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Old March 12th, 2011, 05:32 PM   #1
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Cardioid or omni lav?

Hi:

I am looking for a good lav. mic for use for both on and off camera voice recording. I have a shotgun (AT) to record to the other audio channel for ambient on-image sound. I don't have separate sound equipment so I need to connect to the camera XLR connector.

I have found AT831b and AT803b both support phantom power as well as battery and have TA5F connectors that can be connected to XLR or the 3.5mm jack via converter cables. But one is cardioid the other is omnidirectional, what kind is recommended for this use?

Thanks, Erik
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Old March 12th, 2011, 10:30 PM   #2
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Re: Cardioid or omni lav?

I prefer omni in a lav because it gives you more latitude. My subjects often turn their head away from the mic. The cardioid is better for nosier environments like a interviews at a wedding reception.
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Old March 12th, 2011, 11:25 PM   #3
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Re: Cardioid or omni lav?

In general, use a cardioid on stage to avoid feedback and an omni for video. A cardioid might help in noisy environments, but the mounting becomes critical. I lean toward the more even pickup of the omni over the side rejection of the cardioid - even in a somewhat loud environment. By the time it gets really loud, I'd prefer a handheld or headset mic (or ADR, if for narrative) over a cardioid. But on stage, a cardioid can rescue you from feedback.
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Old March 13th, 2011, 05:52 AM   #4
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Re: Cardioid or omni lav?

Always use an omni - a cardioid tie mic. is horrible.

You can often get better feedback rejection with an omni.

An omni has no proximity effect - so you can take it closer to the mouth without any change in the character of the sound.

The relative distance between an omni and cardioid is 1.7 - so a cardioid at 17cm will have the same sound and feedback rejection as an omni at 10cm.

As a person moves their head you can get dropout with a cardioid far more than an omni - and a cardioid normally needs to be further away.

Remember the inverse-square law: change the distance by a factor of two and the volume changes by a factor of four. To illustrate: if you have a balloon with a diameter of 1 metre and you draw a 1cm square on it - then you blow up the balloon to a diameter of 2 metres - that 1cm square will now be a 2cm square - but - a 2cm square is, in fact, four 1cm squares to make a square 2cm on each side.

So - if you halve the mic. distance you improve the feedback rejection by a factor of four.

You have far more flexibility in moving an omni than you do a cardioid.

Also - the angle of maximum rejection of a cardioid is the rear - clipped to the body this is actually pointing towards the body and absorbent clothing - so it ends up not being very much better than an omni in this position.

The only place where I would use a directional mic. is as a headmic. on a boom close to the mouth where the mic. is pointing towards the mouth and the dead area pointing outwards.

I hope this helps.
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Old March 13th, 2011, 08:28 AM   #5
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Re: Cardioid or omni lav?

Thanks, very useful advice! This is my first lav, so I had no idea. The omni has the additional advantage of being slightly cheaper :)
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Old March 14th, 2011, 09:20 AM   #6
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Re: Cardioid or omni lav?

Also keep in mind the older versions of these two lavs were permanently attached to their phantom/battery power module. This module was in the shape of a box with an XLR output jack that required an XLR cable to attach to the camera's input jack.
The newer versions can be detached from their AT power modules, but they use the TA3F connector. The TA5F connector version was for a very specific AT wireless body pack that was compatible with Lectrosonics lav connectors, not the normal AT 4-pin wireless connector. You can get aftermarket phantom power adapters that use the Lectro standard TA5F, like this one as an example:
http://www.thebroadcastshop.com/sale...TA5F-ACC-PS%2B
The TA3F AT versions can be connected to either the AT phantom/battery "box" or to an AT phantom-only round adapter that can plug directly into the XLR jack on the camera.
So make exactly certain of the version you want to order and have the ability to return or exchange, or be able to work directly with a local dealer so you can see them hands-on.

Last edited by Jay Massengill; March 14th, 2011 at 01:46 PM.
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Old March 14th, 2011, 09:40 PM   #7
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Re: Cardioid or omni lav?

Regarding omni lavs, has anyone used the Audio Technica ATR 3350 ? This is ridiculously cheap at about 25 bucks & uses a 3v button battery, so it's OK for semi-pro gear. Just curious as to its performance for casual use.

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Old March 15th, 2011, 03:55 AM   #8
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Re: Cardioid or omni lav?

Quote:
Originally Posted by Jay Massengill View Post
Also keep in mind the older versions of these two lavs were permanently attached to their phantom/battery power module. This module was in the shape of a box with an XLR output jack that required an XLR cable to attach to the camera's input jack.
The newer versions can be detached from their AT power modules, but they use the TA3F connector. ... The TA3F AT versions can be connected to either the AT phantom/battery "box" or to an AT phantom-only round adapter that can plug directly into the XLR jack on the camera.
So make exactly certain of the version you want to order and have the ability to return or exchange, or be able to work directly with a local dealer so you can see them hands-on.
Thanks for the tip, I ordered the AT803b, the power module is separate with the TA3F connector. Nice that I can get an adapter to plug it directly to the camera XLR, I had understood that some of the mic electronics was in the power module to keep the mic small.

One question, if using an adapter to plug the mic directly to the XLR does this imply some limitation on cable length?

Thanks, Erik
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Old March 15th, 2011, 11:14 AM   #9
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Re: Cardioid or omni lav?

Ron, I haven't used the AT3350 lav so I can only say that it will likely have performance typical for that lowest level product line. You'd have to test it with your equipment to know for sure if it was going to satisfy your needs. With all button-cell mics, keeping the battery perfectly mounted and stable is important for noise-free performance.

Erik, Keep in mind the round AT power adapter is phantom-power only. You can simply add XLR cables if you need more length with any of the XLR output adapters.
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Old March 15th, 2011, 11:14 AM   #10
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Re: Cardioid or omni lav?

My wife has an AT803b for public speaking. You can connect it to as long an XLR cable as you would like.
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