Microphone Positioning: Acoustic String Instruments

Experimentation with mic placement provides the ability to achieve accurate and pleasing sound reproduction on these complex sound sources. It is also an opportunity for exploring sound manipulation, giving the studio engineer many paths to the final mix. Whether you are involved in a music studio, a commercial studio, or a project studio, you should continue to explore different methods of achieving the desired results. The possibilities are limited only by time and curiosity.

Acoustic Guitar (Also Dobro, Dulcimer, Mandolin, Ukelele)

When recording an acoustic guitar, try placing one mic three to six inches away, directly in front of the sound hole. Then put another microphone, of the same type, four feet away. This will allow you to hear the instrument and an element of room ambience. Record both mics dry and flat (no effects or EQ), each to its own track. These two tracks will sound vastly different. Combining them may provide an open sound with the addition of the distant mic.
Giving the effect of two completely different instruments or one in a stereo hallway may be achieved by enhancing each signal with EQ and effects unique to the sound you want to hear. Try the previously mentioned mic technique on any acoustic instrument. Attempt to position the mic in different areas over the instruments, listening for changes in timbre. You will find different areas offer different tonal characteristics.
Soon you should develop “an ear” for finding instruments’ sweet spots. In addition, the artist and style of music should blend with your experiences and knowledge to generate the desired effect.

Acoustic Guitar

Microphone Placement	Tonal Balance	Comments
8 inches from sound hole (see left image below)	Bassy	Good starting placement when leakage is a problem. Roll off bass for a more natural sound (more for a uni than an omni).
3 inches from sound hole	Very bassy, boomy, muddy, full	Very good isolation. Bass roll-off needed for a natural sound.
4 to 8 inches from bridge (see right image below)	Woody, warm, mellow. Mid-bassy, lacks detail	Reduces pick and string noise.
6 inches above the side, over the bridge, and even with the front soundboard	Natural, well-balanced, slightly bright	Less pickup of ambiance and leakage than 3 feet from sound hole.
Miniature microphone clipped outside of sound hole	Natural, well-balanced	Good isolation. Allows freedom of movement.
Miniature microphone clipped inside sound hole	Bassy, less string noise	Reduces leakage. Test positions to find each guitar’s sweet spot.

More to come :D

Mics 101 Condenser and Dynamic Mics

Today's Feature: a basic outline on how condenser and dynamic microphones work.

Condenser Microphones

Condenser means capacitor, an electronic component which stores energy in the form of an electrostatic field. The term condenser is actually obsolete but has stuck as the name for this type of microphone, which uses a capacitor to convert acoustical energy into electrical energy.
Condenser microphones require power from a battery or external source. The resulting audio signal is stronger signal than that from a dynamic. Condensers also tend to be more sensitive and responsive than dynamics, making them well-suited to capturing subtle nuances in a sound. They are not ideal for high-volume work, as their sensitivity makes them prone to distort.

How Condenser Microphones Work

A capacitor has two plates with a voltage between them. In the condenser mic, one of these plates is made of very light material and acts as the diaphragm. The diaphragm vibrates when struck by sound waves, changing the distance between the two plates and therefore changing the capacitance. Specifically, when the plates are closer together, capacitance increases and a charge current occurs. When the plates are further apart, capacitance decreases and a discharge current occurs.
A voltage is required across the capacitor for this to work. This voltage is supplied either by a battery in the mic or by external phantom power.

And a small diagram for good measure:

Cross-Section of a Typical Condenser Microphone

Next up:

Dynamic Microphones

Dynamic microphones are versatile and ideal for general-purpose use. They use a simple design with few moving parts. They are relatively sturdy and resilient to rough handling. They are also better suited to handling high volume levels, such as from certain musical instruments or amplifiers. They have no internal amplifier and do not require batteries or external power.

How Dynamic Microphones Work

As you may recall from your school science, when a magnet is moved near a coil of wire an electrical current is generated in the wire. Using this electromagnet principle, the dynamic microphone uses a wire coil and magnet to create the audio signal.
The diaphragm is attached to the coil. When the diaphragm vibrates in response to incoming sound waves, the coil moves backwards and forwards past the magnet. This creates a current in the coil which is channeled from the microphone along wires. A common configuration is shown below.

One more diagram:

Additional Information: http://www.shure.co.uk/support_download/educational_content/microphones-basics/acoustic_string_instruments