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Why would I need an audio mixer in filmmaking?

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Neil Redman
Why would I need an audio mixer in filmmaking?
on Dec 9, 2011 at 8:29:08 am

Hi, I'm a little confused about what an audio mixer actually does and why I would need one.

So for my purposes I'm mainly shooting short films and events. Lets say I want to record my audio now with a few different mics and hook them up to a recorder, something like a zoom h4n or a tascam dr-100. That way I can already control the gain individually for my microphones and record them to their separate tracks.

So where exactly would a mixer come into play? Is it just that a mixer has more input sources and can a mixer actually record by itself or would I still need to hook it up to a recorder?

As far as I understand it a mixer would take for example two microphones as a source and then output them as a single signal in which I can 'mix' the two sources together as I like. So if this is the case I don't see the advantage why I would do this. Wouldn't it always be better to record everything on its own track and then mix it later in post? I can see how this would be useful, say mixing at a 'live' concert or on the news where there will be no post work done. But as far as I understand it, they are used in feature films as well and I don't see why that would be of advantage.

I hope somebody can enlighten me on this =)


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Ty Ford
Re: Why would I need an audio mixer in filmmaking?
on Dec 9, 2011 at 1:37:38 pm

Hello Neil and welcome to the Cow Audio Forum.

Mixers and the people who operate them are usually related to someone else on the project and are there solely to raise production costs, cause delays and bilk producers out of their money. (that's a joke, ok?)

Mixers are more than knobs that let you vary the volume.

1. They let you vary volumes without shaking the camera or getting in the way of the camera op.
2. You may need to do that a lot with some people. I ride gain even if one person is talking if their voice fades on the end of each line. You can only do this in a relatively quiet environment, otherwise you bring up the ambient noise.
3. Mixer preamps (good ones) sound better than camera preamps.
4. Good mixers have input transformers that scrape off RF before it get into your audio.
5. Good mixers have limiters that allow you to record hotter, keeping your audio further above the noise floor without distorting.
6. Good mixers have EQ that lets you roll of LF HVAC noise before it gets into your audio.
7. Good mixers have mulitple outputs so you can feed more than one camera, or separate recorder simultaneously.
8. Good mixers make your sound better. If they didn't pros wouldn't use them.

Regards,

Ty Ford

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


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Neil Redman
Re: Why would I need an audio mixer in filmmaking?
on Dec 9, 2011 at 6:38:18 pm

Hey, thank you very much for the reply but I'm still not exactly sure about the exact differences between a mixer and an external recorder.

Say you are recording your sound dual system to an external recorder anyways. Wouldn't then all of the points that you just named (except for number 7) also apply to a good external recorder? And for number 7 when would it be of advantage to feed my audio to more than one camera? Would it be for backup purposes and to save time in Post synching up footage?

Could you say that a good recorder (something better than say a zoomh4n, like I mentioned in the first post, but with many input connectors) can essentially do the same things as a mixer, with the difference that a recorder would record the audio to individual tracks and the mixer would feed it to a camera or a recorder?

So bottom line, if I had a recorder that let's say records 8 individual tracks (and thats all I need) letting me control the gain for each of them and that has really good Preamps, EQ's etc. and I want to record dual system, could I then still benefit from a mixer? [Besides slowing down the production and using up all of my budget of course ;)]


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Ty Ford
Re: Why would I need an audio mixer in filmmaking?
on Dec 9, 2011 at 6:58:04 pm

Neil,

If you had an external recorder with good preamps, EQ and limiters (and probably good input transformers), you'd be pretty set for production, but you'd then have to mix everything in postproduction. That takes time and money.

A mixer and the person operating it, mixes on the fly so that there is a complete track that requires little or no post production time. You see it in live or live to tape TV all the time. SNL probably has the budget for a multitrack machine so they can go back in after the show airs live to fix anything they want and then run that to a recorded archive for later use.

In movies production, that's usually just a mix of dialog. Music and effects are recorded separately and mixed during postproduction.

Regards,

Ty Ford

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


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David Jones
Re: Why would I need an audio mixer in filmmaking?
on Dec 9, 2011 at 6:58:42 pm

To answer your question: yes, you can plug your mics into a good 8-track recorder. BUT, you still won't have as much control over the signal as you would with a mixer.

Good mixers have MORE and better control over adjusting the level. They have a trim AND a fader control; recorders and cameras do not (if they do, it's usually menu driven). This can make a big difference with certain mics. Even Sound Devices, which makes maybe the best 8-track recorder, also makes two different kinds of mixers to go along with the recorder.

Don't think that just setting the levels and leaving it will get you good audio. It takes constant adjusting and tweaking of the faders to achieve good results.

Best,

Dave J


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Neil Redman
Re: Why would I need an audio mixer in filmmaking?
on Dec 10, 2011 at 3:56:35 am

Okay thanks to you two. Its starting to make sense to me now ;)


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Craig Alan
Re: Why would I need an audio mixer in filmmaking?
on Dec 11, 2011 at 3:01:35 am

Aside from all the controls that a good mixer adds, during a shoot with so many things that need your attention, ergonomics is often key to getting the results you desire. A high quality audio mixer is designed for a specific task and it does it better than anything else. This is not just a nice luxury if you can afford it. It is the difference between properly set levels and inconsistent levels and often ruined shots as the camera operator fiddles with some small audio control or menu item.

If I am shooting with just a camera or even an audio recorder in a dark auditorium, I need a flashlight in one hand and a delicate touch to adjust the audio levels. And often by the time you do it, the incoming signal has changed dramatically. If I am using a mixer, the LEDS are lit and the knobs are big and easy to adjust even in the dark. Even if you are not a one-man-band, this will help an audio tech if he is using a boom or adjusting several inputs or repositioning mics on the fly.

If you bought a recorder that had what a mixer offers, it would cost you more than a quality mixer and a quality recorder. And a quality mixer can be used with or without a double system.

Another ergonomic advantage is you can run one or two xlr cables or something like Canare BACX25 Cable for Portable Mixers with Monitor Output to your cam instead of attaching a bunch of stuff like cordless receivers, which get in the way. No matter where I mount my cordless receiver to the camera, during a shoot, it’s very hard to read and adjust. Not true when it’s attached to my mixer.

Like you, I am not an audio technician but a generalist and I can tell you this forum is one of the best on the cow or anywhere else for good sound advice (pun intended).

It is interesting to note that if you do a search for say lighting techniques, there are a lot of good hits. Granted none of them can teach you how to be artistic with light, every shoot is different, and the cow’s lighting forum is about the best for specific advice and suggestions, but just the same, a lot of good hits all over the web. But try that for audio and even basic stuff is glossed over and badly presented. The thing I find really ironic is videos posted about how to record sound for video -- the sound quality in the posted videos are often freaking awful. Do as I say not as I do? A good audio mixer won’t make you an audio pro, but it will help you understand how the hell they do it at all.

One last point and I’ll shut up. Whatever camera you buy today will become obsolete sooner than later. When was the last time anyone retired a good audio tool for the newest gizmo?

OSX 10.5.8; MacBookPro4,1 Intel Core 2 Duo 2.5 GHz MacPro4,1 2.66GHz 8 core 12gigs of ram. GPU: Nvidia Geoforce GT120 with Vram 512. OS X 10.6.x; Camcorders: Sony Z7U, Canon HV30/40, Sony vx2000/PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Ty Ford
Re: Why would I need an audio mixer in filmmaking?
on Dec 11, 2011 at 3:26:21 am

[Craig Alan] "Like you, I am not an audio technician but a generalist and I can tell you this forum is one of the best on the cow or anywhere else for good sound advice (pun intended). "

Thank you, Craig! And everyone who has taken the time to enrich this forum with their own experiences and wisdom.

Regards,

Ty Ford

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


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