The Strange Phenomena of Compressorphobia

by John Bosaw

It's Friday, seven p.m.. You're working late in the production studio trying to finish that last minute spot that came in. The AE who dropped this turkey on you in the first place, of course, wants something really wacko, and you're at the end of your creative rope. Suddenly, it's clear to you that your own chords aren't up to the task. It's time to stop screwing around. You reach for the phone to buzz Vern Velvetone, the afternoon drive personality down the hall. Vern, you see, is a master of voices, and given the right creative juices (which flow especially well after he gets off the air), he can do anything.

Vern likes nothing better than a good challenge and screams on over to help you save your bacon, but he says he's only got time for a take or two. Now, you've only been up since 7 a.m. that morning, and your brain is only half on. So you quickly thread up some tape, and when he enters the room, you hand him the script, open the mike, and begin recording. What happens next is covered under Murphy's first law of audio. Vern winds up and does this impersonation of a used camel salesman which turns out to be just perfect. You stop the tape, thank him, and he's out the door. When you play the track back, you notice that the needles are pegged for at least two-thirds of the spot, leaving a grainy distortion that won't go away in the mix no matter how much pixie dust you sprinkle on it. Why didn't you use a compressor? Why is it not an ingrained habit to have the compressor hooked up all the time? It's that old monkey on your back -- Compressor-phobia.

The Audio Purist constantly warns of his fears of losing dynamic range. He allows nothing in the signal path that will even minutely degrade the signal. He insists on controlling the signal by hand instead of allowing the loss of precious dynamic range. Is he crazy? Not really, he's just suffering from acute compressorphobia.

In the past, dynamics processors were known to color the sounds that passed through them. (This is why all those purists are looking for tube limiters and compressors. Purists don't want to use compressors to reduce their dynamic range because of the distortion. But, it's okay to use them as an effect, and besides, tubes give a warm coloration to the signal as well as to the room.) The roots of compressorphobia can be traced back into the Purist's past experience. He once used a compressor ten years ago that made the signal sound mushy, and he could hear the unmusical motion of the audio as it was pumped and squashed. Every time he is forced to reach for a compressor, he still flashes back to that moment.

Classic symptoms of Compressor-phobia: Well, guess what? Compressor-phobia is entirely psychosomatic. Why would audio design engineers invent a product unless it was something that was desperately needed. Necessity is a mother and all that. When someone tells me that they fear losing their dynamic range, I set up the following scenario. (Dissolve to soft focus like the flashback scene in a movie.) We're recording a commercial for a new bathroom bowl cleaner that promises to be both gentle yet strong. Creative's concept is to use two voices, Ginny Gentle, and Bill Brawn. Ginny approaches the mike and seductively whispers her message -- soft, delicate words that draw your listener's attention into the client's message. You, the engineer, set the perfect recording level at 0 VU. Ginny nails it on the second take and leaves. In walks Bill who screams his message into the microphone. Loud, strong and full of energy, Bill's message makes you believe that this bowl cleaner is tougher than the toughest bowl dirt. Again, you set the perfect recording level at 0 VU.

Okay, math students, calculate the dynamic range difference between Ginny and Bill. (Small pause as the calculators come out.) That's right! The dynamic range difference is 0, zip, nada, (zed, if you speak British.) Why the fear of dynamic range loss when you just now created and deliberately zeroed out the dynamic range difference?

The answer is intensity. You don't want the loud voice to be distorted, and yet, you don't want the high end to sound dull because of the compressor. You also don't want the soft voice to be buried in the noise floor, but you don't want to hear the compressor riding the gain. You want to keep the intensity pristine; that lets your ears differentiate the shout from the whisper. Modern day electronics do not affect the sound like the compressors of yesteryear that haunt you in your worst audio nightmare.

Another way of looking at the dynamic range problem is to look at the width of the storage or transmission medium versus the width of the source. The width we're talking about is the dynamic range, not the frequency range (or signal bandwidth). If the signal is 80 dB wide, and the tape machine is only 50 dB wide, then somewhere, you've got to lose 30 dB of dynamic range, or lose something in the process. This is a natural for any compressor.

You say you've got a digital machine? You're not off the hook yet. Try recording on the digital machine at 60 dB. Now, listen. Pretty grainy, huh? What digi-salesman didn't tell you is that your new DAT machine can't record as cleanly at -60 as it does at -10. Once more, another natural for any compressor. Keep the hot stuff out of digital clipping, keep the soft stuff out of the digital grunge generator.

People who try to perform manual compression are also fooling themselves because they must first hear the problematic volume change before they can react to it. By then, it is already too late. (This is the same problem that ancient compressors have.) The attack time of the human hand is hundreds of times slower than the speed at which signals flow through the fader being sweat upon by the hand of the compressorphobic poised for action. Given enough time, the engineer can learn the piece, mark the console with a grease pencil, and make several attempts at controlling the problematic sections, all at the client's expense. The real question is...why? A good compressor can do this in one tenth the learning time, adjust itself for changing audio, and display the amount of gain reduction that it is performing. A fader and a compressor are both nothing more than volume controls. You'll let a machine sequence your music, but you won't let a machine control your volume.

Another behavioral transference is the fear of compressors in audio transfers. Ever notice that instruments fall away as you turn down the volume until all you can hear is the loud stuff? A compressor allows you to listen at lower volumes and yet hear more of the nuances. If your station still uses cart machines, you're probably aware of their limitations. Even a great cart machine has trouble containing all of the dynamic range found on most CDs, unless you compress during the transfer. When transferring a CD to a cart, the cart takes the top (loudest) portion of the audio and forces it into the dynamic acceptance window of the record head and the tape. The things that you lose are the softer signals that help make the stereo image. Carts that have been slightly compressed sound denser, wider, and louder than non-compressed ones. That's right, I said they will sound louder. This is because when you set the input level controls on the cart machine, you position them for the occasional peaks and not the majority of the music. Squashing the signal slightly pulls the peaks down and brings up the average level.

Many mixing engineers mix through a compressor to insure that the end product sounds the same, no matter what medium it ends up on. Any tape being prepared for radio should be compressed during mixing to prevent the station's compressor from drastically altering the mix once it gets on the air. Just remember what audio processor can be found at the output of every radio console. (You're getting good at this.) That's right, a compressor.

Now you see that all your fears were for nothing. You can go back into the world with your head held high knowing that you no longer fear compressors. The only thing the doctor hasn't told you is that you need to be picky about your compressor brand because many manufacturers who are just getting into compression have borrowed or based their designs on the old style of compressor (feed back instead of feed-forward). These inferior compressors are usually made by manufacturers that just want to augment their already dense product line with yet another product. Those manufacturers aren't really proud of their units like a dedicated dynamics processor manufacturer is. They know that most people won't compare compressors, and that by being cheap they will get the first time buyer. Not to worry because that's all they care about. Unfortunately, they have confused the buyer into thinking that all compressors must sound similar.

Acquiring one of these cheap compressors is only a placebo for the real thing. It's a sure way to cause the compressorphobic to regress to his old state of mistrust. Once this happens, it is very hard to ever cure the disease. The best cure is prevention: start with a quality compressor and you will never need to worry about contracting (tympani now, please) ...compressorphobia.