Home > JoeRants, Movies > Getting back to ProLost, Audio pt 1

Getting back to ProLost, Audio pt 1

October 14, 2012

ProLost is an excellent blog by Stu Maschwitz, who wrote an equally good book titled the DV’s Rebel Guide. He recently talked about production audio, and it made me think I should respond and add some thoughts. By the way, Scott Meador’s blog turned me onto that article – thanks, Scott!

Here’s a link to the ProLost article, but the gist is that audio recorders are ripe for a revolution. In fact that’s the title of the article. And he’s not wrong, but his article shows part of the problem. What he’s asking for is for audio to be easier –that some of the thought that goes into making amazing, easy to use cameras be applied to amazing, easy to use audio devices. But there’s a problem.

Stu doesn’t use amazing, easy to use cameras. He uses cameras with Byzantine menu systems and crazy levels of control because he wants to get good pictures. He doesn’t shoot with an iphone because it’s an iphone, not a camera. Actually, he might, and I don’t know, but I’m going to pretend that I know he doesn’t.

He does suggest recording audio to an iphone – not without a microphone and a pro converter, but still…  You don’t get great audio without a good recorder, and that means knowing some stuff. But that’s not really what I want to talk about.

I’m not looking to argue with him, because he’s largely right, the stuff could be way easier, and he complains that pros don’t explain the equipment in a way that he can understand. So I thought I’d give that part a try. This is my next series of articles – how to do production audio.

This isn’t a “why use a mic” or “why record your audio on a separate recorder” article. If you don’t know why you should record your audio separately from the camera, I’ll try and hit that another day. This is for people who know they need a separate audio recorder (which you do), but don’t understand how to use the equipment.

I’m gonna start with the crappy tech stuff , to get is over with. Why does an audio recorder have so many settings? The real answer is because somewhere, someone wants/needs those settings and the audio market is not big enough to leave anyone out. There aren’t the same number of people clamoring for a pro-sumer level “handymic” as there are a similar level handycam. So all that tech stuff needs to be in the recorder so they can sell it to anyone.

The cameras also need those settings because unlike cameras, they recorders rarely have the microphone built in. And if they do, you generally don’t use it – you hook up some other microphone. While some cameras have interchangeable lenses, that’s about as close a metaphor as you get to audio. Lenses are pretty standardized, microphones… kinda… not really.

But I’m already off-topic – here’s my attempt to dig through some of the crap.

First –let’s talk about microphones. Not what to do with them, which I’ll get to, but how they work. They work all sort of different ways. Some microphones have little filaments inside them that vibrate when you speak into them. Some have magnets that do the vibrations. There are even microphones that work with smoke and lasers (I’m not kidding – the sound waves move the smoke, the lasers read the vibrations, bam – there’s sound to be recorded). Some mics use a battery or other power source, and some don’t.

Your recorder needs to be able to record from any source. That’s why there are so many different levels and ways to adjust the levels coming from your mics. You would hope and wish that an audio level was an audio level, whether it’s coming from a handheld mic or a boom or a lav or whatever, but it’s not.  The power coming out of your wall is always 120 volts (in the U.S.), but the power level coming from a microphone can be almost anything.

So your recorder needs to be able to adjust to the power level of the microphone that’s connected to it. If it doesn’t, you may get too weak or too powerful a signal. That can cause one of two things: too week a signal and the recorder won’t be able to boost it enough to make it usable. Too powerful and the signal will overload the circuitry before it even gets to the level/volume control where you can turn it down. That causes overmodulation. Both problems greatly affect the quality of your recording.

So let’s talk about the big differences in audio levels, then the more detailed ones. The biggest “types” of levels are “mic” level and “line” level (there’s also a speaker level, which is the amplified signal that goes to… wait for it… the speakers or maybe the headphones, but that’s not really part of this discussion).

Mic level is generally for microphones, and line level is generally for powered devices, like a CD player. Mic level is a much much lower level, because mics are generally not very powerful. Line level is a much stronger signal, simply because it can be. The more powerful the signal, the less likely there will be interference, so powered equipment uses a stronger voltage.

The metaphor I always use to describe why line level exists is water. You have couple of drops in a glass, and any little dust can quickly turn it into mud. That’s microphone level and interference. If you have a lot of water in the glass (the more powerful line level), then that dust won’t really affect the quality. Line level exists so you signal doesn’t get screwed with as it’s moving along the wires.

Once you know mic and line level, you would hope that you now know everything about audio levels. And you’d be very wrong. Those levels have different standards, depending on what you’re recording from. Let’s start with the easiest– line level.

On the line level side, there’s consumer line level (-10dB, which is a lower level) and professional line level (+4dB, a higher level). You don’t encounter a lot of pro line level stuff during the course of a production day (unless, possibly but not likely, you’re taking a feed from a sound board). Most of the time, unless you know otherwise, you’re recording consumer line level. And most portable audio recorders (below a certain price point) don’t even have a setting for pro line level, because you really don’t come across it outside of a studio, where you’re not recording with a portable audio recorder. So most recorders have a line level setting, and it means consumer level at -10dB.

dB, by the way stands for decibels, which is a term that can be used multiple ways. It may mean a specific volume, or it may mean a comparison of volume, when it becomes a ratio. For our purposes of keeping it simple, just think of a higher dB as being louder, and a lower dB of being lower, and most things will work out OK. The audio techies will hate me for this paragraph.

All right, this is getting much longer than I imagined, so I’m going to call it a night.

In the next couple of days we’ll get into what anyone really wants to know, how the mic level stuff works. It’s a little more complex, but it’s also the part that you really need to know. We’ll get there, I promise.

Categories: JoeRants, Movies
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