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Old November 2nd, 2007, 03:26 AM   #1
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Dealing with loud peaks

So you're shooting a makeshift band on a beach with a single camera-mounted mic and it sounds great to the ear but there's a guy slapping a makeshift drum really hard at the back.

If I set the level for the loud slaps to come below 0dB then the rest of the band and singers are really quiet. So what should I do other than tell him not to slap so hard? Just allow his slaps to shoot over zero so I can get the rest of the band up nearer zero? Or is over-zero a total no-no, even in a case like this?
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Old November 2nd, 2007, 04:01 AM   #2
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So you're shooting a makeshift band on a beach with a single camera-mounted mic and it sounds great to the ear but there's a guy slapping a makeshift drum really hard at the back.

If I set the level for the loud slaps to come below 0dB then the rest of the band and singers are really quiet. So what should I do other than tell him not to slap so hard? Just allow his slaps to shoot over zero so I can get the rest of the band up nearer zero? Or is over-zero a total no-no, even in a case like this?

Assuming your camera is a regular DV camera so that you're recording digitally and your meters are reading as -dBFS with the zero at full scale, you should never, ever, go to or over zero. This is a case study in why mixers are needed as good ones give you the limiters that are rarely found in the camera, helping you keep average levels up while preventing peaks from driving up into the clipping zone. If you can get the drummer to lower his volume without inhibiting his performance go for it, if he's that much louder than the rest of the band the music will be out of balance anyway with the drum too dominant. Get that mic off the camera and into the hands of a sound person who can get move around to find a good position and aim the mic so as to increase the coverage of the band and singers while keeping the drum out of the more sensitive sections of the pickup pattern.
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Old November 2nd, 2007, 07:14 AM   #3
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Thanks Steve, it was a fairly impromptu shoot with an Audio Technica AT825 single point stereo mic on a shock mount on my Sony Z1 HDV camera. So yes, digital.

We also recorded some tracks with the same mic plugged into a Zoom H4 and mounted on a shock mount on the end of a boom pole but basically it was really difficult to reduce those peaks (this shoot was a group of Indonesian dive guides and it was actually a homemade combined drum and bass which needed hitting fairly hard to get the bass to resonate).

We had automatic gain control off on both the camera and the H4 but maybe actually this would be a good instance where AGC is useful? I wonder if the H4 has a peak limiter in without going for full AGC?
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Old November 2nd, 2007, 08:44 AM   #4
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The H4 does have a limiter that can be set in the menu, but it can sound fairly intrusive if you hit it hard. It also has a compressor but I haven't used that yet.
The relationship between your incoming signal, the input sensitivity switches and the level controls for these devices is important. It's easy to overdrive the input and get distortion even though your levels indicate you have headroom. So you have to make sure your sensitivity switches are set to the correct range. With the H4, I often find this difficult because the change in sensitivity for each switch position seems very wide and my signal is often in between the sweet spot of either low or medium sensitivity. This requires either substantial control before the signal gets to the H4 or making big adjustments to the H4 recording levels.
I really doubt auto gain would have improved the situation on either the H4 or the camera, but if you have the time it's worth engaging and testing for a minute or two and find out for sure.
Steve is right, a good field mixer with good limiters is very important.
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Old November 2nd, 2007, 08:45 AM   #5
 
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Nick...
The fundamental problem you're facing is one of inadequate dynamic range in the recording loop. You're kinda between a rock and a hard place, .... enough volume for most of the material, the peaks are clipped; and, if adjusted to not clip peaks, the rest of the material is down in the mud, very bad S/N.

The only workeable solution is to run a compressor or limiter before your recording device.I've had limited succes with a Presonus Comp16 single channel limiter. Settings are preset so I don't have to spend much time setting up. Power is 12v so I can run off a battery.
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Old November 2nd, 2007, 09:58 AM   #6
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I would probably use the autogain in a situation like this.
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Old November 2nd, 2007, 10:03 AM   #7
 
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The problem with auto-gain is that in musical passages where there is a regular drumbeat, the recording starts "pumping". If your recording pumps, there's hell to pay to fix it in post.
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Old November 2nd, 2007, 10:17 AM   #8
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"The problem with auto-gain is that in musical passages where there is a regular drumbeat, the recording starts "pumping". If your recording pumps, there's hell to pay to fix it in post."

Yeah, short of using a limiter (which would sound really crappy on drums anyway) or a compressor, there's no real answer here. It's unlikely many people would hear the pumping, and the autogain would maximize the dynamic range. I've had good luck with it when recording live bands. Just my two cents.
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Old November 2nd, 2007, 11:27 AM   #9
 
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So here's an interesting thought...

You can improve the dynamic range by raising the recording bitrate. People are so used to recording at 16-bit, since that's the old default bitrate. Raising to 24-bit really helps out in situations like this. Not a complete solution, but, a step in the right direction.
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Old November 2nd, 2007, 12:16 PM   #10
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Another Option: 2 mics, one per channel, with a 30 dB pad added to one of the mics to ensure that the loudest drum doesn't clip. ( assuming that you can't set the mic levels seperately )
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Old November 2nd, 2007, 12:22 PM   #11
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I agree with Bill. Recording at 24-bits and a clean pre-amp lets you leave lots of headroom during recording. With a clean recording, you can fine tune your envelopes/compressor/limiter later in post.
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Old November 2nd, 2007, 03:53 PM   #12
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Originally Posted by Bill Ravens View Post
So here's an interesting thought...

You can improve the dynamic range by raising the recording bitrate. People are so used to recording at 16-bit, since that's the old default bitrate. Raising to 24-bit really helps out in situations like this. Not a complete solution, but, a step in the right direction.
Very few situations would overdrive the 16 bit 96 dB dynamic range, almost nothing in real life, and (almost) nobody can recreate that range in their living room. Using 24 bit recording is not really gong to help, even the best dedicated digital recorders do not have more than 18-20 bits worth of dynamic range because the analog stages are not noise free enough.

The only way to deal with the drum problem is to have a good limiter, which compresses the peaks allowing the normal levels to remain high enough. The other road is to record at low enough level to allow peaks to breath freely, and use a compressor in post. Using 24 bit recording would help only if the whole system is on par, noiseless mics, super mic pre-amps etc.
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Old November 2nd, 2007, 04:03 PM   #13
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In post I've fixed the recording up to a point with wavehammer (volume maximizer on and lots of compression).

I don't know much about limiters. If you're using a single channel limiter like Bill mentions then you're stuck with a mono recording or just limiting one half of your stereo, right?

Can I get a really small lightweight limiter or mixer or compressor that would be better than what's built into the H4? I do this sort of stuff as a sideline on dive trips where we're over baggage limits as it is.
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Old November 2nd, 2007, 04:08 PM   #14
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The more I think about it, a previous suggestion to just split the track is the way to go, although I think a 30dB difference is too much. Six to eight dBs ought to do it. Let the drum clip on the hotter track and deal with it in post.
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