Recording Techniques Basics: Microphone Choice and Placement

Creative Commons image Sun Studios by MiiiSH at Flickr

The following material is from page 71 to 81 of The Recording Engineer’s Handbook by Bobby Owsinski

The Secrets to Getting Good Sound

The Player and the instrument – Contribute about 50% to the overall sound (sometimes more, sometimes less—but always the greatest portion).

The Room – Contributes about 20% to the overall sound (even on close-miked instruments, the room is far more responsible for the ultimate sound than many engineers realize).

Mic Position – Contributes about 20% to the overall sound (placement is really your acoustic EQ and is responsible for the instrument’s blend in the track).

Mic Choice – Contributes about 10%to the overall sound (this is the last little bit that takes a good sound and makes it great).

Choosing the Right Mic

There’s no one microphone that does every single thing. — Michael Beinhorn

1. Select a microphone that complements the instrument that you’re 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, because the mic will emphasize those frequencies. 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.

2. 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 response in the high frequencies and as a result can sound dull when placed farther away. Diffuse field mics have a boost in the upper frequencies that makes them sound flat when placed further away.

3. 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.

4. 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.

5. Is proximity effect an issue?

  • If close-miking, will the bass buildup from proximity be too much? If so, consider an omni.

Microphone Considerations

  • 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 with 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.

If you are not getting the sound you want

  • Change the source, if possible (the instrument you are miking).
  • Change the mic placement.
  • Change the placement in the room.
  • Change the mic.
  • Change the mic preamplifier.
  • Change the amount of compression and/or limiting (from none to a lot).
  • Change the room (the actual room you are recording in).
  • Change the player.
  • Come back and try it another day.

Secrets of Mic Placement

Step 1

  1. To Find the “Sweet Spot” To correctly place an omni microphone, cover one ear and listen with the other.
  2. Move around the player or sound source until you find a spot that sounds good.
  3. To place a cardioid microphone, cup your hand behind your ear and listen.
  4. Move around the player or sound source until you find a spot that sounds good.
  5. For a stereo pair, cup hands behind both ears. Move around the player or sound source until you find a spot that sounds good.
Step 2
  1. Get the instrument to make the sound you want to record first. If you can’t hear it, you can’t record it.
  2. Use the cover-one-ear-and-listen technique as described above to find the best place to start experimenting with mic position.
  3. Position the mic and listen. Repeat as much as necessary.

Placement Considerations

“In regards to mic techniques, what I adapted was this classical idea of recording; i.e. the distance of the microphones to the instruments should not be too close if you want to get anything with tremendous depth. Obviously I used close miking techniques as well, but it started with the concept that “Distance Makes Depth” that Bob Auger taught me. Generally the basic philosophy of getting the mics up in the air and getting some room sound and some air around the instrument was what we used. Then you’d fill in with the close mics.” —Eddie Kramer

The 3 to 1 Principle

3 to 1 Principle for Microphone Placement from http://blog.shure.com

The 3 to 1 principle is pretty important when considering any multi-mic setups because, if you observe the rule, you can stop any phase problems before they start. Simply put, the 3 to 1 principle states that in order to maintain phase integrity between microphones, for every unit of distance between the mic and its source, the distance between any other mics should be at least three times that distance. For instance, if a pair of microphones is placed over the soundboard of a piano at a distance of one foot, the separation between the two mics should be at least 3 feet.

Checking Phase

Checking microphone phase should be one of the first things that an engineer does after the mics are wired up and tested. This is especially the case in a tracking session where a lot of mics will be used, since having just one mic out of phase can cause uncorrectable sonic problems that will haunt the session forever. A session that is in phase will sound bigger and stronger, while just a single out-of-phase mic will make the sound tiny and weak.

Also try these options:

  • Checking Phase by Listening
  • Checking Phase with an Ocilloscope
  • Checking Phase with a Phase Meter

Checking Polarity

  • The polarity check is used mainly to be sure that all mics are pushing and pulling the same way and to check for miswired cables

Mic Placement Most Likely to Cause Problems

  • Mics facing each other (like on the opposite sides of a drum).
  • Mics facing the floor. (just angle them a bit).
  • Mics pointing at one source where there is another much louder source nearby with its own mike.

Learn How to Record Instruments and About Recording Equipment

From teachmeaudio.com/recording/instruments/