FS7: Sound levels

M

morgan_moore

Major Contributor
This one slightly embarrases me but came up the other day (after some years of using the camera!)

I know nothing of the numerology of audio.

In the audio menu there is (I think) a db adjustment.

I know I have this right for my trusty Sanken (CS2) mic, but dont actually know what it means/does.

It came up the other day as I was in a configuration where I had my sanken on a long lead in the hand of a reporter and also a sony kit mic (from the F3 or or Ex1) placed as a top mic. Anyway - I could not get the top mic loud enough (by turningthe pot) - Im guessing its less sensitive than the Sanken and nedded to fiddle with that menu setting..

Could someone go through the setting :)

S
 
morgan_moore said:
Could someone go through the setting :)
S
Click to expand...

I will ask the obvious for which I will no doubt be abused for but was the input for the old F3/EX type mic set to mic level and +48 phantom power? Those type of mics require Phantom Power. Also was it assigned correctly in the input menu? if so I would suggest setting the input level to -50dB on the FS7, that's the default from memory. Also try -60dB. If none of that works check the mic elsewhere. I'm using -50dB with an EX type mic with no issues and have plenty of gain.

Chris Young
 
Yep phantom power is selected.

I guess im asking which is loudest -40, -50 or -60 and why might a more negative number be louder.

In Spinal Tap they did not crank thier amps to -11 :)
 
Morgan - Wow, I was surprised by the question but then I remember that your background was still photography . Every shooter ought to know this stuff and if in doubt get on the web and google "impedance." Frankly its a confusing concept and a little counterintuitive, but ultimately those numbers are setting the match up between the incoming signal and the preamp. I think of it as the amount of gain applied to the signal but that's probably technically incorrect. Nevertheless it works as a way of thinking about it. So if a real sound guy chimes in and criticizes me I confess I'm guilty and you can shoot me at the pearly gates. So I incorrectly think of those negative numbers like positive gain numbers: -60 applies more gain to the mic than -40. Nevertheless this will work for your thinking and that's the way I'll explain it.

Impedance of "0" is usually applied to (or matched to ) a true line signal coming from your sound guys mixer. That's what your "line " setting is on the camera . More about that later though. Typical professional microphones in our business work best around -50db which is Sony's default. However the Sony Mic I use for a camera shotgun is too soft at -50db and I use -60 with it. BTW - The F3 and EX1/3 had smaller more precise increments to choose from rather than just -40, -56, -60 etc. I used to set that mic at -57.

At any rate ideally you want to set your impedance so that your volume pot has a good range to adjust your signal volume at whatever sound volume you expect your subject to be putting out. I will turn on a radio so it was a normal volume for people talking then play with the impedance level till it gave me a good signal with the outside pot set in the middle. That way I could adjust up or down for most situations. Sometimes I've been in loud music environments and I've lowered the impedance (lower negative number) so the mic was less sensitive . If your impedance is off you will find it hard to get the range you want for recording and also the mic won't sound as good . It will be slightly distorted if the match isn't ideal. By the way a real sound person might listen to the quality of the mic at different impedances rather than just set it for detente. That was something you have more freedom to do if you have smaller increments to choose from. Typically dynamic mics are softer than powered mics and require a higher impedance setting.

There are a few issues that come up with impedance:
First the line level from most mixers used in live events (those big boards) don't send out the same "line level" as your audio guys mixer. Its a weaker signal and will be too soft if you set your camera for line. But it will be too loud for a -40 mic level. I often set mine for -24 in the EX-1 but can't remember what it is in the FS7 or even if it goes that low. Again experiment with the test signal you get from the mixer, sometimes they can adjust it for you.
Second amateur microphones ( typically those with "mini" plugs) often have a much stronger signal than professional and you need to use a lower impedance setting.
Thirdly when using radio mics you usually have a choice as to how high to set the output of the receiver to the camera and as I recall the corresponding the input setting of the receiver and maybe the out put o the transmitter. All that stuff has to match. If you have a stronger signal from the receiver then your input impedance has to be less sensitive and vice versa. Im not sure if the exact settings matter as long as the match up for a good signal. It gets confusing because the negative numbers on the impedance values on camera , receiver and transmitter all make my head spin. Likewise different lavs often have different sensitivities and they require slightly different impedances on the wirelesses. Nevertheless in the end you need to make things match.

Hope that helps and maybe a true tech can chime in and explain why there are negative numbers properly. (BTW sorry for minor grammatical mistakes- shoot me again.)

Oh yeah phantom power has nothing to do with impedance - that's the electrical power applied to make your mic work at all. usually +48V but older mics sometimes are 12V.

Lenny
 
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FWIW, I think the default level on the FS7 is good for most situations and bring up in post if needed.

I found this article very helpful; http://www.massivemastering.com/blog/index_files/Proper_Audio_Recording_Levels.php

On the other side of side, you have Dean Miles, who wrote Location Audio Simplified, and he swears by recording "hard to the limiter," which is just the opposite of what I see most doing. But he swears it is the way to go.

Personally, I think it is better to bring up in post.

Also, this was very helpful to me too.

http://vashivisuals.com/5-eq-audio-for-video-tips-for-filmmakers/
 
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