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stan welks
omni-directional lavs
on Jul 20, 2008 at 6:17:26 pm

For interviews, is it a bad idea to use a omni-directional miniature lav? Will this pick up too much ambient noise? The mic I am looking at is the COS-11x omni-directional miniature pre-polarized lavalier microphone. What is the intended use for a lav like this?

Thanks.


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Ty Ford
Re: omni-directional lavs
on Jul 20, 2008 at 7:01:21 pm

Hello Stan and welcome to the Cow Audio Forum,

Omnis lavs are almost always preferred over cardioid lavs. Because they are placed closer to the mouth than a boom mic, they pickup the voice quite well, although a good boom mic in the right environment usually wins. You have to try both to see who the winner is.

The COS-11x is an excellent choice. The Countryman B6 is another.

Regards,

Ty Ford

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






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stan welks
Re: omni-directional lavs
on Jul 21, 2008 at 1:54:47 am

What then would be a good use for a cardioid lav?

Thanks!



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Ty Ford
Re: omni-directional lavs
on Jul 21, 2008 at 3:43:13 am

Lots of ambient noise and no head turning.

Regards,

Ty Ford

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






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Danny Grizzle
Re: omni-directional lavs
on Jul 20, 2008 at 7:09:24 pm

I only buy omni lavaliers. You get some degree of directionality from lav placement, usually a person's body. Close placement is the only reason lav mics exist. An omni mic worked close always beats a shotgun worked too far away. In other words, hyper cardiods exist only for situations where close mic placement is not possible.

The physics of sound dictate that every time you double the distance from sound source to mic, the level is not half as much, but one fourth. Conversely, if you can halve the distance between mic and source, you quadruple the signal.

This is the exact reason why mics used in high ambient noise environments such as aviation use boom mics to place the mic directly in front of the mouth. Up close, small distances dramatically change the ratio of wanted vs. unwanted sound.

All this means, that at close distances such as lavalier mic placement, directionality becomes much less important, because you are by definition working with a much higher signal-to-noise ratio from the get-go.

Whenever circumstances permit, omni mics almost always sound better than directional mics. Since most production audio takes place in the real world, usually not on sound stages and the studio, cardiod mics tend to be the workhorse in most sound guy's kit. But don't take this to mean they are the best mic in all situations and applications. Lavaliers are the exception, where an omni pattern is almost always better than cardiod.

Some manufacturers make directional lavaliers, and there may be special applications where they are useful. But a quality omni lav is certainly your first choice. I've never tried a directional lavalier, but I have read that they are problematic for use with body packs and talent. They are small, hard to keep positioned correctly, and vulnerable to wide swings in sound quality as talent moves, turns their head, etc.

BTW - You've seen the TV commercials with Vince selling ShamWow towels. His boom mic is totally unnecessary, a practical prop. It does create the trade show floor ambiance of a barker working his demo. Boom mics can be useful in sound reinforcement applications and concerts, where high volume levels would otherwise lead to feedback amplification.





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Rodney Morris
Re: omni-directional lavs
on Jul 22, 2008 at 12:17:21 am

Well Danny, I'm going to call into question your statement:

"The physics of sound dictate that every time you double the distance from sound source to mic, the level is not half as much, but one fourth."

This is not accurate, not as I've learned. The physics of sound, in regards to the measuring of acoustic power are bound by the inverse square law. In practice this means that every time you double the distance from your sound source to your measuring point, the power decreases by 6dB. So if you have a sound source emitting sound at 80dB at a distance of one meter, it's power at 2 meters (doubling it's distance) would be 74dB, not 20dB (which would be one fourth the power). Maybe I misunderstood your statement.

Most of us use omni-directional mics as our primary lav mics. However, I will use a cardioid lav mic when necessary. Most of the time you use cardioid lavs in an amplified sound environment (use with a PA system). Omni lavs tend to feed back too easily in this type of environment due to their polarity characteristics.

I use a Sennheiser MKE-102 on Dick Vitale in his office when I do live hits for ESPN. If you know who Mr. Vitale is, you know he is a very loud individual. His office has very hard surfaces and tends to echo easily and has a very "hollow" sound. I've tried the Sennheiser MKH60, Schoeps MK41, Sanken COS-11, Tram TR50 and Countryman EMW mics on him in this room and none sound as good as the cardioid Sennheiser MKE-102. This is just about the only time I use the MKE-102 (the Sanken and Tram mics are my "go-to" lavs). But, cardioids do have their uses.

However, cardioid lav mics don't hide well - they pick up too much clothing noise. Cardioid lavs are bigger than omnis, not smaller. Also, if you accidently block the ports on the side of mic head (with gaff tape), you essentially turn it into an omni mic.

Hope this helps.

Freelance Sound Technician/Mixer


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