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boom microphones and directional characteristics

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Roger Schroeder
boom microphones and directional characteristics
on Jul 23, 2013 at 5:18:23 pm

We all know how acoustic fins create directional mics.

What I want to know is how a headset mic like a Countryman over the ear boom mic gets it's directionality?

On a Countryman you can switch sides of the head, but you dont have to rotate the capsule. You can slip an endcap over the capsule to make a cardioid a hyper, but as near as I can tell from pictures there are no fins cut out.

Is the apex of the mic's cardioid shape parallel to the diaphragm or is the talent talking slightly off center of the sweet spot? Are the fins opaque to the eye but not to sound?

Thank you for your time in this very important matter!;)


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Eric Toline
Re: boom microphones and directional characteristics
on Jul 23, 2013 at 8:12:10 pm

The change in pattern is caused by the size of the opening in the directional cap and the caps length. Be aware that directional microphones are more prone to "P" pops & breath blasts than Omni pattern mics.

OTOH the headworn mics like the Countryman E6 will get you 8-10db more gain before feed back in a live PA environment because of the proximity to the mouth.

Eric

"I push the RECORD button and hope for the best"


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Roger Schroeder
Re: boom microphones and directional characteristics
on Jul 23, 2013 at 9:33:36 pm

So there is an air gap between the cap and the microphone element allowing sound to travel to the back of the diafram. The longer the cap the more directional the mic. Sounds like this method would color the sound of the mic.

Thanks,

I push the record button and hope the client doesn't look over my shoulder and try to tell me how to do it.


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Eric Toline
Re: boom microphones and directional characteristics
on Jul 23, 2013 at 9:55:40 pm

All directional mics color the sound a bit by enhancing the low end compared to an Omni pattern mic. Directional mics are basically only directional at the mid & higher frequencys. Look at a frequency response graphs of any mic that's available in an Omni & Cardioid or hyper cardioid pattern and you'll see the difference.

Eric

"I push the RECORD button and hope for the best"


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Ty Ford
Re: boom microphones and directional characteristics
on Jul 25, 2013 at 2:36:03 am

Hello Roger and welcome to the Cow Audio Forum.

I don't know exactly what you're referring to when you say "fins."

The physics behind omni and directional mics has to do with ports behind the diaphragm..

Single diaphragm omni mics don't have them. Cardioid mics do. The small time delay that results from some of the audio entering the port behind the diaphragm is what causes a mic to be directional.

Take a directional mic like a common SM58. Plug it into a PA. Turn up the gain to just below feedback. Grab the mic in such a way as to cover up the bottom half of the ball with your hands. FEEDBACK!!!

Why? Because by blocking the rear ports, you just turned the mic into an omnidirectional mic and it's now picking up sound from the PA.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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