music & musings

Twenty Questions about using Microphones

Posted on February 2, 2014 Updated on March 6, 2018

Q#1 – Where should you place a microphone (ideally) to record vocals?

Firstly, if you clap your hands and get an echo effect, you should consider deadening the room using carpet, blankets, drapes, or other sound absorbing materials. Move your mic setup toward the room’s center to avoid reflective surfaces (walls/glass/etc).   Vocalist should be roughly 6 – 8 inches away from the microphone. Getting too close to the microphone tends to increase bass response and can create problems with plosive sounds – those popping Ps, Bs, Ds, and Ts.   Too much further increases the risk of picking up room ambiance and the effect of the vocalist “being in a bowl”.  A constant distance from the microphone will provide the greatest tonal balance

Q#2 – What’s a simple way to prevent unwanted noise?

Use a pop shield between the mic and the vocalist to prevent “bumping” sounds on “B” and “P” sounds.  A nylon stocking stretched over a wire (or wooden) hoop works.  Place the shield midway between the mouth and the microphone

Q#3 – Is there a way to test microphone placement?

To find the best location, wear fully enclosed headphones to monitor the microphone output while you move the mic around the performer.  As he/she through the material, you can choose the best microphone position by ear

Q#4 – What is “close miking”?

When miking at a distance of 1 inch to about 1 foot from the sound source. This technique generally provides a tight, present sound quality and does an effective job of isolating the signal and excluding other sounds in the acoustic environment

Q#5 – What is “distance miking”?

Distant miking refers to the placement of microphones at a distance of 3 feet or more from the sound source. This technique allows the full range and balance of the instrument to develop and it captures the room sound. This tends to add a live, open feeling to the recorded sound, but careful consideration needs to be given to the acoustic environment

Q#6 – What is “ambiant miking”?

Placing the microphones at such a distance that the room sound is more prominent than the direct signal. This technique is used to capture audience sound or the natural reverberation of a room or concert hall

Q#7 – How do you reduce the risk of phase anomaly when “stereo miking”?

This risk of phase anomaly can be reduced by using the X/Y method, where the two microphones are placed with the grills as close together as possible without touching. There should be an angle of 90 to 135 degrees between the mics. This technique uses only amplitude, not time, to create the image, so the chance of phase discrepancies is unlikely

Q#8- How can you use microphone placement to reflect different sound character ?

When you are getting a microphone placement for your singer, make sure to move the mic around sideways and up & down to see if you can get a better sound. Get closer and farther away. Change the angle and experiment with different polar patterns (pickup patterns).  When you do that, you’ll notice the sound changing character. A breathy sound close, more natural farther away. There are a lot of different subtle voice character changes in relation to position to the voice.   Keep in mind the style and spirit of the song. Some songs need a different character of voice (i.e. bright and bold vs. soft and dreamy). The singer can also change positions and vocal techniques during the song to change the character.   This is the real art in mic placement and technique. There is no shortcut to this other than experience

Q#9 – What is “bleeding” and how do you avoid it?

Bleeding occurs when the signal is not properly isolated and the microphone picks up another nearby instrument. This can make the mixdown process difficult if there are multiple voices on one track. Use the following methods to prevent leakage:

 

Place the microphones closer to the instruments

Move the instruments farther apart

Put some sort of acoustic barrier between the instruments

Use directional microphones

Q#10- Do foam wind shields prevent popping?

Some microphones come with foam wind shields that fit over the microphone grille, but in practice they tend to be ineffective against anything more than a gentle breeze, and they are no match for a full-on plosive. Furthermore, the thickness of foam invariably absorbs some high frequencies, causing the sound to become noticeably duller than it should be. Wind shields can be handy in live performance to stop the mic filling with drool, but they have a very limited effect on popping

Q#11 – How do you mike an acoustic guitar?

There are two optimum points for microphone positioning – either near the bridge or by the twelfth fret.  Placing the microphone in front of the instrument’s sound hole,  usually increases low frequency response to the point of making the instrument sound “boomy.”

 

Twelfth Fret Placement: Placing the microphone roughly 2 – 4 inches from the twelfth fret and aimed directly at the strings will generally produce a warm, full bodied sound with good tonal balance. Using this technique, the sound hole’s contribution will be moderated since the microphone is not pointed directly at it.

Bridge Placement: Similarly, you can position the microphone so it is 3 – 6 inches from the guitar’s bridge. This will generally produce a somewhat brighter tonal quality. You should also be prepared to experiment positioning the microphone slightly off-axis should you find yourself capturing too much low frequency response from the guitar’s sound hole

Q#12 – How do you mike a piano?

Ideally, you’ll want a minimum of two microphones. Usually, the microphone capturing the higher strings is assigned to the left channel and the microphone capturing the lower strings is assigned to the right channel in the final stereo mix, though the stereo spread generally is not hard left and right. While a single microphone can be used, the lower and upper extremities of the instrument will likely be compromisedIf you are using a single microphone to record a grand piano, position the microphone approximately 8 inches from the piano hammers (to reduce mechanical noise) and 8 – 11 inches above the strings – centered over the piano’s mid point. Pan position should be centered and the piano’s lid should be at full stick

Using a single microphone for an upright piano, it is generally recommended that you record from above, as placement of the microphone in the lower center may interfere with the performer’s ability to access the pedals and the microphone will likely pick up excessive pedal and other mechanical noise. Position the microphone just over the open top, centered over the instrument:

Q#13- How do you mike a drum kit?

Stereo Overhead Pair: Position the two microphones approximately 16 – 20 inches above the performer’s head – separated laterally by roughly 2 – 3 feet and placed 5 – 6 feet out in front of the drum kit. Adjust the two microphone’s Pan position so that you achieve a good stereo spread, though generally not hard left and right
Single Overhead Microphone: Position the microphone approximately 16 – 20 inches above the performer’s head – centered in front of the drum set, and placed 5 – 6 feet out in front. The microphone’s Pan position should be centered for mono drums

Q#14 – How do you mike an amplified speaker?

The mic should be placed 2 to 12 inches from the speaker. Exact placement becomes more critical at a distance of less than 4 inches. A brighter sound is achieved when the mic faces directly into the center of the speaker cone and a more mellow sound is produced when placed slightly off-center. Placing off-center also reduces amplifier noise.  A bigger sound can often be achieved by using two mics. The first mic should be a dynamic mic, placed as described in the previous paragraph. Add to this a condenser mic placed at least 3 times further back (remember the 3:1 rule), which will pickup the blended sound of all speakers, as well as some room ambience. Run the mics into separate channels and combine them to your taste

Q#15 – How does a Dynamic microphone work?

A microphone is a transducer, a device that changes information from one form to another. Sound information exists as patterns of air pressure; the microphone changes this information into patterns of electric current. In the magneto-dynamic, commonly called dynamic, microphone, sound waves cause movement of a thin metallic diaphragm and an attached coil of wire. A magnet produces a magnetic field which surrounds the coil, and motion of the coil within this field causes current to flow. The principles are the same as those that produce electricity at the utility company, realized in a pocket-sized scale. It is important to remember that current is produced by the motion of the diaphragm, and that the amount of current is determined by the speed of that motion. This kind of microphone is known as velocity sensitive

Q#16 – How does a Condensor microphone work?

In a condenser microphone, the diaphragm is mounted close to, but not touching, a rigid backplate. (The plate may or may not have holes in it.) A battery is connected to both pieces of metal, which produces an electrical potential, or charge, between them. The amount of charge is determined by the voltage of the battery, the area of the diaphragm and backplate, and the distance between the two. This distance changes as the diaphragm moves in response to sound. When the distance changes, current flows in the wire as the battery maintains the correct charge. The amount of current is essentially proportional to the displacement of the diaphragm, and is so small that it must be electrically amplified before it leaves the microphone

Q#17 – What are the various microphone pick-up patterns?

Q#18 – What is a “ribbon” microphone?

 

also known as a ribbon velocity microphone, a ribbon microphone uses a thin, electrically conductive ribbon placed between the poles of a magnet to generate voltages by electromagnetic induction.  Ribbon microphones are typically bidirectional, meaning they pick up sounds equally well from either side of the microphone

Q#19 – What is “reflection” & “absorption” of sound waves referring to?

Sound waves are reflected by surfaces if the object is as large as the wavelength of the sound. It is the cause of echo (simple delay), reverberation (many reflections cause the sound to continue after the source has stopped), and standing waves (the distance between two parallel walls is such that the original and reflected waves in phase reinforce one another).  Sound waves are absorbed by materials rather than reflected. This can have both positive and negative effects depending on whether you desire to reduce reverberation or retain a live sound

Q#20 – What is “diffraction” & “refraction” of sound waves referring to?

Objects that may be between sound sources and microphones must be considered due to diffraction. Sound will be stopped by obstacles that are larger than its wavelength. Therefore, higher frequencies will be blocked more easily than lower frequencies.  Sound waves bend (refraction) as they pass through mediums with varying density. Wind or temperature changes can cause sound to seem like it is literally moving in a different direction than expected