Thursday, September 27, 2012

Dear SNR: Nate DeMare - Mic Patterns

Today we hear from friend and young Jedi in training Nate DeMare who has contributed questions before. A big round of applause for being willing to admit his ignorance and seek the wisdom of his elders. Here's a quick primer on mic types and patterns.
Dear SNR,
I was researching pickup patterns and frequency responses on some mics i will be working with in the near future and mics i have worked with. In my travels of the internet I discovered that I don't actually know the difference between condensers and dynamics (much to my shame). I thought the SM57 was a condenser and thus had a cardioid pickup pattern vs. the 58 with a hypercardioid pickup. So mighty brethren of the knob and fader I beg of you to share your great knowledge with this young padawan.
  To start off, the good old Shure 57 and 58 are both the same mic inside. They use the same capsule but the 58 has a windscreen designed to make it perform better for vocalists (helping eliminate popped Ps and other wind noise) and the 57 is intended more for instruments but you can still sing on it. Both of these mics are dynamic cardioids.

Let's start with dynamic versus condenser. A dynamic mic has a diaphragm attached to a coil of wire that moves back and forth in a magnetic field. The tiny amounts of electricity generated are what give you your signal. A condenser mic has two charged plates set a small distance apart with one attached to the diaphragm and able to move a little. The gap between the plates is a capacitor. The old word is condenser and it's still used in this case. The movement of the diaphragm changes the value of the capacitor and on board electronics process that into useable audio. The major difference is that condensers need power to run where dynamics make their own, however tiny. So a condenser will always have a battery, power supply, or need phantom power sent to it from a console to charge the plates in the capacitor and run the associated amplifier. 

A quick side note on phantom power. We have the telephone companies to thank for coming up with this method of sending power down a signal line. In a mic cable you have three conductors, a ground, a "hot" with the signal on it, and the third has that same signal but polarity inverted, sometimes called the "cold". Phantom power travels on both the signal lines and uses the same ground. What that means is that you can connect a dynamic mic to a line with phantom on it and because the two signal lines both have the same voltage on them the mic doesn't "see" any voltage and the coil won't be damaged. If you have a bad cable though it's possible to send 48 volts through some very delicate parts so if at all possible it's a good idea to turn phantom off for dynamic mics.

As for characteristics, dynamic mics in general are able to withstand higher sound pressure levels (SPLs) than condensers but are usually less sensitive to some degree. Condensers are generally known for having wider frequency response and exhibiting less proximity effect. That's when you get a boost in the low if a singer gets right on the mic.

As for patterns,  cardioid, super cardioid, aren't particular to dynamic or condenser mics. The Shures we talked about earlier have a cardioid pattern. That means that their pickup pattern is sort of heart shaped with the main lobe pointing right where you'd put your mouth. The weak side of the mic is directly behind it which is good in a lot of cases because that's where the monitor and or the crowd is and picking up less in that direction is a good thing. Super and hyper cardioid designs make the hot zone even tighter but there's a trade off. Rejection directly off axis isn't good. When using a hyper card mic it's a good idea to look up the pattern so you know how far off to the side to put a wedge.

That's just the tip of the iceberg Brethren of the Knob and Fader. Every paragraph of this post could be developed into a chapter in a book at least. That's the basics though and now if you're still in the dark you've at least got something to steer you in the right direction with your continued research. One last thing. Mics are nearly always labeled as to whether they're dynamic or condenser and often the pattern as well. For the pattern it might be words or a tiny picture. There you go, get micing!

1 comment:

  1. Also, hard panning effects like reverb and delay away from center will help to add depth to the mix while maintaining clarity in the center for the vocal.


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