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Audio Disaster at Live Event – Line vs Mic
I assure you I’m not an audio professional. But I hope y’all don’t mind me getting some expert feedback, so to speak.
I was shooting a live event and decided to double-up on audio. I’m still pretty new at this so it was the first time I managed to get a line from the sound board. I put that in Channel 2 and attached a boom to Channel 1. The boom was pointed at the stage, which was bordered by the speakers.
Unfortunately, the pre-show DJ used a different setup and I didn’t have the chance to test the line-out. Once the mc took the mic and started the event, I heard a strange buzz in one ear and nothing in the other. But the venue was too damn loud for me to tell what was going on through the headphones, so I relied solely on the levels on my camera, which never went far above or below -12. In fact neither channel spiked to red, though Channel 2 (the line) hit its level and stayed there with very little movement.
So now I’m digitizing and I realize that the ear I heard nothing from was the mic and it was good – it matched the venue so well that I couldn’t tell the difference. The line channel, however, has distortion, particularly when the MC is talking (she was very, very loud). But the waveform looks strange:
The left side is the Line, the right side is the Mic. As you can see, the line is completely blown out. But it’s also restricted – it’s thinner than the mic line.
I don’t know enough about audio to tell what’s going on here, much less if there’s any recovering from it. Worst case scenario I can use the mic channel. Even though it’s boomy it has great audience feedback. But I’d love to know how NOT to let this happen again.
I have a hunch – is this even possible? What if the line out from the board was cranked too high? Would that distort the signal going OUT? So that there was no way for me to control it from the camera except to make the distorted signal louder or softer? Could it have something to do with the cable, which included an adapter and 2 50′ lines covered with schmutz and vodka?
Thanks for the help. Let me know if you need more data.
Justin
Justin Whitney
https://www.justinwhitney.com -
21 Replies
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Justin,
Yes, the line input is what is called “clipped”. Where you see that the waveform is squared off, the audio has just been cut or clipped off at that point because it was too high for your camera. Does your camera accept line level signals or were you feeding a line level signal into a mic level input? If so, that would definitely cause it to be clipped. Mic level is typically about -60 to -50db while line level is either -10db or +4. You would need to convert from line to mic level. If your camera CAN accept line level, then you had the level control set too high, which caused the clipping. Unfortunately once clipped, there is very little that can be done to try to make the audio usable. Adobe Audition has a “Clip Restoration” feature and EQing can help a little, but you’ll still have something that sounds pretty bad. Glad you had the shotgun on the other channel!!
Have fun!
Rob
Rob Neidig
R&R Media Productions
Eugene, Oregon -
Hi Justin,
Since the clipped audio never goes over -12dB, your camera clearly did not do the clipping. You are absolutely correct in thinking the clip was elsewhere and you could only control the level of the clipped audio. It may have something to do with the engineer sending you a -10dBV signal while all his internal bussing and levels were for his main +4dBU outs. That’ll cause havoc on many makes of live boards. Bad cables can do lots of stuff to your audio, but clipping the signal isn’t one of them. Vodka has a negligeable effect on audio as well. A good thing that is, too.
Sadly, there ain’t no going back now. That audio is clipped forever. There are tools to remove a clip here and there, but what I see in those screenshots is pretty much a lost cause. I hope you had everything on your mic channel.
JC Boulay
Audio Z
Montreal, Canada
http://www.audioz.com -
Hi Justin and welcome to the Cow Audio Forum,
JC and Rob are spot on here. As amazing as it seems, you can actually send line level audio to a mic level input, set what looks like a decent level, and if you don’t bother to listen, get total crap.
The clip occurs at the camera input before the meters, so the meters look good.
You were in a tough situation with high sound levels. Just because someone is standing at a console, doesn’t mean that person knows what level is coming out of every jack. On numerous occasions, I have been told a feed is mic or line and found it was the opposite or something in between. My best defense is my Sound Devices 442 mixer. It takes mic or line inputs and delivers mic, -10 or line outputs. I have not yet been in a situation where that mixer hasn’t been able to handle the incoming audio.
The best advice I can offer for the future is to use closed-back headphones, like the Sony MDR-7506 and ALWAYS listen. You may even find that during the shoot the levels to your camera will change. That’s because the audio feed you’re getting from the console is post fader, not prefader. If the audio is post fader, every time the sound operator changes a fader on the console, the audio level to your camera changes.
Some operators know their setup really well and make few changes. You can actually use the post fader feed. Having said that. if you are a one-person operation and can’t pay total attention to the audio, you can end up getting badly burned.
Regards,
Ty Ford
Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Watch Ty play guitar -
Thanks for the advice, Ty. I’m going to do a little more research on the technical bits you’re dropping so I can wrap my head around that. But at least it’s a place to start.
“if you don’t bother to listen”
Sorry if I sound defensive, but this seems to imply some sort of carelessness. I was actually straining to hear the feed through my headphones, but like I said the venue was so damn loud I couldn’t make out what was happening, which is why I had to rely on visual levels. I’ll take a look at the headphones you mentioned. That may help. The setup was also a bit of a problem since I was set up at the very back of the audience and the DJ was literally on stage with the performers. I couldn’t leave my equipment alone to go up mid-performance and try to investigate the problem (even if I knew where to look). That’s why I’m searching for a camera-side solution. So, just a tough situation all the way around, which is why I want to avoid it in the future. With the great info I’m getting from you guys, I think I’ll be much better prepared next time.Thanks again for the help!
Justin Whitney
https://www.justinwhitney.com -
Rob, thanks! Your response reminded me of an important detail I left out. When I first heard about doing this, my memory played tricks on me and re-imagined my camera has having a separate line/mic switch for each channel. But once I was set up, I realized that I only have 1 master switch for both. When it was on “line”, the mic channel went dead. When it was on “mic”, they were both live. I thought it better to keep it on mic and hope for the best rather than risk it all on 1 channel.
So now I know. I never imagined that there was such a huge difference. I’d love to keep recording both mic and line input, but it sounds like I shouldn’t run them both into my camera? I’m using a Canon XH-A1. I’ve heard of other people using setups with independent audio recorders but I’m worried that syncing will be a huge hassle. I’m taping dance events, so it’s vital that the music is synced to perfection with the movement onstage.
Justin Whitney
https://www.justinwhitney.com -
Thanks, JC.
So, I’m a little confused about “-10dBV signal” vs “+4dBU outs” but I can research that separately. (I’m REALLY inexperienced at audio engineering.) If the sound guy had dropped the signal on the line out, do you think that would’ve solved the problem? Or is the root of the problem the fact that I had a line going into a mic input?
I also just remembered that the sound guy couldn’t even find an XLR out and had to use an adapter. I don’t know if that makes any difference at all or is unusual. I assumed sound boards had XLR outs for just this kind of setup. We ended up spending precious setup time going through a huge cardboard box looking for the right adapter. Bit of a clusterf***, really.
Thanks for the help!
Justin Whitney
https://www.justinwhitney.com -
[Justin Whitney] “”if you don’t bother to listen”
Sorry if I sound defensive, but this seems to imply some sort of carelessness. “Sorry Justin, I frequently go into “broad mode”, speaking/writing to group. I did read what you wrote.
Yes, yours was a tough situation. We’ve all had them. Getting there early helps somtimes, sometimes not.
Regards,
Ty Ford
Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Watch Ty play guitar -
Ty, I just looked up the field mixer you mentioned – wow! What a great tip. I didn’t even know that existed (though I should expect it). That’s going to be a huge help in the future. You’re right – I can’t always rely on the talents of the guy behind the board.
As far as the headphones, I’ll check but that looks like the model I’m already using. They *look* the same, at least, but I can’t remember the exact model number. Unfortunately, they didn’t help in this case. Like I said, the venue was really, really loud. I spent the entire 5-hour event listening through the headphones and they were pretty useless. Unless I encase my head in a bubble, I just don’t know how to avoid that in the future. That mixer, multiple capture devices, and a small blessing to the sound gods may be my best hope.
Justin Whitney
https://www.justinwhitney.com -
[Justin Whitney] “So, I’m a little confused about “-10dBV signal” vs “+4dBU outs” but I can research that separately. (I’m REALLY inexperienced at audio engineering.) If the sound guy had dropped the signal on the line out, do you think that would’ve solved the problem? Or is the root of the problem the fact that I had a line going into a mic input?
>> The latter. There are basically 3 levels. From low to high; mic, -10 consumer and +4 professional line. There are actually some inbetween there, but the three are the main ones.
>>Mic levels can vary by maybe 20 dB with ribbon mics usually being the least sensitive and condenser mics being the most sensitive. All of these will be on balanced XLR connectors. (there are very cheap unbalanced mics. you don’t want them.)
>>-10 is consumer level. You usually only see it output on 1/4″ TS or RCA jacks.
>>Line level can be 0, +4 or +8. Either 1/4″ TRS jacks or XLRs
I also just remembered that the sound guy couldn’t even find an XLR out and had to use an adapter. I don’t know if that makes any difference at all or is unusual. I assumed sound boards had XLR outs for just this kind of setup. We ended up spending precious setup time going through a huge cardboard box looking for the right adapter. Bit of a clusterf***, really.”
>>That’s why I use the 442 mixer. I can take in mic, -10 or line and output mic -10 or line separately to each channel and I can feed three separate stereo inputs.
I humbly suggest you click on the “bootcamp field guide” link below.
Regards,
Ty Ford
Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Watch Ty play guitar -
Sony MDR7506 or Audio Technica ATH-M50 are good.
If you need more: tp://www.eham.net/reviews/detail/2041
Regards,
Ty Ford
Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Watch Ty play guitar
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