Part 11 – How To Choose a Microphone

Choosing a microphone is not a big deal if you do your homework. Also accept this fact, more money doesn’t mean best microphone for you and your recording situation. The Beastie Boys had a hit using Radio Shack microphones that you could buy for $49.99. In home recording you will discover it is not always the equipment that makes or breaks the sound but how you use it.

Our first hard, fast and no fluff look is at vocal microphones. Your first consideration is the sound and tone of your voice. Microphones can enhance or take away from your natural voice characteristics. Microphone sound (color) characteristics can be anywhere from “brittle” (accentuating high frequencies) to “boomy” (accentuating low frequencies).

If your voice is bassy you would want to use a vocal mic that will accentuate highs and not the lows. Conversely, if you have a thin, bright sounding voice you will want to consider a mic that accentuates lower frequencies and / or rolls off higher frequencies.

One way to determine your vocal characteristics is to simply sing into a cassette recorder and simply listen. If you have any type of equalizer or tone (bass/treble) controls you can play with that and determine what you did to make your voice sound better. You can get a good evaluation by going to a local recording studio and spend an hour with an engineer there.

Next spend some time looking at microphone frequency response charts. These are graphic representations of tests performed on their microphones in controlled environment to give a basic, “what can you expect” guide to their products. Examples here are the Shure KSM27 and KSM32 studio vocal mics:

You will notice on the KSM32 response chart below that this microphone has 3 different settings. Normal which gives a flat response on the lower frequencies and also a low frequency cutoff and low frequency roll-off. Microphones of this type are great when you need basically one mic for a couple of different voices or instruments. 

It is true that you can use your equalizer to alter any mic characteristic, but it is always better to get the best sound you can without any processing then cut or boost as necessary.

General purpose instrument microphones are really no different than any other microphone except you need to consider SPL (sound pressure level) when micing instruments, especially kick drums and amplifiers. SPL is the microphones ability to handle high-pressure sound waves (volume levels) without damaging or distorting the microphone. Another difference may be in frequency response, as mics that have a specific purpose generally are built with certain frequency responses in mind like a kick drum mic or a piano mic.

Some people are under the mistaken impression that an instrument microphone can not be used as a vocal microphone. Case in point, an SM57 is considered an instrument microphone and an SM58 is a vocal microphone. The SM57 is every bit the vocal microphone as the SM58, why because they are the same microphone except the SM58 has a ball type grille on top and the SM57 has a flat or rather concaved grille. The only consideration is the way they diffuse air as it enters the grill to aid in reducing breath sounds. The SM58 will diffuse, designed for vocals so it will sound a bit warmer as the distance between the screen and diaphragm is greater while rolling off the frequencies above 10kHz and the SM57 will not diffuse, making it cheaper to manufacture and optimized for close micing for instruments. So an SM57 can be used as a vocal mic if you know to sing off axis (not directly into it). The SM57 catalog price is $79.99 and the SM58 is $89.99. Personally I have recorded vocals, acoustic guitar, guitar amplifiers, kick drums, bass etc., with SM57s. I also have wide open access to many high dollar microphones, but I like the SM57 and I use it the most for home recording. In the studio for pro recording, you will still find a lot of SM57s though they will generally be limited in use.

Below are side by side response charts. Notice the difference at 10kHz to 15kHz. These frequencies are the highs that give a brightness and brilliance to sound. The splash of cymbals are here, the brilliance of acoustic guitar and piano are in this range and also the breathy sound of vocals are here as well. When looking at the charts, and this is important, notice the rate of decay between the 2 at 10kHz and 15kHz. At 10k the SM58 drops rapidly making it not a good choice for instrument micing whereas the SM57 maintains good performance up thru 15k then falls off. But in the fundamental vocal range ( 87Hz to 2kHz) they are nearly identical except for barely measurable differences in bass frequencies, again this is due to construction. And in most studio situations you will roll off the "bottom-end" frequencies to control proximity effect. Proximity effect is the "boominess" of a directional microphone as it gets closer to the sound source. Proximity effect can be a good thing for close micing in live situations, but for recording you want to have control over the bottom end. Control of proximity effect is the chief  benefit of the KSM32 roll-off and cut-off feature we looked at above. So the value of these charts (although relative to the testing environment) is you can determine the best microphone for a given purpose.

If you get serious about recording, understanding microphones will be extremely important. Knowing how to use them will be key to using any microphone successfully and a future topic.

Basic Home Recording ©2003 by Jim Goodman. All rights reserved. You may download and reproduce entire document only for non-commercial purposes providing this copyright exists on all copies. All other uses require a written request to jgoodman@alltel.net or thru http://psalm149.com

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