser mic, the proper orientation is to hold the axis towards the source.

[Ty Ford]

Unless, of course, the condenser mic is an end address mic.

Here's the thing. Mics are either end address or side address. End address mics you talk into the end of, like a shotgun, most of which are condenser mics, or a beyer m160 ribbon.

There are side address mics like a Neumannn U 87 condenser, or an RCA 77DX ribbon.

Most of the graphs I've seen show an overhead view of the mic's pattern. A hypercardioid has a big front lobe and a tiny back lobe.

Figure of eight patterns pickup (more or less) equally from front and back.

Regards,

Ty Ford

[Paul Cascio]

Ty, do you mean an overhead that assumes the mic is in a vertical position witht the cord pointing down?


So, if a group of people were formed a circle with the mic in the center, the mic would pickup sound about equally from anyone in the circle, assuming the people are the same height?

[Ty Ford]

No. I mean the overhead assumes you're looking down over the mic and that it's pattern extends horizontally.

An end address mic will have its body parallel to the floor.

A side address mic will have its body perpendicular to the floor.

Regards,

Ty Ford

[Paul Cascio]

Okay Ty, so a hypercardioid actually picks up sound fairly well from behind it, correct? Hence the small lobe?

[Steve House]

Originally Posted by Paul Cascio

Okay Ty, so a hypercardioid actually picks up sound fairly well from behind it, correct? Hence the small lobe?

Jumping in if I may, no it doesn't. It picks up SOME sound from a narrow cone directly behind it but not nearly enough to categorize as "fairly well", ie, the level when its backside is pointed at a sound source is going to be 15dB to 20dB lower than when the front of the mic is pointed at it. In other words, I wouldn't want to hold it up on a line between an interviewer and an interviewee and try to use the front lobe to capture the subject and the back lobe to capture the interviewer. It's more a matter of it rejects noise a bit better to the sides of directly astern (abaft of the beam, me hearties - yarrrrr) 30 to 60 degrees on either side of straight back than it does dead astern along its axis.

[Ty Ford]

STOP JUMPING IN!


No, the small lobe means it's really small relative to a big one. Or, that it picks up VERY LITTLE relative to the front, but still picks up some.

Regards,

Ty

[Paul Cascio]

Okay, I understand. The small lobe is much smaller, therefore less sensative, than the large.

So what is the benefit of that small lobe, as opposed to using a Shotgun, which I presume rejects almost all aft sound.
Also, could you compare the purpose of a Supercardioid, which has a narrower back lobe?


Thanks maties. Rum for everyone.

[Ty Ford]

It's not like designers can do whatever they want. They are limited by physics.

Shotguns do have a rear component and they are more omni directional at mid and low frequencies. That's why they suck in live slappy interiors, or even on big flat hard parking lots. Someone starts a car 90 degrees one side or the other and you'll hear it.

Regards,

Ty Ford