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The physics behind polar patterns
Old 9th August 2009
  #1
Gear Head
 

The physics behind polar patterns

I'm trying to get a good grasp on the physics behind the way polar patterns work.

I've been looking everywhere online, but can't seem to find anything in depth enough.

So, in most cases, you get a tighter polar pattern by exposing the back of the diaphragm physically (say, in the case of a hypercardioid, there are generally larger vertical slots in the body right behind where the diaphragm is), which creates a directional polar pattern.

However, the most directional of polar patterns, the line (shotgun), is created by cancellation that (again, physically) happens in front of the capsule, not behind it.

And then there are the mics that do the same electronically, like the C414 that can change between 5 polar patterns. Or the Josephson Series 7 that lets you change the polar pattern after you've recorded it.

Obviously all of this has to do with phase cancellation, but I just can't find any specifics on exactly how the phase cancellation works in each type of mic. Why does the cancellation in a shotgun happen in front of the diaphragm instead of the back? What components are electronically changing the phase? Equations that are involved?

Thanks for your help!
Old 9th August 2009
  #2
I would be interested in the answer as well.
Old 9th August 2009
  #3
Lives for gear
 
big country's Avatar
 

most directional being parabolic

Parabolic microphone - Wikipedia, the free encyclopedia
Old 9th August 2009
  #4
Gear Maniac
 
mister sunshine's Avatar
 

Microphones Technology and Techniques written by John Borwick does an excellent job of explaining the basics of the concepts and designs that result in the various pickup patterns.

It also illustrates specific implementations of a dozen or more mics you are likely to be familiar with.

best regards,
mike
Old 9th August 2009
  #5
Motown legend
 
Bob Olhsson's Avatar
 

There are two basic patterns.

Mikes with a sealed back only respond to pressure changes and are omni-directional.

Mikes that have an open back respond to the velocity of sound and are bi-directional.

Everything else is a mix of the two accomplished by various methods. 50/50 is cardioid.
Old 9th August 2009
  #6
Gear Head
 

Quote:
Originally Posted by big country View Post
A parabolic shield is a microphone accessory that attaches to a less directional microphone.
Old 9th August 2009
  #7
Gear Head
 

Quote:
Originally Posted by mike_mccue View Post
Microphones Technology and Techniques written by John Borwick does an excellent job of explaining the basics of the concepts and designs that result in the various pickup patterns.

It also illustrates specific implementations of a dozen or more mics you are likely to be familiar with.

best regards,
mike

Thanks! I'll look into that!
Old 9th August 2009
  #8
Lives for gear
 
big country's Avatar
 

Quote:
Originally Posted by moink123 View Post
A parabolic shield is a microphone accessory that attaches to a less directional microphone.
cool thanks!
Old 9th August 2009
  #9
Gear Nut
 
lazzaro's Avatar
 

Good book derived from a BBC training manual ...

The book below is long out of print, but it does a really good job
of explaining the physics of microphones without assuming much
in the way of physics or math background -- it teaches all of the
physics and math you need to understand microphone operation
as it goes along. Perhaps your local library has a copy, or maybe
you can find a used copy on sale somewhere.

Author: British Broadcasting Corporation. Engineering Training Dept.
Title: Microphones, by the staff of the Engineering Training Dept., British Broadcasting Corporation.
Publisher: London, Published for "Wireless world" [by] Iliffe [1951]
Description: 114 p. illus. 22 cm.
Series: BBC engineering training manuals
LCCN: 52004790
Old 9th August 2009
  #10
Lives for gear
 
Teddy Ray's Avatar
 

you want these answers, and pretty much everything there is to know about microphones??

simple.

Get this book. Now. Best book on microphones ever...by the genius John Eargle(RIP), one of the best engineers, scientists, and brightest minds , period, to have graced the recording world..

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