Microphone Techniques for Recording
A Shure Educational Publication
Microphone Techniques
Ta b l e o f C o n t e n t s
Introduction: Selection and Placement of Microphones ............. 4
Section One .................................................................................. 5
Microphone Techniques ........................................................ 5
Vocal Microphone Techniques ............................................... 5
Spoken Word/“Podcasting” ................................................... 7
Acoustic String and Fretted Instruments ................................ 8
Woodwinds .......................................................................... 13
Brass ................................................................................... 14
Amplified Instruments .......................................................... 15
Drums and Percussion ........................................................ 18
Stereo .................................................................................. 21
Introduction: Fundamentals of Microphones,
Instruments, and Acoustics ....................................................... 23
Section Two ................................................................................ 24
Microphone Characteristics ................................................. 24
Instrument Characteristics ................................................... 27
Acoustic Characteristics ....................................................... 28
Shure Microphone Selection Guide ..................................... 32
Shure Recording Microphone Lockers ................................ 33
Glossary ............................................................................... 34
On the cover: Shure’s Performance Listening Center
featuring state-of-the-art recording and product testing
capabilities. Photo by Frank Dina/Shure Inc.
Appendix A: The Decibel ..................................................... 37
Internal application photography by Cris Tapia/Shure Inc.
About the Authors ................................................................ 39
Appendix B: Transient Response ......................................... 38
Microphone Techniques
The selection and placement of microphones can have
a major influence on the sound of an acoustic recording.
It is a common view in the recording industry that the music
played by a skilled musician with a quality instrument
properly miked can be sent directly to the recorder with little
or no modification. This simple approach can often sound
better than an instrument that has been reshaped by a
multitude of signal processing gear.
In this guide, Shure Application Engineers describe
techniques to pick up a natural tonal balance, techniques
to help reject unwanted sounds, and even techniques to
create special effects.
Following this, some fundamentals of microphones,
instruments, and acoustics are presented.
Section One
Microphone Techniques
Microphone Techniques
Here is a very basic, general procedure to keep in mind
when miking something that makes sound:
1) Use a microphone with a frequency response that is
suited to the frequency range of the sound, if
possible, or filter out frequencies above and/or below
the highest and lowest frequencies of the sound.
2) Place the microphone at various distances and
positions until you find a spot where you hear from the
studio monitors the desired tonal balance and the
desired amount of room acoustics. If you don’t like it,
try another position, try another microphone, try
isolating the instrument further, or change the sound
of the instrument itself. For example, replacing worn
out strings will change the sound of a guitar.
3) Often you will encounter poor room acoustics, or
pickup of unwanted sounds. In these cases, place
the microphone very close to the loudest part of
the instrument or isolate the instrument. Again,
experiment with microphone choice, placement and
isolation, to minimize the undesirable and accentuate
the desirable direct and ambient acoustics.
Microphone technique is largely a matter of personal taste.
Whatever method sounds right for the particular sound,
instrument, musician, and song is right. There is no one ideal
way to place a microphone. There is also no one ideal microphone to use on any particular instrument. Choose and place
the microphone to get the sound you want. We recommend
experimenting with all sorts of microphones and positions until
you create your desired sound. However, the desired sound
can often be achieved more quickly by understanding basic
microphone characteristics, sound-radiation properties of
musical instruments, and basic room acoustics.
Vocal Microphone Techniques
Individual Vocals
Microphones with various polar patterns can be used in
vocal recording techniques. Consider recording a choral
group or vocal ensemble. Having the vocalists circle
around an omnidirectional mic allows well trained singers
to perform as they would live: creating a blend of voices by
changing their individual singing levels and timbres. Two
cardioid mics, positioned back to back could be used for
this same application.
An omnidirectional mic may be used for a single vocalist as
well. If the singer is in a room with ambience and reverb
that add to the desired effect, the omnidirectional mic will
capture the room sound as well as the singer’s direct voice.
By changing the distance of the vocalist to the microphone,
you can adjust the balance of the direct voice to the
ambience. The closer the vocalist is to the mic, the more
direct sound is picked up relative to the ambience.
The standard vocal recording environment usually captures
the voice only. This typically requires isolation and the use of
a unidirectional mic. Isolation can be achieved with baffles
surrounding the vocalist like a “shell” or some other method
of reducing reflected sound from the room. Remember even
a music stand can cause reflections back to the mic.
The axis of the microphone should usually be pointed somewhere between the nose and mouth to pick up the complete
sound of the voice. Though the mic is usually directly in front
of the singer’s mouth, a slightly off-axis placement may help
to avoid explosive sounds from breath blasts or certain
consonant sounds such as “p”, “b”, “d”, or “t”. Placing the
mic even further off-axis, or the use of an accessory pop
filter, may be necessary to fully eliminate this problem.
While many vocals are recorded professionally in an
isolation booth with a cardioid condenser microphone,
other methods of vocal recording are practiced. For
instance, a rock band’s singers may be uncomfortable in
the isolated environment described earlier. They may be
used to singing in a loud environment with a monitor
loudspeaker as the reference. This is a typical performance
situation and forces them to sing louder and push their
voices in order to hear themselves. This is a difficult
situation to recreate with headphones.
A technique that has been used successfully in this
situation is to bring the singers into the control room to
perform. This would be especially convenient for project
studios that exist in only one room. Once in that
environment, a supercardioid dynamic microphone could
be used in conjunction with the studio monitors. The singer
faces the monitors to hear a mix of music and voice
together. The supercardioid mic rejects a large amount of
the sound projected from the speakers if the rear axis of the
microphone is aimed between the speakers and the speakers
are aimed at the null angle of the mic (about 65 degrees on
either side of its rear axis). Just as in live sound, you are using
Microphone Techniques
0.6 - 1m
(2 - 3 ft)
1.8 - 3m
(6 - 9 ft)
Choir microphone positions - top view
the polar pattern of the mic to improve gain-before-feedback
and create an environment that is familiar and encouraging
to the vocalists. Now the vocalist can scream into the late
hours of the night until that vocal track is right.
Ensemble Vocals
A condenser is the type of microphone most often used
for choir applications. They are generally more capable of
flat, wide-range frequency response. The most appropriate
directional type is a unidirectional, usually a cardioid.
A supercardioid or a hypercardioid microphone may be
used for a slightly greater reach or for more ambient sound
rejection. Balanced low-impedance output is used
exclusively, and the sensitivity of a condenser microphone
is desirable because of the greater distance between the
sound source and the microphone.
Application of choir microphones falls into the category
known as “area” coverage. Rather than one microphone
per sound source, the object is to pick up multiple sound
sources (or a “large” sound source) with one (or more)
microphone(s). Obviously, this introduces the possibility of
interference effects unless certain basic principles (such as
the “3-to-1 rule”) are followed, as discussed below.
For one microphone picking up a typical choir, the suggested placement is a few feet in front of, and a few feet
above, the heads of the first row. It should be centered in
front of the choir and aimed at the last row. In this configuration, a cardioid microphone can “cover” up to 15-20
voices, arranged in a rectangular or wedge-shaped section.
For larger or unusually shaped choirs, it may be necessary
to use more than one microphone. Since the pickup
angle of a microphone is a function of its directionality
(approximately 130 degrees for a cardioid), broader
coverage requires more distant placement.
In order to determine the placement of multiple microphones for choir pickup, remember the following rules:
observe the 3-to-1 rule (see glossary); avoid picking
up the same sound source with more than one
microphone; and finally, use the minimum number
of microphones.
For multiple microphones, the objective is to divide the
choir into sections that can each be covered by a single
microphone. If the choir has any existing physical divisions
(aisles or boxes), use these to define basic sections. If the
choir is grouped according to vocal range (soprano, alto,
tenor, bass), these may serve as sections.
If the choir is a single, large entity, and it becomes
necessary to choose sections based solely on the coverage
of the individual microphones, use the following spacing:
one microphone for each lateral section of approximately
6 to 9 feet. If the choir is unusually deep (more than 6 or
8 rows), it may be divided into two vertical sections of
several rows
each, with
0.6 - 1m
aiming angles
(2 - 3 ft)
In any case, it is
better to use too
few microphones
0.6 - 1m
than too many.
(2 - 3 ft)
In a goodsounding space,
a pair of microphones in a stereo
configuration can
provide realistic
Microphone positions - side view
(See page 22.)
Microphone Techniques
Spoken Word/ “Podcasting”
Countless “how-to” articles have been written on
podcasting, which is essentially a current trend in
spoken word distribution, but few offer many tips on
how to properly record the human voice. Below are
some suggestions:
1. Keep the microphone 6 –12” from your mouth.
Generally, keep the microphone as close as possible
to your mouth to avoid picking up unwanted room
reflections and reverberation. Do not get too close
either. Proximity effect, which is an increase in low
frequency response that occurs as you get closer to
a directional microphone, can cause your voice to
sound “muddy” or overly bassy.
2. Aim the microphone toward your mouth from
below or above.
This placement minimizes “popping” caused by
plosive consonants (e.g. “p” or “t”).
3. Use an external pop filter.
Though most microphones have some sort of builtin windscreen, an additional filter will provide extra
insurance against “p” pops. The pop filter can also
serve as a reference to help you maintain a consistent distance from the microphone. (See Image 1.)
4. Keep the microphone away from reflective
Reflections caused by hard surfaces, such as
tabletops or music stands, can adversely affect the
sound quality captured by the microphone. (See the
section “Phase relationships and interference
effects” page 30.)
Image 1: Example of an external pop filter
5. Speak directly into the microphone.
High frequencies are very directional, and if you turn
your head away from the microphone, the sound
captured by the microphone will get noticeably duller.
Microphone Techniques
Acoustic String and Fretted 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.
Various microphone positions for acoustic guitar
Microphone Techniques
Microphone Placement
Tonal Balance
Good starting placement when leakage is a
problem. Roll off bass for a more natural
sound (more for a uni than an omni).
2 3 inches from sound hole
Very bassy, boomy,
muddy, full
Very good isolation. Bass roll-off needed
for a natural sound.
3 4 to 8 inches from bridge
Woody, warm,
mellow. Mid-bassy,
lacks detail
Reduces pick and string noise.
slightly bright
Less pickup of ambiance and leakage
than 3 feet from sound hole.
Miniature microphone clipped
outside of sound hole
Good isolation. Allows freedom of
Miniature microphone clipped
inside sound hole
Bassy, less
string noise
Reduces leakage. Test positions to find
each guitar’s sweet spot.
3 inches from center of head
Bassy, thumpy
Limits leakage. Roll off bass for natural sound.
3 inches from edge of head
Limits leakage.
Miniature microphone clipped to
tailpiece aiming at bridge
Limits leakage. Allows freedom of movement.
Well-balanced sound.
Well-balanced sound, but little isolation.
Minimizes feedback and leakage.
Allows freedom of movement.
Acoustic Guitar:
1 8 inches from sound hole
(see image 2)
(see image 3)
4 6 inches above the side, over
the bridge, and even with the front
Violin (Fiddle):
A few inches from side
1 foot from bridge
All String Instruments:
Miniature microphone attached to
strings between bridge and tailpiece
Image 2: Acoustic guitar position 1
Image 3: Acoustic guitar position 3
Microphone Techniques
Microphone Placement
Tonal Balance
Acoustic Bass: (Upright Bass, String Bass, Bass Violin)
6 inches to 1 foot out front,
just above bridge
Natural sound.
A few inches from f-hole
Roll off bass if sound is too boomy.
Wrap microphone in foam padding
(except for grille) and put behind
bridge or between tailpiece and body
Full, “tight”
Minimizes feedback and leakage.
Aiming toward player at part of
soundboard, about 2 feet away
See “Stereo Microphone Techniques”
section for other possibilities.
Tape miniature microphone to
Minimizes feedback and leakage.
Grand Piano
1 4
7 2
Microphone Techniques
Microphone Placement
Tonal Balance
Less pickup of ambience and leakage than 3 feet
out front. Move microphone(s) farther from
hammers to reduce attack and mechanical noises.
Good coincident-stereo placement. See “Stereo
Microphone Techniques” section.
slightly bright
Place one microphone over bass strings and one
over treble strings for stereo. Phase cancellations
may occur if the recording is heard in mono.
3 Aiming into sound holes
Thin, dull, hard,
Very good isolation. Sometimes sounds good for
rock music. Boost mid-bass and treble for more
natural sound.
4 6 inches over middle strings,
Muddy, boomy,
dull, lacks attack
Improves isolation. Bass roll-off and some treble
boost required for more natural sound.
Bassy, full
Unobtrusive placement.
Bassy, dull, full
Unobtrusive placement.
Grand Piano:
1 12 inches above middle strings,
8 inches horizontally from hammers
with lid off or at full stick
2 8 inches above treble strings,
as above (see image 4)
(see image 5)
8 inches from hammers,
with lid on short stick
5 Next to the underside of raised lid,
centered on lid
6 Underneath the piano, aiming up
at the soundboard
7 Surface-mount microphone mounted Bright,
on underside of lid over lower treble
strings, horizontally, close to hammers for brighter sound, further from
hammers for more mellow sound
8 Two surface-mount microphones
positioned on the closed lid, under
the edge at its keyboard edge,
approximately 2/3 of the distance
from middle A to each end of the
9 Surface-mount microphone placed
vertically on the inside of the frame,
or rim, of the piano, at or near the
apex of the piano’s curved wall
Image 4: Grand piano position 2
Excellent isolation. Experiment with lid height
and microphone placement on piano lid for
desired sounds.
strong attack
Excellent isolation. Moving “low” mic away from
keyboard six inches provides truer reproduction
of the bass strings while reducing damper noise.
By splaying these two mics outward slightly, the
overlap in the middle registers can be minimized.
Full, natural
Excellent isolation. Minimizes hammer and
damper noise. Best if used in conjunction with two
surface-mount microphones mounted to closed
lid, as above.
Image 5: Grand piano position 3
Microphone Techniques
Microphone Placement
Tonal Balance
Upright Piano:
1 Just over open top, above treble
Natural (but lacks
Good placement when only one
deep bass), picks up microphone is used.
hammer attack
2 Just over open top, above bass
3 Inside top near the bass and
treble stings
4 8 inches from bass side of
5 8 inches from treble side of
6 Aiming at hammers from front,
several inches away (remove
front panel)
1 foot from center of soundboard on
hard floor or one-foot-square plate
on carpeted floor, aiming at piano
(soundboard should face into room)
Slightly full or tubby,
picks up hammer
Mike bass and treble strings for stereo.
Natural, picks up
hammer attack
Minimizes feedback and leakage.
Use two microphones for stereo.
Full, slightly tubby,
no hammer attack
Use this placement with the following
placement for stereo.
Thin, constricted,
no hammer attack
Use this placement with the preceding
placement for stereo.
Bright, picks up
hammer attack
Mike bass and treble strings for stereo.
good presence
Minimize pickup of floor vibrations by
mounting microphone in low-profile
shock-mounted microphone stand.
1 2
Microphone Techniques
Microphone Placement
Tonal Balance
With the saxophone, the sound is fairly well
distributed between the finger holes and the bell.
Miking close to the finger holes will result in key noise.
The soprano sax must be considered separately
because its bell does not curve upward. This means
that, unlike all other saxophones, placing a microphone
toward the middle of the instrument will not pick-up the
sound from the key holes and the bell simultaneously.
The saxophone has sound characteristics similar to
the human voice. Thus, a shaped response microphone
designed for voice works well.
Image 6: Example of saxophone mic placement
for natural sound
A few inches from and aiming into bell
Minimizes feedback and leakage.
A few inches from sound holes
Warm, full
Picks up fingering noise.
A few inches above bell and aiming at
sound holes (see image 6)
Good recording technique.
Miniature microphone mounted on bell
Bright, punchy
Maximum isolation, up-front sound.
The sound energy from a flute is projected both by the embouchure and by the first open fingerhole. For good pickup,
place the mic as close as possible to the instrument. However, if the mic is too close to the mouth, breath noise will be
apparent. Use a windscreen on the mic to overcome this difficulty.
A few inches from area between
mouthpiece and first set of finger
Natural, breathy
Pop filter or windscreen may
be required on microphone.
A few inches behind player’s head,
aiming at finger holes
Reduces breath noise.
About 1 foot from sound holes
Provides well-balanced sound.
A few inches from bell
Minimizes feedback and leakage.
Oboe, Bassoon, Etc.:
Microphone Techniques
Woodwinds (continued)
Microphone Placement
Tonal Balance
Full, bright
Minimizes feedback and leakage.
Microphone may be cupped in hands.
One or two feet in front of instrument,
Full range,
natural sound
Use two microphones for stereo or to pick up
bass and treble sides separately.
Miniature microphone mounted
Minimizes leakage.
Allows freedom of movement.
Tonal Balance
Very close to instrument
Microphone Placement
Trumpet, Cornet Trombone, Tuba:
The sound from most brass instruments is very directional. Placing the mic off axis with the bell of the instrument will
result in less pickup of high frequencies.
1 to 2 feet from bell (a couple of
instruments can play into one
On-axis to bell
sounds bright; to
one side sounds
natural or mellow
Close miking sounds “tight” and minimizes
feedback and leakage. More distant placement
gives fuller, more dramatic sound.
Miniature microphone mounted
on bell
Maximum isolation.
Watch out for extreme fluctuations on VU meter.
French Horn:
Microphone aiming toward bell
Microphone Techniques
Amplified Instruments
Another “instrument” with a wide range of characteristics
is the loudspeaker. Anytime you are recording a guitar or
bass cabinet, you are confronted with the acoustic nature
of loudspeakers. A single loudspeaker is directional and
displays different frequency characteristics at different
angles and distances. On-axis at the center of a speaker
tends to produce the most “bite”, while off-axis or edge
placement of the microphone produces a more “mellow”
sound. A cabinet with multiple loudspeakers has an even
more complex output, especially if it has different speakers
for bass and treble.
As with most acoustic instruments, the desired sound
develops at some distance away from the speaker.
The most common approach is to close-mic an individual
speaker. This is a habit people develop from viewing or doing
live sound. In the live sound environment, most audio
sources are close-miked to achieve the highest direct to
ambient pickup ratios. Using unidirectional mics for close
miking maximizes off-axis sound rejection as well. These
elements lead to reduction of potential feedback
opportunities. In the recording environment, the loudspeaker
cabinet can be isolated and distant-mic techniques can be
used to capture a more representative sound.
Often, by using both a close and a distant (more than a
few feet) mic placement at the same time, it is possible to
record a sound which has a controllable balance between
“presence” and “ambience”.
Placement of loudspeaker cabinets can also have a
significant effect on their sound. Putting cabinets on
carpets can reduce brightness, while raising them off the
floor can reduce low end. Open-back cabinets can be
miked from behind as well as from the front. The distance
from the cabinet to walls or other objects can also vary the
sound. Again, move the instrument and the mic(s) around
until you achieve something that you like!
See page 16 for placement key.
Microphone Techniques
Microphone Placement
Tonal Balance
Electric Guitar:
The electric guitar has sound characteristics similar to the human voice. Thus, a shaped response microphone
designed for voice works well.
1 4 inches from grille cloth at
Small microphone desk stand may be used if
loudspeaker is close to floor.
Minimizes feedback and leakage.
3 Off-center with respect to
Dull or mellow
Microphone closer to edge of speaker cone results
in duller sound. Reduces amplifier hiss noise.
4 3 feet from center of speaker cone
Thin, reduced bass
Picks up more room ambiance and leakage.
3 & 4 Good two-mic technique
Use condenser microphone for position
4 – adjust spacing to minimize phase issues.
Miniature microphone draped over
amp in front of speaker
Easy setup, minimizes leakage.
Microphone placed behind open
back cabinet
Depends on
Can be combined with mic in front of
cabinet, but be careful of phase cancellation.
center of speaker cone
2 1 inch from grille cloth at
center of speaker cone
speaker cone
(see image 7)
Image 7: Example of a good “two mic technique” for electric guitar amp
Microphone Techniques
Bass Guitar:
If the cabinet has only one speaker a single microphone
should pick up a suitable sound with a little
experimentation. If the cabinet has multiple speakers of
the same type it is typically easiest to place the microphone
to pick up just one speaker.
Microphone Placement
Placing the microphone between speakers can result in
strong phase effects though this may be desirable to
achieve a particular tone. However, if the cabinet is stereo
or has separate bass and treble speakers multiple
microphones may be required.
Tonal Balance
Depends on
brand of piano
Roll off bass for clarity, roll off high
frequencies to reduce hiss.
Aim one microphone into top
louvers 3 inches to 1 foot away
lacks deep bass
Good one-microphone pickup.
Mike top louvers and bottom bass
speaker 3 inches to 1 foot away
Excellent overall sound.
Mike top louvers with two
microphones, one close to each side;
pan to left and right; mike bottom
bass speaker 3 inches to 1 foot away
and pan its signal to center
Stereo effect.
Electric Keyboard Amp:
Aim microphone at speaker as
described in Electric Guitar
Amplifier section
Leslie Organ Speaker:
Microphone Techniques
Drums and Percussion
Drum Kit Miking – The drum kit is one of the most
complicated sound sources to record. Although there are
many different methods, some common techniques and
principles should be understood. Since the different parts
of the drum kit have widely varying sound they should be
considered as individual instruments, or at least a small
group of instrument types: Kick, Snare, Toms, Cymbals,
and Percussion. Certain mic characteristics are extremely
critical for drum usage.
Dynamic Range – A drum can produce very high Sound
Pressure Levels (SPLs). The microphone must be able to
handle these levels. A dynamic microphone will usually
handle high SPLs better than a condenser. Check the
Maximum SPL in condenser microphone specifications.
It should be at least 130 dB for closeup drum use.
Directionality – Because we want to consider each part of
the kit an individual instrument; each drum may have its
own mic. Interference effects may occur due to the close
proximity of the mics to each other and to the various
drums. Choosing mics that can reject sound at certain angles and placing them properly can be pivotal in achieving
an overall drum mix with minimal phase problems.
Proximity Effect – Unidirectional mics may have excessive
low frequency response when placed very close to the
drums. A low frequency roll-off either on the microphone
or at the mixer will help cure a “muddied” sound. However,
proximity effect may also enhance low frequency response
if desired. It can also be used to effectively reduce pickup
of distant low frequency sources by the amount of lowrolloff used to control the closeup source. Typically, drums
are isolated in their own room to prevent bleed through to
microphones on other instruments. In professional studios
it is common for the drums to be raised above the floor. This
helps reduce low frequency transmission through the floor.
Image 8: Example of bass (kick) drum mic placement
A microphone for this use should have good low frequency
response and possibly a boost in the attack range,
although this can be done easily with EQ. The mic should be
placed in the drum, in close proximity (1 - 6 inches), facing
the beater head. (See position D in diagram on the following
page.) Or for less “slap” just inside the hole. (See image 8.)
2 Snare Drum – This is the most piercing drum in the kit
and almost always establishes tempo. In modern music it
usually indicates when to clap your hands! This is
an extremely transient drum with little or no sustain
to it. Its attack energy is focused in the 4 - 6kHz range.
Typically, the drum is miked on the top head at the edge
of the drum with a cardioid or supercardioid microphone.
(See position C in diagram on the following page; see image 9.)
Here is a basic individual drum miking technique:
1 Bass (Kick) Drums – This drum’s purpose in most
music is to provide transient, low-frequency energy bursts
that help establish the primary rhythmic pattern of a song.
The kick drum’s energy is primarily focused in two areas:
very low-end timbre and “attack”. Although this varies
by individual drum, the attack tends to be in the 2.55kHz range.
Image 9: Example of snare drum mic placement
Microphone Techniques
3 Hi-Hats – These cymbals are primarily short, high
frequency bursts used for time keeping, although the
cymbals can be opened for a more loose sound. Many times
the overhead mics will provide enough response to the high
hat to eliminate the need for a separate hi-hat microphone.
If necessary, a mic placed away from the puff of air that
happens when hi-hats close and within four inches to the
cymbals should be a good starting point. (See position G in
diagram to right; see image 10.)
Simpler methods of drum
miking are used for jazz
and any application where
open, natural kit sounds
are desired. Using fewer
mics over sections of the
drums is common.
Also, one high quality
mic placed at a distance
facing the whole kit may
Image 10: Example of
capture the sounds of kit
mic placement for hi-hats
and room acoustics in an
enjoyable balance. Additional mics may be added to reinforce certain parts of the kit that are used more frequently.
5 Overheads – The cymbals perform a variety of sonic
duties from sibilant transient exclamation points to high
frequency time keeping. In any case, the energy is
mostly of a high-frequency content. Flat frequency
response condenser microphones will give accurate
reproduction of these sounds. Having microphones with
low frequency roll-off will help to reject some of the sound
of the rest of the kit which may otherwise cause phase
problems when the drum channels are being mixed. The
common approach to capturing the array of cymbals that
a drummer may use is an overhead stereo pair of
microphones. (positions A and B)
4 Tom Toms – While the kick and snare establish the
low and high rhythmic functions, the toms are multiple
drums that will be tuned from high to low between the
snare and kick. They are primarily used for fills, but
may also be consistent parts of the rhythmic structure.
The attack range is similar to the snare drum, but often
with more sustain.
An individual directional mic on the top head near the edge
can be used on each drum and panned to create some
spatial imaging. A simpler setup is to place one mic slightly
above and directly between two toms. (See position E in
diagram to right; see image 11. )
Front view
Image 11: Example of “simpler” mic set-up for tom toms
Top view
Microphone Techniques
When there are limited microphones available to record a drum kit use the following guidelines:
Number of microphones
Positioning Alternative (Positioning reference)
Use as “overhead” ( 5 )
Kick drum and overhead ( 1 and 5 )
Kick drum, snare, and overhead or kick drum ( 1 , 2 , and 5 )
Kick drum, snare, high hat, and overhead ( 1 , 2 , 3 , and 5 )
Kick drum, snare, high hat, tom-toms, and overhead ( 1 , 2 , 3 , 4 , and 5 )
Microphone Placement
Tonal Balance
Provides full sound with good attack.
Experiment with distance and angles if sound
is too bright.
Bright, with
plenty of attack
Allow clearance for movement of pan.
Timbales, Congas, Bongos:
One microphone aiming down between
pair of drums, just above top heads
One microphone placed 6 to 12
inches from instrument
Steel Drums:
Tenor Pan, Second Pan,
Guitar Pan
One microphone placed
4 inches above each pan
Microphone placed underneath pan
Cello Pan, Bass Pan
One microphone placed 4 - 6
inches above each pan
Decent if used for tenor or second pans.
Too boomy with lower voiced pans.
Can double up pans to a single microphone.
Pan two microphones to left and right for stereo.
See “Stereo Microphone Techniques” section.
Bright, with
lots of attack
For less attack, use rubber mallets instead of metal
mallets. Plastic mallets will give a medium attack.
Xylophone, Marimba, Vibraphone:
Two microphones aiming down toward
instrument, about 1 1/2 feet above it,
spaced 2 feet apart, or angled 1350 apart
with grilles touching
One microphone placed 4 - 6 inches
above bars
Microphone Techniques
Stereo Microphone Techniques – One of the most popular
specialized microphone techniques is stereo miking.
This use of two or more microphones to create a stereo
image will often give depth and spatial placement to an
instrument or overall recording. There are a number of
different methods for stereo. Three of the most popular are
the spaced pair (A/B), the coincident or near-coincident pair
(X-Y configuration), and the Mid-Side (M-S) technique.
The spaced pair
(A/B) technique
uses two cardioid or
omni directional
microphones spaced
3 - 10 feet apart
from each other
panned in left/right
configuration to
capture the stereo
image of an
ensemble or
Effective stereo
A/B top view
separation is very
wide. The distance
between the two microphones is dependent on the
physical size of the sound source. For instance, if two
mics are placed ten feet apart to record an acoustic guitar;
the guitar will appear in the center of the stereo image.
This is probably too much spacing for such a small sound
source. A closer, narrower mic placement should be used
in this situation.
The drawback to A/B stereo is the potential for undesirable
phase cancellation of the signals from the microphones.
Due to the relatively large distance between the
microphones and the resulting difference of sound arrival
times at the microphones, phase cancellations and
summing may be occurring. A mono reference source can
be used to check for phase problems. When the program
is switched to mono and frequencies jump out or fall out of
the sound, you can
assume that there
is phase problem.
This may be a
serious problem
if your recording is
going to be heard
in mono as is typical
in broadcast or
soundtrack playback.
X-Y top view
The X-Y technique uses two cardioid microphones of the
same type and manufacture with the two mic capsules
placed either as close as possible (coincident) or within
12 inches of each other (near-coincident) and facing each
other at an angle ranging from 90 - 135 degrees,
depending on the size of the sound source and the
particular sound desired. The pair is placed with the center
of the two mics facing directly at the sound source and
panned left and right.
Due to the small distance between the microphones,
sound arrives at the mics at nearly the same time, reducing
(near coincident) or eliminating (coincident) the possible
phase problems of the A/B techniques. The stereo
separation of this technique is good but may be limited if
the sound source is extremely wide. Mono compatibility is
fair (near-coincident) to excellent (coincident).
The M-S or Mid-Side stereo technique involves a cardioid
mic element and a bi-directional mic element, usually
housed in a single case, mounted in a coincident
arrangement. The cardioid (mid) faces directly at the source
and picks up primarily on-axis sound while the bi-directional
(side) faces left and right and picks up off-axis sound. The
two signals are combined via the M-S matrix to give a
variable controlled stereo image. By adjusting the level of
mid versus side signals, a narrower or wider image can be
created without moving the microphone. This technique is
completely mono-compatible and is widely used in
broadcast and film applications.
Microphone Techniques
(see image 12)
Stereo Microphone Techniques
Image 12: Example of “X-Y” stereo miking technique
using Shure A27M stereo microphone adapter
Microphone Techniques
The world of studio recording is much different from that of
live sound reinforcement, but the fundamental characteristics
of the microphones and sound are the same. It is the ability
to isolate individual instruments that gives a greater element
of control and freedom for creativity in the studio. Since there
are no live loudspeakers, feedback is not an issue.
The natural sound of the instrument may be the desired
effect, or the sound source can be manipulated into a sound
never heard in the natural acoustic world.
In order to achieve the desired result it is useful to understand
some of the important characteristics of microphones,
musical instruments, and acoustics.
Section Two
Microphone Techniques
Microphone Characteristics
There are three main considerations when choosing
a microphone for recording applications: operating
principle, frequency response, and directionality.
Operating Principle – A microphone is an example of a
transducer, a device which changes energy from one form
into another, in this case from acoustic into electrical.
The type of transducer is defined by the operating
principle. In the current era of recording, the two primary
operating principles used in microphone design are the
dynamic and the condenser.
Dynamic microphone elements are made up of a
diaphragm, voice coil, and magnet which form a
sound-driven electrical generator. Sound waves move
the diaphragm/voice coil in a magnetic field to generate
the electrical equivalent of the acoustic sound wave.
The signal from the dynamic element can be used
directly, without the need for additional circuitry. This
design is extremely rugged, has good sensitivity and
can handle the loudest possible sound pressure levels
without distortion.
The dynamic has
some limitations at
extreme high and
low frequencies. To
compensate, small
resonant chambers
are often used to extend the frequency
range of dynamic
Ribbon microphone elements, a variation of the
dynamic microphone operating principle, consist of a
thin piece of metal, typically corrugated aluminum,
suspended between two magnetic pole pieces. As with
moving-coil dynamics, no additional circuitry or
powering is necessary for operation, however, the
output of ribbon microphones tends to be quite low.
Depending on the gain of the mixer or recording device
to which the microphone is connected, additional
pre-amplification may be necessary. Note that ribbon
microphones are not as rugged as moving-coil dynamic
microphones. The ribbon element itself is typically no
more than a few microns thick, and can be deformed
by a strong blast of air, or by blowing into the
microphone. Also, phantom power applied to the
ribbon microphone could be harmful. Ribbon
microphones are highly regarded in studio recording
for their “warmth” and good low frequency response.
Condenser microphone elements use a conductive
diaphragm and an electrically charged backplate to form a
sound-sensitive “condenser” (capacitor). Sound waves
move the diaphragm in an electric field to create the
electrical signal. In order to use this signal from the
element, all condensers have active electronic circuitry,
(often referred to as the “preamp”) either built into the
microphone or in a separate pack. This means that
condenser microphones require phantom power or a
battery to operate. (For
a detailed explanation
of “phantom power”,
see the sidebar.)
However, the condenser
design allows for smaller
mic elements, higher
sensitivity and is inherently capable of smooth
response across a very
wide frequency range.
The main limitations of a condenser microphone relate to
its electronics. These circuits can handle a specified
maximum signal level from the condenser element, so a
condenser mic has a maximum sound level before its
output starts to be distorted. Some condensers have
switchable pads or attenuators between the element and
the electronics to allow them to handle higher sound levels.
If you hear distortion when using a condenser microphone
close to a very loud sound source, first make sure that the
mixer input itself is not being overloaded. If not, switch in the
attenuator in the mic (if equipped), move the mic farther
away, or use a mic that can handle a higher level. In any
case, the microphone will not be damaged by excess level.
A second side effect of the condenser/electronics design
is that it generates a certain amount of electrical noise
(self-noise) which may be heard as “hiss” when recording
very quiet sources at high gain settings. Higher quality
condenser mics have very low self-noise, a desirable
characteristic for this type of recording application.
Most modern condenser microphones use solid state
components for the internal circuitry, but older designs
employed vacuum tubes (also known as “valves”) for this
purpose. The subjective qualities imparted by vacuum
Microphone Techniques
tube electronics, often described as “warmth” or
“smoothness,” have led to a resurgence in the popularity
of vacuum tube-based condenser microphones. These
sonic advantages come at the expense of higher self-noise
and fragility. Vacuum tubes typically have a limited life
span, and eventually need to be replaced. Most vacuum
tube microphones require an external power supply, as
standard 48V phantom power is not sufficient. Some power
supplies offer the ability to switch polar patterns remotely
on microphones that feature dual-diaphragms (see
Directionality for a discussion of microphone polar patterns).
Frequency response – The variation in output level or
sensitivity of a microphone over its useable range from
lowest to highest frequency.
Virtually all microphone manufacturers will list the
frequency response of their microphones as a range, for
example 20 - 20,000Hz. This is usually illustrated with a
graph that indicates relative amplitude at each frequency.
The graph has the frequency in Hz on the x-axis and
relative response in decibels on the y-axis.
A microphone whose response is equal at all frequencies
is said to have a “flat” frequency response. These
microphones typically have a wide frequency range. Flat
response microphones tend to be used to reproduce
sound sources without coloring the original source. This is
usually desired in reproducing instruments such as
acoustic guitars or pianos. It is also common for stereo
miking techniques and distant miking techniques.
A microphone whose response has peaks or dips in certain
frequency areas is said to have a “shaped” response. This
response is designed to enhance a frequency range that is
specific to a given sound source. For instance, a microphone
may have a peak in the 2-10Khz range to enhance the
intelligibility or presence of vocals. This shape is said to have
a “presence peak”. A microphone’s response may also be
reduced at other frequencies. One example of this is a low
frequency roll-off to reduce unwanted “boominess”.
Although dynamic microphones and condenser
microphones may have similar published frequency
response specifications their sound qualities can be quite
different. A primary aspect of this difference is in their
transient response. See the appendix for an explanation
of this characteristic.
Directionality is usually plotted on a graph referred to as a
polar pattern. The polar pattern shows the variation in
sensitivity 360 degrees around the microphone, assuming
that the microphone is in the center and 0 degrees
represents the front or on-axis direction of the microphone.
There are a number of different directional patterns
designed into microphones. The three basic patterns are
omnidirectional, unidirectional, and bidirectional.
The omnidirectional microphone has equal response at
all angles. Its “coverage” or pickup angle is a full 360
degrees. This type of microphone can be used if more
room ambience is desired. For example, when using an
“omni”, the balance of direct and ambient sound depends
on the distance of the microphone from the instrument,
and can be adjusted to the desired effect.
Phantom Power
Phantom power is a DC voltage (usually 12-48 volts)
used to power the electronics of a condenser
microphone. For some (non-electret) condensers it
may also be used to provide the polarizing voltage
for the element itself. This voltage is supplied through
the microphone cable by a mixer equipped with
phantom power or by some type of in-line external
source. The voltage is equal on Pin 2 and Pin 3 of a
typical balanced, XLR-type connector. For a 48 volt
phantom source, for example, Pin 2 is 48 VDC and
Pin 3 is 48 VDC, both with respect to Pin 1 which is
ground (shield).
Because the voltage is exactly the same on Pin 2 and
Pin 3, phantom power will have no effect on balanced
dynamic microphones: no current will flow since
there is no voltage difference across the output.
In fact, phantom power supplies have current limiting
which will prevent damage to a dynamic microphone
even if it is shorted or miswired. In general, balanced
dynamic microphones can be connected to phantom
powered mixer inputs with no problem.
Directionality – The sensitivity to sound relative to the
direction or angle of arrival at the microphone.
Microphone Techniques
125 degrees for the supercardioid and 110 degrees for the
hypercardioid. When placed properly they can provide
more “focused” pickup and less room ambience than the
cardioid pattern, but they have less rejection at the rear:
-12 dB for the supercardioid and only -6 dB for the
Flat frequency response drawing
The bidirectional microphone has full response at both 0
degrees (front) and at 180 degrees (back). It has its least
response at the sides. The coverage or pickup angle is only
about 90 degrees at the front (or the rear). It has the same
amount of ambient pickup as the cardioid. This mic could be
used for picking up two sound sources such as two vocalists
facing each other. It is also used in certain stereo techniques.
Shaped frequency response drawing
The unidirectional microphone is most sensitive to sound
arriving from one particular direction and is less sensitive
at other directions. The most common type is a cardioid
(heart-shaped) response. This has full sensitivity at 0
degrees (on-axis) and is least sensitive at 180 degrees
(off-axis). Unidirectional microphones are used to isolate
the desired on-axis sound from unwanted off-axis sound.
In addition, the cardioid mic picks up only about one-third
as much ambient sound as an omni.
For example, the use of a cardioid microphone for a guitar
amplifier, which is in the same room as the drum set, is
one way to reduce the bleed-through of drums on to the
recorded guitar track. The mic is aimed toward the
amplifier and away from the drums. If the undesired sound
source is extremely loud (as drums often are), other
isolation techniques may be necessary.
Cardioid (unidirectional)
Unidirectional microphones are available with several
variations of the cardioid pattern. Two of these are the
supercardioid and hypercardioid.
Both patterns offer narrower front pickup angles than the
cardioid (115 degrees for the supercardioid and 105
degrees for the hypercardioid) and also greater rejection of
ambient sound. While the cardioid is least sensitive at the
rear (180 degrees off-axis), the least sensitive direction is at
Microphone Techniques
Understanding and choosing the frequency response and
directionality of microphones are selective factors which
can improve pickup of desired sound and reduce pickup
of unwanted sound. This can greatly assist in achieving
both natural sounding recordings and unique sounds for
special applications.
Instrument Characteristics
Microphone polar patterns compared
Other directional-related microphone characteristics:
Musical instruments have overall frequency ranges as found
in the chart below. The dark section of each line indicates the
range of fundamental frequencies and the shaded section
represents the range of the highest harmonics or overtones
of the instrument. The fundamental frequency establishes
the basic pitch of a note played by an instrument while the
harmonics produce the timbre or characteristic tone.
Ambient sound sensitivity – Since unidirectional
microphones are less sensitive to off-axis sound than
omnidirectional types, they pick up less overall ambient or
room sound. Unidirectional mics should be used to control
ambient noise pickup to get a “cleaner” recording.
Distance factor – Since directional microphones have
more rejection of off-axis sound than omnidirectional
types, they may be used at greater distances from a
sound source and still achieve the same balance
between the direct sound and background or ambient
sound. An omnidirectional microphone will pick
up more room (ambient) sound than a unidirectional
microphone at the same distance. An omni should be
placed closer to the sound source than a “uni”– about
half the distance – to pick up the same balance
between direct sound and room sound.
Off-axis coloration – A microphone’s frequency response
may not be uniform at all angles. Typically, high
frequencies are most affected, which may result in an
unnatural sound for off-axis instruments or room ambience.
Proximity effect – For most unidirectional types, bass
response increases as the microphone is moved closer to
the sound source. When miking close with unidirectional
microphones (less than 1 foot), be aware of proximity
effect: it may help to roll off the bass until you obtain a
more natural sound. You can (1) roll off low frequencies at
the mixer, (2) use a microphone designed to minimize
proximity effect, (3) use a microphone with a bass roll-off
switch, or (4) use an omnidirectional microphone (which
does not exhibit proximity effect).
Chart of instrument frequency ranges
Also, an instrument radiates different frequencies at different
levels in every direction, and each part of an instrument
produces a different timbre. This is the directional output
of an instrument. You can partly control the recorded tonal
balance of an instrument by adjusting the microphone
position relative to it. The fact that low frequencies tend to
be omnidirectional while higher frequencies tend to be
more directional is a basic audio principle to keep in mind.
Most acoustic instruments are designed to sound best at a distance (say, two or more feet away). The sounds of the various
parts of the instrument combine into a complete audio picture
at some distance from the instrument. So, a microphone
placed at that distance will pick up a “natural” or well-balanced
tone quality. On the other hand, a microphone placed close to
the instrument emphasizes the part of the instrument that the
microphone is near. The sound picked up very close may or
may not be the sound you wish to capture in the recording.
Microphone Techniques
Acoustic Characteristics
Since room acoustics have been mentioned repeatedly,
here is a brief introduction to some basic factors involved
in acoustics.
Sound Waves – Sound waves consist of pressure variations
traveling through the air. When the sound wave travels, it
compresses air molecules together at one point. This is
called the high pressure zone or positive component(+).
After the compression, an expansion of molecules occurs.
This is the low pressure zone or negative component(-).
This process continues along the path of the sound wave
until its energy becomes too weak to hear. If you could view
the sound wave of a pure tone traveling through air, it
would appear as a smooth, regular variation of pressure
that could be drawn as a sine wave. The diagram shows
the relationship of the air molecules and a sine wave.
wave motion
Frequency, Wavelength, and the Speed of Sound –
The frequency of a sound wave indicates the rate of
pressure variations or cycles. One cycle is a change from
high pressure
one cycle or one period
to low pressure
and back to high
pressure. The
number of cycles
per second is
called Hertz,
abbreviated “Hz.”
So, a 1,000Hz
tone has 1,000
Wave amplitude
cycles per second.
The wavelength of a sound is the physical distance from the
start of one cycle to the start of the next cycle. Wavelength
is related to frequency by the speed of sound. The speed of
sound in air is 1130 feet per second or 344 meters/second.
The speed of sound is constant no matter what the
frequency. You can determine the wavelength of a sound
wave of any frequency if you understand these relationships:
for a 500Hz sound wave:
1,130 feet per second
wavelength =
wavelength = 2.26 feet
Approximate wavelengths of common
100 Hz: about 10 feet
1000 Hz: about 1 foot
10,000 Hz: about 1 inch
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
The Wave Equation: c = f • l
speed of sound = frequency • wavelength
speed of sound
wavelength =
Loudness –
The fluctuation
of air pressure
created by sound
is a change above
and below normal
pressure. This is
what the human
ear responds to.
The varying amount
of pressure of the
air molecules
compressing and
expanding is related
Ambient sounds
to the apparent
loudness at the
human ear. The greater the pressure change, the louder
the sound. Under ideal conditions the human ear can
sense a pressure change as small as .0002 microbar. One
microbar is equal to one millionth of atmospheric pressure.
The threshold of pain is about 200 microbar. Obviously,
the human ear responds to a wide range of amplitude of
sound. This amplitude range is more commonly referred
to in decibels. Sound Pressure Level (dB SPL), relative to
.0002 microbar (0dB SPL). 0 dB SPL is the threshold of
hearing and 120 dB SPL is the threshold of pain. 1 dB is
about the smallest change in SPL that can be heard.
A 3 dB change is generally noticeable, while a 6 dB
change is very noticeable. A 10 dB SPL increase is
perceived to be twice as loud!
Microphone Techniques
Sound Transmission – It is important to remember that
sound transmission does not normally happen in a
completely controlled environment. In a recording studio,
though, it is possible to separate or isolate the sounds being
recorded. The best way to do this is to put the different
sound sources in different rooms. This provides almost
complete isolation and control of the sound from the voice
or instrument. Unfortunately, multiple rooms are not
always an option in studios, and even one sound source
in a room by itself is subject to the effects of the walls, floor,
ceiling and various isolation barriers. All of these
effects can alter the sound before it actually arrives at the
3. Diffraction – A sound wave will typically bend around
obstacles in its path which are smaller than its wavelength.
Because a low frequency sound wave is much longer than
a high frequency wave, low frequencies will bend around
objects that high frequencies cannot. The effect is that high
frequencies are more easily blocked or absorbed while low
frequencies are essentially omnidirectional. When isolating
two instruments in one room with a gobo as an acoustic
barrier, it is possible to notice the individual instruments
are “muddy” in the low end response. This may be due to
diffraction of low frequencies around the acoustic barrier.
Applications Tip:
In the study of acoustics there are three basic ways in
which sound is altered by its environment:
1. Reflection – A sound wave can be reflected by
a surface or other object if the object is physically
as large or larger than the wavelength of the sound.
Because low-frequency sounds have long wavelengths,
they can only be reflected by large objects. Higher
frequencies can be reflected by smaller objects and
surfaces. The reflected sound will have a different
frequency characteristic than the direct sound if all sounds
are not reflected equally. Reflection is also the source of
echo, reverb, and standing waves:
Echo occurs when an indirect sound is delayed long
enough (by a distant reflective surface) to be heard by the
listener as a distinct repetition of the direct sound.
Reverberation consists of many reflections of a sound,
maintaining the sound in a room for a time even after the
direct sound has stopped.
Standing waves in a room occur for certain frequencies
related to the distance between parallel walls. The original
sound and the reflected sound will begin to reinforce
each other when the wavelength is equal to the distance
between two walls. Typically, this happens at low
frequencies due to their longer wavelengths and the
difficulty of absorbing them.
2. Refraction – The bending of a sound wave as it passes
through some change in the density of the transmission
environment. This change may be due to physical objects,
such as blankets hung for isolation or thin gobos, or it may
be due to atmospheric effects such as wind or temperature
gradients. These effects are not noticeable in a studio
Absorption (beware of carpets!)
When building a project studio or small commercial
studio, it is usually necessary to do some sound
treatment to the walls and possibly build some isolating
gobos for recording purposes. Many small studios
assume they can save money and achieve the desired
absorption effect by using inexpensive carpet. This is a
bad assumption.
Absorption is the changing of sound energy into heat
as it tries to pass through some material. Different
materials have different absorption effects at multiple
frequencies. Each material is measured with an
absorption coefficient ranging between 0-1 (sabins).
This can be thought of as the percentage of sound that
will be absorbed.
For instance: a
material may have
an absorption
coefficient of
.67 at 1,000 Hz.
This would
mean the
material absorbs
67% of the
1,000 Hz
applied to it.
Here is a chart
showing the
advantages of
acoustic foam
over bare walls
or carpeting.
Microphone Techniques
Direct vs. Ambient Sound – A very important property
of direct sound is that it becomes weaker as it travels
away from the sound source, at a rate controlled by the
inverse-square law. When the distance from a sound
source doubles, the sound level decreases by 6dB. This
is a noticeable audible decrease. For example, if the
sound from a guitar amplifier is 100 dB SPL at 1 ft. from
the cabinet it will be 94 dB at 2 ft., 88 dB at 4 ft., 82 dB
at 8 ft., etc. When the distance is cut in half the sound
level increases by 6dB: It will be 106 dB at 6 inches and
112 dB at 3 inches.
On the other hand, the ambient sound in a room is at
nearly the same level throughout the room. This is because
the ambient sound has been reflected many times
within the room until it is essentially non-directional.
Reverberation is an example of non-directional sound.
This is why the ambient sound of the room will become
increasingly apparent as a microphone is placed further
away from the direct sound source. The amount of direct
sound relative to ambient sound can be controlled by the
distance of the microphone to the sound source and to a
lesser degree by the polar pattern of the mic.
However, if the microphone is placed beyond a certain
distance from the sound source, the ambient sound will
begin to dominate the recording and the desired balance
may not be possible to achieve, no matter what type of
mic is used. This is called the “critical distance” and
becomes shorter as the ambient noise and reverberation
increase, forcing closer placement of the microphone
to the source.
+ =
”1800 out
of phase”
+ =
“phase shifts”
+ =
Phase relationships
Two identical sound waves starting at the same point in
time are called “in-phase” and will sum together creating
a single wave with double the amplitude but otherwise
identical to the original waves. Two identical sound waves
with one wave’s starting point occurring at the 180degree point of the other wave are said to be “out of
phase”, and the two waves will cancel each other
completely. When two sound waves of the same single
frequency but different starting points are combined, the
resulting wave as said to have “phase shift” or an
apparent starting point somewhere between the original
starting points. This new wave will have the same
frequency as the original waves but will have increased or
decreased amplitude depending on the degree of phase
difference. Phase shift, in this case, indicates that the
0 degree points of two identical waves are not the same.
Phase relationships and interference effects – The phase
of a single frequency sound wave is always described
relative to the starting point of the wave or 0 degrees.
The pressure change is also
one cycle or one period
zero at this point. The peak
of the high pressure zone is at
90 degrees, and the pressure
change falls to zero again at
180 degrees. The peak of the
low pressure zone is at 270
degrees, and the pressure
change rises to zero at 360
Sound pressure wave
degrees for the start of the
next cycle.
Most soundwaves are not a single frequency but are
made up of many frequencies. When identical multiplefrequency soundwaves combine, there are three
possibilities for the resulting wave: a doubling of amplitude
at all frequencies if the waves are “in phase”, a complete
cancellation at all frequencies if the waves are 180 degrees
“out of phase”, or partial cancellation and partial
reinforcement at various frequencies if the waves have
intermediate phase relationship.
Microphone Techniques
The last case is the most likely, and the audible result is a
degraded frequency response called “comb filtering.” The
pattern of peaks and dips resembles the teeth of a comb
and the depth and location of these notches depend on
the degree of phase shift.
With microphones this effect can occur in two ways. The
first is when two (or more) mics pick up the same sound
source at different distances. Because it takes longer for
the sound to arrive at the more distant microphone, there
is effectively a phase difference between the signals from
the mics when they are combined (electrically) in the
mixer. The resulting comb filtering depends on the sound
arrival time difference between the microphones: a
large time difference (long distance) causes comb
filtering to begin at low frequencies, while a small time
difference (short distance) moves the comb filtering to
higher frequencies.
The second way for
this effect to occur is
when a single
microphone picks
up a direct sound
and also a delayed
version of the same
sound. The delay
may be due to an
acoustic reflection of
the original sound or
Multi-mic comb filtering
to multiple sources of
the original sound. A guitar cabinet with more than one
speaker or multiple cabinets for the same instrument
would be an example. The delayed sound travels a longer
distance (longer time) to the mic and thus has a phase
difference relative to the direct sound. When these sounds
combine (acoustically) at the
microphone, comb
filtering results.
This time the effect
of the comb filtering
depends on the
distance between
the microphone and
the source of the
reflection or the
distance between the
Reflection comb filtering
multiple sources.
The goal here is to create an awareness of the sources of
these potential influences on recorded sound and to
provide insight into controlling them. When an effect of this
sort is heard, and is undesirable, it is usually possible to
move the sound source, use a microphone with a
different directional characteristic, or physically isolate the
sound source further to improve the situation.
Applications Tip:
Microphone phase
One of the strangest effects that can happen in
the recording process is apparent when two
microphones are placed in close proximity to the
same sound source. Many times this is due to the
phase relationship of the sounds arriving at the
microphones. If two microphones are picking up
the same sound source from different locations,
some phase cancellation or summing may be
occurring. Phase cancellation happens when two
microphones are receiving the same soundwave
but with opposite pressure zones (that is, more
than 180 degrees out of phase). This is usually not
desired. A mic with a different polar pattern may
reduce the pickup of unwanted sound and reduce
the effect, or physical isolation can be used.
With a drum kit, physical isolation of the
individual drums is not possible. In this situation
your choice of microphones may be more dependent on the off-axis rejection of the mic.
Another possibility is phase reversal. If there
is cancellation occurring, a 180 degree phase
flip will create phase summing of the same
frequencies. A common approach to the snare
drum is to place one mic on the top head and one
on the bottom head. Because the mics are
picking up relatively similar sound sources at
different points in the sound wave, you are
probably experiencing some phase cancellations.
Inverting the phase of one mic will sum any
frequencies being canceled. This may sometimes
achieve a “fatter” snare drum sound. This effect
will change dependent on mic locations.
The phase inversion can be done with an in-line
phase reverse adapter or by a phase invert switch
found on many mixer inputs.
Microphone Techniques
Selection Guide
Shure Microphone Selection Guide
Solo Vocal
Guitar Amplifier
BETA 181
BETA 56A/57A
BETA 181
55SH Series II
Acoustic Guitar
BETA 181
Bass Amplifier
Acoustic Bass
BETA 181
BETA 91A (under lid)
BETA 181
BETA 181
BETA 181
BETA 181
Kick Drum
Snare Drum (top)
BETA 181
BETA 181
Leslie Cabinet
Top: KSM32
Top: BETA 57
Top: BETA 181
Top: SM57
Top: PG57
Bottom: BETA 52A
Bottom: SM7B
Bottom: PG52
Stereo Recording
Snare Drum
BETA 181
Rack/Floor Toms
BETA 56A/57A
BETA 181
BETA 181
BETA 56A/57A
BETA 181
BETA 181
Auxiliary Percussion
BETA 181
BETA 181
KSM44A (pair)
BETA 181 (Pair)
Spaced Pair
BETA 181
Microphone Techniques
Selection Guide
Shure Recording Microphone Lockers:
If you are just getting started, and need a basic selection of microphones to get your
studio up and running, select the studio situation below that most closely resembles
the type of recording you will be doing.
Home Studio
Basic (overdubs, vocals, acoustic guitar):
2 – SM57
1 – PG27 (multi purpose)
1 – PG42 (vocals)
Home Studio
Advanced (tracking, overdubs, drums, guitars, vocals):
1 – Beta 52A*
3 – SM57*
2 – SM137
1 – SM27
Project Studio
Commercial (tracking, overdubs, professional voice-overs,
larger ensembles, drums, piano):
1 – Beta 52A
4 – SM57
2 – KSM137
2 – KSM32
1 – KSM44A
1 – SM7B
*Available as model number DMK57-52, which includes
all four mics, plus three A56D drum mounts.
Beta 52A
Microphone Techniques
3-to-1 Rule - When using multiple microphones, the distance
between microphones should be at least 3 times the distance
from each microphone to its intended sound source.
Absorption - The dissipation of sound energy by losses due to
sound absorbent materials.
Active Circuitry - Electrical circuitry which requires power to
operate, such as transistors and vacuum tubes.
Ambience - Room acoustics or natural reverberation.
Amplitude - The strength or level of sound pressure or voltage.
Audio Chain - The series of interconnected audio equipment
used for recording or PA.
Backplate - The solid conductive disk that forms the fixed half
of a condenser element.
Balanced - A circuit that carries information by means of two
equal but opposite polarity signals, on two conductors.
Bidirectional Microphone - A microphone that picks up
equally from two opposite directions. The angle of best
rejection is 90 degrees from the front (or rear) of the
microphone, that is, directly at the sides.
Boundary/Surface Microphone - A microphone designed to
be mounted on an acoustically reflective surface.
Cardioid Microphone - A unidirectional microphone with
moderately wide front pickup (131 degrees). Angle of best
rejection is 180 degrees from the front of the microphone,
that is, directly at the rear.
Cartridge (Transducer) - The element in a microphone that
converts acoustical energy (sound) into electrical energy
(the signal).
Clipping Level - The maximum electrical output signal level
(dBV or dBu) that the microphone can produce before the
output becomes distorted.
Current - Charge flowing in an electrical circuit. Analogous to
the amount of a fluid flowing in a pipe.
Decibel (dB) - A number used to express relative output
sensitivity. It is a logarithmic ratio.
Diaphragm - The thin membrane in a microphone which
moves in response to sound waves.
Diffraction - The bending of sound waves around an object
which is physically smaller than the wavelength of the sound.
Direct Sound - Sound which travels by a straight path from a
sound source to a microphone or listener.
Distance Factor - The equivalent operating distance of a
directional microphone compared to an omnidirectional microphone to achieve the same ratio of direct to reverberant sound.
Distant Pickup - Microphone placement farther than 2 feet
from the sound source.
Dynamic Microphone - A microphone that generates an
electrical signal when sound waves cause a conductor to
vibrate in a magnetic field. In a moving-coil microphone,
the conductor is a coil of wire attached to the diaphragm.
In a ribbon microphone, the diaphragm is the conductor.
Dynamic Range - The range of amplitude of a sound source.
Also, the range of sound level that a microphone can
successfully pick up.
Echo - Reflection of sound that is delayed long enough
(more than about 50 msec.) to be heard as a distinct repetition
of the original sound.
Electret - A material (such as Teflon) that can retain a
permanent electric charge.
EQ - Equalization or tone control to shape frequency response
in some desired way.
Close Pickup - Microphone placement within 2 feet of a sound
Feedback - In a PA system consisting of a microphone,
amplifier, and loudspeaker, feedback is the ringing or howling
sound caused by amplified sound from the loudspeaker
entering the microphone and being re-amplified.
Comb Filtering - An interference effect in which the frequency
response exhibits regular deep notches.
Flat Response - A frequency response that is uniform and
equal at all frequencies.
Condenser Microphone - A microphone that generates an
electrical signal when sound waves vary the spacing between
two charged surfaces: the diaphragm and the backplate.
Frequency - The rate of repetition of a cyclic phenomenon
such as a sound wave.
Critical Distance - In acoustics, the distance from a sound
source in a room at which the direct sound level is equal to
the reverberant sound level.
Frequency Response Tailoring Switch - A switch on a
microphone that affects the tone quality reproduced by the
microphone by means of an equalization circuit.
(Similar to a bass or treble control on a hi-fi receiver.)
Microphone Techniques
Frequency Response - A graph showing how a microphone
responds to various sound frequencies. It is a plot of electrical
output (in decibels) vs. frequency (in Hertz).
NAG - Needed Acoustic Gain is the amount of gain that a
sound system must provide for a distant listener to hear as if
he or she was close to the unamplified sound source.
Fundamental - The lowest frequency component of a complex
waveform such as musical note. It establishes the basic pitch
of the note.
Noise - Unwanted electrical or acoustic interference.
Noise Cancelling - A microphone that rejects ambient or
distant sound.
Gain - Amplification of sound level or voltage.
Gain-Before-Feedback - The amount of gain that can be
achieved in a sound system before feedback or ringing occurs.
NOM - Number of open microphones in a sound system.
Decreases gain-before-feedback by 3dB everytime NOM
Gobos - Movable panels used to reduce reflected sound
in the recording environment.
Omnidirectional Microphone - A microphone that picks up
sound equally well from all directions.
Harmonic - Frequency components above the fundamental
of a complex waveform. They are generally multiples of the
fundamental which establish the timbre or tone of the note.
Output Noise (Self-Noise) - The amount of residual noise (dB
SPL) generated by the electronics of a condenser microphone.
Hypercardioid - A unidirectional microphone with tighter front
pickup (105 degrees) than a supercardioid, but with more rear
pickup. Angle of best rejection is about 110 degrees from the
front of the microphone.
Overload - Exceeding the signal level capability of a
microphone or electrical circuit.
PAG - Potential Acoustic Gain is the calculated gain that a sound
system can achieve at or just below the point of feedback.
Impedance - In an electrical circuit, opposition to the flow of
alternating current, measured in ohms. A high-impedance
microphone has an impedance of 10,000 ohms or more. A lowimpedance microphone has an impedance of 50 to 600 ohms.
Phantom Power - A method of providing power to the electronics
of a condenser microphone through the microphone cable.
Interference - Destructive combining of sound waves or
electrical signals due to phase differences.
Pickup Angle/Coverage Angle - The effective arc of coverage of
a microphone, usually taken to be within the 3dB down points
in its directional response.
Phase - The “time” relationship between cycles of different waves.
Inverse Square Law - States that direct sound levels increase
(or decrease) by an amount proportional to the square of the
change in distance.
Pitch - The fundamental or basic frequency of a musical note.
Isolation - Freedom from leakage; the ability to reject
unwanted sounds.
Polar Pattern (Directional Pattern, Polar Response) - A graph
showing how the sensitivity of a microphone varies with the
angle of the sound source, at a particular frequency. Examples
of polar patterns are unidirectional and omnidirectional.
Leakage - Pickup of an instrument by a microphone intended
to pick up another instrument. Creative leakage is artistically
favorable leakage that adds a “loose” or “live” feel to a recording.
Polarization - The charge or voltage on a condenser
microphone element.
Maximum Sound Pressure Level - The maximum acoustic
input signal level (dB SPL) that the microphone can accept
before clipping occurs.
Pop Filter - An acoustically transparent shield around a
microphone cartridge that reduces popping sounds.
Often a ball-shaped grille, foam cover or fabric barrier.
Microphone Sensitivity - A rating given in dBV to express how
“hot” the microphone is by exposing the microphone to a
specified sound field level (typically either 94 dB SPL or 74 dB
SPL). This specification can be confusing because
manufacturers designate the sound level different ways.
Here is an easy reference guide: 94 dB SPL = 1 Pascal = 10
microbars. To compare a microphone that has been measured
at 74 dB SPL with one that has been measured at 94 dB SPL,
simply add 20 to the dBV rating.
Pop - A thump of explosive breath sound produced when a
puff of air from the mouth strikes the microphone diaphragm.
Occurs most often with “p”, “t”, and “b” sounds.
Presence Peak - An increase in microphone output in the
“presence” frequency range of 2,000 Hz to 10,000 Hz.
A presence peak increases clarity, articulation, apparent
closeness, and “punch.”
Microphone Techniques
Proximity Effect - The increase in bass occurring with most
unidirectional microphones when they are placed close to an
instrument or vocalist (within 1 foot). Does not occur with
omnidirectional microphones.
Supercardioid Microphone - A unidirectional microphone with
tighter front pickup angle (115 degrees) than a cardioid, but with
some rear pickup. Angle of best rejection is 126 degrees from
the front of the microphone, that is, 54 degrees from the rear.
Rear Lobe - A region of pickup at the rear of a supercardioid
or hypercardioid microphone polar pattern. A bidirectional
microphone has a rear lobe equal to its front pickup.
3-to-1 Rule - (See top of page 34.)
Reflection - The bouncing of sound waves back from an
object or surface which is physically larger than the
wavelength of the sound.
Timbre - The characteristic tone of a voice or instrument;
a function of harmonics.
Transducer - A device that converts one form of energy to
another. A microphone transducer (cartridge) converts
acoustical energy (sound) into electrical energy (the audio signal).
Refraction - The bending of sound waves by a change in
the density of the transmission medium, such as temperature
gradients in air due to wind.
Transient Response - The ability of a device to respond to a
rapidly changing input.
Resistance - The opposition to the flow of current in an electrical
circuit. It is analogous to the friction of fluid flowing in a pipe.
Unbalanced - A circuit that carries information by means of
one signal on a single conductor.
Reverberation - The reflection of a sound a sufficient number
of times that it becomes non-directional and persists for some
time after the source has stopped. The amount of reverberation
depends on the relative amount of sound reflection and
absorption in the room.
Unidirectional Microphone - A microphone that is most
sensitive to sound coming from a single direction-in front of
the microphone. Cardioid, supercardioid, and hypercardioid
microphones are examples of unidirectional microphones.
Rolloff - A gradual decrease in response below or above some
specified frequency.
Sensitivity - The electrical output that a microphone produces
for a given sound pressure level.
Shaped Response - A frequency response that exhibits
significant variation from flat within its range. It is usually
designed to enhance the sound for a particular application.
Signal to Noise Ratio - The amount of signal (dBV) above the
noise floor when a specified sound pressure level is applied to
the microphone (usually 94 dB SPL).
Sound Chain - The series of interconnected audio equipment
used for recording or PA.
Sound Reinforcement - Amplification of live sound sources.
Speed of Sound - The speed of sound waves, about 1130 feet
per second in air.
SPL - Sound Pressure Level is the loudness of sound relative to
a reference level of 0.0002 microbars.
Standing Wave - A stationary sound wave that is reinforced by
reflection between two parallel surfaces that are spaced a
wavelength apart.
Vacuum Tube (valve) - An electric device generally used to
amplify a signal by controlling the movement of electrons in a
vacuum. Vacuum tubes were widely used in the early part of
the 20th century, but have largely been replaced by transistors.
Voice Coil - Small coil of wire attached to the diaphragm of a
dynamic microphone.
Voltage - The potential difference in an electric circuit.
Analogous to the pressure on fluid flowing in a pipe.
Wavelength - The physical distance between the start and end
of one cycle of a soundwave.
Appendix A
Microphone Techniques
Appendix A: The Decibel
The decibel (dB) is an expression often used in electrical
and acoustic measurements. The decibel is a number that
represents a ratio of two values of a quantity such as voltage. It is actually a logarithmic ratio whose main purpose
is to scale a large measurement range down to a much
smaller and more useable range. The form of the decibel
relationship for voltage is:
Since the decibel is a ratio of two values, there must be an
explicit or implicit reference value for any measurement
given in dB. This is usually indicated by a suffix on the dB.
Some devices are measured in dBV (reference to 1 Volt =
0 dBV), while others may be specified in dBu or dBm
(reference to .775V = 0dBu/dBm). Here is a chart that
makes conversion for comparison easy:
dB = 20 x log(V1/V2)
where 20 is a constant, V1 is one voltage, V2 is a reference
voltage, and log is logarithm base 10.
What is the relationship in decibels between
100 volts and 1 volt? (dbV)
dB = 20 x log(100/1)
dB = 20 x log(100)
dB = 20 x 2
(the log of 100 is 2)
dB = 40
That is, 100 volts is 40dB greater than 1 volt.
What is the relationship in decibels between
.0001 volt and 1 volt? (dbV)
dB = 20 x log(.001/1)
dB = 20 x log(.001)
dB = 20 x (-3) (the log of .001 is -3)
dB = -60
That is, .001 volt is 60dB less than 1 volt.
Audio equipment signal levels are generally broken into 3
main categories: Mic, Line, or Speaker Level. Aux level
resides within the lower half of line level. The chart also
shows at what voltages these categories exist.
If one voltage is equal to the other,
they are 0dB different.
If one voltage is twice the other,
they are 6dB different.
If one voltage is ten times the other,
they are 20dB different.
One reason that the decibel is so useful in certain audio
measurements is that this scaling function closely
approximates the behavior of human hearing sensitivity.
For example, a change of 1dB SPL is about the smallest
difference in loudness that can be perceived while a 3dB
SPL change is generally noticeable. A 6dB SPL change is
quite noticeable and finally, a 10dB SPL change is
perceived as “twice as loud.”
Microphone Techniques
Appendix B
Appendix B: Transient Response
The ability of a microphone to respond to a
rapidly changing sound wave.
A good way to understand why dynamic and condenser
mics sound different is to understand the differences in
their transient response.
In order for a microphone to convert sound energy into
electrical energy, the sound wave must physically move
the diaphragm of the microphone. The speed of this
movement depends on the weight or mass of the
diaphragm. For instance, the diaphragm and voice coil
assembly of a dynamic microphone may have up to
1000 times the mass of the diaphragm of a condenser
microphone. The lightweight condenser diaphragm
starts moving much more quickly than the dynamic’s
diaphragm. It also takes longer for the dynamic’s
diaphragm to stop moving in comparison to the
condenser’s diaphragm. Thus, the dynamic’s transient
response is not as good as the condenser’s transient
response. This is similar to two vehicles in traffic: a
truck and a sports car. They may have engines of equal
power, but the truck weighs much more than the car.
As traffic flow changes, the sports car can
accelerate and brake very quickly, while the semi
accelerates and brakes very slowly due to its greater
weight. Both vehicles follow the overall traffic flow but
the sports car responds better to sudden changes.
The picture below is of two studio microphones responding
to the sound impulse produced by an electric spark:
condenser mic on top, dynamic mic on bottom. It is
evident that it takes almost twice as long for the dynamic
microphone to respond to the sound. It also takes longer
for the dynamic to stop moving after the impulse has
passed (notice the ripple on the second half of the graph).
Since condenser microphones generally have better
transient response then dynamics, they are better suited
for instruments that have very sharp attacks or extended
high frequency output such as cymbals. It is this transient
response difference that causes condenser mics to have
a more crisp, detailed sound and dynamic mics to have a
more mellow, rounded sound.
Condenser/dynamic scope photo
Microphone Techniques
About the Authors
Gino Sigismondi
Tim Vear
Gino is a Shure Associate since 1997 and has been active
in the music and audio industry for over twenty years. In addition
to his work as a live sound and recording engineer, Gino’s
experience also includes performing and composing. Gino
earned his BS degree in Music Business from Elmhurst College,
where he was a member of the Jazz Band, as both guitar player
and sound technician. Currently leading the Systems Support
group at Shure, Gino and his team provide technical support for
high-end Shure wireless and conferencing products that rely on
software, firmware, and networking. Additionally, he conducts
training seminars for Shure customers, dealers, distribution
centers, and internal staff.
Tim has come to the audio field as a way of combining a
lifelong interest in both entertainment and science. He has
worked as an engineer in live sound, recording and broadcast,
has operated his own recording studio and sound company, and
has played music professionally since high school.
Currently, Tim is a Lead Systems Support Engineer. In his
tenure at Shure, Tim has served in a technical support role for
the sales and marketing departments, providing product and
applications training for Shure customers, dealers, installers, and
company staff. He has presented seminars for a variety of
domestic and international audiences, including the National
Systems Contractors Association, the Audio Engineering Society
and the Society of Broadcast Engineers. Tim has authored
several publications for Shure and his articles have appeared in
several trade publications.
Rick Waller
An interest in the technical and musical aspects of audio
has led Rick to pursue a career as both engineer and musician.
While at the University of Illinois at Urbana/Champaign,
he performed with the Marching Illini, DJ'ed more wedding
receptions than anyone should, and received a BS degree
in Electrical Engineering, specializing in acoustics, audio
synthesis and radio frequency theory.
Rick joined Shure in 1995 and has traveled throughout
North America, Europe and Asia conducting seminars on multiple
audio topics. Currently he is a Senior Applications Engineer,
providing technical support to customers, conducting seminars,
and developing many online tools and wizards. Since 1999, Rick
has administered and developed the Shure online Knowledge
Database, used by 1400+ people every day. His quest for
efficient customer service leads him to scan and make available
more than 2000 vintage Shure catalogs and user guides.
Rick is an avid home theater and home automation
hobbyist, amateur auto racer and master of never ending
home improvement projects.
Additional Shure Publications Available:
Printed and electronic versions of the following guides are available free of charge.
To obtain your complimentary copies, call one of the phone numbers listed below or
visit www.shure.com/literature.
• Selection and Operation of Personal Monitor Systems
• Selection and Operation of Wireless Microphone Systems
• Microphone Techniques for Live Sound Reinforcement
Other Sources of Information:
There are books written about acoustics and how to mathematically determine their effects.
Here are a few:
Our Dedication to Quality Products
Shure offers a complete line of microphones and wireless microphone systems for everyone
from first-time users to professionals in the music industry–for nearly every possible application.
For over eight decades, the Shure name has been synonymous with quality audio.
All Shure products are designed to provide consistent, high-quality performance under the
most extreme real-life operating conditions.
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