Can you help me understand Polar Patterns at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > All Things Audio

All Things Audio
Everything Audio, from acquisition to postproduction.


Reply
 
Thread Tools Search this Thread
Old May 15th, 2007, 01:51 PM   #1
Trustee
 
Join Date: Sep 2004
Location: Bristol, CT (Home of EPSN)
Posts: 1,182
Can you help me understand Polar Patterns?

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?
__________________
Paul Cascio
www.pictureframingschool.com

Last edited by Paul Cascio; May 15th, 2007 at 02:25 PM.
Paul Cascio is offline   Reply With Quote
Old May 15th, 2007, 03:09 PM   #2
Regular Crew
 
Join Date: Apr 2005
Location: Fairbanks, Alaska
Posts: 138
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.
__________________
After years of lurking, I finally made the mistake of opening my mouth.
Doug Lange is offline   Reply With Quote
Old May 15th, 2007, 03:13 PM   #3
 
Join Date: Nov 2001
Location: santa fe, nm
Posts: 3,264
Images: 10
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.
Bill Ravens is offline   Reply With Quote
Old May 15th, 2007, 05:07 PM   #4
Inner Circle
 
Join Date: Nov 2004
Location: Baltimore, MD USA
Posts: 2,323
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
Ty Ford is offline   Reply With Quote
Old May 15th, 2007, 05:19 PM   #5
Trustee
 
Join Date: Sep 2004
Location: Bristol, CT (Home of EPSN)
Posts: 1,182
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?
__________________
Paul Cascio
www.pictureframingschool.com
Paul Cascio is offline   Reply With Quote
Old May 15th, 2007, 05:23 PM   #6
Inner Circle
 
Join Date: Nov 2004
Location: Baltimore, MD USA
Posts: 2,323
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
Ty Ford is offline   Reply With Quote
Old May 15th, 2007, 05:44 PM   #7
Trustee
 
Join Date: Sep 2004
Location: Bristol, CT (Home of EPSN)
Posts: 1,182
Okay Ty, so a hypercardioid actually picks up sound fairly well from behind it, correct? Hence the small lobe?
__________________
Paul Cascio
www.pictureframingschool.com
Paul Cascio is offline   Reply With Quote
Old May 15th, 2007, 06:20 PM   #8
Inner Circle
 
Join Date: Mar 2005
Location: Hamilton, Ontario, Canada
Posts: 5,742
Quote:
Originally Posted by Paul Cascio View Post
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.
__________________
Good news, Cousins! This week's chocolate ration is 15 grams!
Steve House is offline   Reply With Quote
Old May 15th, 2007, 06:29 PM   #9
Inner Circle
 
Join Date: Nov 2004
Location: Baltimore, MD USA
Posts: 2,323
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
Ty Ford is offline   Reply With Quote
Old May 15th, 2007, 06:54 PM   #10
Trustee
 
Join Date: Sep 2004
Location: Bristol, CT (Home of EPSN)
Posts: 1,182
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.
__________________
Paul Cascio
www.pictureframingschool.com
Paul Cascio is offline   Reply With Quote
Old May 15th, 2007, 07:22 PM   #11
Inner Circle
 
Join Date: Nov 2004
Location: Baltimore, MD USA
Posts: 2,323
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
Ty Ford is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > All Things Audio

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 07:54 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network