Saturday, July 31, 2010

Expanding Your Possibilities

About a year ago, I read a blog from a fellow voice actor who wanted to know how everyone else dealt with the problem of eliminating breaths from a voice track. Like any wind instrument, the human voice requires a moment of intake to supply the vast amount of output going on during a session. The half-second needed to refuel for another ten seconds of output can stir up quite a hurricane, often passing right next to the microphone's sensitive capsule. It's inevitable that some of those big draws will stick out, especially if a beefy amount of compression is being used for a high-energy broadcast spot. Her solution was to edit out the breaths in the DAWS, filling in any pauses with a small amount of studio ambiance recorded in the clipboard. It worked, but it was a slow, methodical solution. Was there a faster, easier way?

I remember commenting at the time that I had rarely run into the issue even in radio unless someone had tinkered with the mic processing. In my home studio the only curious knob turner is me, so things just work. But I couldn't help but wonder why some people had more trouble with breathing than others.

A few days ago, I was reminded of the issue while listening to a recent hit song via CD. The trend nowadays in the studio seems to be to pump up the compression - probably at the mastering stage - to the point where I can hear the vocalist's every breath... along with his mouth noises and even some plosives straining against the pop filter. Now, you could say a good vocalist should spot the problem and make an adjustment to fix it - change how he addresses the mic, back away during big breaths. But I found myself wondering why the producer thought I wanted to hear this guy breathe? Furthermore, this band does a lot of concerts. Surely, this vocalist doesn't huff at his audience all night, especially when he's eating a dynamic with the low end trimmed and the sound guy is using-


Of course. That was the answer. Sound guys on the road use expansion on the mics to prevent feedback and reduce the comb filter effect when multiple mics are open in a given space. In broadcasting, we use expanders as noise gates for the same reasons and to cut unwanted noise in the studio or the booth. Coming from a broadcasting background, it was automatic to me set up and use the expander/gate on my mic processing and not give it a second thought.

Expanders work like compressors in reverse. While a compressor reduces the gain of a signal once it passes above a certain threshold, an expander reduces the gain of a signal once it passes below a certain threshold. The overall effect, depending on how the expander is set, will be to increase dynamic range of something that needs to decay faster after it's initial attack, some percussion instruments, for example, or to allow only desirable signal levels to pass while cutting out anything that just lies there trying to cause trouble.

In broadcasting, the ultimate example of expander/gates doing their job is during The View. Without expanders set to serve as gates to stop the mic leakage, the whole show would sound like a cat fight in a parking garage. Watch Mike and Mike In The Morning on The Deuce and see how they eat those RE-20's. Again, that's live sound configuration with the mics EQ'd to filter off the low end to stop popping and excessive proximity so that the talent can eat the mics to break open the expander/gates. Without the gates, the studio ring (comb filter effect) would drive the radio listeners right up a wall.

So, how does an expander help the voice over artist? Easy. With the threshold set properly, the gate will "close" whenever you stop talking, thus reducing your breathing. No more breath cutting sessions in the DAWS. Plus, you're eliminating studio background noise so that your ambient "open mic" noise is virtually no noise at all. That makes editing much easier, especially if you're punching in something you recorded today into something you recorded last week.

Setting the expander isn't all that difficult, but it does require a bit of trial and error. And the setting you choose may be a bit of a compromise. You don't want the expander slicing off the trailing edges of your voice, and setting it too fast can make you sound like you have a cold, but you also want it to kick in fast enough to stifle the breaths. Some practice and experience voicing with the expander will help. A tweak here, a tweak there, and you'll get it. Just two rules to remember: don't set the expander threshold near or above your compression threshold, and don't set your compression threshold so far down it enters the threshold of the expander. Break these rules and you'll hear the expander working, causing a click or thump every time it attacks. A good starting point for your expander is -40db. Hopefully, you can tweak it down from there.

An expander does not solve all your problems. If there is noise in your mic cable, you will still have noise in your recordings, just only during the times you were talking. Same goes for bad acoustics. An expander can eliminate that last stubborn bit of room ring, but it's no substitute for proper room treatment, especially if you work farther from the mic.

I haven't had any success with plug-in expanders in the DAWS. They either chop words or sound like a bad noise gate on a 16mm movie. Personally, I believe in the "garbage in, garbage out" theory of production. Just like setting a high-pass filter on the preamp or using a quality pop filter instead of EQ, I believe you should eliminate the problem as early in the audio chain as possible. And besides, like front end compression, it sounds good in your headphones.

In broadcast level channel strips, the expander/gate is standard equipment, assumed to be essential to get the job done. I was surprised to find that many high-end recording studio channel strips from names like Avalon and Focusrite don't include an expander in the chain. I guess the feeling behind that is that serious project studios are quiet enough not to need gating. Maybe the practice of tracking makes mic gating redundant. Or maybe it's a way of forcing the studio owner into the "up sale" to a top-of-the-line model with expansion. Whatever. But it sounds to me like some record producers might want to look into buying a simple but effective DBX unit.

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