Crown PZM-10 User guide

127018-1
7/00
Crown International, Inc
P.O. Box 1000, Elkhart, Indiana 46515-1000
[phone] Fax [phone]
www.crownaudio.com
© 2000 Crown International, All rights
reserved PZM®, PCC®, SASS®and
DIFFEROID®,areregisteredtrademarksof
CrownInternational,Inc.Alsoexported
as Amcron®
PZM, PCC, SASS AND BOUNDARIES

Contents
Background toboundarymicrophones 1
Howtheboundarymicrophoneworks 2
ThePCCmicrophone 3
Boundarymicrophonetechniquesforrecording 4
Boundarymicrophonetechniquesforsound reinforcement 8
PZM boundaries 9
TheSASSPZMstereo microphone 17
HowtousetheSASSmicrophone 20
21
Fig.60
Moving vehicles
(car hood, handlebars)
We recommendthat you devise a shock-mount system
to be used under the microphone.Alsobe sure to put
on the windscreen,and enable the low-cut switch(or
use low-cut filters in your mixer).
Electronic News Gathering (E.N.G.)
You can often record an announcer and ambience with
the SASSalone,without an extra handheld orlavalier
mic onthe announcer.If the ambient noise level istoo
high,use a mixerto blend a close-upmicrophone
(pannedto center)with the SASS.
The SASS will give a slight but not noticeable boostto
the appropriate side if the talent moves away from frame
center.IftheSASSiscameramounted,usethewindscreen
tosubduewindnoisecausedbycameramovement.
Because of its light weight,the SASS can be mounted
on afishpole,floor stand,boom stand,or tripod,
in addition to the handgrip.
Samples and sound effects
If you sample a sound source in a particular off-center
position,the SASS will accurately reproduce the image
location.Recorded ambience will sharpen theimage,
but isnotnecessary.
If you record ambience along with the sample,the ambi-
encewill be reproduced whenever the sample isplayed.
So you may want to make several samples of one source
at different distances to include the range of added
reverberance or ambience.
Suppose you’re samplingin stereo and pickingup ambi-
ence.If the sample is pitch-shifted,the direction of the
imagesandperceivedsizeoftheroomwillbeaffectedby
mostpitch-changingalgorithms.Youcanminimizethese
effectsbysamplingatintervalsofone-thirdoctaveorless.
When looping,try to controlthe room ambience so itis
consistentbefore and after the sample (unless reverber-
ant decayis desired aspart of the sample).
When recording a moving sample or effect,experiment
withthe distance between the microphone and the clos-
est pass of the sound source.The closerthe SASS is to
the path of the subject,the more rapidly the image will
pass the center point (almost hopping from one channel
to the other).To achieve a smooth side-to-side move-
ment,you may needto increase the distance.
CHOOSING THE RIGHT CROWN BOUNDARY MICROPHONE
Application Suggested Model
Recording PZM-30D Rugged,usewithdetachablecable.
PZM-6D Inconspicuous,permanentlyattachedcable.
MultipleBoundaryRecording/P.A. PZM-6D Unscrewcantileverfromplate.
StereoRecording SASS-P MK II StereoPZMmicrophone.
StageFloor PCC-160
ConferenceTable PCC-170 Supercardioid.
PCC-170SW Supercardioidwithpush on/offmembraneswitch.
PCC-130 Smallcardioid.
PCC-130SW Smallcardioidwithpushon/offmembraneswitch.
MiniBoundaryMicrophones :Verysmallmicswithahalf-supercardioidpattern.
Fivemodelsareavailable:
ModelsMB-1,MB-2,andMB-4Erequirean MB-1:Plugsintoabrasscupinthetable.
MB-100orMB-200interface.TheMB-200 MB-2:Plugsintoajackinthetable.
interfaceallowsremotesensing ofswitch MB-3:Tubular;mountsinceiling,wallortable.
closure,soitcanbeusedwithavideoswitcher. MB-4:Fortemporaryuse.HasathincablewithXLRconnector.
MB-4E:Lowestcost.Cablefitsthroughsmallholeintable.
PianoSoundReinforcement PZM-30D,PZM-6D or PCC-160 onundersideoflid.
Ambience PZM-30D orPZM-6D onwalls.
Security/Surveillance PZM-11,PZM-11LL,PZM-10,PZM-10LL

In live-to-2-trackrecording,we recommend that the
final placement decisions be made while monitoring on
loudspeakers for more-accurate imaging.
If the correctly monitored stereo spread isexcessive
(because of close mic placement),run the SASS signals
through a stereo mixer with pan pots,and pan the two
channels toward center until the stereo spreadis correct.
This can be done during recording or post-production.
Fig.58
Center sound source too close to
SASS:mic capsules can't“hear”it,
because its sound is blocked.Re-
sult:weak center image.
CentersoundsourcefarfromSASS:
bothmiccapsuleshearit.Results:
strong center image.
Fig.59
20
mics have weakdeep bass.The SASS does nothave this
problem because it is not directional atlowfrequencies.
It has excellent bass response extending to 20 Hz.
Simple to Use
Mid-side stereo microphones require a matrix box be-
tween the microphone and recorder.This box converts
the mid and side signals from the microphone to left
and right signals for stereo recording.The SASS already
hasleftandrightoutputs,soitneedsnoin-linematrixbox.
It’s easyto tell where to aim the SASS by looking atit.
In contrast,some stereo microphones are difficult to
aim properly.
Excellent Performance
The SASS has very wide-range,smooth frequency
response (20 Hz–18 kHz),and very low pickup of
mechanicalvibrations and wind noise.
Summary
The SASS is a stereo microphone using PZM® technol-
ogy.The unit provides excellent stereo imaging,hasa
natural tonal balance,ismono-compatible,iseasyto
use,and costs less than the competition.It comeswith
a carrying case and a full line of accessories.
HOW TO USE THE SASS
Do not place the SASS closer than 3 feet from the
sound source,or the centerimage will be weak or
muffled (Fig.58).
Large musical ensembles (orchestra,
band, choir, pipe organ)
Place the SASS 4 to 15 feet from the front row of
musicians.Angleitdown so that itwill be aimed at the
performers when raised,and raise it about 15 feethigh
on amicrophone stand (Fig.59).Closer placement to
the performers will sound more edgy,detailed,and dry:
farther placement will sound more distant,blended and
reverberant.Try to find a spot where you heara pleasing
balance betweenthe direct sound from the ensemble
and the hall ambience.
Because the SASS is quite sensitive to the sides aswell
as the front,closer placement will notbe asdry as with
directional microphones.Hence,the SASS canbe placed
into an ensemble farther than is ordinarily possible,
providing greater detailand spread,if that is desired,
withoutfeelingforced or unnatural.The centerof the
sound image and the hall reverberation are still retained.
If you are recordinga choir that is behind an orchestra,
experiment with the stand heightto find the best
balance betweenthe two sources.The stringsproject up-
ward while the choir projectsforward,so you might find
a better balance at,say,9 feet high rather than 15 feet.
Small musical ensemble or soloist
(quartet, small combo, background
harmony vocals, solo piano, harp,
or guitar)
Place the SASS 3 to 8 feet away at ear height.Move closer
for less reverb andnoise,farther formore hall acoustics.
For a grand piano,place the SASS in-line withthe lid.
Placement near the hammers sounds more trebly; place-
ment near the tail sounds more bassy.
Drum set
See Fig.60.Place the SASS above the level of the snare
drum,below the cymbals,aiming at the snare drum
about 3 feet away,midway between the mountedtom
and floor tom.Youmay needto boost afewdB around
10 kHz - 15 kHz.Add another microphone of your
choice in the kick drum.The SASS alsoworks well as
an overhead mic.
INTRODUCTION
A boundary microphone is a miniature microphone
designedto be used ona surface such as apiano lid,
wall,stage floor,table,or panel.Mounting aminiature
mic ona surface gives several benefits:
•A clearer,more natural sound quality
• Extrasensitivity and lowernoise
• Consistent tone qualityanywhere around the
microphone
• Natural-soundingpickupof room reverberation
Crownboundarymicrophonesinclude the PZM,PCC,
MB,and SASS series microphones.This guide explains
howthey work and how to use them.For information
on the CM,GLM,and LMmodels,please see theCrown
MicrophoneApplicationGuide.
BACKGROUND
Inmanyrecordingandreinforcement applications,
the sound engineerisforced to place microphonesnear
hard reflective surfaces.Some situations where this
might occurare recording an instrument surrounded
byreflective baffles,reinforcing drama or opera with the
microphonesnear the stage floor,or recordinga piano
withthe microphone close to the open lid.
When a microphone isplaced near a reflective surface,
sound travels to the microphone via two paths: (1) di-
rectlyfrom the sound source to the microphone,and
(2) reflected off the surface (as in Fig.1-A).Note that
the reflected sound travels alonger paththan the direct
sound,so the reflected sound is delayed relative to the
directsound.The direct and delayed sounds combine
at the microphone diaphragm.
All frequencies in the reflectedsound are delayed by the
same time.Havingthe same time delayfor all frequen-
ciescreatesdifferentphase delays foreachfrequency,
because different frequencies have different wave-
lengths.For example,a time delay of 1 millisecond
causes a 360-degree phrase shift for a 1000-Hz wave,
but only a180-degreephase shift for a 500-Hz wave.
Fig.2 illustratesthispoint.
At frequencies where the direct and delayed sounds are
in-phase (coherent),the signals add together,doubling
the pressure and boosting the amplitude 6 dB.At fre-
quencies where the direct and delayed signals are out-
of-phase,the signals cancel eachother,creating a dip
ornotch in the response.There results a series of peaks
and dips in the net frequencyresponse calleda comb-
filter effect ,so named because the response looks like
the teeth of a comb.(Fig.1-B).
This bumpyfrequencyresponse colors the tonal repro-
ductions,giving an unnatural sound.To solve thisprob-
lem,we need to shorten the delayof the reflected sound
so thatit arrives at the microphone atthe same time the
directsound does.
If the microphone is placed on the reflective surface (as
in Fig.3),the direct and reflectedsound paths become
nearlyequal.There isstill ashort delay in the reflected
sound because the center of the microphone diaphragm
(where the two sound paths combine) is slightly above
the surface.Consequently,the highfrequencies may be
cancelled,giving adull sound quality.
1
Fig.2 -Example ofwave addition and
cancellation at two differentfrequencies.
Fig.1

HOW THE BOUNDARY
MIC WORKS
Byorientingthe diaphragm parallel withthe boundary
(as in Fig.4),the diaphragm can be placed asclose to
the boundaryas desired.Then the direct and reflected
waves arrive simultaneouslyat the microphone sound
entry(the slit between the microphone diaphragm and
the boundary).Any phase cancellationsare moved out-
side the audible band,resultingina smooth frequency
response.
response isnotseverely degraded.
The Pressure Zone can be defined another way: The
Pressure Zone is the distance from the boundary that
the microphone diaphragm must be placed toachieve
the desired high-frequency response.The closer the
diaphragm is placed tothe boundary(uptoa point),
the more extended is the high-frequency response.
Let’s show some examples.
For a frequencyresponse down a maximum of 6 dB
at 20 kHz,the mic-to-boundary spacing should be .11."
Or you could say the Pressure Zone is.11" thick.This
spacingcorrespondsto1
⁄6wavelengthat20 kHz.
For a response down 3 dB maximum at 20 kHz,the
spacing should be .085" (1
⁄8wavelengthat20 kHz).
For a response down 1 dB maximum at 20 kHz,the
spacing should be .052" (1⁄13 wavelengthat20 kHz).
Note that the thickness of the Pressure Zone is an arbi-
trarynumberdependingonfrequency.For example,
the direct and reflected waves of a 100-Hztone are
effectively in-phase within a Pressure Zone 10" thick.
The Crown PZMmicrophone-to-boundary spacing
isonly.020",which relates to 1 dB down at52 kHz.
Pressure doubling
Asstated earlier,comb-filteringis eliminated when the
directand reflected waves add together in-phase.There
is another benefit: the sound pressure doubles,givinga
6 dB increase in acoustic level at the microphone.Thus
the effective microphone sensitivity increases 6 dB,and
the signal-to-noise ratio also increases 6 dB.
Consistent tonal reproduction
independent of source height
The microphoneplacements shown in Figs.1 and 3
cause another probleminaddition to rough response.
Asthe sound source moves up or down relative to the
surface,the reflected path length changes,which varies
the comb-filter notch frequencies.Consequently,the ef-
fective frequency response changes as the source moves.
Butwith the PZM,the reflected path lengthstays equal
to the direct path length,regardless of the sound-source
position.There is no change in tonequality as the
source moves.
Lack of off-axis coloration
Yetanotherproblemoccurswithconventionalmicro-
phones:off-axiscoloration.Whileamicrophonemayhave
aflatresponsetosoundsarrivingfromstraightahead
(on-axis),itoftenhasarolled-offorcoloredresponseto
soundsarrivingfromotherdirections(off-axis).
That fault is mainly due to the size of the microphone
and itsforward orientation.When sound strikes the mi-
crophone diaphragm on-axis,a pressure boost occurs at
The technique of mounting a microphone in this man-
ner is called the Pressure RecordingProcessTM (invented
byEd Long and RonWickersham).Theydeveloped the
first microphone to use this process.The first manufac-
tured microphone using the principle was the Pressure
ZoneMicrophone®(developed by KenWahrenbrock).
PZM®s are now manufactured by Crown International,
the first company licensed tothe build microphones
using the Pressure Recording Process.
The Pressure Zone is the region next to the boundary
where the direct and reflected waves are in-phase (or
nearlyso).There may be a slightphase shift between
the direct and reflected waves,as long as the frequency
2
Fig.3-Conventionalmicrophoneonfloorreceiving
directsoundandslightly delayedreflectedsound.
Fig.4
How the SASS Works
Back to the SASS.It uses two small microphones spaced
a few inches apart.Eachmicrophone is on a surface that
blocks sound from the rear,and these surfacesare
angledapart (Fig.55).In other words,the surfaces make
the microphones directional.So the SASS is like a near-
coincident pair,in which two directional micsare angled
apart and spaced horizontally afewinches.
19
Fig.55–PartsofSASS
The surfacesmake the microphonesdirectional only at
mid-to-high frequencies.At lowfrequencies,the micro-
phonespickupall around them—they are omnidirec-
tional.
The SASS produces stereo in differentways at differ-
entfrequencies.Atlow frequencies,the SASS actslike
a spaced pair,producing time differences between
channelsto makeastereoeffect.Athighfrequencies,
the SASSacts like coincident pair,producing mostly
loudness differences between channels to make a stereo
effect.At mid-frequencies,the SASSacts like a near-
coincident pair,using both loudness andtime differ-
ences to make stereo.
This is the same way the human hearing systemworks.
Our earsare omnidirectional at low frequencies,direc-
tional athigh frequencies (because the head blocks
sounds),and are spaced apart afew inches.
Since the SASS hears sounds the same wayour ears do,
itproducesvery natural stereo with easy-to-localize im-
ages.It also givesa pleasingsense of spaciousness,a
sense of the environmentin which the sound was re-
corded.Boththese attributes can be heard over loud-
speakersorover headphones.
The coincident-pairmethod gives a narrow stereo
spread over headphones.The spaced-pair method
makes imagesthat are poorly focused orhard-to-local-
ize when heard with speakers(Fig.56).The SASS has
neither of these problems.It gives accurate,wide stereo
overheadphones,and makesimages that are sharpand
correctlyplacedwhenheardwithspeakersorheadphones.
Fig.56
The SASS Is Mono Compatible
It’s important for stereo recordingsto be mono compat-
ible.Thatis,the tone qualitymust be the same whether
the program is heard in mono or stereo.
With spaced-pair or near-coincidentrecordings,the
microphonesare spaced apart.Sound arrives at the two
microphonesat different times.Thus,the left and right
signalsare in phase at some frequencies,and out-of-
phase at other frequencies.If the two channels are com-
bined for mono listening,the out-of-phase frequencies
cancel out.This makes dipsin the frequency response
(Fig.57).The non-flat response gives a filtered,colored
tone qualityto whatever is recorded.
Fig.57
Recordings made with the SASS do nothave this prob-
lem.That’s because it’s made with a special block of
dense foam between the mic capsules.This foam barrier
absorbs sound.Itprevents sound from the rightside
from reaching the leftmicrophone,and vice versa.Thus,
the signal ismuchlouder in one channel than the other.
For a phase cancellation to be completewhentwo chan-
nels are combined to mono,the levels in both channels
must be aboutthe same.Butthe levels in bothchannels
are different in the SASS (due to the foam barrier be-
tween capsules),so phase cancellation in mono isrela-
tively slight (Fig.57).Thus the tone qualitystaysthe
same in stereo ormono withthe SASS.
Better Bass Response
All directional microphones have reduced output in the
deepbass.Thus,stereo methodsthat use directional

frequencies where the wavelength is comparable to
the microphone diameter (usually above about 10 kHz).
Thisphenomenoniscalleddiffraction. Soundsap-
proaching the microphonefrom the sides or rear,
however,do not experience apressure boost at high
frequencies.Consequently,the high-frequencyresponse
is greater on-axis than off-axis.The frequency response
varies with the position of the sound source.
Since the PZM capsule is very small,and because all
sound entersthe capsule through a tiny,radially sym-
metric slit,the response staysconstant regardlessof the
angle atwhichsound approaches the microphone.The
effective frequencyresponse is the same for sounds
from the front as it isfor soundsfrom other directions.
In otherwords,there islittle or no off-axiscoloration
withthe PZM.The reproduced tone quality doesn’t
change when the sound source moves.
Asfurther benefit,the PZM hasan identicalfrequency
response for random-incidence sound as it has for di-
rectsound.Direct sound is sound travelingdirectly
from the source to the microphone;randomincidence
sound is sound arriving from all directions randomly.
An example of random-incidence sound is ambience
orreverberation –sounds reflected off the walls,ceiling,
and floorof the recordingenvironment.
With most conventional microphones,the response
to reverberant,random-incidence sound is rolled off in
the high frequencies compared to the response to direct
sound.The direct sound may be reproduced accurately,
but the reproduced reverberation maysound duller
thanin real life.
This fact leads to some problemsin recording classical
music withthe microphones placed far enoughaway to
pick up concert-hall ambience.The farther from the
sound source the microphone is placed,the more rever-
berantisthe sound pickup,and so the duller the sound
is.The effective microphone frequencyresponse may
become duller (weaker in the high frequencies) as the
microphone is placed farther from the sound source.
Thisdoesn’t occur with the PZM whenit’s used on the
floor.The effective response stays the same regardless
of the mic-to-source distance.The response to ambient
sound (reverberation) is justas accurate as the response
to the direct sound from the source.As a result,the total
reproduction is brighterand clearer.
Reach
“Reach”isthe abilityto pick upquiet distant sounds
clearly.“Clearly”means with a high signal-to-noise ra-
tio,a wide smooth frequencyresponse,and a highratio
of directsound to reverberantsound.
Asdescribedearlier;thePZMhasseveralperformanceat-
tributesthatcontributetoexcellentreach.Thesignal-to-
noiseratioishighbecausethesignalsensitivityisboosted
6dBbytheon-surfacemounting.Thefrequencyresponse
iswideandsmoothbecausecombfilteringiseliminated,
andbecausereverberantsoundispickedupwithafull
high-frequencyresponse.Thedirect-to-reverberantsound
ratioishighbecausethedirectsoundisboosted6dBnear
thesurface,whilethereverberantsound,beingincoherent,
isboostedonlyabout3dB.
IfthePZMelementismountedinacorner,thedirectsound
isboosted18dB,whilereverberantsoundisboostedonly
9dB.ThisgivesthePZMa9dBadvantageoveraconven-
tionalomnidirectionalmicrophoneintheratioofdirect-to-
reverberantsound.Inotherwords,distantsourcessound
closerandclearerwiththePZMthantheydowithacon-
ventionalomnidirectionalmicrophone.
Low vibration sensitivity
The low mass and high damping of the PZM diaphragm
make itrelativelyinsensitive to mechanical vibrations
such as table andfloor thumpsand clothing noise.
The only pickupof thesessoundsis acoustic pickup
through the air,not mechanical pickup through the
microphone housing.
Small size
In addition to the acoustic benefitsof the PZM,there are
psychologicalbenefits related to its low-profiledesign.
Its inconspicuous appearance reduces“mic fright.”Since
the PZM does notpoint at the performers,they may feel
more relaxed in not having to aim their instrumentsat
the microphone.
PZMs can be hidden intheatre sets.InTV-studio appli-
cations,the PZMpracticallydisappearson-camera.
PZMs reduce clutter on the conference tables and lec-
terns,givingthe feeling that no microphones are in use.
THE PCC
The Phase CoherentCardioid (PCC) is a surface-
mounted supercardioid microphone which provides
the same benefits previously mentioned for thePZM.
Unlike the PZM,however,the PCC uses a subminiature
supercardioid mic capsule.Its directional polar pattern
improvesgain-before-feedback,reduces unwanted room
noise and acoustics,and rejects sound from the rear.
Fig.5 showsthe difference inconstruction and polar
patternsof the PZM and PCC.
In the Crown PCC,the microphone diaphragm is small
enough so that any phase cancellations are above the
audible range (Fig.6).This results in a wide,smooth fre-
quency response free of phaseinterference.In contrast,
the mic capsules inconventional microphonesare rela-
tively large.As aresult,reflections are delayed enough to
cancel highfrequencies,resultingin dull sound (Fig.3).
3

BOUNDARY MICROPHONE
TECHNIQUES FOR RECORDING
Before placingmicrophones,workon the“live”sound
of the instrument or ensemble to be recorded.Do what
you can to improve its sound in the studio.
To determine a good starting microphone position,close
one ear with your finger; listen to the instrumentwith
the other,and move around untilyoufind a spot that
sounds good.Putthe PZM there,or put iton the floor
ortable at that distance.
Moving the microphone around the instrument will
varythe tone quality,because an instrumentradiates a
different spectrum in everydirection.Place the PZM to
get the desired tone quality,then use equalization only
if necessary.Note thatthe response of the PZM does not
change withthe angle of incoming sound,but the spec-
trum of the instrument does change depending on how
itis aimed at the PZM.
To reduce pickup of acoustics,leakage from other in-
struments and background noise,move the PZM closer
to the sound source.Mike only ascloseas necessary,
since too-close placement may result in an unnatural
tonalbalance.Move the PZM farther from the source
to add ambience or“artistic leakage”to the recording.
To further reduce pickup of unwanted sounds,mount
the PZM on alarge baffle or acoustic panel placed be-
tween the PZM and the offending noise source.
Use the smallest number of microphonesthat provide
the desired sound; use as fewas necessary.Sometimes
this can be done by coveringseveral sound sources with
a single microphone.The wide polar pattern of the PZM
allowsyouto pickupseveralinstrumentsorvocalistson
a single microphone with equal fidelity.
Follow the 3:1 rule:When multiple microphones are
mixed to the same channel,the distance between the
microphonesshould be at least three times the mic-
to-source distance.This procedure reduces phase inter-
ference between the microphones.Forexample,if two
microphonesare eachplaced 2 feet from the instruments
they cover,the mics should be at least 6 feetapart.
PZMs used in multiple-microphone applications may
pick up alot of leakage (“off-mic”sounds from other in-
struments).This leakage usually sounds good,however,
owing to the PZM’s uncolored off-axis response.Artistic
usage of leakage can add pleasing“liveliness”tothe re-
cording.
When a PZM is mounted on a wall,the wall becomes
a part of the microphone.When a PZM is mounted in
a corner,then all three walls become part of the micro-
phone.The Pressure Zonesof all the walls combine to
reinforce the sound pickup.Use this fact to your advan-
tage bymounting the PZM capsule at the junction of
multiple boundaries wheneverpossible.
Fig.5
4
Technically,the PCC is not a Pressure Zone Microphone.
The diaphragm of a PZM is parallelto the boundary;
the diaphragm of the PCC is perpendicular to the
boundary.Unlike a PZM,the PCC“aims”along the
plane on which it is mounted.In other words,the main
pickup axisisparallel with the plane.
Because of its supercardioid polar pattern,the PCChas
nearlya6 dB higherdirect-to-reverberation ratio than
the PZM; consequently,distantsources sound closer and
clearer withthe PCC than withthe PZM.
Fig.6

The followingare some guidelinesfor PZM placement
in variousrecording applications.Many were provided
byusers.Although these techniqueshave worked well
in many situations,theyare just suggestions.
Acoustic guitar, mandolin, dobro,
banjo:
•On panel in front,about2 feetaway,guitar height.
• On panelin frontand overhead to avoid interference
withaudience viewing.
•On floor(forsoloist).
String section:
• On panel above and in front of the entire section.
•On panel midwaybetween twoinstruments,about
6feet high.
Fiddle or Violin:
•On panel in frontoroverhead.
• On music stand.
Cello or acoustic bass:
• On panelonfloor,in front,tilted toward performer.
• On panelin frontand above.
•On floor(forsoloist).
String quartet:
• Spaced pair on floor about 3 to6 feet apart.
• Spaced pair on panels in frontand above,spaced
3to 6 feet apart.
Harp:
•On panel about 21 ⁄2feet away,aiming toward treble
partof sound board.
Sax, flute, clarinet:
• On panelin frontand slightly above.
• On music stand.
Horns, trumpet, cornet, trombone:
• On wall,on hard-surface gobo,or on control-room
window.Performersplay to the wall or goboa few feet
away.Since their sound bounces off the wall back to
them,they canhear eachotherwellenough to produce
a natural acoustic balance.
•On panel infrontof andbetweeneverytwoplayers,
1to 2 feet away.
• On music stand.
•Tuba–onpanel overhead.
Grand Piano:
• Tape a PZM to the underside of the lid in the middle
(Fig.7).Putthe lid on the longstickfor bestsound
quality.To reduce leakage andfeedback,put the lid on
the shortstick orclose the lid and coverthe piano with
aheavyblanket.
• For stereo,use two PZMs taped underthe lid –one
overthe treble strings near the hammers,one over the
bass strings well away from the hammers.Microphone
placement close to the hammers emphasizes attack;
placement farfrom the hammers yields more tone.
• To pick up the piano and room ambience with a single
microphone,place aPZM on a panel about6 to 8 feet
from the piano,4 feet high.Putthe lid on thelongstick,
and face the panel at the piano with the panel perpen-
dicular to the lid.
• To add ambience to a close-mikedpiano,mixin aPZM
ortwo placed on awall far from the piano.
•Forsingerswhoaccompany themselves onapiano,
mounttwo PZMs on opposite sidesof a panel.Place the
panel about where the music rackwould be.For stereo,
use alonger panelwith two microphones on each side
of the panel.
Amplifier/speaker for electric guitar,
piano, bass:
•On panelin frontof amp.
•On floorafewfeetinfrontof amp.Foraninteresting
coloration,add a panel afew feetbehind the micro-
phone.
• Inside the cabinet.
Leslie organ cabinet:
• Two PZMs on either side of the rotating horn,inside the
topof the cabinet.Place another PZM inside the bot-
tom cabinet.
Drum set:
• On panelorhard gobo,1 to 2feet in frontof set,just
above the level of the tom-toms.Use two microphones
3 feet apart for stereo.The drummer can balance the
sound of the kit as he or she plays.Also hang a small-
plate PZM verticallyin the kickdrum facing the beater
head,withapilloworblanketpressingagainstthe
beater head.The high sound pressure level will not
cause distortion in the PZM’s signal.
• Try twoPZMs overhead,each mounted on a 1-foot
square panel,angled to form a“V,”withthe point of the
“V”aimingdown.Omit the panel for cymbal miking.
• Two PZMs on a hard floor,about2 feetto the left and
right of the drummer.
• Tape a PZM to a gauze pad and tape the pad to the kick
drum beater head near the edge.This mic will also pick
up the snare drum.
• See percussion below.
Fig.7
5

Percussion:
• Use a PZM strapped to the chest of the player.The mi-
crophone is carried by the percussionist as he orshe
movesfrom instrument to instrument.
Xylophone, marimba, vibraphone:
• Use two PZMsabove instrument,over bass and treble
sides,with or without panels.
Lead Vocal:
• In the studio,mount a PZM on a wall,control-room
window or panel a foot in front of the performer.The
panel can be used in place of a music stand to holdthe
lyric sheet.Use the supplied foam windscreen to pre-
vent“popping”sounds from the letter“P.”
• To reduce leakage in the vocal mic,(1) overdub the vo-
cal,(2)use gobos,or (3)use awell-damped isolation
booth withone hard wall tomountthe PZM on.Note:
the PZM does nothave proximityeffect (up-close bass
boost).Use console EQ to add extra warmth if neces-
sary.
Background harmony vocals:
•On awallorpanel.
• Use one or two on both sides of a gobo,with singers
surrounding the gobo.
Combos, small groups:
For small musical groupswith a good naturalacoustic
blend,suchas bluegrass,old-time,ethnic groups,blues
groups,orbarbershopquartets.
•On floor–twofor stereoabout 3to 5 feet apart(Fig.8).
• On panels infront,or on panels on the floor,angled
toward performers.
Drama, theatre, opera:
Fig.8
Fig.9
For maximum clarityand maximum gain before feed-
back,turn up only the microphone nearest the person
talking.
Showthe performers and the custodian where the PCCs
are located so theyaren’t kicked ormopped.
To reduce pickup of the pit orchestra,put a 2' x2' piece
of 4" thick Sonex foam about 1" behind each PCC.
The excellent“reach”of the PCC provides clearpickup
of rear-stage actionin most cases.Butif you needextra
reinforcement,place PZMs on the rear wall,on panels
overhead,ona tableunder a table cloth,behind posts,
undereaves,oronscenery.
Orchestra Pit:
•Tape two PZMsto the wall on either side of the
conductor’spodium,about 20feet apart,facing
eachsection of the orchestra.
• Use a separate PZM on a panel for each section of
the orchestra.
Orchestra, marching band, jazz
ensemble, pipe organ:
These large sound sources typically are recorded at
adistance,usingtwomicrophonesforstereo pickup.
• Mount aPZM 6 inches from the edge of a 2-foot square
panel.Mountanother PZM similarlyon another panel.
Tape together the panel edgesnearest the micro-
phones,forminga“V.”Aim the pointof the“V”at the
center of the sound source.Angle the panels about
70 degreesapart (asin Fig.10).Thisassembly is called
a PZM wedge.
6
• Try one to three PCCs acrossthe front edge of the
stage,about 1 foot from the edge of the stage (Fig.9).
One ortwo PCCs are usually sufficient for small
stages,and they clearly pick up stage action for dress-
ing room cues.Place two PCCs about 20 feet apart;
place three PCCs about 15 feetapart.
Fig.10

The wedge can be suspended,or can be placed on edge
on the floor,with the PZMsat the junction of the floor
and the vertical panels (as in Fig.11).
Recording a conference:
Note: Thesesuggestions are for recording,not for
teleconferencing sound reinforcement.For teleconfer-
encingsound reinforcementapplications,see the Crown
Microphone Application Guide for Teleconferencing
andDistanceLearning.
For maximum clarity,hold the conference in an acousti-
cally“dead”room with carpeting,drapes,and acoustic-
tile ceiling.
• Laya single PZM in the middle of the table(Fig.12).
• Place two panel-mounted PZMs about3 to 12 feet
apart,14 feet high,and 5 to 20 feetfrom the first row
of players.Place the microphonesfarther apartto
widen the stereo spread,closer together tonarrow
the spread.
•Fornoncritical documentaryrecordings,PZMscan
be taped to the proscenium arch,the backstage wall,
orthe floor in front of the ensemble.
Choirs:
• Try two PZMs onpanels,5 feet above and3 to 15 feet
in front of the choir.Coverage is wide and the re-
sponse is uncolored off-axis.
• For small choirs singing in an open area,place PZMs
orPCCs on the floorin front of the group.
• For choirs seated on oneside of a churchchancel or
small chapel facingthe other side of the chancel or
chapel,mount a PZM on the wall opposite the choir.
Ambience:
• One ortwo PZMs on the walls give an uncolored
sound.
• One ortwo PZMs on the walls of an echochamber
provide ambientrichness and naturalness.
Audience:
• On panelssuspendedover left and right sides of audi-
ence.
• Two PZMs on the front face of the stage about 4 feet
apart.
Altars:
• Place a PZM or PCC on the altar table (perhaps under
the table cloth).
Fig.12
• On alongtable,use one PZM inthe middle of every
4 to 6 people.No person should be more than 3 feet
from the nearest microphone.
• For permanentinstallations,use the PZM-20R,a
recessed microphone withall electronicsand cabling
under the table.Before installing it,firstcheck thatthe
pickup will be adequate bytesting aregularPZM lying
on the table.
•TryaPCC-170,aPCC-130oraMiniBoundarymic
at arm’s length for everyone or two people.
• For more clarity,feed the PCCs intoan automatic
mixer.
• If table placement is undesirable,try mounting aPZM
on the ceiling.
• Remove the plate from a PZM-6D.Install the capsule/
holder in an upper corner of the room as in Fig.13.
This arrangement increases microphone outputby
12 dB and givessurprisingly clear reproduction.Large
rooms mayrequire such a pickup in all fourcorners.
7
Fig.11 -Near-coincident-stereo arrangement on floor
Fig.13

Security/Surveillance:
• Try the ceilingorcorner placements mentioned
above.
• Use a PZM-10,PZM-10LL,PZM-11,or PZM-11LL.
The PZM-10 flush-mounts in a ceiling or wall.The
PZM-11 mountsin an electrical outletbox.
Lectern:
• Place a PCC on the lectern shelf top,outside of any
cavities (Fig.14).If the lectern has araised edge,place
the PCC at least twice as farfrom the edge as the edge
is high.Set the BASS TILT switchto FLATorBOOST,
accordingtoyourpreference.
• For lecternswithraised edges,you can modifyyour
PZM as follows:remove the capsule holder byremov-
ing the twoscrewson the underside of the plate.Save
the screws and plate for possible reassembly.Mount
the capsule holder inthe corner of the recess,with the
holder pointingintothe corner (as in Fig.16).This
configuration makes the pickup more directional but
allowslesstalkerwandering.
Fig.15 shows how the frequency response of the PCC
varies depending on where it is placed.
Fig.14
Note: If you need toreturn the PZM for service,reat-
tach the capsule/holder to the plate.Theplate contains
the identification number necessary for warranty ser-
vice.
Fig.15
Courtrooms:
•A PCC on the bench or witness stand can be perma-
nently mounted and permits freedom of movement
withoutlost speech.It provides excellentclarity and
intelligibility.It alsois farless intimidatingto the wit-
ness thantraditionalmicrophones.
Sport events:
Basketball–
• On the basketball backboard under the hoop to pick
up the sound of the ball hittingthe backboard.
• On the floorjustoutside the boundary at center court
to pick up footand ball noises and audience reaction.
•Ona 2' x2'panel suspendedover centercourt,using
two PZMs oneither side for stereo pickup.
Football–
•A PZM pyramid aimed at the field clearly picksupthe
quarterback calling the plays.
Boxing–
• Mount aPZM on acornerpostorpanel overhead.
Bowling–
• Place a PZM on the back wall of the alley,high enough
to avoid being hit,to pick up the pin action.
Golf –
• Try a PZM on the ground near the tee.Insulate the mic
from the ground toavoid ground loops.
Hockey–
• Tape a PCC-160 to a post,aiming down,to pick up ac-
tion near the mic.
Indoorsports–
• Sports such as weight-lifting or fencingcanbe picked
up with aPZM on the floor.
BOUNDARY MICROPHONE
TECHNIQUES FOR SOUND
REINFORCEMENT (P.A.)
ConventionalCrownmicrophones(suchastheLM,CM,
andGLMseries)workbetterthanPZMsandPCCsfor
soundreinforcementofmusicalinstrumentsandvocals.
PleaseseetheCrownMicrophoneApplicationGuideforsug-
gestionsonusingconventionalCrownmicrophones.
8
Fig.16
Cornerplacementfor lectern

PZMs and PCCs can be used for sound reinforcement
in many applications.These are described below.
Altar table:
• Place a PCC on the altar table as in Fig.17.The PCC is
available in black orwhite.
Courtroom proceedings:
• Place a PCC-170 or PCC-130 on the witness stand
and judge’s bench.
Horns
•TapeaPZMonthemusicstandabovethesheetmusic.
Grand piano:
• Tape one or two PZMs or PCCs tothe underside
of the lid,about8" horizontally from the hammers
(see Fig.19).To reduce feedback,close the lid.
Upright piano:
• Tape two PZMs 3' apart on the wall,3' up.Place the
piano frame 1" from the wall so that the PZMspick
up the soundboard.
Fig.17
Showthe performers and the custodian where the PCCs
are located so the PCCs are not kicked ormopped.
To reduce pickup of the pit orchestra,put a 2' x 2' piece
of 4" thick Sonex foam about 1" behind each PCC.
The excellent reach of the PCC provides clear pickup of
rear-stage actionin most cases.Butif youneed extra re-
inforcement,place PZMs on the rear wall,on panels
overhead,onatableunderatablecloth,behindposts,
undereavesor scenery.
Fig.18
Fig.19
9
Conferences, teleconferences, group
discussions, interviews:
See the Crown MicrophoneApplicationGuide for
Teleconferencing andDistance Learning.
Drama, theatre, musicals, opera
• Try one to three PCC-160s across the frontedge of the
stage,about 1 foot from the edge of the stage (Fig.18).
One ortwoPCCs are usually sufficient for small stages,
and they clearly pick upstage action for dressing-
room cues.Place two PCCs about20 feet apart; place
three PCCs about 15 feet apart.
For maximum clarityand maximum gain before feed-
back,turn up only the microphone nearest the person
talking.
Drum set or percussion:
• Tape a PZM to the drummer’s chest.Hanga PZM verti-
callyin the kick drum with the microphone side of the
plate aiming toward the beater.
PZM BOUNDARIES
You can greatly broaden your range of PZM®applica-
tions bymountingthe PZMson one or more boundaries.
A boundary is a stiff,nonabsorbentsurface such as a
floor,table,or plexiglass panel.PZM boundariesare
usually constructed of clear acrylic plastic (plexiglass)
to make them less themless conspicuous,butany stiff,
sound-reflective material can be used.
Byaddingboundaries toa PZM,youcan tailorthe
microphone’s frequency response and directional pat-
tern.Such flexibility makesthe PZM one of the world’s
mostversatile microphones.
This section explains the theory,benefits and drawbacks
of singleand multiple boundaries.Also covered are con-
struction methods for several types of PZM boundary
assemblies.
Credit is due KenWahrenbrock for his pioneeringwork
in multiple boundary experiments,and for many of the
boundaryarraysuggestionsin this section.
A PZM is designed to be mounted very near aboundary
to prevent acoustic phase cancellations.The boundaries
,

mentioned in thisguide will degrade the frequency re-
sponse and polar patternsof conventional microphones.
OnlyPZMscanbeusedeffectivelyinmultipleboundaries.
The size,shape and number of boundaries all have pro-
found effects on the performance of a PZM mounted on
those boundaries.Let’s discuss these effects in detail.
Sensitivity Effects
Imagine a PZM mic capsule in open space,away from
any boundaries.This microphone has a certainsensitiv-
ityinthis condition(Fig.20).
plate.The net gain in sensitivity from these three
boundariesisapproximately16 dBratherthan 18 dB.
Direct-to-Reverb Ratio Effects
We mentioned thatsensitivity increases 6 dB per
boundaryadded.Thatphenomenonappliestothe
direct sound reaching the microphone.Reverberant
orrandom-incidence sound increases only3 dB per
boundary added.Consequently,the direct-to-reverb
ratio increases 3dB(6-3dB)wheneveraboundaryis
added atrightangles topreviousboundaries.
A highdirect-to-reverb ratio sounds close andclear;
a low direct-to-reverb ratio sounds distantor muddy.
Adding boundariesincreases the direct-to-reverb ratio,
so the subjective effect is to makethe sound source
audiblycloserorclearer.Thatis,“reach”isenhanced
byadding boundaries.
Frequency-Response Effects
The size of the boundary on whichthe PZM is
mounted affects the PZM’s low-frequency response.
The bigger the boundary,the better the bass.Specifi-
cally,the response begins to shelve down 6 dB atthe
transitionfrequencyFT,where
FT= 750/D
D isthe boundary dimension in feet.The response is
down 6 dB at the frequency F-6 where
F-6 = 188/D
For example,if the boundary is2 feet square,
FT= 750/D = 750/2 = 375Hz.
F-6 = 188/D = 188/2 = 94 Hz.
That is,the microphone startsto shelve down at 376 Hz
and isdown 6 dB at and below94Hz.(See Fig.21).
10
Fig.20
Fig.21
Now suppose the PZM capsule is placed verynear
(within .020" of) asingle large boundary,suchas awall.
Incoming sound reflectsoff the wall.The reflected
sound wave adds to the incoming sound wave in the
“pressure zone”next tothe boundary.This coherent
addition of sound waves doubles the sound pressure at
the microphone,effectively increasing the microphone
sensitivity6dB.
In short,adding one boundary increases sensitivity
6dB.This is free gain.
Now suppose the PZM capsule is placed at the junction
of two boundaries atrightanglestoeach other,suchas
the floor and a wall.Thewall increases sensitivity6 dB,
and thefloor increasessensitivity another6 dB.Thus,
addingtwoboundaries atright anglesincreases sensitiv-
ity12 dB.
Now let’s place the PZM element at the junction of three
boundaries at right angles,such as in the corner of
the floor and two walls.Microphone sensitivity will be
18 dBhigherthanwhatitwasinopenspace.Thisis
increased gain with no increase in noise!
Note that the acoustic sensitivity of the microphone rises
as boundaries are added,butthe electronicnoise of the
microphone stays constant.Thus,the effective signal-to-
noise ratio of the microphone improves 6 dB every time
a boundary is added atright angles toprevious bound-
aries.
If a PZM is in the corner of three boundaries that
are NOT atrightangles to eachother,the sensitivity
increases less than 6dB perboundary.Forexample,
aPZM-2.5 boundaryisbuiltwith twopanels at 135
degrees.This panelassemblyisat rightangles toa base
Below94 Hz,the response is aconstant6 dB belowthe
upper-mid frequency level.Note thatthere isa response
shelf,notarolloff.
If a PZM is mountedona 4' square boundary,
FT= 750/4 = 178 Hz
F-6 = 188/4 = 47 Hz.
Thisresult has beenloosely calledthe“4' –40 Hz”rule.
Fig.22 shows the PZM response on various sizes of
boundaries.
What if the PZM is on a rectangular boundary? Let’s
callthelongside“Dmax”andtheshortside“Dmin.”
The response is down 3 dB at188/Dmax,and isdown
another 3 dB at188/Dmin.

AsFig.23 shows,the low-frequency shelf varies with
the angle of the sound source around the boundary.At
90 degrees incidence (sound wave motion parallel to the
boundary),there is no low-frequency shelf.
• The low-frequencyshelf (most visible at 30 and 60
degrees).
• The lack of low-frequency shelving at 90 degrees
(grazingincidence).
• The 10 dB rise in response at 497 Hz.
• Less interference at increasinganglesupto 90º.
•Greaterrearrejectionof high frequencies than low
frequencies.
What are the acoustic causes of
these frequency-response effects?
When sound waves strike aboundary,pressure doubling
occurs at the boundary surface,butdoes not occur out-
side the boundary.Thus there isa pressure difference at
the edge of the boundary.Thispressure difference cre-
ates sound waves.
These sound waves generated at the edge of the bound-
ary travel to the microphone inthe center of the bound-
ary.At lowfrequencies,these edge waves are opposite
in polarity to the incoming sound waves.
Consequently,the edge waves cancel the pressure
doublingeffect.
Thus,at low frequencies,pressure doublingdoes not oc-
cur; but at mid-to-high frequencies,pressure doubling
does occur.The net effectis a mid-to-high frequency
boost,or– looked atanother way – a low-frequency loss
orshelf.
Incoming waves havingwavelengthsaboutsix times
the boundarydimensions are cancelled byedge effects;
waves of wavelength much smaller than the boundary
dimension are not cancelled by edge effects.
Waves having wavelengthson the order of the boundary
dimensions are subject to varying interference vs.fre-
quency;i.e.,peaks and dips in the frequencyresponse.
At the frequency where the wavelengthequals the
boundary dimension,the edge wave is in phase with the
incomingwave.Consequently,there isa response rise
(about 10 dB above the low-frequency shelf) at that fre-
quency.Above that frequency,there is aseries of peaks
and dips thatdecrease in amplitude with frequency.
The edge-wave interference decreases if the incoming
sound wavesapproach the boundary at an angle.
Interference also isreduced byplacing the mic capsule
off-center.This randomizesthe distances from the edges
to the mic capsule,resulting in a smoother response.
Directional Effects
The polar pattern of a PZM on alarge surface is hemi-
spherical.The microphone picks up equally well in any
direction above the surface plane,atall frequencies.
Byaddingboundaries adjacentto this PZM,you can
shape its directional pickup pattern.Boundaries make
11
The depth of the shelf also varieswith the distance of the
sound source to the panel.The shelf starts to disappear
when the source is closer than a panel dimension away.
If the source is very close to the PZMmounted on a
panel,there is no low-frequency shelf;the frequency
response if flat.
If the PZM is at the junction of two ormore boundaries
at right anglesto each other,the response shelves down
6dBper boundary at the frequency mentioned above.
For example,a two-boundary unitmade of 2-foot
square panels shelvesdown 12 dB at and below94Hz.
There are other frequency-response effects in addition
to the low-frequencyshelf.Forsound sources perpen-
dicular to the boundary,the response rises about 10 dB
above the shelf atthe frequency where the wavelength
equals the boundary dimension (see Fig.23).
For a square panel,Fpeak = .88C/D,where C = the speed
of sound (1130 feet per second) andD = the boundary
dimension infeet.For acircularpanel,Fpeak = C/D.
Asexample,a 2' square panel has a 10 dB rise above
the shelf at.88C/D = 88 x1130/2 = 497 Hz.
Note that this response peakisonlyfor the direct sound
of an on-axis source.If the sound field at the panel is
partlyreverberant,or if the sound waves strike the panel
at an angle,the effect is much less.The peak is also re-
duced if the mic capsule is placed off-center on the
boundary.
Fig.23shows the frequency response of a PZM mounted
on a2' square panel,at various angles of sound inci-
dence.Noteseveral phenomena shown in the figure:
Fig.22
Fig.23

the PZM reject sounds coming from behind the bound-
aries.In addition,makingthe PZM directional increases
itsgain-before-feedback in live reinforcement applica-
tions.DirectionalPZMs also pick upahigher ratio of
directsound to reverberantsound,so the resulting au-
dio sounds“closer”and“clearer.”
Ingeneral,sound pickupis fairlyconstantfor sound
sources at any angle in front of the boundaries,and
drops off rapidly when the source moves behind the
boundaries.
For soundsapproachingthe rear of the panel,low
frequencies are rejected least and highfrequencies
are rejected most.
A small boundary makes the PZM directional only
athigh frequencies.Lowfrequenciesdiffractorbend
around a small boundary as if it isn’t there.The bigger
you can make the boundary assembly,the more direc-
tional the microphone will be acrossthe audible band.
The bigger the boundary,the lowerthe frequency at
whichthe PZM becomes directional.A PZM on a square
panelisomnidirectionalatvery lowfrequencies,and
startsto become directionalabove the frequency F,
where F =188/D and D isthe boundary dimension in
feet.Sound familiar? That’s the same equation used to
predict the 6-dB-down point in the frequencyresponse.
Boundaries create differentpolar patterns at different
frequencies.For example,a 2' square panel is omnidirec-
tional atand below94 Hz.At mid-frequencies,the polar
patternbecomessupercardioid.Athigh frequencies,the
polar pattern approaches ahemisphere (as in Fig.24).
Two boundariesare more directional than one,and
three are more directional than two.
directivity boundary horn,the horn mustflare out
exponentially like awell-designed loudspeakerhorn.
Disadvantages of Boundaries
Boundaries mustbe large to be effective.Their size
and weightmakes them cumbersome to mount or hang.
Large boundaries are also visually conspicuous,butthis
problem is reduced by using clear plastic.
Many users claim that the sound quality and flexibility
if multiple-boundaryPZMsoutweighthedisadvantages.
For those userswho need a directional PZM but prefer
notto use boundaries,Crown makes the PCC®-160 and
PCC-170,whichare supercardioid surface-mountedmi-
crophones.Theyuse a directional mic capsule,rather
than boundaries,to makethe microphone directional.
The PCC-130 is cardioid.
Summary
• Microphone sensitivity increases 6 dB forevery
boundaryadded atrightangles to previousbound-
aries (less than 6 dB if not at rightangles).
• For a flat panel,the frequency response beginsto
shelve downat the transition frequency FT = 720/D,
where D =boundarydimension in feet.The response
shelves down 6 dB at and below the frequency
F-6 = 188/D.Thisshelf disappears if the sound source
is at the side of the panel,or if the source is very close
to the microphone (lessthan apanel dimension away).
• For a square panel,the frequency response rises about
10 dB above the low-frequency shelf (when the source
is perpendicular to the boundary) at the frequency
F = .88C/D,where C = the speed of sound (1130 fps)
and D = the boundary dimension in feet.
• The PZM/panel assembly is omnidirectional at and be-
lowthe frequency F = 188/D,where D = the boundary
dimension in feet.The panelbecomes increasingly
directionalasfrequencyincreases.
• Use the biggest boundaries that are not visually
conspicuous.Big boundaries provide flatter response,
better bass,and more directionality than small
boundaries.
• The flattest response for asingle panel occurs for
anglesof incidence between 30º and 90ºtothe axis
perpendicular to the boundary.
• For the flattest response,place the PZM 1⁄3 of the way
off-center(say,4" off-centerfora 2' panel).Forflattest
response on multiple boundaries,place the tip of the
PZM cantilever touching against the boundaries(leav-
ing the usual gap under the mic capsule).
• To increase directionality and reach,increase bound-
ary size or add more boundaries.
Construction Tips
You can obtain clearacrylic plastic (plexiglass) from
a hardware store, plastic supplier ora fabrication com-
pany.Plastic1⁄4" thickis recommended forgood sound
Fig.24 –Polar responseof2–foot square boundary
12
With multiple boundaries,the shape of the pickup pat-
tern approximates the shape of the boundaryassembly.
For example,aV-shaped boundaryproducesa polar
pattern with alobe whose sides are defined by the sides
of the“V.”Note,however,that the polar pattern varies
withfrequency.
This“V”-shaped boundary works like a horn loud-
speakerinreverse.Speaker horntheoryappliesto mi-
crophone horns.Forinstance,if you want a constant

rejection.Many vendors can heat and shape the plastic
accordingto your specifications.They use their own ad-
hesiveswhich are usually proprietary.
Cyanoacrylate adhesive (“SuperGlue”) or RTV
(“Sealastic”) have worked well in some instances.Or you
can join several pieces of plastic with metal brackets,
bolts and nuts.
If you intend tohang or“fly”the boundaryassembly,
drill holes in the plastic for tying nylon line.To prevent
cracksin the plastic,use ceramic drill bits orstartwith
smalldrill-bit sizes and workup.You may want to paint
the boundaryedges flatblackto makethem less visible.
When makinga multi-boundary assembly,be sure to
mountthe PZM mic capsule as close aspossible to the
junction of the boundaries.Let the tipof the cantilever
touch the plastic,but leave the usual gap under the mic
capsule.
NOTE:Some older PZMs include asmall block of foam
under the mic capsule for acoustical adjustment.If your
PZM has this foam block,trapitunder the mic capsule
before screwing the PZM cantilever tothe boundary.
The PZM model used for multi-boundary assemblies is
the PZM-6D.When drilling the screwholes for the can-
tilever,make them 5/32" diameter,.563" center-to-cen-
ter,and countersunk .250" x 90°.
2-Foot-Square Flat Panel
This boundary(Fig.25)ismostoften used for direc-
tional pickup of soloinstruments,choirs,orchestras,
and bands.Two PZMs back-to-back on a panel form a
“bipolar”PZM forcoincident stereo.Place the assembly
about 14 feet above the stage floor.
frequencyshelf at 497 Hz fordirect sound atnormal in-
cidence (Fig.23).F-6=94 Hz.
The polar pattern is omnidirectional at low frequencies,
supercardioid at mid frequencies,and hemispherical at
high frequencies (see Fig.26).
Fig.25 –A two-foot square flatpanel
13
For near-coincidentstereo miking,place two panels
withedges touching to form a“V”(Fig.10).Aim the
point of the“V”at the sound source.Mount aPZM
about 4" off-center on each panel,toward the point of
the“V”forbetterstereo imaging.Thisassemblypro-
vides a higherdirect-to-reverb imaging.This assembly
provides a higher direct-to-reverb ratio (a closer per-
spective)than the bipolar PZM mentioned above.It also
rejects sounds approachingthe rear of the panels.
The frequencyresponse of a flatpanel is the smoothest
of all the boundary assemblies in this booklet.Fora 2-
foot square panel,there is a 10-dB rise above the low-
Fig.26 –Polarresponse of a2 foot-square boundary.
Fig.27–PZM-2
Random EnergyEfficiency= –3 dB at highfrequencies.
The assembly has 3dB less reverb pickupthan an omni-
directional microphone in open space at the same dis-
tance.
Distance factor =1.41.That is,the microphone/panel
can be placed 1.41.times as far from the source as an
omnidirectional microphone for the same direct-to-
reverb ratio.
PZM-2
Thismodeluses twopanels atright anglestoeachother.
One of the panels is placed on a large flatsurface such as
a table or floor.
One configuration uses a1'x2' vertical panel.When this
verticalpanel isplaced on a horizontal surface,the verti-
cal panel is“reflected”inthe horizontalsurface.The
panel and itsreflection appearto be a 2'x2' panel witha
94-Hz shelvingfrequency.
Random Energy Efficiency =–6 dB.The assembly has
6 dB less reverb pickupthan an omnidirectional mic in
open space as the same distance.

PZM-2.5
This model provides about 10 dB of forward gain at mid
frequencies compared to a PZM on the floor.The assem-
blyisplaced on alarge horizontal surface suchas a stage
floor.
An 18"tall unit workswellforspeech pickup of drama,
musicals,and opera; cello,stringbass,and kick drum.
F-6=160 Hzfor12"tall model.Polarpattern (12"model):
See Figs.28 and 29.
PZM Dish
The PZM Dishhasan uneven response on-axis,but is
usefulforitsexcellent directionalityatmid-to-highfre-
quencies.Dishes have been used over orchestral sections
for isolation,and for long-reach speech applications.
PZM Pyramid
This model can be made of three orfour sides.It
emphasizes mid frequencies and is recommendedonly
forspeech.Itshighlydirectionalpatternmakesituseful
for long-distance pickup of quarterback calls.Pyramids
also have been hung overstagesfor pickup of rear-stage
dialog.
Since aplexiglasspyramid can be quite heavy,you may
wantto makeitoutof sheetmetal.
PZM-3
Thismodel has a tighter polar patternthan the
PZM-2.5,so itcan be used to isolate soloists.Again,the
assembly is placed on a large horizontal surface such as
a stage floor.
F–12 (two 1' square panels on floor) =94 Hz.
Random Energy Efficiency =–9 dB.The assembly has
9 dB less reverb pickupthan an omnidirectional micro-
phone in open space at the same distance.
Fig.28 –12"tall PZM-2.5:horizontal-plane polar response.
Fig.29 –12"tall PZM-2.5:vertical plane polarresponse.
Fig.30–PZM2.5
Fig.31–PZM3
Fig.32–PZMPyramid
Fig.35–PZMdish.

The dishis not a parabolic microphone.The PZM is
placed on the dish,rather thanat the focus of a parabolic
surface.The dish obtains itsdirectionalityfrom diffrac-
tion (blocking sound waves from certain directions),
while aparabolic microphone obtainsitsdirectionality
byfocusingsound energy from a particular direction
on the mic capsule.
F–12=250 Hz.
Frequency response: See Fig.33.
Polar pattern:See Fig.34.
1560, 2260, 4060, 7260
These models have the same basic shape – two panels
angled60 degrees apart—buthave differentsizes.In
general,the bigger the panels,the better the low-end
response and the lower in frequency the directivity
extends.
The 1560 istypically used on lecterns.Its response and
polar patterns are shown in Figures37,38and 39.
The 7260 hasbeen used forstereo pickup of xylophones
orbrass sections.Itisassembled in two halves for easier
transport.
PZM Cone
This model is highly directional and emphasizes mid-
frequencies.It has been used as a“follow”mic for a
rovingTV camera,and provides a close-up audio
perspective.
Random Energy Efficiency (for a cone witha 90-degree
included angle) =–8.3 dB.The cone rejects reverb by 8.3
dB compared to an omnidirectional microphone in
open space atthe same distance.
Distance factor:2.6.That is,the cone can be placed 2.6
times as far from the source as anomni mic for the same
direct/reverb ratio.
Fig.33 –PZMdish frequency response.
Fig.36–PZMcone.1'long,1'diameter
Fig.34
15
Fig 37 –Frequency response ofPZM-6D on1560 boundary.
Fig38 –1560:horizontal-planepolar response.
Fig.39 –1560:vertical-plane polar response.
Fig.40–2260
Fig.41–7260

1560 with Side Boundaries
This is a basic 1560 modified with two side boundaries
at 45 degrees on each side (Fig.42).The side boundaries
provide additional discrimination of loudspeakers to
either side of the lectern.
L2Array
This multipurpose array (Fig.43)was designedby
recordingengineer Mike Lamm.Mike hasused this
arrayextensively for overallstereo or surround pickup
of large musical ensembles.
L2Floor Array
Here’s another stereo PZMarray(Fig.47) designed by
recordingengineersMike Lammand John Lehmann.
It simulates the O.R.T.F.stereo mic technique.According
to one user,“You can take thisarray,set it down,and just
roll.You geta veryclose approximation of the real event.”
Suspendingtheinvertedarrayresultsinlessbassandmore
highs,whileplacingitonthefloorreversesthebalance.
When this arrayis used on astage floor,the construction
shown in Fig.48 is useful.It has decreased side pickup
and increasedpattern overlap.The axes of the left and
right polar patterns maybe at any desired angle,just so
the 120° boundaryangle and6.7-inch capsule spacing
are maintained.
The hinged,sliding panels can be adjusted to obtain
almost any stereo pickup pattern.A complete descrip-
tion of the L2Arrayis inAESpreprint 2025(C-9),
“The Use of Boundary Layer Effect Microphones in
Traditional Stereo MikingTechniques,”presentedat
the 75th Convention of theAudio EngineeringSociety,
October 1983.The frequency response isshown in
Figures 45 and 46.
FIg.42 – 1560 with side boundaries.
Fig.46–PolarresponseofL2array,120ºbetweenboundaries.
Fig.44–FrequencyresponseofL2array(withPZM-6D capsule).
120º betweenboundaries.
Fig.45–PolarresponseofL2array,120ºbetweenboundaries.
16
FIg.43

PZM Wedge or Axe
This stereo PZM arrayhas been used extensivelyby
recordingengineersMike Lammand John Lehmann.
It simulates the O.R.T.F.stereomicrophonetechnique.
Stereo imaging is precise and coverage is even.
Place the mic capsules 21⁄2" belowthe center of the pan-
els to smooth the frequencyresponse.To compensate for
the bass shelvingof the panels,boostthe bass
+6 dB at and below 141 Hz.
A panel containinga 5
⁄8"-27Atlas flange can be fastened
to the bottom of the array for stand mounting.
Fig.47–L2floor array –designed by Mike Lammand John
Lehmann canbe set on the floor,seton a Cstand or hung
invertedfromtheceiing.
17
Fig.48 –Another version ofthe L2floor array.
Fig.49 –PZM wedge or axe (top view).
Aim the point of the wedge atthe center of the sound
source,and raise the array about 14 feet off the floor.
The wider the angle between boundaries,the more
frontal is the directivity.Increasing the anglemakes the
sound source appear to be closertothe listener.The ar-
ray is mono compatible to a great extent.
A wedge used by Gary Pillon of General Television
Network,Detroit,uses 2'-square panels.The mics are
4" off-center toward the point of the“V”.To compensate
for bass shelving of these panels,boostthe bass+3 dB
at94Hz.
Pillon Stereo PZM Array
This stereo PZM arraywasdevised by Gary Pillon,a
sound mixer at GeneralTelevision Networkof Detroit,
Michigan.A documentary recordinghe madewith this
arraywon an Emmy.The assembly can be stand-
mounted from the backside orhandheld,if necessary.
The stereo image,whichis partly a result of the 8" cap-
sule spacing,is designed to be like thatproduced by a
binaural recording,but with more realistic playback
over loudspeakers.Ideally,this device would mount
on aSteadicam platform and give an excellent match
between audio and video perspectives.
THE SASS®PZM STEREO
MICROPHONE
Asexplainedearlier,one way to record in stereo with
PZMs isto mounttwoPZMs ona wedge:two 2'-square
panels,angledapart to form a“V”.This arrangement
can be cumbersome.Butrecent research has led to a
unique applicationusingPZMs on a smallerhead-size
boundary:The Crown SASSmicrophone.
The Crown SASS® orStereoAmbientSampling System
isanewkindof stereo microphone.Itdoes anexcellent
job recording sounds in stereo,suchas:
• orchestras,choirs,symphonic bands,pipe organs
•newsevents
• sportsambience andcrowdreaction
• background sounds for films
•stereo samplesfor keyboards
• stereo sound effects
Fig.50–PillonstereoPZM
L= 8" and A= 90ºfor speechuse
L= 12"andA= 120ºfor musicuse

Before explaininghow the SASS makessuchgood stereo
recordings,let’s describe how stereo itself works.
How Stereo Works
Normally youlistentostereo over twospeakers,one
placed in front of you tothe left,and one to the right.
When youlistentoastereorecordingof an orchestra,
you can hear strings on the left,basses on the right,and
woodwinds in the middle.That is,you hear an image of
eachinstrumentin certainlocationsbetween speakers
(Fig.51).
right mic is closer to the sound source.Thus,the left
channel will be delayed and you’ll hear the imageto the
right.
With near-coincidentmiking,a pair of directional mi-
crophonesisangledapart and spaced aparta few inches
horizontally (Fig.54).A sound source on the right will
be louder inthe rightchannelAND delayed in the left
channel.These two effects add together,so you’ll hear
the image to the right.
Fig.51–Stereoimages.
Fig.52–Coincident-pair steromiking.
Fig.53–Spaced-pair stereomiking.
18
If you sendthe same audio signal to the two speakers,
you hear an image in the middlebetween the two speak-
ers.
How do recording engineers make
the images appear left or right?
One way is to make the signal louder in one channel
than the other.For example,if you feed the same signal
to bothchannels,but turn up the volume of the right
channel,the image shifts to the rightspeaker.
Another way is to delay the signal in one channel.If you
feed the same signal tobothchannels,butdelay the left
channel one millisecond,the imageshifts to the right
speaker.
So,various image locations can be created byrecording
loudness differences and/or time differences between
channels.We wanta sound source on the right to make
a louder signal in the right channel than the left.Or we
want a sound source on the rightto make a signal
sooner in the rightchannel than the left.
This is done with stereo microphone techniques.There
are three basic stereo techniques;coincident pair,spaced
pair,and near-coincidentpair.
With coincident-pairmiking,a pair of directional mi-
crophonesis placed withgrilles touching,one mic above
the other,and angled apart (Fig.52).A sound source to-
ward the right will produce astronger signal from the
mic aiming toward it than from the mic aiming away
from it.Thus,the right channel will be louder and you’ll
hear the image to the right.
With spaced-pair miking,a pair of microphonesis
placed severalfeetapart,aiming straightahead (Fig53).
Sounds from asource toward the rightwill reach the
right mic sooner than the left mic,simplybecause the
FIg.54 – Near-coincident stereomiking.