Heil Sound Microphone Primer Page 6 Of 13

Bob Heil Microphone Primer

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6--Microphone Characteristics

Here are some of the important characteristics that influence how a microphone will actually sound.

Frequency Response

Of all the specifications, frequency response is the most important in determining how a particular microphone will behave. The band edges are set by where the lowest and highest response will be -3 dB. A graph of the response will tell you if the microphone is perfectly flat or has any coloration or shaped peaks or valleys. It is preferable to have a flat response but a response can be shaped to greatly enhance the performance of a particular microphone. The design engineer will shape the frequency response to give the microphone a personality or a very distinct sound which allows it to achieve much better performance for most applications. Flat is not always best.

Proximity Effect

One of the most degrading effects to a cardioid microphone's frequency response is what's called "proximity effect". Proximity effect has to do with distance that a microphone is "worked" and can be a blessing or a curse. When a sound source gets closer to the cardioid microphone the bass frequencies can be boosted up to as much as 18 dB in some cases! The closer the source the "boomier" the bass! Singers often use the proximity effect unconsciously, bringing the microphone closer to their lips for a warmer, more intimate tone. But in large scale sound systems bass can be an enemy, making it harder to understand the words and having the levels change drastically as the performer unconsciously moves the microphone around in front of them. It also is a disaster when using a microphone with heavy proximity effect up close on an instrument, such as a piano, acoustic guitar or other "natural" sounding instrument. It will completely change the sound as though you turned the bass to "max" on the equalizer. No amount of bass cut will fix it, for the frequency "center" of the proximity effect is not where in the frequency "center" of your bass EQ is.

You will simply have to experiment with a microphone to actually understand each model's unique proximity effect behavior as it is not shown on a specification sheet. With proximity effect, close is not always better. Sometimes its best to place the mic back 6 or even 12 inches from the source to avoid proximity effects, but then you risk picking up everything from the 20th row to the back stage wall! The other damaging effect is that when using a microphone with your lips on it, the diaphragm will in many cases be overloaded, therefore the output will not be clean and articulate. No amount of EQ will help as it all starts at the the microphone and when it comes to the mixer full of low end distortion there is little hope.

Remember: You Can't Fix Acoustic Problems With Electronic "Fixes"!