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Audio Disaster at Live Event - Line vs Mic

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Justin Whitney
Audio Disaster at Live Event - Line vs Mic
on Jan 16, 2009 at 6:10:50 am

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
http://www.justinwhitney.com


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Rob Neidig
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 16, 2009 at 6:27:13 pm

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


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Justin Whitney
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 18, 2009 at 2:37:43 am

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
http://www.justinwhitney.com


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Elijah Lynn
Re: Audio Disaster at Live Event - Line vs Mic
on Feb 15, 2009 at 10:15:19 am

You can carry some inline XLR attenuators in the future if you can't control each channel separately.

B & H sells some that have 3 levels of attenuation.



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Justin Whitney
Re: Audio Disaster at Live Event - Line vs Mic
on Feb 16, 2009 at 5:44:27 am

You saying that reminds me that I have attenuator switches on my camera for each line. You think that would help? That's sort of an advance feature for me - I haven't used it yet.

Justin Whitney
http://www.justinwhitney.com


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Ty Ford
Re: Audio Disaster at Live Event - Line vs Mic
on Feb 16, 2009 at 3:19:30 pm

Justin,

input pads on cameras usually referred to as attenuators, usually aren't designed to knock line level down to mic level.

Regards

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Justin Whitney
Re: Audio Disaster at Live Event - Line vs Mic
on Feb 16, 2009 at 9:19:10 pm

Cool, thanks, Ty.

Justin Whitney
http://www.justinwhitney.com


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Elijah Lynn
Re: Audio Disaster at Live Event - Line vs Mic
on Feb 18, 2009 at 12:58:10 am

As Ty said, the attenuators on the camera won't knock it down that to that degree. Here are the Hosa attenuators I have. They are not the highest of quality and one of them had it's screws loose underneath the sticker that I had to tighten so the switches worked properly. I like these because they do -20, -30 and -40 db and you can use them in conjunction with the built in camera attenuators to get a total arsenal of 6 different attenuation levels.

I needed them quick and they worked well. I am glad to have them in my gear collection.

If a camera can knock it down it will usually have a settings for "mic level" or "line level" for its inputs. Normally found on high end cameras.

Cheers,



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JC Boulay
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 16, 2009 at 7:13:26 pm

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


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Ty Ford
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 17, 2009 at 2:37:29 pm

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






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Justin Whitney
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 18, 2009 at 2:32:20 am

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
http://www.justinwhitney.com


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Ty Ford
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 18, 2009 at 2:51:48 am

[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






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Justin Whitney
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 18, 2009 at 2:53:05 am

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
http://www.justinwhitney.com


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Ty Ford
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 18, 2009 at 3:31:08 am

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






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Justin Whitney
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 18, 2009 at 2:44:25 am

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
http://www.justinwhitney.com


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Ty Ford
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 18, 2009 at 3:10:35 am

[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






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Guy Cochran
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 19, 2009 at 12:01:00 am

You might considering getting a handy little device to pack along if you plan on doing more of these events like an Audio-Technica AT8202 Attenuator with 10, 20 or 30 db of Selectible Attenuation - In-Line XLR Barrel http://www.audio-technica.com/cms/electronics/a05620466ab0ce16/index.html/




Guy Cochran
DVcreators.net - DVeStore


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Justin Whitney
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 19, 2009 at 4:13:08 am

Hm. That reminds me - my camera has an attenuator switch for each channel. Is this something I could've used to cut the signal back? (Ok, my ignorance is REALLY showing now.)

Justin Whitney
http://www.justinwhitney.com


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Ty Ford
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 19, 2009 at 1:40:44 pm

Hello Brian,

The attenuation you're seeing is probably on the camera mic circuit. Please consult your users manual for the exact implementation.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Randy Wheeler
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 19, 2009 at 10:58:52 pm

The other thing you can do as a habit when initially setting up and checking the audio levels from your camera that is being sent from a unfamiliar mix board is to see if you can get a decent level on your audio meters using the line level first before switching/checking it to mic level.

If your audio meters are way too low at line level no matter how much you increase the levels then switch to mic level (after lowering the audio controls back to 0 or something low to start off with) and watch the meters to see what the difference is after switching and adjusting the faders up on your camera.

The majority of the time the feed from a mix board at a club or band is going to be at line level, especially if you are having to use a 1/4" to XLR adapter to connect from the mixer to your camera.

Line level first then Mic level, that's what I do. Oh, and I always have my own field mixer between any audio I get before it goes to my camera for any surprises.

Randy


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Justin Whitney
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 19, 2009 at 11:01:32 pm

Ahh - that's a great tip. Thanks!

Justin Whitney
http://www.justinwhitney.com


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Jordan Wolf
Re: Audio Disaster at Live Event - Line vs Mic
on Jan 22, 2009 at 6:21:17 am

You might also want to buy a couple of isolation transformers that have a 1:1 turn ratio. ProCo has some that are great for balancing long runs of cable (plus they have Pin-1 Lifts for those times when there's hum).

Wolf
<><


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