4. Power & Distribution
Do you know the difference between 110-volt and 220-volt AC power in the U.S., beyond the fact that 220 is basically twice as much voltage? How about 3-phase power?
While we’re at it, what’s “AC” actually mean? If you’re even slightly fuzzy on these concepts, time to get busy and learn.
I’ve found that understanding 110 versus 220 power has even made me more handy (and safe) around the house, since there are usually some 220 appliances around.
It’s also a good idea to be familiar with the peak and average current draw from all components in a sound system, and how to best manage the AC power. Remember the story about how Aerosmith lost power at Sturgis in 2009?
Someone plugged something (non-audio in this case) into a power distro and drew too much current, tripping a breaker.
The show was temporarily paralyzed, and Steven Tyler ended up falling off the stage and requiring hospitalization. All because someone ignored a power issue. Don’t be that guy.
3. Microphone Proximity Effect
Know the difference between omnidirectional and directional microphones with respect to proximity effect?
How about the difference of proximity effect between cardioid and hypercardoid mics? What do those little lines and dashes mean on a microphone frequency response plot below 100 Hz?
In a nutshell, proximity effect is something that directional mics exhibit, and true omni mics do not. The closer the microphone gets to the sound source, the more the low frequencies are boosted.
But don’t forget that it also works the other way – the further a mic is located from the sound source, the more the low frequencies are attenuated. The more directional the mic, the more proximity effect it will exhibit.
2. Polarity vs. Phase
These terms are often erroneously interchanged by those who either do not recognize the difference or don’t care enough to make the distinction. Some manufacturers even use “audio phase” where they mean “polarity”. So let’s straighten it out.
Polarity refers to swapping the positive for the negative, either in terms of speaker terminals, microphone signals, or the electrical signals within a console.
Phase refers to the relationship between signals in terms of “degrees of phase”. One place where these ideas appear to merge is when it is said that “flipping polarity is the same thing as the audio being 180 degrees out of phase”.
Yes, I suppose this is true, but it confuses the issue. Normally, a number of degrees of being “out of phase” refers to a specific frequency. In other words, you might be 90 degrees out of phase at 1 kHz, but it would be a different number at 2 kHz. Get the picture?
1. Gain Structure
I saved it for last because it’s the one I see done wrong more than any other. If you “use your gut” to set levels, and if you like to mix by the light of the clip indicators because your idol says, “I like to hit the buses hard” – you’re in for some trouble.
Unless you’re looking for a specific effect (i.e., some oversaturation in the sound), it’s best to gain stage the signal from start to finish so that you’re maximizing the dynamic range of the system, minimizing the noise floor, and avoiding distortion. There are many sources of good information and instruction about gain structure.
Learn it, know it, live it.
Karl Winkler serves as vice president of sales/service at Lectrosonics and has worked in professional audio for more than 25 years.