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Old August 2nd, 2008, 01:05 PM   #1
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-12 / -20 db audio attenuation on the ProHD camera ?

Yesterday I shot a concert with my HD251, and the sound was distorted because i was to close for the sound. But i have to do it again.

In the audio part, i don't see clearly if there something like this. There's something like "audio ref level" with -12/-20 but it's written to be the audio référence on the tape.

There also imput 1 mic ref, with -50 or -60, but i don't really understand what is it for. Yesterday my camera was on -50.

Can someone bring my light.

Perhaps will i need some external attenuator ? Tonight i will probably use my beta58 to see if it's better (i know, it's a mic for singer (that i am)).
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Old August 2nd, 2008, 02:48 PM   #2
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Originally Posted by Fabrice Hoffmann View Post
Yesterday I shot a concert with my HD251, and the sound was distorted because i was to close for the sound. But i have to do it again.

In the audio part, i don't see clearly if there something like this. There's something like "audio ref level" with -12/-20 but it's written to be the audio référence on the tape.

There also imput 1 mic ref, with -50 or -60, but i don't really understand what is it for. Yesterday my camera was on -50.

Can someone bring my light.

Perhaps will i need some external attenuator ? Tonight i will probably use my beta58 to see if it's better (i know, it's a mic for singer (that i am)).

Distortion can happen at multiple pathways in the signal.

1) The mic.
Some mics (condensers) cannot handle much over 120 db. Know your mics limitations. Dynamic mics can handle loud SPL's in a distortion friendly way.

2) The input.
Sending line level into a jack set to mic level will always cause distortion.

3) The signal.
The signal is simply recorded too hot without a limiter.

In a concert setting with a lot of dynamic range, the reference signal should be set at -20. Now, that is just the tone refence set when recording Bars & tone. The input levels need to be set to MANUAL and adjusted so the the peeks occassionally splash over -20.

If the mic level is really hot, it can be padded down from -60 to -50.

Once the levels are adjusted, turn on the limiter. Any distortion that occurs from that point on would be from the mic itself.


In a better scenario, you would go through an external mixer with quality mic preamps and quality limiters (SD 302) and send LINE level to the camera...setting up the signal path so that it NEVER goes above -10.
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Old August 2nd, 2008, 05:34 PM   #3
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Fabrice, not that I have anything to suggest here, but I just wondered if you thought starting a new thread on the same subject will get you any more responses than the other one? http://www.dvinfo.net/conf/showthrea...694#post915694

It's always best to stay in one thread.
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Old August 4th, 2008, 02:58 AM   #4
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Fabrice, not that I have anything to suggest here, but I just wondered if you thought starting a new thread on the same subject will get you any more responses than the other one? http://www.dvinfo.net/conf/showthrea...694#post915694

It's always best to stay in one thread.
Bill, i don't think it's a double post. On the thread you link to, i asked questions about mics, here it's more about how to handle the sound with the JVC camera setting. At the end some answers can be close, but i think it's different subject.
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Old August 4th, 2008, 03:27 AM   #5
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Originally Posted by Jim Boda View Post
1) The mic.
Some mics (condensers) cannot handle much over 120 db.
=> the new version of the Rode Nt2 goes up to 135 db (145 with a build in -10 db). So i think the earlier version can work more or less near 135.

Quote:
2) The input.
Sending line level into a jack set to mic level will always cause distortion.
=> Do you want to say that this kind of my can never handle this amount of sound, or they cannot without a -12/-20 db attenuator ?

Quote:
3) The signal.
The signal is simply recorded too hot without a limiter.

In a concert setting with a lot of dynamic range, the reference signal should be set at -20. Now, that is just the tone refence set when recording Bars & tone. The input levels need to be set to MANUAL and adjusted so the the peeks occassionally splash over -20.

If the mic level is really hot, it can be padded down from -60 to -50.

Once the levels are adjusted, turn on the limiter. Any distortion that occurs from that point on would be from the mic itself.
=> But i think my mistake is here : i didn't know the good way to set the volume. I explain : until now, i didn't really care about the -20 or -12 reference point. The way i was setting the volume was : a little bit before it clip. But in channel line in manual, had the limiter (channel 2 was on auto and also had crap sound). Doing that way if i understand well, the sound was to lound and completely compressed by the limiter ?

As i understand you, the good way to set volume is really care about the -12 or -20 db ref. point, and put the limiter which will work on sounds that will cross this reference point. But setting the sound just before clipping (when the limiter is off, and also worse when it's on) cause distorsion and is not the good way. I thought doing this i could have more dynamic range.

The -60 to -50 focntion works like an attenuator ?

Sure, having an external mixer could be better.
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Old August 4th, 2008, 11:18 AM   #6
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Originally Posted by Fabrice Hoffmann View Post
=>...As i understand you, the good way to set volume is really care about the -12 or -20 db ref. point, and put the limiter which will work on sounds that will cross this reference point. But setting the sound just before clipping (when the limiter is off, and also worse when it's on) cause distorsion and is not the good way. I thought doing this i could have more dynamic range...
In a digital recording, the recording levels are critical. Any audio that goes above 0 is crushed and is a useless distorted mess.

So, when I'm recording a basic interview type of setting without a lot of dyanamic range...I want the levels to average around -16 DB with some occasional peeks at -12. Always, set the limiter on to protect from the unexpected. The limiter should kick in just before 0. I'm not sure if the limiter is adjustable on the JVC. It is adjustable on a quality external mixer like the SD 302.

At a much louder event w/ more dynamic range. I want to protect from distortion a little more and record at a lower level w/ the occassional peaks touching -20... especially if I'm going direct into the mic input without the control of an external mixer.

A good way to do this type of protected recording is to keep both tracks on MANUAL recording levels, but lower the second track another 10 or so DB to protect from unexpected peaks and use it as a safety track.

Remember, you can normalize the levels in post with good results and still retain dynamic range...unless you are crashing the limiter and crushing the input level above 0.
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Old August 5th, 2008, 08:00 AM   #7
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I'm not sure if the limiter is adjustable on the JVC.
I don't think it has, but perhaps i didn't find it.

But thanks a lot for yours answers. The last one was really what i was looking for.

And if i understand you well, i normally have to set the "input mic 1 ref" at -60. And if the sound is really loud or my mic is really sensitive (hot), i would have to put the ref at -50. That's it ?
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Old August 5th, 2008, 08:44 AM   #8
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Originally Posted by Fabrice Hoffmann View Post
And if i understand you well, i normally have to set the "input mic 1 ref" at -60. And if the sound is really loud or my mic is really sensitive (hot), i would have to put the ref at -50. That's it ?
Unless I'm reading you wrong, you have it backwards. -60dB is more attenuated than -50dB.
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Old August 5th, 2008, 10:02 AM   #9
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Originally Posted by Fabrice Hoffmann View Post
....And if i understand you well, i normally have to set the "input mic 1 ref" at -60. And if the sound is really loud or my mic is really sensitive (hot), i would have to put the ref at -50. That's it ?
You got it. I always go in at LINE LEVEL routed through a quality external mixer w/ good limiters and acurate meters.

LINE LEVEL = ...................+4
Consumer LINE LEVEL = ....-10
MIC Att Level = ..............-40 to -50 (*some camera's have a -20 pad)
MIC LEVEL = ..................-60

In your loud concert example, you needed a little more than the -50 pad level. Having a mic w/ a built in -10 db pad would have been very helpful.
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Old August 5th, 2008, 10:39 AM   #10
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Having a mic w/ a built in -10 db pad would have been very helpful.
You're right : listening with headphones, the sound is louder at -60 than at -50

I've been told the new rode nt2 had one, but not the one i bought one year ago. Do you thing i need an external "attenuator" ? Is it this kind of thing ?
http://store.shure.com/store/shure/e...ctID.104210500

And finaly, do you think i will have a better sound with my nt2 condenser mic, or the bigger capsule of the beta58 can handle better loud sound ?

Thanks.
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Last edited by Fabrice Hoffmann; August 5th, 2008 at 11:13 AM.
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Old August 5th, 2008, 12:29 PM   #11
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...I've been told the new rode nt2 had one, but not the one i bought one year ago. Do you thing i need an external "attenuator" ? Is it this kind of thing ?
http://store.shure.com/store/shure/e...ctID.104210500

And finaly, do you think i will have a better sound with my nt2 condenser mic, or the bigger capsule of the beta58 can handle better loud sound ?

Thanks.
The Shure attenuator does look like a good tool to have in the sound kit. It will allow you to keep your level at -60 and dial in the right amount of attenuation -15, -20, or -25. It may be a bit awkward to use with a camera mounted mic.

As far as your mic choice, neither mic is ideal...but, you will just have to trust your ears as to which mic does a better job until you can get a more suitable mic.
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Old August 5th, 2008, 12:47 PM   #12
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... until you can get a more suitable mic.
Just to keep it in mind when i will earn more money, what is a more suitable mic for you ? :-)
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Old August 5th, 2008, 06:44 PM   #13
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Just to keep it in mind when i will earn more money, what is a more suitable mic for you ? :-)
Well, for a very loud Rock concert setting...It might be nice to have a Sennheiser 421.
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Old August 6th, 2008, 02:28 AM   #14
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Not so expansive. Will see if i do a lot of concert, but it will look a little bit weird on a camera.

Once again, thanks a lot for all your answers !
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Last edited by Fabrice Hoffmann; August 6th, 2008 at 02:59 AM.
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Old August 6th, 2008, 09:58 AM   #15
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I've used the Audio Technica pad a number of times at the House of Blues to help cut the signal from the board down. I also make sure it's in my camera bag because you never know..
http://www.audio-technica.com/cms/el...e16/index.html
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