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05-30-2009, 12:35 PM   #1
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K-7 Movie "Sound" Primer

NED BUNNELL: K-7 Movie "Sound" Primer

Some photos of an external mic on a K-7 from Ned.B as he prepares his video samples

05-30-2009, 01:03 PM   #2
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Hummm I got the older mono video mic, but have a discount on the newer one Ned is gonna use. Wondering if I shuold get one for the K7
05-30-2009, 01:04 PM   #3
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Looks like he has a chinchilla on the mic for a wind-screen lol
05-30-2009, 01:19 PM   #4
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Original Poster
QuoteOriginally posted by BrendanPK Quote
Looks like he has a chinchilla on the mic for a wind-screen lol
Haha yes they seem to be known as a "dead cat/kitten" in the trade :

05-30-2009, 01:33 PM   #5
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Looks like the Klingons have found a new use for Tribbles.
05-30-2009, 02:07 PM   #6
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QuoteOriginally posted by dopeytree Quote
Haha yes they seem to be known as a "dead cat/kitten" in the trade :
yes, but thats for shotgun/boom mics. This is smaller. hence the chinchilla

It will be interesting to here qualit of audio from the camera, and if the user can adjust the mic input any
05-31-2009, 10:40 AM   #7
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QuoteOriginally posted by BrendanPK Quote
Looks like he has a chinchilla on the mic for a wind-screen lol
LOL. Video noobs
05-31-2009, 10:57 AM   #8
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I'd so be attaching googley eyes to that.

05-31-2009, 11:14 AM   #9
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QuoteOriginally posted by kenyee Quote
LOL. Video noobs
hahhahaa
05-31-2009, 06:12 PM   #10
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Ned's 720p K-7 video with sound on Vimeo:
06-01-2009, 01:30 AM   #11
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I've got both of the RØDE videomics. The RØDE Videomic is a short shotgun mono mic. It has a permanently-fitted foam windsock. Over this you can fit a Dead Cat furry windshield (not included with the mic, but a good idea, as shotguns, being more directional, are more affected by the wind). I usually use it this way outdoors, or even indoors when ceiling fans are present. The initial version of the Videomic (which I have) had no output attenuator and this makes it output level a bit too high for camera inputs in loud situations. Later versions have an -10/-20 dB attenuator switch.

The RØDE Stereo Videomic is a crossed-cardioid stereo mic. It is less directional than the Videomic, but is also a little less coloured to my ears. It has a switchable -10dB output level attenuator and can handle high levels. (Both mics have an max. SPL rating of 134 dB SPL). It comes with a Dead Kitten furry windshield. While smaller than the Videomic, it is also 60% heavier due to its rugged metal construction.

Both mics are suspended in compliant rubber o-rings. This greatly reduces handling noise & the mechanical transfer of camera noises to the mic, but can't stop acoustic pickup (but the directional pattern of the mics at medium & high frequencies helps here). The mic mounts are also threaded so you can mount them up close to the source on a mic stand or on a telescopic hand-held boom.

Dan.

Last edited by dosdan; 06-01-2009 at 01:58 AM.
06-01-2009, 01:50 AM   #12
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Great that someone has both to compare. The stereo mic is more expensive altho comes with the dead kitten as mentioned. i guess there are wirelss transmitters so you can place the mic somewhere off camera or on a stick, altho I guess that kinda gear would be expensive
06-01-2009, 02:07 AM   #13
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just read a review of the stereo mic saying the video mic would be better for general use since the stereo mic is not good at picking up sounds from a distance and the video mic is more directional and ignores sounds from the sides, focusing on what you are pointing your lens on. any comments to to that?
06-01-2009, 03:53 AM   #14
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QuoteOriginally posted by and Quote
just read a review of the stereo mic saying the video mic would be better for general use since the stereo mic is not good at picking up sounds from a distance and the video mic is more directional and ignores sounds from the sides, focusing on what you are pointing your lens on. any comments to to that?
You need to understand the concept of Directivity Factor/Index. Take an omni-directional mic for comparison. This has virtually no directivity (although HF from the rear is reduced slightly). Say this mic is 10m from a musical instrument. By definition, it has a DF of 1.0. Now replace it with a cardioid. Because it is more directional we can move it back to 17m before it hears the same ratio of direct-to-reverberant sound as the omni does at 10m. We say it has a DF of 1.7, meaning it can be uses 70% further away and still have the same pickup balance as the omni. A super-cardioid, in this example, could be situated 19m away (DF 1.9), while a hyper-cardioid could be situated 20m away (DF 2.0)

All the mics mentioned in the previous paragraph should sound similar, with the same balance of direct-to-reverent sound. However, in reality the size of the mic capsule and the shape of the casing causes the mic to depart from the uniform directional pattern at both LF & HF. The more directional the mic, the more uneven the off-axis response. The general rule is that the more directional the mic, the more coloured it sounds.

Typical directional mics are not like zoom lens. They don't magnify the level of the desired sound. They reject the off-axis contribution more effectively. To actually "magnify" the direct sound you would need to use a mic mounted in a parabolic reflector, but the magnifications falls off at LF because a typical reflector is not big enough to reflect long wavelengths (LF). This is why a parabolic mic is OK for bird-song, but not for music recording.

The RØDE Stereo VideoMic is a cardioid (DF 1.7). The RØDE VideoMic has a super-cardioid capsule (DF 1.9) with a line gradient tube mounted in front of the capsule. This will boost the DF to somewhere between 2.5-3.0. RØDE does not publish a DF factor for this model and neither does any other manufacturer because of its variability against frequency. Short shotguns tend to be quite directional in the MF & HF, but not at LF. Long shotguns are a better, but are more expensive and too unwieldy to be practicable mounted on most cameras.

So yes, the RØDE VideoMic, in our example, could be used at 25-30m from the source compared to the Stereo VideoMic at 17m, but the StereoMic will sound better, particularly if you're recording violin or acoustic guitar rather than speech. And you lose a awful lot of the "life" & the feeling of "being there" when you go from stereo to mono. Say you have kids playing. You want to capture the life, the ambiance and and their movement in the soundfield, while hopefully reducing distracting sound sources (cars, airplanes etc.)

The BEST solution is to use either an omni (cleaner - no proximity effect - better resistance to wind noise) or a cardioid up close rather than mounted on the camera. The typical professional answer is to use a hyper-cardioid mounted on a boom up close. On-camera sound in rarely used, except in ENG (Electronic News Gathering) where it may not be possible to have a separate boom operator/soundman.

Dan.

Last edited by dosdan; 06-01-2009 at 04:48 AM.
06-01-2009, 04:57 AM   #15
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QuoteOriginally posted by dosdan Quote
You need to understand [...]
Dan, thanks for your explaination. I learned a lot from it.

Since you seem to be fairly knowledgeable, let me ask one more question:

Are there microphones out there which compute their directional response from an array of inputs, say three or more microphones? From a physics point of view, this should be doable. It could be even possible to "zoom" them just like some flashes
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