While it’s safe to say that most engineers rely on experience when choosing which microphone to use in a given situation, these are some things to consciously consider when selecting a microphone. Here’s a list of items to think about from the latest edition of my Recording Engineer’s Handbook.
- There’s no one mic that works well on everything. Just because you have what could be considered a “great” mic doesn’t necessarily mean that it will be the best choice in all situations. There are times when the characteristics of that mic just don’t match up with the instrument you’re recording, and another mic will work better. In fact, sometimes even an inexpensive mic can work better than an expensive one.
- Select a microphone that complements the instrument you’ll be recording. For instance, if you have an instrument that has a very edgy top end, you normally wouldn’t want to choose a mic that also has that quality, since those frequencies will be emphasized. Instead, you might want to choose a mic that’s a bit mellower, such as a ribbon. This is one of the reasons that a ribbon mic is often preferred on brass, for instance.
- Is the mic designed to be used in the free field or in the diffuse field? Free-field means the sound that comes directly from the source dominates what the mic hears. Diffuse-field means that the room reflections play a large role in what the mic hears. Mics designed for free-field use tend to have a flat frequency response in the high frequencies, and as a result can sound dull when placed farther away in room from the sound source. Diffuse-field mics have a boost in the upper frequencies that make them sound flat when placed farther away. A good example of a diffuse-field mic is the esteemed Neumann M 50, which was meant to be placed somewhat away from an orchestra, so it has a high-frequency boost to compensate for the distance.
- Select a mic that won’t be overloaded by the source. Some mics are sensitive enough that you must be aware of how they’re used. You wouldn’t want to put certain ribbon or condenser mics on a snare drum with a heavy-hitting drummer, for instance. Even some dynamic mics have little tolerance for high sound-pressure levels, so always take that into account.
- 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 (at the front), it probably will roll off some of the highs when it’s 90 degrees off-axis (on the side). If it’s flat 90 degrees off-axis, it may have a rising high end when it’s on-axis.
- Is proximity effect an issue? If you intended to place the mic within 6 inches or closer from the source, will the bass buildup from the proximity effect be too much? If you think that may be the case, consider an omni pattern instead.
- A large-diaphragm condenser mic is not necessarily better than small-diaphragm condenser. Believe it or not, small diaphragm condenser microphones can sometimes capture the lower frequencies better, are generally less colored off-axis than large-diaphragm mics, and have a smoother frequency response. Large-diaphragm mics are a little less noisy, though.
You can read more from The Recording Engineer’s Handbook and my other books on the excerpt section of bobbyowsinski.com.