Audio clipping (argh!)

Ferdi Willemse

Ferdi Willemse

Well-known member
Hi guys,

I filmed a loud wedding last night and somehow the audio was clipping all the time. We used both an Audio Technica 4073a and a Sennheiser ME66 as a secondary backup microphone. Tuning down the audio input levels on the camera's did not do the job. Is there anything I could have done to prevent this clipping? The speeches etc are all recorded very well, but the drums and the music clipped.

How would you guys handle something like this?

BT, I tried using the Mic Attenuation, but it didn't help. Is that weird?

Thanks in advance!
 
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Ferdi Willemse said:
Hi guys,

I filmed a loud wedding last night and somehow the audio was clipping all the time. We used both an Audio Technica 4073a and a Sennheiser ME66 as a secondary backup microphone. Tuning down the audio input levels on the camera's did not do the job. Is there anything I could have done to prevent this clipping? The speeches etc are all recorded very well, but the drums and the music clipped.

How would you guys handle something like this?

BT, I tried using the Mic Attenuation, but it didn't help. Is that weird?

Thanks in advance!
Click to expand...

Live music or recorded and played through PA?
 
It sounds to the mic capsules themselves were overloaded. There is a point where the diaphragm just can't handle the sound levels and start distorting the signal. It won't matter if you pad the signal down, it's like that when it comes out of the mic.

For situations like that I would suggest using a dynamic mic like an inexpensive SM57.

I imagine you are roaming around near the speakers and that's why your mics are overloading. If you have another camera available, set it up at the mix position with a wide shot of your scene. Set up a dynamic mic into one audio channel and ask for a feed from the board for your second channel. You may need to supply your own cable to go from your camera to the board, make sure its a long one so you have options on where to set the camera. With this setup you can get clean audience audio for applause etc, a clean signal of the mix, plus you can keep rolling this camera while the floor camera starts and stops tape. As a bonus you have a safety wide shot of the scene.
 
Thanks, yes - it is definitely overloaded. The mic's dynamic range just isn't big enough for this amount of noise. I'll think about your setup next time, but with most weddings there isn't a big enough budget for a third camera with good audio capabilities. I guess I'll have to go into the audio edit room and try to clean up the audio as much as possible.

Thanks again!!
 
Thats it, you can overload the mic inputs even when the VU bar showes a max -12db reading, so without going extreme on the meters, you are overloading the input...

I had the same in a disco, close to the speakers. Mic Attenuation does help to bring the high input a little down, but a meter that is showing you that the input is way to loud would help more! It's like the A1 meters go on automatic gain/level control peaking up to -20 db max during heavy overload. But in reality it is a above 0db reading..

You can hear it though on the cans.
 
Michael brings up an important, though oft overlooked issue. High-quality professional monitoring headphones are essential for identifying and correcting issues such as overloaded mics or distorted inputs, as well as fine-tuning mixes and mic placement. iPod earbuds, consumer headphones, or noise-cancelling headsets will only tell you that something is getting to the tracks but they simply aren't designed for critical evaluative monitoring.

Sony MDR-7506 headphones are the industry standard, and for good reason. Also, they're a cost-effective alternative to adding studio monitors to your editing workstation. They also provide a fair amount of isolation in noisey environments such as live music venues. If you're frequently shooting in particularly noisey situations, look into a set of Remote Audio's HN-7506 (a pair of 7506 drivers built into big-honkin' baffled isolation cups). I spent much of this past week recording heavy-industry effects (often in excess of 113 dB), and I'd have been unable to record without my shiney new HN-7506's.

As for keeping your mics from overloading, your to best weapons are mic selection and mic placement. Moving a microphone away from a sound source will lower the amount of energy with which that sound hits the diaphragm (see also "inverse squares, law of"), although you will wind up hearing more of the "room". You can also take advantage of the mic's polar pattern by keeping quieter sounds on-axis and moving louder or more strident sounds off-axis (note: the ME-66 has a very coloured off-axis response, and you will still have to take reflected sound into account).

As for mic choice, go out and buy a dynamic mic. Dynamic mics are inexpensive, don't require phantom power, work extremely well in high-SPL situations, and are by far the most rugged variety of mic. However, they are also relatively insensitive (especially in the higher frequencies), and are usually best positioned close to a sound source. As Jockomo pointed out, a Shure SM-57 is a very good investment. Its one of those "must have" mics for music and sound-reinforcement work, equally at-home on a drum kit, guitar cab, or podium. The SM-58 is a similar mic with an added mesh screen and pop-filter (the classic ice-cream cone mic), very popular for stage vocals. Electrovoice's 635a(b) and RE-50 mics are both omni-directional dynamics built specifically for broadcast video and journalism, and are perfect for ENG-style handheld mic'ing. I've become a real cheerleader for the 635a(b), and in my opinion one should be tucked into the pouch of every video camera bag.
 
Thanks for your great comments, SMuir!

I do actually have, and did use my Sony MDR-7506 on this wedding. They are indeed awesome. I heard the audio clipping at the wedding already, so I experimented with some settings but found out there was nothing I could do at that moment. I also poses a SM-58 for voice purposes. I'll take it with me the next time I'm going to a loud place. In case my AT4073a can't handle the noise I'll have to find a way to strap the SM-58 to my camera one way or the other. It doesn't have a regular shotgun mic shape, so I'll have to be creative. If the budget allows it I'll put an additional mic somewhere else in the room to get some good ambient sound and also usable music etc.

Again, thank you guys for your awesome help. And Michael, thanks - I'll look into it.

P.S. just a little tip: Did you guys know that the SM-58 is the same as the SM-57 when you remove the pop filter? ;)
 
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