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Old December 20th, 2005, 07:17 AM   #1
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screwed audio...... What??

I shot a VERY important gig the other day. I was packing REALLY light and was in a hurry. I just grabbed my pd-150, an ntg-1 and a tape........ I set the pres low so I didn't bother setting the two channels at different volumes in case the band got louder as the set progressed. Now here is what doesn’t make sense....... I had it set WELL below the digital clipping point. But ALL the audio is REALLY distorted. The max spl of the mic is about 139db. The band wasn't really, really loud or anything. Is 139db too low? Like I said it wasn't a REALLY loud band. I think, the loudest band I have seen recently was a few guys that call them selves "Black Dice". Even with my custom-made earplugs these guys were killing me. Anyway, let’s get back on track……

I wish I had of remembered my headphones..... The audio is that bad you can't distinguish anything. I reset up my camera that night same cable, mic. And it sounded fine. In a “normal” environment though. My question is how can it distort if the in camera reads are well below clipping?? The only thing I can think of is I set it up in the dark and maybe I didn't plug the XLR in all the way. I don't think this happened though. I have shot quite a few other bands and NEVER had this problem.... I normally don't mount the mic on my cam though. I stick it on a stand. I was standing pretty close the stage this time. Does the mic distort before the pre? So even it the levels look fine it is clipping at the mics end?

So now I am stuck with 100mins of "Stephen Malkums and the Jicks" with very usable video and no audio.... I think it is Waaaaaaaaaaaaaaaaaayyyyy too screwed to selvage anything.

I’ll try get together a clip for you guys if you want.

I am tired. I'll think about this more tomorrow.

Thanks for reading my ranting guys. Any help would be much appreciated.
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Old December 20th, 2005, 07:53 AM   #2
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Sony Noise Reduction 2.0, "Clipped Peak Restoration" may help, but probably not.

From your description, your audio may be too far gone to be corrected.

I would import your audio into Vegas, or another NLE that shows the audio waveform. Then I would examine to determine if the audio is occassionally clipped, or clippped amost 100% of the time. If the latter, then Noise Reduction 2.0 will not be able to help much.
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Old December 20th, 2005, 08:15 AM   #3
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It sound likely that the sound level / mic output level was high enough to overload the camera's preamps before the signal ever got to the camera's level controls? Clipping more likely took place at the input to the camera's preamps rather than in the mic itself. The recording level indicators come after the level control. If the signal is too hot and clipping takes place before it gets to that stage, the recording level could appear within normal limits and yet still be distorted. A tip-off is where you have to set the level controls to get normal meter indications - if you're getting proper levels with the control about 3/4 of the way up you should be okay. But if you have to turn the control down into the lowest part of its range to prevent the meter from pegging full scale, there's a good chance you're already clipped before the controls have a chance to do anything about it. The solution is to kick in the attenuator and/or add a pad in the line between the mic and camera.
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Old December 21st, 2005, 04:48 AM   #4
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Thanks guys. I appreciate you help and speed.

I still don't quite understand how it can clip between the pre and the mic but I'll and get an AT 8202 and see what happens. Don't you turn down the gain on the pres to avoid distortion? (I think) The bars on the onscreen audio readouts were okay.


Max levels looked like this>>> IIIIIIIIIIIIIIII--------

But do these bars do not matter?? Attenuate before the pres? What stage does it clip? How does it clip before the gain? Am I missing something?? Sorry, I'm starting to confuse myself.

It is also strange that I have shot in these volumes before and it has been fine.

Here is some of the footage.

http://www.grandpastudios.com/sm/sm_01.mov

http://www.grandpastudios.com/sm/sm_02.mov

http://www.grandpastudios.com/sm/sm_03.mov

Are there any Stephen fans here?? HAhahaa
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Old December 21st, 2005, 05:43 AM   #5
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Sure sounds like overload at the input to me.

Look in your owner's manual for an audio block diagram and you'll see what I mean. The incoming signal goes through several stages from the XLR connector to the final recording signal. As it enters the camera it goes through a head amp and the attenuator if it's turned on, an unbalancing circuit, the preamp, perhaps a recording amp, and the A/D converter. The level control adjusts the OUTPUT of the preamp stage and the meters monitor those levels. But that's fairly late in the game and there's already a lot of stuff that has been going on upstream. If overload and overdriving occur in the circuitry before the preamp level control, the signal has noise garbage in it before it ever gets a chance to be cut back and the pre's controls are adjusting the level of what is already a mix of desired signal and noise. The result is a meter indication exactly as you saw - normal levels coming OUT of the preamp but the signal had been trashed going IN to the preamp.

Of course with that music how can you tell? Pulled out some Dire Straits last night - now that's Rock! <Geezer mode off - LOL>
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Old December 21st, 2005, 05:53 AM   #6
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Thanks for that Mr. geezer!!! I understand now. I never said was a Stephen Malkmus fan.... Slop-rock isn't really my thing. I just shot the event. Hahahaha. Is the max spl fine for your average rock gig? I plan on buying a few new mics after I come back from overseas. I have some stuff to shoot before I go though.

Thanks again.

Shea
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Old December 21st, 2005, 10:57 AM   #7
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Quote:
Originally Posted by Shea Goodall
Thanks for that Mr. geezer!!! I understand now. I never said was a Stephen Malkmus fan.... Slop-rock isn't really my thing. I just shot the event. Hahahaha. Is the max spl fine for your average rock gig? I plan on buying a few new mics after I come back from overseas. I have some stuff to shoot before I go though.

Thanks again.

Shea
I'll let others more conversant with shooting rock concerts reply to that. But the Rode is reputed to be a decent mic. Might be interesting to get a cheap sound pressure meter from somplace like Radio Shack and measure the levels at your normal mic position during a gig. I got one a few years ago for about $75 that would suffice.
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Old December 22nd, 2005, 04:00 AM   #8
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Thanks for the idea!!
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Old December 25th, 2005, 10:30 AM   #9
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That to me sounds like the mic is overloading. When you are that close to a PA system, you are talking some serious volume. not too many mics can handle that, especially condenser mics. it's possible that the input is overloading but most likely the amp in the mic got hit the worst. You have to use a mic that has a selectable pad that can drop the level by at least 20db.
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Old December 25th, 2005, 11:48 AM   #10
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Quote:
Originally Posted by Michael Fossenkemper
That to me sounds like the mic is overloading. When you are that close to a PA system, you are talking some serious volume. not too many mics can handle that, especially condenser mics. it's possible that the input is overloading but most likely the amp in the mic got hit the worst. You have to use a mic that has a selectable pad that can drop the level by at least 20db.
I may be wrong but it seems if the overloading is occuring internally in the mic itself, a pad on its output level would come too late to do any good. OTOH, if the overload is at the preamp inputs, you're correct in that a pad on the mic OR a pad on the preamp would be equally effective. It's too bad Rode didn't see fit to put a low-cut filter and switchable pad on the NTG1 and NTG2 :(

Addendum:

Just found some discussion on Rycote's Microphone Data Information site that suggests some condenser mics with a switchable pad put it between the capsule and the internal preamp. However, according to Jörg Wuttke, Technical Director at Schoeps, writing on the same site ... "Still, the front end of the microphone is the worst possible place for such a pad; a much better place for it is at the opposite end of the cable, right at the input itself. Not only would the signal then be reduced, but also the noise output voltage of the microphone and any interference that had been induced into the cable." So far as I've looked at manufacturer's specs they've only indicated the presence of a pad, not where in the chain it's located. So we're back where we started. Wonder if the typical placement when there is a pad supplied is between capsule and preamp or on the output side?
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Last edited by Steve House; December 26th, 2005 at 07:21 AM.
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Old December 26th, 2005, 12:41 PM   #11
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In general, the pad is placed between the capsule and the amplifier of the mic. I've never used a mic that wasn't built like this. I'm sure there are mics that are though. The whole purpose of a pad is to knock down the level of the signal so it doesn't distort the electronics of the mic. Mics like Shoeps actually have screw on pads that are placed right after the capsule. maybe not the ideal place as it raises the noise level in relation to the signal, but at least it's not distorting. The NTG2 does have a high pass filter on it, but no pad. This could be that the capsule will distort at around the same level as the electronics would.
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Old December 26th, 2005, 02:22 PM   #12
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Shea, did you have the PD set to "MIC" or "MIC ATT".
I shoot bands professionally and you must have
the PD in MIC ATT when shooting near bands to
avoid distortion at the point where the mic is
plugged into the cam.
My guess is that it is not the mic itself that is
distorting.
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Old December 27th, 2005, 06:19 PM   #13
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Shea,

There's been a good discussion of what went wrong, but here are a couple ideas of how to salvage the situation.

1) See if you can get ahold of a tape the band may have made at their main (FOH) mixing board.

3) If he/they allow taping by fans, see if you can get ahold one of their tapes of the show. I guess this would be a good place to start:
http://www.stephenmalkmus.com/punbb/upload/

But I'm sure you're way ahead of me. As for recording future shows, don't depend too much on your camera mic. Usually you want an even stereo sound, like you'd get from in front of their FOH board, but for images, those nice angles you have in your samples are the way to go (for at least part of the show)...Geez, it must be tough to cover a show with one camera...
So anyway, maybe a mic like a Rode NT4 would be a good, simple bet...

<http://www.rode.com.au/?pagename=Products&product=NT4>

Send that to some recording medium (DAT, hard drive recorder, mixer/another stationary camera covering the whole stage, whatever).

Then sync in post...

Sorry if this is all too obvious.

Jim
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Old December 28th, 2005, 05:14 AM   #14
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Thanks for all the info guys!!! I hope you all had a great Christmas!

Jim, thanks for the ideas. I have already tried those chanels. Sadly, no one else recorded the audio.

Dave, what kind of mic set-up do you use? I would love to see some of your work. I had it set to "Mic ATT".

In future the audio will be recorded to a flash recorder with a stereo mic set-up and a second cam. This set-up has to wait until I come back from overseas. Hence why I was using an onboard Rode. Hmmmmm, I was standing under the PA. I think more about that next time.

Maybe I can scrape together enough for an AT3032 for the time being until I have some free cash.I seem to remember that only having -10db. Has a higher sound pressure rating too. A single omni mic is probably better for me until I get my other gear. Maybe I'll try pick up that inline. The shop where I buy all my audio gear from is have a huge closed door sale over the next few days... I'll see If I can skip work......

I still have a few weeks until my next big attempt... I guess I better go practise some more with a few local bands before.

Oh, and if you were wondering, I am going to Japan in March. Not that it means much to you when you don't know what corner of the globe I live...

Thanks again.

Yours,
Shea

I live in Australia.
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Old December 28th, 2005, 05:26 AM   #15
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Shea, that's what I use: 3032 with a PD.
You need to use the -10dB mic pad and also
use MIC ATT when out in front of the band.
If you get close to their speakers (like in
your video) I would also put a 10dB attenuator
either into the end of the mic, or sticking
out the XLR connector on your cam. That's
what I do. The attenuator only costs
around US$15 or so.
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