Here’s an excerpt from The Recording Engineer’s Handbook, available here.
While it’s safe to say that most engineers rely on experience when choosing microphones, there are some things to think about when selecting a microphone.
“There’s no one microphone that does every single thing.”—Michael Beinhorn
Select a microphone that compliments the instrument that you’ll be recording. For instance, if you have an instrument that has a very edgy top end, you wouldn’t want to choose a mic that also has that quality since those frequencies will be emphasized.
Instead, choose a mic that’s a bit more mellow, such as a ribbon. This is one of the reasons that a ribbon mic works so well on brass, for instance.
Is the mic designed to be used in the “free-field” or in the “diffuse-field”? Free field means that the sound source dominates what the mic hears. Diffuse field means that the reflections play a large role in what the mic hears.
Mics designed for free field use have a very flat frequency response in the high frequencies, and as a result can sound dull when placed further away. Diffuse field mics have a boost in the upper frequencies that make them sound flat when placed further away.
Select a mic that won’t be overloaded by the source. You wouldn’t want to put a ribbon mic or many condensers on a snare drum with a heavy hitting drummer, for instance.
Choose the right polar pattern for the job. If leakage is a consideration, then choose a mic with the proper directional capabilities for the job. If a mic is flat on-axis, it will roll off the highs when it’s 90 degrees off-axis. If it’s flat 90 degrees off-axis, it will have a rising high end when it’s on-axis.
Is proximity effect an issue? If close-miking, will the bass buildup from proximity be too much? If so, consider an omni.
• Condensers of a given polar pattern will tend to give you more room sound than dynamics of the same polar pattern
• Omnis will give you lower bass extension compared to cardioids
• Large diaphragm condensers have lower self noise than small diaphragm condensers
• Small diaphragm condensers are generally less colored off-axis than large diaphragm condensers
The Secret Of Getting Good Sounds
Contrary to what many who are starting out in recording might think, just having great equipment doesn’t guarantee a great sound. While you can’t really quantify how much each variable contributes to how something ultimately sounds (since each situation, even within the same project, is unique), you can generally break it down to something like this:
• The player and the instrument contribute about 50 percent to the overall sound (sometimes a little more, sometimes a little less – but always the greatest portion)
• The room contributes about 20 percent to the overall sound (even on close-miked instruments, the room is far more responsible for the ultimate sound than many engineers realize)
• The mic position contributes about 20 percent to the overall sound (placement is really your acoustic EQ and is responsible for the instrument’s blend in the track)
• The mic choice contributes about 10 percent to the overall sound (this is the last little bit that takes a good sound and makes it great)