AKG Places of Worship Guide

A decision-mAking guide for Architects, designers, And religious communities

Using microphones in places of worship

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AKG microphones in places of worship 3

tAble of contentsFaith lives by the word.“In the beginning was the word …” is the opening line of St. John‘s Gospel, emphasizing the significance of the spoken word for the passing on of religious knowledge. Even in our digital age, the spoken word is still our most important means of transmitting information. Today, sound systems have become an integral part of this process in such diverse areas as business meetings, podcasts, or religious services and ritual celebrations.

All these systems need to provide perfect intelligibility of speech, so they need to be planned carefully for each application and must never fail during a ceremony. The performance of any sound system depends on the perfor-mance of the microphones. After all, it is the microphone that converts acoustic speech signals into electronic sig-nals, in other words, the microphone is the first link in the electronic audio chain. It is impossible – or extremely costly – to compensate later on for anything the microphone failed to pick up.

Part One of this planning guide is a detailed introduction to room acoustics and general properties of sound system equipment, specifically of microphones. Part Two describes concrete sound systems designed for specific applications, and how they fit into the different acoustic environments of historic and modern places of worship.

If you have any questions beyond the scope of this book-let, please email us at [email protected] or visit www.akg.com, where you will finda technical knowledge base that is regularly updated and expanded.

Optimum intelligibility

DO IT rIGhT In ThE fIrST PlAcE ___ 4

hOw fEEDbAck cOmES AbOuT ____ 6

ThE PIckuP PATTErn ______________ 8

mIcrOPhOnE TyPES _____________ 10

A major objective in designing a place of worship has always been to ensure good intelligibility of speech during each ceremony. choosing the right microphones goes a long way toward achieving this goal.

intelligent signal prOcessing

wIrElESS mIcrOPhOnE SySTEmS 13

AuTOmATIc mIcrOPhOnE mIxErS 14

PA-SySTEmS _____________________ 16

During a ritual ceremony, different types of signals need to be processed, from sound to audio and radio signals. A good de-sign takes all of these requirements into account from the start.

glOssary

ExPlAInInG TEchnIcAl TErmS ___ 28

chEcklISTS fOr DESIGnErS _____ 34

Explanations of technical terms and detailed checklists make designing a sound system easier.

real-wOrld applicatiOns

ThE AlTAr AnD lEcTErn _________ 18

mIkInG ThE cOnGrEGATIOn ______ 20

SOlO vOcAl _____________________ 21

chOIr ___________________________ 22

InSTurmEnTS AnD EnSAmblES __ 24

whatever is being said, the closer the microphone sits to the sound source, the better the words come across.

Editorial

4

basics oF sound rEinForcEmEnt

almost no reverberation. usually, small, inconspicuous column speakers are used that blend in well with traditional environments and meet conservation requirements. Sound systems in old build-ings should primarily ensure optimum intelligibility of speech, while miking up musical instruments in such difficult acoustic spaces is largely a matter of finding a good compromise.

The room acoustics and audio characteristics of modern places of worship, however, are rather similar to those of theaters. The acoustics of such halls can be designed primarily for high sound pressures and perfect conditions for miking up a variety of instru-ments. what types of microphones to use and how many of them, will depend largely on the actual local acoustic environment.

Treating microphones as mere interior decoration items or annoy-ing gimmicks can be expensive and all but ruin the performance of any sound system, because none of the other system components from mixers and amplifiers to the loudspeakers can compensate for poor microphone signals. In the worst case, a ceremonial hall cannot be used for its intended purpose.

The starting point for any electronic sound system is the micro-phone. Therefore, the most important thing is to select the right microphones with the right pickup patterns and to place them optimally in the hall. This does not only result in much better intel-ligibility but also reduces total system cost for both traditional and modern places of worship, for although their acoustics may differ, the basic laws of physics are the same everywhere.

Traditional places of worship date back to times when micro-phones were not available yet. These buildings were designed to carry the sound all the way to the far corners and back rows. what was an advantage at the time is a problem today: loud signals travel across the entire hall and return almost as loud as they were generated. In many halls, this reverberation only tapers off after several seconds, thereby severely degrading intelligibility.

To prevent this effect, many narrow column speakers (page 16 and 17) are distributed in the hall in such a way that each speaker will cover only a few yards in front of it. Such a system generates

Small, traditional house of worship

dO it right in the first place

using the wrong microphones leads to poor intelligibility as well as poor vocal and instrument sound – an unacceptable situation. Therefore, it pays to spend some time to learn how microphones work and how to use them in the best possible way. Once you un-derstand microphones, you will easily find a visually attractive and optimally sounding microphone for any acoustic environment.

when designing a sound system for optimum intelligibility, be sure to talk with everyone involved – the architect, designers, acousti-cians, representatives of the congregation, and the persons who will operate the system. This is the only way to make sure the congregation‘s needs, legal and design requirements, and existing experience are all taken into account and used to best effect. This design guide contains many helpful hints for mastering these tasks in any hall, independently of its architectural and acoustical characteristics. you will find lots of tips and tricks you can use even if you are new to sound reinforcement.

Sound reiforcement basics

large, traditional house of worship

large, modern house of worship

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sUmmarySound reinforcement baSicS

impOrtant pOints tO remember when designing a sOund system

The unusual architectural design of many places of worship presents a great challenge for the sound system designer. historical buildings in particular pose many acoustical problems you need to overcome in designing a sound system. but no matter whether the building is old or new, your job is to find the best solution for an optimized sound system.

before choosing suitable system components, ask yourself the following questions (for details, see the checklists on pages 34 and 35):

• In what type of building (small/large traditional, modern/contemporary) will the system be installed?

• Which areas within the hall are active, which passive?

• How long is the reverberation time?

• What sound absorption material has been installed?

• How much amplification will be required?

• Where are the loudspeakers installed? What are their projection patterns?

• What microphone types and pickup patterns can be used? See page 10.

• How many microphones will be permanently installed and how many should be available for mobile use?

• Is there a need for a wireless microphone system? See page 13.

• What mechanical stress will the microphones be exposed to?

• What visual requirements do the microphones have to meet?

• Will the system be operated by a sound engineer or controlled by an automatic mixer? See page 14.

• What will microphones be used for: speech, vocals, instruments?

Akg microphoneS in placeS of worShip 5

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optimum intElligibility

Every room, depending on its acoustic treatment, will generate a certain amount of reflections. These add up to form the so-called “diffuse sound field”, which, like ambient noise, can mask the wanted signal and thus reduce its intelligibility. Increasing system gain to simply drown out the unwanted reverberation does not work at all, though. Injecting more sound energy into the room also increases the energy of the reflections and therefore the reverberation. The louder you turn up the volume control, the louder the noise will get, too.

Thus, your sound system should basically use unidirectional microphones and many quiet directional loudspeakers. This has to do with basic laws of physics. The inverse-distance law states that the sound pressure decreases by 6 db or 50% as the distance from the sound source doubles. conversely, the sound pressure in front of a microphone doubles as the distance between the sound source and microphone (the “working distance”) is reduced by 50%.

This law has a direct influence on every room‘s acoustics as it governs the difference in level between the direct sound and reverberation. while the direct sound level decreases by 50% as the distance doubles, the reverberation level remains constant be-cause the energy of the reverberation depends on the volume and sound absorption of the hall. As a result, the direct sound becomes less intelligible as you move away from the sound source and the diffuse sound field masks more and more of the direct sound.In theory, it makes no difference in terms of perceived loudness whether you turn the amplifier gain up by 6 db or move to a point 50% closer to the loudspeaker. In real life, there is a difference, however. Increasing the volume by 6 db increases the total sound energy inside a hall including the reverberation. On the other hand,

In any place of worship, ensuring optimum intelligibility for everyone participating in a service takes top priority. Ideally, what the talker says should be understood clearly by all others in the hall. In real life, however, there are always unwanted sound sources getting in the way, such as sounds made by the worshippers, rattling pews, people coughing or clearing their throats, reflections form the walls and ceiling, footfall or even traffic noise.nature has endowed us with the capability to listen selectively, so we can concentrate on what we want to hear and ignore what we do not want to hear (such as ambient noise). however, this pro-cess of evaluating and accepting or rejecting acoustic information only works as long as the wanted sound is perceptibly louder than any unwanted sound and comes from the expected direction.

As soon as the wanted sound is less than about 25 db louder than unwanted noise, it becomes difficult for our brain to distinguish between wanted and unwanted sounds. we cannot hear the talker clearly, listening becomes strenuous, and we have difficulty con-centrating. we do not feel comfortable in such an environment.

Technology can help solve this problem. microphones and sound systems do not, however, provide the same complex evaluation algorithm as the human brain for wanted and unwanted informa-tion. Every sound is captured and amplified, no matter whether it is a wanted sound or just noise. Therefore, knowing about the psychoacoustic mechanisms underlying our selective-listening ability helps us design better sound systems.To optimize intelligibility, it is not enough just to turn up the volume. Instead, we need to maintain at least a certain minimum differ-ence in level between the wanted signal and unwanted noise. The louder the speech signal compared to unwanted noise, the more intelligible it will be. Therefore, designing a sound system is really about selectively amplifying the wanted signal.

➊ Direct sound; reflections by: ➋ ceiling; ➌ walls; ➍ floors

➊

➊➋

➌

➍

stOp the hOwling befOre it starts


if you move closer to the loudspeaker, the sound energy in the hall remains the same while the ratio between the signal and noise levels improves, resulting in better intelligibility.

here is where directional loudspeakers come in. rather than projecting sound uniformly in all directions, they focus the sound in one direction so they can be aimed exactly at the desired coverage area. The benefit is twofold. On the one hand, persons sitting along the axis of the loudspeaker feel they are closer to the loudspeaker. On the other hand, the sound energy is focused on the listeners so there is less sound energy left for reflections and reverbera-tion buildup. The latter is a particularly important point in places of worship where hard walls, high ceilings, and low sound absorption factors lead to critical reverberation times and levels.microphones are similar to loudspeakers in several ways. Omnidi-rectional microphones capture sounds from all directions indis-criminately, including reflections and ambient noise. This means that ambient noise is amplified by the same amount as the wanted

sound, making the parson‘s words much less intelligible. As the microphones pick up the amplified reflections and loud-speaker sounds, another acoustic monster rears its ugly head: feedback!

feedback can be described as a fatal lap-type journey of the signal through the sound system components. The microphone picks up a sound, the amplifier makes it louder and the loudspeaker pro-jects it into the room. Then the microphone picks up the amplified sound again and feeds it back into the amplification chain, so the signal travels through this feedback loop yet again. A ringing tone is the first sign that the sound system is becoming unstable. The final stage is an ear-splitting, painful howling sound. A heavy feed-back attack may cause temporary tinnitus in listeners, reducing intelligibility for a while.

using a unidirectional microphone provides two benefits. It attenu-ates sounds from other directions than its preferred direction, re-ducing unwanted ambient noise. Also, a unidirectional microphone delivers a stronger output signal at the same working distance than

its omnidirectional counterpart, so you will get the same loudness at a lower sound system volume setting. now the microphone will pick up less loudspeaker sound and there will be less sound energy in the hall for reflections. All this adds up to much better intelligibility. In other words, using unidirectional microphones is a good way to avoid creating a feedback loop.

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Omnidirectional loudspeakers distribute the sound evenly within a room and generate lots of reverberation.

Directional loudspeakers focus the sound on smaller areas, leaving less energy for reverberation buildup.

To reduce or avoid feedback, place the microphone as close as possible to the talker‘s mouth and as far away from the loudspeakers as possible.

Amplifier

unwanted signal

wanted signal

Signal processing

The microphones are the “ears” of your sound system. The more ears there are, the more they will hear, and unfortunately, this goes for unwanted reverberation, too. Therefore, to optimize intelligibility and avoid feedback, as few microphones as possible should be open at any time, at best only the one that is being talked into at the moment. If we reduce the number of open microphones, say, from four to two, the proportion of ambient noise and loudspeaker sound in the master output signal of the mixing desk or automixer decreases by 3 db.

In most cases, there is no sound engineer available to operate the mixing desk. Therefore, automatic microphone mixers (such as the AkG Dmm4/2/2, see page 14) provide a convenient solution for managing open microphone channels as they automatically activate only as many microphones as actually needed. This also dramati-cally reduces the risk of feedback in any room. So, no matter whether your system will use a manual or automatic mixer, always remem-ber to keep the number of open microphones as low as possible.unlike studio microphones, microphones in traditional places of worship are supposed to pick up only that part of the sound spec-trum that is relevant for speech and to ensure maximum intelligibility.

In other words, they should only capture the talker‘s voice and reject reverberation (even though it is audible, too) as well as any frequencies, particularly bass sounds, that may reduce intelligibility. but beware of cutting out the low frequencies too radically by using an equalizer, narrow-band loudspeakers, and extremely speech-optimized microphones: your system may end up sounding like a telephone receiver! Select components that allow a good sound engineer to achieve a well-balanced, inspiring sound.

sUmmaryoptimum intelligibility

it‘s the balance that cOunts• A place of worship should provide optimum conditions for

intelligible speech reinforcement during ceremonies. This depends primarily on good room acoustics. for a sound system to deliver the desired results, keep reverberation energy at a feasible minimum. To this end, use unidirectional microphones and loudspeakers and place them appropriately in the hall. Acoustic treatment of the walls and ceiling is another important factor.

• These are the most important rules: > keep the wanted signal level significantly higher than the unwanted signal level. > keep the direct sound level significantly higher than the reverberation level.

• The reverberation level depends on the level of the amplified wanted signal. Increasing the direct sound level by turning up the master volume control necessarily increases the reverberation level, too (which, after all, depends on the direct sound energy).

• The microphone is the first and most important link of any electronic sound reinforcement chain. choosing microphones is therefore one of the most consequential decisions in the design process. by selecting the right type (see next section) and pickup pattern, you can maximize the direct sound proportion and minimize the ambient noise component in your signal.

• The more microphones are open, the lower the sound pressure the system can generate before feedback occurs. Therefore, it is important to minimize the number of open microphones and switch only the one that is currently being used through to the amplifier. This can be done either by a sound engineer at the mixing desk or an automatic microphone mixer.

• Directional loudspeakers focus the sound in a single direction, projecting the sound energy directly at the listeners so there is less energy available for reflections and reverberation buildup. This is especially beneficial in places of worship with hard walls, high ceilings, and low sound absorption coefficients.

Omnidirectional pickup pattern:The microphone “hears” equally well in all directions.

Hypercardioid pickup pattern:The microphone “hears” best in one preferred direction and all but ignores sound (ambient noise) from other directions.

good pick-up

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muted


choosing thE right microphonEThe performance of any sound system depends essentially on the suitability of the microphones for the intended application. The microphone is the interface between sound and the electronic amplification chain, converting sound into an electrical signal. Any loss of signal quality at this stage is impossible – or at best extremely expensive – to compensate for at a subsequent stage. A poorly miked signal will not sound any better when amplified and projected by a loudspeaker.

microphones are electroacoustic transducers that convert vari-ations in air pressure (sound waves) into electrical signals. most professional sound engineers use two types of transducers, dynamic microphones and (conventional or electret) condenser microphones. The latter are usually much smaller and lighter than dynamic designs. This is why most head-worn and lavalier micro-phones are (electret) condenser types. microphones designed for high mechanical stress and high sound pressure levels generally use dynamic transducers because these are more mechanically rugged than condenser transducers. most dynamic microphones are handheld models.because of their small dimensions, condenser transducers are also used in gooseneck microphones. All condenser microphones need a polarization voltage, which in most cases is fed from the mixer to the microphone via the cable using a technique called “phantom powering”. Dynamic microphones need no powering.

condenser microphones are often used for quiet sound sources. because of their higher sensitivity, they sound louder than dynamic mi-crophones at the same gain setting. The sensitivity of a microphone is stated as its output voltage at a specified sound pressure; the respec-tive unit is mv/Pa. The higher a microphone‘s sensitivity, the less you have to amplify the signal, and the less background hiss you will get.

The essential information of a speech signal is found in a range from 300 hz to 3.2 khz. most microphones have a flat frequency response within this band. consonants, which are essential for keeping a speech signal intelligible, are sounds at frequencies between 2.5 khz and 15 khz. Therefore, speech-optimized micro-phones boost these frequencies. for other applications such as instrument miking, however, a flat frequency response is ideal for clear, uncolored reproduction.

The frequency response traces of the ck31 and ck91 cardioid capsules illustrate this difference. The modular Gooseneck Series ck31 is a speech-optimized microphone. Its sensitivity rolls off per-ceptibly below 150 hz to reduce mechanical noise and proximity effect. It also shows a slight peak in the consonant range.

The frequency response of the ck91 blue line Series recording microphone, by contrast, is almost perfectly flat for miking up a wide range of instruments without coloring their sound.

microphone‘s frequency response may also be designed to roll off at low frequencies to minimize the pickup of mechanical and handling noise. This also reduces pop noise (plosive sounds with a large proportion of frequencies below 150 hz). low-frequency attenuation is a must mainly for unidirectional microphones, to compensate for their proximity effect.

Talking into such a microphone from a very short distance will boost the low frequencies dramatically. To avoid this effect, switch in the bass-cut filter (aka highpass filter) found in the preamplifier sections of many condenser microphones. The green line in the ck91 frequency response trace shows how the bass-cut attenuates the low frequencies.

ck31

ck91

aKg cK31 frequency respOnse

aKg cK91 frequency respOnse

Boost (presence, consonants, …)

Attenuation (mechanical noise etc.)

the perfect sOlutiOn fOr every applicatiOn

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here are some general remarks on unidirectional microphones. unidirectional microphones appear to sit closer to the talker than they actually do. They prefer the wanted signal (the talker’s voice) coming from one direction and attenuate unwanted noise from around the talker. (This is similar to the effect of placing a hand be-hind your ear: sounds from certain directions are attenuated while sounds from other directions seem louder). This minimizes the risk of feedback and improves intelligibility.

The polar diagram of a cardioid microphone illustrates in which direction its sensitivity is highest (0 degrees) and in which direc-tion the microphone is more or less “deaf” (180 degrees). cardioid microphones should therefore be your first choice in situations with a noise source or loudspeaker directly opposite the talker.

The hypercardioid provides its highest attenuation at approx. 125 degrees off-axis, so it is very efficient at rejecting reflections from the ground or table-top. The hypercardioid and shotgun are the polar patterns with the highest off-axis rejection. compared to an omnidirectional microphone, a hypercardioid picks up four times more wanted sound than ambient noise, so these microphones should be your preferred choice for halls with high noise levels.

The overall performance of a sound system often depends on the polar patterns of the microphones used. real-life polar patterns are not the same at all frequencies. The directivity is usually higher at mid frequencies than it is at the low end. This has its implications for designing a system because most ambient noise is in the low-frequency band, so using a highpass filter definitely makes sense.

gooSeneck microphoneS

besides having different technical and sonic properties, micro-phones come in different sizes and shapes. Gooseneck micro-phones are particularly suited for permanent installation (e.g., on a lectern), for it is obvious into which end the user has to talk, and the microphone is usually close enough to the talker‘s mouth to ensure good intelligibility. choosing a microphone with a polar pattern optimally suited for the application will further improve intelligibility and gain before feedback.

Gooseneck microphones are available in various lengths and can be bent so that the talker will stand or sit in front of the micro-phone in a comfortable position and at the ideal distance. They are available in various colors to blend in with the envisaged interior decoration. various types of installation accessories allow you to minimize mechanical noise (e.g., if a microphone is mounted on a piece of furniture).

Thanks to a choice of different lengths and a flexible joint, the gooseneck can be optimally adjusted to any position.

Gn15 m with ck41 + ST45 Table Stand Gn30 m with ck43

+ mf m flush mount

Gn50 m with ck49 + h500 Shock mount

Gn15 m with ck43 + h600 Shock mount

pOlar respOnse micrOphOne types


boundary microphoneS

In some cases, no microphones must be seen. In these halls, boundary microphones can be an alternative to gooseneck types as they can be mounted almost invisibly, for instance, on a lectern, or in a tabletop. boundary microphones pick up all signals arriving from above the boundary (in this example, the tabletop). In other words, they have a pickup angle of about 180 degrees. when in-stalling a boundary microphone, make sure to install it in a surface as large as the wavelength of the lower frequency limit.

boundary microphones differ from gooseneck mics in that they are more sensitive to unwanted noise from the tabletop (users knock-ing on it, shuffling papers, etc.) and place the transducer further away from the talker. Also, many users put papers on top of the boundary microphone so it cannot function properly anymore. In areas near loudspeakers, boundary microphones may not be the best solution, because they increase the risk of feedback. Sound systems with boundary microphones need to be designed extra carefully, and it may be a good idea to use special designs with a a preferred pickup direction.

overhead microphoneS

Even nearly invisible boundary microphones may sometimes be perceived as too intrusive or it may be impossible for architectural reasons to run cables to the lectern or pulpit. In such cases, you can use special overhead microphones suspended from the ceiling or boundary microphones flush-mounted in the ceiling. note, how-ever, that this solution has inherent acoustical drawbacks.loudspeakers are often installed in the walls or ceiling and many of them may be closer to the microphone than the talker is. Such a system would wreak havoc on the sound in terms of gain before feedback and intelligibility.

lavalier and head-worn microphoneS

for talkers roaming around, the best solution is to use a wire-less microphone. These microphones use a radio transmitter and receiver instead of a cable. handheld radio microphones have a built-in transmitter, which comes in handy if a single microphone needs to be passed from talker to talker. head-worn and lavalier microphones are connected to a separate “body-pack” transmitter.

The closer a microphone sits to the talker‘s mouth, the higher is the system‘s gain-before-feedback. head-worn microphones also mini-mize handling noise and maintain a constant output level as the dis-tance between the microphone and sound source hardy ever varies.

being an omnidirectional microphone, the ck77 wr is very small. It is also highly humidity (perspiration) proof.

The ck99 cardioid is much bigger than the ck77 wr because unidirectional microphones need a larger body for physical reasons.

c547 blpcc160

boundary microphones keep a low profile in fixed and mobile systems.

The hc577 head-worn micro-phone sits extremely close to the sound source to ensure optimum audio quality.

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Overhead microphones hm1000 m and chm99 (cardioid)

c214

c414 Xlii

microphoneS for muSical inStrumentS

Just like musical instruments differ widely in size, shape, and range, a wide variety of microphones for picking up their sounds can be found on the market today. Some microphones were specifically developed for certain instruments, such as the D112 for capturing low-frequency sounds inside kick drums or in front of bass amplifiers. On a different note, many clip-on microphones were designed to look good on specific instruments.

Still other microphones are suited for a range of different applica-tions. Some “large-diaphragm condenser microphones” originally designed for studio use are also excellent for miking up instru-ments in live sound situations. large-diaphragm microphones use transducers with a diameter of 1 inch or larger. The sensitivity of a condenser microphone being directly proportional to the surface area of its transducer, these microphones are more sensitive and less noisy than condenser microphones with smaller diaphragms.

The AkG c214 and c414 large-diaphragm condenser microphones are excellent choices for miking up speech, solo singers and choirs as well as entire ensembles. The AkG c414 is available in two versions, the c414 xlII with a slight presence peak for good intelligibility and the c414 xlS with an ultra-linear frequency response for instrument miking.

For details on proven microphones and miking techniques, see the “Applications” section on page 18.

sUmmarymicrophone Selection

the right micrOphOne fOr every situatiOn.• Microphones come in many different types, sizes, and shapes.

• Microphones are electro-acoustic transducers that convert sound waves into electrical signals.

• There are two basic varieties: dynamic microphones and (electret) condenser microphones.

• Dynamic microphones are more rugged than condenser transducers, while the latter are smaller and therefore used in head-worn, lavalier, and gooseneck microphones.

• Condenser microphones need a supply voltage; dynamic microphones need no powering.

• Unidirectional microphones can be used to pick up sound from a preferred direction and reject sound from other directions: > use a cardioid if there are any noise sources or loudspeakers opposite the talker. > use a hypercardioid if there is any noise coming from below (the ground, lectern, tabletop).

• Use a supercardioid in halls with high noise levels from all directions.

• For talkers moving about, your best choice is a wireless microphone.

• Head-worn microphones provide a consistent signal level, and lavalier microphones minimize handling noise.

• For different talkers speaking from the same microphone position, gooseneck microphones are a good choice. They come in different lengths.

• Where microphones must not be visible, consider installing boundary microphones. Like hanging microphones, they are more likely to pick up ambient noise.

12

If hardwire microphones are banned for esthetic or practical reasons, go for wireless microphone systems. In most cases, the microphone of choice will be a head-worn or lavalier model be-cause they stay put near the talker‘s mouth and therefore provide a consistently good sound. for situations where a microphone needs to be passed on from one talker to the next, we recommend handheld wireless microphones.

Any wireless microphone system comprises at least one trans-mitter and one receiver. If you are going to use several wireless microphones simultaneously, assign each transmitter to a separate receiver tuned to the same frequency as the transmitter. The trans-mitter may be integrated in a handheld microphone or a separate body-pack transmitter. A body-pack transmitter allows you to con-nect a variety of different microphone types. many handheld trans-mitters are available with a choice of dynamic and/or condenser microphone elements and polar patterns.

The criteria for selecting a type of microphone and polar pat-tern for a wireless system are the same as those for its hardwire counterpart. The difference, however, is the greater mobility of the user. Since talkers are free to move around in the room, they may pass into the coverage area of a loudspeaker or other source of unwanted noise. A microphone with the appropriate polar pattern can help reduce the risk of feedback.

The antenna is the “eye” of any wireless system. Accordingly, it is important not only to position the antenna correctly, but also to select the antenna type that is best suited for a given application. The transmitter signal does not always arrive at the receiver ingood condition. reflections and shadow effects (due, e.g., to large metal grid structures) can weaken the radio signal or even cancel it out completely (the places where this happens are called “dead spots”). Any persons present in the room may also attenuate the

radio signal, because radio waves behave in a similar way as light waves, differing only in wavelength. Therefore, always make sure that the talker can see the receiver from wherever they use the microphone.

Other kinds of disturbances include interference and intermodula-tion. These may arise when a receiver picks up several rf signals at different frequencies at the same time. Interference is a type of disturbance caused by external sources such as Tv transmitters, cell phones, or wlAn networks.

5 m (16.5 ft)

hT45 handheldtransmitter

Sr45 receiver

PT45 body-pack transmitter and ck99 lavalier microphon

perfect radiO transmissiOn• A wireless microphone system comprises a transmitter

and a receiver, between which there should always be an uninterrupted line of sight.

• The transmitter may be a handheld model or a body-pack trans-mitter, to which you can connect a variety of microphones.

• Handheld transmitters are available with dynamic or condenser elements with various polar patterns for optimum gain-before-feedback.

• Smooth operation of a multichannel wireless system depends on competent frequency management.

AkG Perception Series wireless system

WirElEss mobilitygOOd cOmmunicatiOn, nO cables

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sUmmarywireleSS microphone SyStemS


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One way to ensure that only the practical minimum number of microphones is open during a ceremony is to ask a sound engi-neer to operate the mixing desk manually. Small congregations, however, may not have the required resources. And the acoustical problems caused by too many open microphones may not be the only undesirable effects.

nOm limitation (limitation of the number of open microphones) is necessary because each additional open microphone destabilizes the sound system, reducing gain before feedback and increasing ambient noise so the sound becomes muddy and less intelligible. In an acoustically critical environment, four or more open microphones can make the input signal almost unusable. Again, remembering a few basic facts about acoustics and spending your funds accord-ingly will go a long way toward a perfectly functioning sound system.An automatic microphone mixer (“automixer”) can prevent a number of problems. for instance, many talkers forget to switch off their microphone after finishing their statement (not all microphone have an on/off switch, either). Some talkers may even forget to switch their microphone on before talking.

basically, automatic mixers are “electronic switches”. The micro-phone signal at the input will not be fed to the amplifier unless the signal meets certain input parameters. Otherwise, the channel remains silent. The automatic mixer thus distinguishes between active and inactive microphones, muting (or attenuating) the inactive microphones to optimize the overall system level.

Simple automatic mixers use a noise gate in each channel that feeds the microphone signal to the output stage as soon as the input level exceeds a defined threshold. This is a very simple and efficient technique. On the down side, however, these mixers would open all microphone channels whose input levels exceed

the turn-on threshold. In the worst case, the sound of a single loud ceremonial bell could open all microphone channels. Picked up by all microphones, the bell sound could be amplified to the point that the risk of feedback would rise sharply within seconds. To avoid this situation, good quality automatic mixers feature an nOm attenuation algorithm. This function automatically reduces the levels of all open microphone channels to keep overall system gain constant (at the same level as for a single open microphone) and prevent feedback.

Intelligent mixers also provide an algorithm that not only evaluates the level but also the spectrum of a microphone signal. This “noise Detection” algorithm can distinguish between noise and speech signals and opens a microphone only when it is actually being talked into. A similar algorithm is very useful for panels with several micro-phones, as it will open only the one microphone where the loudest speech signal is detected. This function is known as “best mic On”.

The “last mic On” function, by contrast, keeps the last active micro-phone open in order to feed some ambience to the loudspeakers. This is generally perceived as a pleasant “acoustic backdrop” – as opposed to the breathing sound associated with the automatic opening and muting of microphones.Even skilled audio mix operator cannot anticipate with perfect accuracy which participant will speak next. Sudden interjections may be lost completely, or the beginning of a word may be absent because the operator cannot respond quickly, here a properly adjusted auto-mixer can prevent losing words.

high-tech automatic mixers do not even switch the microphones on and off completely. Instead, they attenuate the signals of inactive microphones such that the operation of the mixer remains completely inaudible. many automatic mixers also provide one or more priority levels to which each microphone can be assigned, allowing, for in-stance, the altar microphone to override all other microphones. Advan-ced auto mixers even feature equalizers and other audio processors.

dmm4/2/2dmm4/2/4

The Dmm4/2/4 is a high-performance digital automatic mixer with four balanced microphone inputs, two stereo Aux inputs and one Stereo master output. The mixer offers a full stereo bus and an intelligent mixing algorithm for seamless mixing, including all functions of the Dmm4/2/2.

The Dmm4/2/2 is a high-performance digital automatic mixer with four balanced microphone inputs, two Aux inputs and one mono master output. Each input channel features low-cut, lf and hf shelving filters, a dbx® compressor/limiter, switchable input gain, switchable phantom power and an incremental level control with lED level and peak hold display.

intElligEnt signal procEssingautOmated equipment is tOday‘s standard

Even with no mic active the mixer will not switch off the inputs completely but will attenuate the signal of all input channels instead.

when a second microphone gets active the mixer will share the gain between the two microphones to keep the overall level fairly underneath the feedback threshold.

when all mic are active, the attenuation is such that the overall level will be underneath the feedback threshold.

As soon as one microphone is active the mixer is able to bring up the volume instantly – thus no syllable will be lost at the beginning of a sentence.

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sUmmaryintelligent Signal proceSSing

intelligent electrOnics fOr Optimum cOmmunicatiOn• Auto-mixers balance multiple sound sources based on each

source‘s level by quickly adjusting the various signal levels automatically. Auto-mixers are used in live sound reinforcement to maintain a steady limit on the overall signal level of the microphones.

• In order to avoid feedback, it is necessary to limit the number of open microphones. An automatic microphone mixer automatically controls all microphone levels and optimizes the overall volume level of the sound system.

• Automixers use noise gates to open microphone channels on detecting sounds louder than a defined level. An nOm attenuation algorithm prevents channels from being opened by unwanted noise and maintains a consistent system volume level.

• The Noise Detection algorithm will only switch on the one microphone that is actually being talked into, thus preventing comb filter effects.

• A gain sharing algorithm will perfectly balance the volume of the single microphones and in this way prevent feedback problems.

• Many automatic mixers also provide one or more priority levels to which each microphone can be assigned, allowing, for instance, the altar microphone to override all other microphones.

• The Last Mic On function leaves the last open microphone on to feed some ambient sound to the system. Advanced auto-mixers attenuate microphone signals rather than switching them off completely, and provide simple equalizers.


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Small houSe of worShip

This is the plan of a small house of worship typical of many rural villages and small towns. most of these houses of worship use no sound system at all, which is perfect for crowds of less than thirty persons. for larger crowds, we recommend installing a simple sound system. better intelligibility makes it easier, particularly for the elderly, to take part in the services without strain.

In most cases, a single microphone on the altar and another one on the lectern will do. Gooseneck microphones work best for both locations. The gooseneck places the microphone rather close to the priest‘s mouth, ensuring good audio quality.

It is common practice to place the mixer and amplifier(s) in an adjacent room. An active mixer (a mixer with a built-in amplifier) is a good choice for a small system, but be sure to purchase a model with phantom power on all microphone channels. remember that condenser microphone will not work without phantom power.

The amplified signal (a mono feed will do for most small places of worship) then needs to be fed to the column speakers in the nave. A proven way to do this is to use a 70/100v distribution system, which keeps signal attenuation low even if the loudspeaker cables are rather long. mount the column speakers on the walls or pillars, about six feet above the floor, and aim them obliquely into the nave. make absolutely sure that none of the speakers will project directly into any of the microphones!

large houSe of worShip

many large houses of worship provide separate areas for specific ceremonies. while some celebrations may typically fill the entire house of worship, other rites such as baptisms or requiem masses etc. may involve fewer persons and are therefore held in a smaller area, e.g., the side aisle.

The size and type of sound system needed depends on the size and type of celebration held. below are two typical solutions for two different situations.

Situation 1: Mass in the naveThe pews face the main altar. Since more microphones may be re-quired here, we recommend using an automatic microphone mixer. It limits the number of microphones that are open at any time to prevent feedback loops (see page 14).

The microphones used on such occasions often include one or more radio microphones. The assigned receivers are usually hidden in a separate “control room” behind walls that may be many feet thick, so remote antennas are a must. Omnidirectional antennas are the preferred choice, because they are small and inconspicuous. If a wireless microphone is to be used in more than one area, e.g., within the nave and the side aisle, you may need to install another pair of antennas in each of these areas. never place the two antennas of a diversity receiver at two different areas of the house, e.g., antenna A near the altar and antenna b for the aisle. This would defeat the receiver‘s diversity function and cause

sound rEinForcEmEntpa-systems

dropouts. To find out how many antennas you will need, consult your AkG dealer or the sound system installation firm. In any case, a detailed floor plan will be needed to design an an-tenna system. In many places of worship, a test run of the system will be required to identify areas with poor radio coverage. (for details on wireless transmission technology, refer to page 13).

In a hall as large as the one in this example, the signals fed to the loudspeakers need to be delayed individually in order to prevent annoying echo effects. Effects units and matrix mixers provide appropriate “delay lines” for this purpose. The speed of sound be-ing roughly 1,000 feet per second, sound travels about 1 foot per millisecond, so, as a rule of thumb, the distance from the sound source in feet is roughly equal to the delay time in milliseconds. measure the distance from the main altar to the first row of speak-ers and set the delay line for these speakers to the time (msecs.) equal to the distance in feet. repeat this operation for each row of speakers. Delay compensation creates a pleasant, natural sound and improves intelligibility. Aim all column speakers at the last row, at an angle of approx. 15 to 20 degrees off the wall, so that those sitting in the front rows will not hear the delayed signals projected by the speakers further in the rear.

Situation 2: Side chapelThe pews face the side altar, and in most cases only this part of the audio system is used while the rest of the speakers remain muted, so other visitors are only minimally distracted from their

prayers. If the chapel is small, you will need no delay lines. Good quality matrix mixers allow you to store several system setups in memory and recall them at the push of a button. unless you use only wireless microphones in the side chapels, consider installing floor sockets for the hardwire microphones to eliminate the risk of somebody tripping over a cable.

modern houSeS of worShip

while many houses of worship in the uS and canada are similar to the two types described above, some contemporary places of worship resemble modern multipurpose halls in terms of both architectural design and equipment. Some preachers inspire their congregations to extremely moving, intense spiritual experiences rather than silent contemplation. many of these houses of worship seat tens of thousands, and the way services are celebrated there requires sound systems similar to those for large theatres or rock concerts.

These systems are too large and complex to be described here. you can find detailed information on all the components for this kind of sound system at: www.harman.com.

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sUmmarySound reinforcement

it´s all abOut the placement

• In most cases, small houses of worship only need a single microphone on the altar and another one on the lectern. A few column speakers will provide enough sound pressure level for a good intelligibility, when placed correctly. As near as possible to the audience and fairly away from the microphones.

• Many large houses of worship provide separate areas for specific ceremonies. Each area needs to be planned specifically. The larger the space, the more speakers need to be placed. Often you will need to provide appropriate “delay lines” to prevent echoes in the hall.

• If a wireless microphone is to be used in more than one area, e.g., within the nave and the side aisle, you may need to place different pairs of antennas in each of these areas (for details on wireless transmission technology, refer to page13).


18

is at the center of many religious ceremonies. while no microphone should be visible there, it is the spot where most of the liturgical texts are recited. The best way to reconcile these conflicting re-quirements would be a lavalier microphone for the priest. Although many of them – particularly if they are older – would refuse to have themselves “tethered” to the sound system, lavalier microphones do provide obvious benefits: the microphone sits close and at a constant distance to the talker‘s mouth. consequently, they pro-vide maximum mobility.

Since multichannel systems are usually not required, a wireless system is an affordable alternative. Systems with selectable car-rier frequencies such as the wmS45 Presenter System are highly recommendable as they allow you to “shun” interference signals. before installing a wireless system, be sure to check that the wall

between the altar area and the room where the receiver, mixer, and amplifier will be installed does not block the radio signal. If it does, install the receiver near the altar. As a slightly more expensive al-ternative, consider a system with unobtrusive removable antennas that can be mounted near the altar.

If a wireless microphone is absolutely out of the question, a bound-ary microphone is another viable choice. boundary microphones are so thin they almost disappear when placed on the altar table. use a unidirectional model (e.g., AkG Pcc160 or AkG c547 bl), to avoid picking up sounds from unwanted directions. Also, position it where the priest is least likely to silence the microphone by placing a book on top of it. The altar table acting as the boundary surface for the microphone, unwanted noise such as the turning of pages will sound rather loud. Also, the talker‘s mouth will be relatively far away from the microphone while the book on the alter lies next to (if not on top of) the microphone. Since the priest may move in front of the altar, we recommend using two boundary microphones.

is a rather easy miking situation because most preachers address the worshippers from a single spot. Since the lectern is less visu-ally critical than the altar, using two gooseneck microphones has become a standard technique. which polar pattern you should use depends on where the nearest loudspeaker is located. This is a straightforward technique in terms of both design and everyday use, for the positions of the lectern and loudspeakers are known and do not change during a ceremony. The risk of sudden feed-back attacks is therefore minimal.

To ensure perfect intelligibility, remember the following points. never place the loudspeakers where they would project directly into any microphone. In order to avoid reflections that might start a feedback loop, do not place the lectern near highly reflective surfaces (windows, concrete walls).

Gooseneck microphones are an excellent choice for use on a lec-tern. The microphone is near the talker‘s mouth and since the talker can see the microphone, they know right away in which direction to speak. The flexibility of the gooseneck allows you to position the microphone with precision, and unidirectional microphones with a narrow pickup angle efficiently reject unwanted sounds.

Preachers turn their head from side to side as they address differ-ent worshippers when speaking to their congregation. To maintain a consistent signal level, use two microphones – and under all cir-cumstances connect them to an automixer! If two closely spaced microphones are open at the same time, two effects may reduce intelligibility. for one thing, two open microphones reduce gain-before-feedback, and for another, the so-called “comb filter effect” may cause a “tubby” sound.

Since a talker will hardly ever stand exactly in the middle between the two microphones, the sound will arrive at the two microphones about equally loud, but at slightly different times. when the mixer combines these signals, parts of the resulting audio signal are

application arEasthe altar the lectern

canceled. This so-called “comb filter effect” is especially marked at frequencies of 1 khz to 2 khz (equivalent to a path length differ-ence of 3.15 to 5.91 inch). Automatic microphone mixers minimize these two effects because they only switch on one microphone at a time, namely, the one with the better (louder) signal.

using two microphones in order to have a backup in case one microphone fails is a different story. In this case, place the two microphones as close as physically possibly to each other – ideally, one above the other. This makes sure that comb filtering will only occur at very high frequencies where it is not audible. Again, be sure to connect the two microphones to an automatic mixer!

To get the best possible signal in a place of worship, the microphone should sit as close to the talker’s mouth as possible. Therefore, choose

a gooseneck that is long enough to be adjusted to talkers of different heights and to leave enough room for turning the pages of a book. In order to provide high-quality solutions for these applications, AkG introduced the Discreet Acoustics modular Series offering a choice of polar patterns, gooseneck lengths, and connectors you can combine as desired. A common problem with lecterns is mechanical or knocking noise. To suppress mechanical noise, try one or both of the following:

1.) use a shock mount such as the AkG h600 or mfm to install the gooseneck microphone. Their soft rubber mixture absorbs any vibrations before they get to the microphone, making sure that no knocks will be heard on the loudspeakers.

2.) Switch in a highpass filter. knocks are usually low-pitched (low-frequency) sounds. The electronic highpass filter inside the con-nector shell of most AkG goosenecks (see the related instruction manuals) eliminates knocking noise as well as wind noise caused by a talker blowing into the microphone.

Optimum rejection of mechanical noisewhile conventional rubber mix-tures (fig. 1) are slow in absorb-ing vibrations, the special AkG rubber mixture (right) absorbs vibrations almost instantly (fig. 2).

fig. 1 fig. 2

basic altar and lectern miKing facts• Sound systems for lecterns are easy to design for minimum

feedback.

• In terms of audio quality, the best miking solution for the altar is a lavalier or headworn microphone connected to a wireless system.

• Make sure no loudspeaker projects directly into any microphone.

• Do not place the lectern in front of highly reflective surfaces.

• Use a high-quality shock mount for each microphone.

• Use unidirectional microphones to avoid amplifying off-axis noise.

• Boundary and gooseneck microphones on lecterns: > boundary microphones are almost invisible when installed, but may create acoustical problems > Gooseneck microphones can be placed near the alker‘s mouth, which is a great advantage in terms of gain-before-feedback and intelligibility.

• When using two microphones, always connect them to an automixer.

sUmmaryapplicationS - altar and lectern


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phones in their pockets. Some of these interference sources may be nearer to the receiving antennas than the wireless microphones, causing severe disturbances. The only way to work around such interference is to use professional frequency management to avoid these unwanted frequencies.

To mic up a moving talker, use a body-pack transmitter and head-worn or lavalier microphone (fig. 1), or a handheld wireless microphone (fig. 2).

where none of the above is practicable, use hanging microphones or directional microphones positioned farther away. These may cause considerable problems, though, and should always be con-trolled by a sound engineer or automixer.

There are two obvious approaches to miking members of the con-gregation. from an acoustic point of view, setting up one or more stand-mounted microphones is the best solution because you can place them at spots where the risk of feedback is low. Also, they are unlikely to pick up handling or other unwanted noise.

A more convenient solution for the worshippers is to pass a radio microphone from one person to the next so they can talk from the pew. To reduce handling noise, be sure to ask a sound engineer to control this microphone manually or use an automixer.

In large places of worship, this application requires a sophisticated antenna network, which is an important factor to be taken into ac-count when designing a sound system. The human body is highly efficient at absorbing radio waves, so placing the antennas care-fully helps prevent dropouts and shadow effects.

radio microphones are susceptible to interference from other radio sources. many believers go to house of worship with their cell

fig. 2fig. 1

applications

sUmmaryapplicationS

amplifying vOices frOm the cOngregatiOn

• Your best option is to place one or more stand-mounted microphones in the hall.

• Passing on a radio microphone is more convenient, but its signal always needs to be controlled by a sound engineer or automixer.

• Careful, line-of-sight antenna placement prevents dropouts and shadow effects.

miKing the cOngregatiOn

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Applications

To mic up solo vocals, you can use either dynamic or condenser microphones. which type you will actually use is a matter of taste and depends on the cantor‘s style and timbre. As mentioned before, dynamic microphones are usually more mechanically rugged, so less experienced users are less likely to overload the microphone.To reduce the risk of feedback, use a unidirectional microphone,

i.e., a cardioid, hypercardioid, or supercardioid. Excellent vocal microphones include the D5 supercardioid dynamic or c5 car-dioid condenser. A good choice for smaller budgets is the P5 supercardioid dynamic mic.

All the microphones mentioned above are available in both hard-wire and wireless versions. which version to use will depend primarily on technical and visual considera-

tions. If the cable does not intrude visually and no staff is available to operate the sound system, always use a hardwire microphone.

microphones for solo vocals are often mounted on a microphone stand. Some singers, however, prefer holding the microphone in their hand. This allows them to vary their sound in several ways, for in-stance, by varying the distance between their mouth and the micro-phone, utilizing the so-called “proximity effect”. As you move closer to the microphone, the low frequency range of your voice in the output signal grows louder, adding power and warmth to the sound.

holding a microphone in your hand is not without risks, however. unlike stand-mounted microphones, handheld microphones may transmit handling noise. An even greater risk is that of triggering feedback by grabbing the mic by the wrong end. unidirectional micro-phones turn into omnidirectional microphones as soon as your hand covers the rear sound entries. This may start a feedback loop and make the system howl instantly. Therefore, always make sure to hold the microphone by the handle, never by the wire-mesh cap.

microphone care

The sound of a heavily used vocal microphone may become duller over time, losing sparkle and intelligibility. This is caused by dirt collecting in the internal windscreen. using equalization to boost the high frequencies may seem to be an easy solution, but beware: boosting any frequency range increases the risk of feedback – the microphone becomes more likely to “howl”. The safer, simpler, and more hygienic approach is to wash the windscreen and your microphone will sound “as new” again. remove the windscreen from the microphone and wash it in soap suds. clean the wire-mesh cap with alcohol. Once the windscreen has dried completely, replace it and put the microphone back together.

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perfect sOund fOr the parsOn • Use a unidirectional dynamic or condenser microphone.

• You can use hardwire or wireless microphones.

• When using a handheld microphone, the singer should never cover the rear sound entries.

• Regularly clean the built-in windscreen.

sUmmaryapplicationS - Solo vocalS

sOlO vOcals


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we recommend using a cardioid microphone (ck31) mounted either on a high microphone stand, e.g., the Gn155, or “flown” from the ceiling with an hm1000 hanging kit. The latter approach allows you to leave the microphone(s) in place without them getting in anybody‘s way. If you place the microphones farther away (espe-cially if you hang them from the ceiling), remember you will need a narrower pickup angle, and use shotgun microphones such as the ck47 instead of cardioids.

In order to minimize feedback hazards, use as few microphones as possible with narrow pickup angles (hypercardioids to shotguns). for many small choirs, two microphones hung in front of the choir will do. make sure, though, that the back rows are less than twice as far from the microphones than the front row. Otherwise, the voices in the back would sound too weak on the loudspeakers. for large choirs therefore, hang more than one row of microphones.

which and how many microphones to use depends above all on the size of the choir. The criteria for miking backing or small choirs are similar to those for solo vocals. Ideally, provide one microphone for each singer. use hypercardioids or supercardioids to prevent crosstalk between the voices. If “single miking” is impractical, two or three singers may share a microphone. In this case, use cardioid microphones because they have a wider pickup angle than hyper-cardioids and thus provide more room to move. Ask the singers to stand in a semicircle in front of the microphone.

To mic a larger choir, use one microphone for each section. Place the microphones in front of the choir, above the singers‘ heads. Each microphone‘s distance from the choir depends on its pickup angle (polar pattern). Again, the general rule is “the closer the better”, as long as all persons to be covered stand within the pickup angle.

applications

chOir

In any case, four to seven microphone should do. for choirs on steps or risers (a standard arrangement), hang the microphones for the back rows higher than those for the front singers. If a choir is

not only to be amplified by the sound system but recorded at the same time, consider stereo miking. you will find detailed descrip-tions of various stereo miking techniques at www.akg.com.

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sUmmaryapplicationS - choir

capture that great, big chOral sOund• Depending on the size of the choir, use one microphone for

each singer or one microphone per section.

• Be sure to choose the right pickup pattern for the job at hand.

• If several singers need to share a microphone, that microphone should be a cardioid because its pickup angle is wide enough to even allow the singers to move a bit.

• The closer you place the microphones to the singers, the better their voices will sound and the higher the system‘s gain-before-feedback will be.

• Mount the microphones on suitable stands or hang them from the ceiling.

• When using “flown” microphones, take into account the differences in height between the steps or risers on which the singers stand.


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grand/upright piano

The concert grand has a wide range and complex sound radiation pattern. how to mic it up depends on the style of music played and the acoustics of the hall. Stereo miking techniques such as m/S ste-reo are relatively straightforward and can reproduce the entire sound spectrum of a grand. In a large, reverberant hall, however, remember that gain-before-feedback will be rather limited because stereo mics should be placed rather far from the instrument.

Therefore, try placing the microphones inside the piano to minimize the risk of feedback. note that the piano will sound the punchier and more percussive the closer the microphones sit to the strings. close-miking reduces ambience pickup, though. note that if you place the mics very close to the strings, the proximity effect may boost the low frequencies. To avoid masking other bass sounds, use microphones with a switchable bass-cut filter or atenuate the low frequencies on the mixer.

If you want to capture more ambience for a rounder sound, place the microphones further away from the strings, outside the instru-ment. Alternatively, you could combine close-in and ambience microphones. you can also get excellent results by combining a stereo pair with spot microphones close to the strings (or close-in mics and ambience microphones hung above the grand). note, however, that more open microphones will reduce gain-before-feedback and increase spillover from other instruments.

In halls with extremely poor acoustics, even two microphones placed close to the strings may cause feedback. In this case, close the lid. clip-on or boundary microphones placed inside the grand can give very good results. you can use similar miking techniques for the upright piano. Placing two microphones, e.g., in a stereo configuration, outside (behind) the piano is an easy way to get a good, full sound. In a live-sound situation with several instruments and loudspeakers in a small space, place the microphones inside the instrument to avoid feedback and crosstalk problems. Again, bound-ary microphones or clip-on microphones (especially if you close the lid) are a good choice for this technique.

before miking an instrument, study its acoustic “personality”. This is important, because every instrument is different. A house of worship organ will need no electronic amplification to fill even a very large hall with its overwhelming sound. wind instrument sounds carry well, too and usually need no microphone. bowed and plucked string instruments, however, do depend on sound reinforcement. In reinforcing ensembles, a mixing desk helps balance the different volumes of the individual instruments. with no mixer, loud instruments such as electric guitars, a drum kit, or wind instruments might drown out the more delicate sounds in a reverberant environment. balancing the sound of an ensemble is no easy task, though, and requires a lot of practice.

for places of worship where some masses are accompanied by an entire orchestra, a separate mixing console (e.g., a SOunDcrAfT EPm or Efx Series) for the orchestra might be a good idea. you can then feed its master output signal to the main sound system mixer.here are some standard miking techniques for frequently used instruments.

applicationsinstruments and ensembles

wide range – cOmplex miKing• The best way to capture the full sound of a concert grand is

to place the microphones outside the instrument – if at the expense of reduced gain-before-feedback.

• To increase gain-before-feedback, place the microphones inside the piano, bearing in mind that this will change the sound.

• A carefully tweaked combination of close-in and far-field miking can provide a very natural reproduction of the piano sound.

sUmmaryapplicationS - grand/upright piano

acouStic guitar

you can mic up a guitar in many ways. Piezoelectric and vibration pickups attached to the guitar are a good way to avoid feedback. These pickups capture the vibrations of the strings or the body, not the airborne sound. To capture the entire sound spectrum including string and fingering noise as well as room ambience, you will need to use a microphone.

Since the guitar radiates the low frequencies from the sound hole and the high frequencies by the strings and top, microphone placement is critical. If you place the microphone too close to the sound hole, the low frequen-cies will be boosted excessively. for a better-balanced sound, aim the microphone at a point near the bridge, taking care not to place it so close that the player keeps hitting it with their hand. To avoid such collisions, position the mic a little lower than the guitar body.

for best results, set the microphone up about eight to ten inches from the guitar. Turn the microphone toward or away from the sound hole to boost or cut the bass range without using the equal-izer. for a punchier, sparkling sound, aim the microphone between the sound hole and the fingerboard. Again, turn the microphone to adjust the amount of low frequencies in the signal. If proximity effect makes the guitar sound excessively bass-heavy, switch in the bass cut filter on the microphone (if it has one) or the highpass filter on the mixer. If the guitarist roams around the stage, the varying microphone distance will cause unwanted volume vari-ations. In this case, use a pickup or attach a clip-on microphone to the guitar. To get a well-balanced sound, you might also consider combining a microphone and pickup.

electric guitar and baSS

There are basically two ways to feed the signal of an electric guitar or bass to your sound system. One is to feed the instrument signal di-rectly to the mixer via the line output of the amplifier, an effect pedal, or a DI (Direct Injection) box. This technique provides a clean, neutral signal with no feedback risk. To get a more vivid, powerful sound

and capture the specific timbre of the guitar or bass amplifier, place a microphone in front of the loud-speaker, as near as possible with-out introducing distortion. you can tweak the sound by changing the microphone position. for a bright signal, aim the microphone at the center of the loudspeaker. The

further off-center you point the microphone the more bass-heavy the sound will be. The best “mark” for a guitar amplifier is a point halfway between the rim and center of the loudspeaker diaphragm – giving a bright yet not harsh sound. for a bass amplifier, aim the microphone at a point near the diaphragm rim to emphasize the low frequencies. using both a DI box and a microphone provides excellent results, too; note, however, that you will need two mixer inputs per instrument.

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clean, pOwerful sOund• To amplify an acoustic guitar, use a pickup and/or microphone.

• Pickups are less susceptible to feedback but deliver a limited sound spectrum.

• Never place the microphone in front of the sound hole but near the bridge or the fingerboard/top.

• For an electric guitar or bass, you have two options: connecting the instrument directly to the mixer through a DI box or placing a microphone in front of the amplifier speaker.

• DI‘ing delivers a feedback-resistant but neutral signal, while miking the amplifier gives a more vivid, sparkling sound.

• The ultimate guitar/bass sound depends on where you place the microphone in relation to the loudspeaker diaphragm.

sUmmaryapplicationS - guitar and baSS


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violinTo pick up a violin, be sure to use a high quality cardioid condenser microphone. Place the microphone about 6 to 8 feet above the ground and align it with the f holes perpendicularly to the soundboard. If far miking is impractical for the reasons mentioned above, use a vibration pickup, e.g., a c411. Attached to the bridge or tailpiece of the violin, the c411 picks up the vibrations of the soundboard.

for physical reasons, pickups are rather weak on bass and treble. To augment the frequency spectrum of the amplified sound, consider using a head-worn microphone. Sitting close to the player‘s cheek, this type of microphone is at an almost ideal position to capture the full sound of the violin. To avoid capturing breathing-noise, do not place the microphone too close to the violinist‘s mouth. As an added benefit, a head-worn microphone picks up less mechanical noise because it is not mounted on the instrument. To mic up the viola, use the same techniques with slightly longer working distances.

cello Similarly to the violin, attach a pickup to the bridge or tailpiece, below the strings. Again, the pickup will not adequately capture the characteristic overtones of the cello. whenever the sound reinforcement situation permits, place a microphone, preferably a cardioid condenser, in front of the instrument. Position the

bowed String inStrumentS The best way to reproduce the full sound of bowed string instruments, particularly in classical music, would be to use far-miking techniques that can capture the room sound as well. In reverberant halls with highly reflective walls, far miking is out of the question. To ensure reasonable gain-before-feedback, use lavalier microphones or pickups. Since each type of bowed string instrument has a different range and radiates its sound in a different way, you will need to use different mics for different instruments or sections.

microphone within the main radiation angle, about 10 to 45 degrees to the right (as seen by the player), at a maximum distance of 20 inches.

double baSS

To avoid feedback, attach a pickup to the bridge. Since this technique delivers a rather hard sound and emphasizes the mid frequencies, consider using an additional spot microphone to capture the rest of the instrument‘s sound spectrum. Set up a dynamic microphone about 16 inches from the bass and align it with one of the f holes. when miking up the bass together with an ensemble, reduce the working distance and use a hypercardioid microphone to prevent spillover from other instruments.

applicationsinstruments and ensembles

treat yOur string sectiOn gently• The violin sound, delicate and rich in overtones as it is, may need

reinforcement so it won‘t be drowned out by louder instruments.

• You can use microphones and/or pickups on all bowed string instruments.

• A microphone/pickup combination provides a well-balanced sound and captures little unwanted noise.

sUmmaryapplicationS - String inStrumentS


On special occasions, particularly in places of pilgrimage, services may be held out-of-doors to accommodate larger crowds. Also, processions may move through the streets in the neighborhood. These situations place additional requirements on the sound system.

for outdoor processions, you can only use wireless microphones. To ensure adequate radio reception along the entire route of a procession, you will need to install a distributed antenna system. Distribute several antennas for each diversity input along the route, assigning antennas alternately to input A and input b. connect all antennas for antenna input A to an antenna combiner and all antennas for input b to another combiner. connect each combiner output to the appropriate receiver input. This system ensures that

the same radio signal is always received by both diversity circuits, thereby preventing dropouts. when setting up antennas, check that at least one antenna is visible from every point along the route. mount the antennas on lamp posts or corners of buildings.

At most locations, omnidirectional antennas will work perfectly as they are equally sensitive to signals from all directions. At some locations, where two antennas in the same diversity circuit might receive equally strong signals from different directions, you will have to use directional antennas. These capture signals from a preferred direction and reject signals from other directions, much like direc-tional microphones.

A

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B

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Antenna Cablecable specifically designed for rf signals. used for connecting a remote antenna to a receiver. Antenna cables are typically coaxial and symmetrical. Signal attenuation de pends on the frequency band of the signal as well as the length and quality of the cable and is quoted for a 100-m run of cable.

Antenna SplitterElectronic network specifically designed for rf signals. Distributes an antenna output signal to several receivers. Powered antenna splitters use an amplifier to compensate for cable attenuation while passive antenna splitters have no amplifier.

Balanced/Unbalanced Connectionsmicrophones can be connected to an ampli fier with either ba-lanced or unbalanced cables. In a balanced cable, the signal is carried by the two inner conductors and the shield is not part of the signal path. Even with long cable runs, any external in ter-ference signal (such as power line hum) would be induced equally in both conductors and thus be canceled. un balanced cables use only one center conductor as the “hot” wire, the shield being the ground (“cold”) lead. while this arrangement works well with cables up to 10 meters in length low-frequency, long-wave hum interference may be picked up by longer cables which act as a long-wave antenna.

BNCconnector specifically designed for rf lines.

BoosterAmplifier for rf signals. boosters are connected between a transmitter output and the antenna in order to increase radiated power (custom product).

Condenser MicrophoneThe transducer element consists of a vibrating diaphragm (me-talized foil) only about a ten thousandth of an inch thick and a fixed metal electrode (back plate). The two electrodes make up a capacitor (condenser) charged by an externally applied Dc voltage 1" polarizing voltage or carrying its own permanent charge. The sound waves driving the diaphragm will vary the capacitance of the capacitor and consequently the microphone output voltage will vary in step with the sound waves. condenser microphones, also called “capacitor microphones”, need an impedance converter (preamplifier) to match the very-high-impedance condenser trans-ducer to low-Z inputs. condenser microphones usually have a flat frequency response, high sensitivity, and good transient response.

They require a power supply. All AkG condenser microphones are designated by the letter(s) “c” or “ck” in front of the model number.

Connecting AKG MicrophonesAll handheld microphones are low-impedance 1,200 to 620 incorpo-rating a balanced output on a 3-pin male xlr connector. conforming to IEc 268-12, pin 1 is ground, pin 2 high, and pin 3 low. The output is compatible with all mixers, tape recorders, etc. To connect an AkG microphone to an input jack, wire the microphone cable as follows: connect the sleeve of the jack plug (ground) to the cable shield and the shield to pins 1 and 3 on the xlr connector. The center (“hot”) wire connects pin 2 to the jack plug tip (see diagram 1).

If your installation uses pin 3 as “high” or “hot”, bridge pins 1 and 2 for unbalanced connections and make sure to follow the same convention for all cables in order to avoid phase reversal problems. very old sound systems sometimes have high-impedance micro-phone inputs.Should the signal of a low-impedance mic ro phone be too weak, insert a 1:10 step-up transformer at the amplifier input. long cable runs used with high-impedance equipment cause high-frequency loss. The same applies if you connect a microphone to a high-impedance guitar amplifier input.

glossary

1

explaining technical terms – frOm a tO d

unbalanced Input jack balanced Input

modified Input with phantom powering

modified Input (xlr) with phantom powering

xlr – Input


Connecting Condenser Microphonescondenser microphones – except for the battery powered c1000 S – require an operating voltage that needs to be fed through the microphone cable (phantom powering). This can be done in several ways:

1. from a mixer with built-in phantom power (9 to 52 v).2. by modifying the mixer or tape recorder to provide phantom power: find a regulated Dc voltage between 9 and 52 v in the power supply. All modern AkG condenser microphones accept any voltage within this range. wire the input(s) as shown. current consumption of the phantom circuit is negligible (about 1 mA per mic). replace the input jacks with xlr sockets if possible. while stereo jacks will work as well, there may be a risk of mista-king them for send/returns or the like. use the following standard resistances (IEc 26815) for rv: voltage resistance12 v (±2 v) 680 Ω +10%24 v (±4 v) 1.2 kΩ ±10%48 v (±4 v) 6.8 kΩ ±10%make sure to use resistor pairs whose combined actual value is within 0.4 % of the specified value!

3. by inserting n62 E or n66 E Ac power supplies between the mixer and microphones.

4. by using the b18 battery power supply which is ideal for outdoor recording.

CrosstalkThe undesired coupling of signals from one channel to another channel.

dB SPLDecibel Sound Pressure level. A measure of the sound level referenced to 20 µPa (the sound pressure corresponding to the threshold of human hearing). A 6-db increase in SPl would sound about twice as loud.

Deep Fademassive decline of received signal strength due to cancel-lation of the carrier in multipath transmission situations.

Directivity FactorThe directivity of a microphone can be expressed in terms of the amount of sound energy it absorbs out of a diffuse sound field. The directivity factor indicates how much less sound energy is absorbed by a directional microphone than an omnidirectional microphone.

DistortionDynamic microphones virtually never dis tort the signal. To be precise, their distortions at very high sound pressure levels (<130 db) cannot be measured because loudspeakers are incapable of reproducing such levels distortion free. for this reason, we state no maximum SPl for dynamic microphones. however condenser microphones with their built-in preamplifier may overload at high sound levels. when close miking (from a few inches) loud instru-ments such as drums or trumpets the microphone sensitivity should be reduced. with the c535, simply use the preattenuation switch.

Directional AntennaAntenna whose sensitivity is highest within a limited angle in front of the antenna. Directional antennas are used mainly where standard receiving antennas cannot be mounted within the range of the transmitters so the transmitter signals must be picked up from greater distances (e.g., in open-air arenas).

Diversityreception technique that ensures clear reception even in difficult envi-ronments. Diversity receivers use several antennas for the same carrier frequency and some models use several receiving sections, too.

DowntimePeriod of time during which a system is inoperative.

Dropoutmomentary loss of signal due to squelch operation or interference.

Dynamic MicrophoneA coil attached to a diaphragm is driven by the sound waves and vibrates between the poles of a magnet. This movement induces in the coil a voltage which corresponds to the sound pressure. Dynamic microphones handle high sound levels without overloading and are very rugged. They require no operating voltage. Dynamic micro-phones from AkG are designated by the letter “D” in front of the model number. Also known as “moving coil microphone”.

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Inside a bass drum 3 cm (1 in.) from the head

Tom-toms 3 cm (1 in.)distance;60 watt guitar amp, at 30 cm (12 in.) distance

loud vocals at 15 cm (6 in.) dis-tance

Acoustic guitar chords strummed with plect-rum, at 40 cm (16 in.)

Acoustic guitar, at 40 cm (16 in.) played “fin-gerpicking”

noise level in an average city apparte-ment

loud vocals, measured in front of the mouth; threshold of pain

congas, 2 cm (1 in.) from the head; cowbell at 10 cm (4 in.) distance

Saxophone, trombone, played p, at 40 cm (16 in.) distance

Piano, played pp, at 1 m (3 ft.) dis-tance

whispering at distance of 10 cm (4 in.), quiet conver-sation at 1 m (3 ft.) distance

noise level in a good sound-isola-ted studio

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Electret Condenser Microphonecondenser microphone that needs no polarization voltage. Instead, a special metalized plastic “electret foil”, in which a permanent electrical charge has been stored by application of heat and a high polarizing voltage, is used either for the diaphragm or the fixed electrode. The latter type is called “back plate electret microphone”.

Electromagnetic Wave Spectrumrange of frequencies of electromagnetic radiation.

EnvironmentDynamic microphones will generally stand up to extreme environ-mental con ditions such as temperatures from -25 °c to +70 °c and high humidity.

condenser microphones, however, are susceptible to humidity and condensation. when an object is damp and colder than its environment, condensation water will form on its surface. Drops of condensation water inside the transducer or high-impedance preamplifier will cause crackling noises.

Storing condenser microphones: 1. Store the microphone in a dry and warm place. It should never be colder than its environment. If it has been transported in acold car or van, allow it to warm up before use.

2. The supplied silica gel absorbs humidity. It will maintain this property as long as you keep it in the sealed package and may be regenerated in the oven if necessary.

3. be sure to protect condenser microphones from rain when using them outdoors.

Equivalent Noise LevelSince condenser microphones incorporate a preamplifier, they introduce a low amount of self-noise which appears at the micro-phone output as an unwanted signal voltage. This noise voltage is measured using standard weighting filters and the result stated as the equivalent noise level in db. An equivalent noise level of 20 db, for instance, means that the self-noise of the microphone is as loud as a sound at 20 db SPl (see db SPl).

Noise level in quiet recording studio:A low equivalent noise level means that the microphone’s self-noise is low. The self-noise voltage is weighted either conforming to IEc 268-1 and DIn45 405 using the filter according to ccIr 468-3 with the “quasi-peak” value being quoted, or in accordance with IEc

651 or DIn45 412 using the A-weighting curve with the rms value being quoted. Studio engineers seem to prefer the ccIr weighting while A-weighting is still accepted as well.

ERPEquivalent radiated Power, a measure of a transmitter’s rf output.

Far-Near DifferenceThe difference between the shortest and the longest distance between stage and antenna.

Feedbackwhen a microphone picks up amplified sound from a loudspeaker this signal will be reamplified, picked up again, etc., until the commonly known shrill howling (sometimes a lower midrange rumbling) sets in. In small rooms, feedback is usually caused by reflections. In this case, acoustic treatment of the walls should help. On stages with correct-ly set up fOh speakers it is the monitor speakers that may cause feedback. A very good hypercardioid microphone (e.g. a D3900) may sometimes provide a few extra db’s of gain-before-feedback. Place the monitors slightly off-axis (135-) where the microphone is least sensitive.

Frequency ManagementOrganization of frequency resources.

Frequency ModulationA technology that alters (modulates) carrier frequencies to transmit information.

Frequency RangeThe frequency range of a microphone is usually stated as the

glossary

The conversion of a low-frequency into a high-frequency signal and vice versa is accomplished via frequency modulation, i.e., by applying a high-frequency sinus carrier wave (hf) to the low-frequency audio signal (lf).

Time scale

Amplifier

unwanted signal

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explaining technical terms – frOm e tO n


upper and lower frequency limits within which the microphone delivers a useful output signal.

Frequency Responsemicrophones are not equally sensitive to all notes. The frequen-cy response indicates the relationship between sensitivity and pitch. The 0-db reference being the output voltage at 1 khz, the frequency response is measured at constant sound pressure level, from about 20 hz (lowest note) to 20 khz (above the upper limit of human hearing).

Hum Sensitivitymagnetic fields from amplifiers, long power cables, and lighting systems in particular may induce hum in microphones. A micro-phone’s hum sensitivity gives an indication of how susceptible it is to this kind of interference. values are 3 µv/5 µT for dynamic microphones with hum suppression coil, 30 µv/5 µT for dynamics with no suppression coil (D90, D95, D190), and up to 10 µv/5 µT for condenser microphones. In practice, though, it is the micropho-ne cables, most of all unbalanced ones, and mixer inputs, that are most likely to pick up hum.

Impedancefrequency dependent Ac resistance of a microphone. Always quoted at 1 khz the actual impedance at other frequencies may differ slightly from this reference value. Also known as “source impedance”.

Intercept PointThe Intercept Point (IP) provides a measure for an amplifier’s resis-tance to intermodulation distortion. IP3, for example, is the reci-procal value of the third-order coefficient of an amplifier’s nonlinear transmission polynomial.

InterferenceDisturbance in transmission caused by extraneous signals.

IntermodulationA nonlinear (multiplicative) combination of signals with different carrier frequencies that will produce completely new frequencies, called intermo dulation products.

LimiterElectronic circuit that prevents subsequent circuits being overloa-ded by excessive signal levels that would also cause distortion.

Line MicrophoneThe directivity factor of conventional unidirectional microphones is limited by the laws of physics. This can be overcome by installing

a slotted tube in front of the diaphragm (“interference tube”). Off-axis sounds are canceled through interference, which results in an ultradirectional polar pattern.

Matchingmicrophones should operate in an open circuit. This is the case if the input impedance of the preamplifier or mixer is at least 2 to 5 times as high as the microphone’s rated impedance. The appro-priate value is quoted in the specifications of each microphone as “recommended load impedance”.

Maximum SPLThe highest sound pressure level (loud ness) a microphone can handle without introducing more than a specified amount of “Total harmonic Distortion” (1 %), in other words, without distorting the signal. usually measured at 1 khz, except for the c460 b ulS Series where it is quoted from 30 hz to 20 khz.

Mechanical NoiseSee “vibrational noise”.

Memory EffectThe loss of capacity which occurs in nickel-cadmium storage batte-ries if they are not completely discharged prior to recharging.

Modulation/DemodulationA sine-wave carrier starting at a time of minus infinity and ending at a time of plus infinity contains no information. however, any change in amplitude or frequency at any time (e.g., a pulse-like change) adds information to the carrier. This process is called “modulation”. The process by which a receiver detects and extracts this informa-tion from the carrier is called “demodulation”.

Multichannel SystemA wireless microphone system that allows several radio micro-phones to be operated simultaneously in the same room.

Noise Burstbrief disruption of the desired signal by noise from a transient interference source (e.g., ignition spark).

Noise SkirtAn ideal carrier spectrum would be a line. As the carrier is modulated, the noise inherent in the switching signals makes the transients look ragged. This raggedness ultimately frequency-modulates the carrier with noise. Once that happens, the carrier spectrum is no longer a line but a noise spectrum that tapers off to either side of the wanted fre-quency, which is why this part of the spectrum is called a “noise skirt”.

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NOM (number of Open mics limit)Good auto mixers feature a special nOm limitation algorithm (num-ber of Open mics limit). The nOm limitation automatically adjusts the level of the microphones open at the same time, thus ensuring constant overall system gain without feedback.

Phantom Power to IEc 2681 5/DIn 45596condenser microphones require an operating voltage. It can be fed to the microphone either by a-b powering or phantom powering. In a-b powering, the operating voltage is fed to the balanced audio wires without using the shield. a-b powering is incompatible with dynamic microphones since the operating voltage would flow through the moving coil and destroy it. In phantom powering, the negative terminal is connected to the cable shield and the positive terminal is split via decoupling resistors to the balanced audio wi-res. Since both audio wires carry the same potential, no current will flow through the coil of a dynamic microphone so there is no risk of destroying it even if the phantom power is accidentally left on.

when adding phantom power to a single ended (grounded) input or an input with no front-end transformer, either capacitors or an optional transformer need to be wired into the audio lines as shown below, to prevent leakage currents from entering the input stage.

PolarityIf you use more than one microphone for a recording, they should be of the same polarity. This means that if the diaphragms move in the same direction, the output voltages of all microphones should have the same polarity. If they don’t there will be signal cancellation effects causing sound coloration – particularly in the bass range – as soon as you mix the microphone output signals together.

Pop NoiseIn order to avoid those unpopular pop noises on stage, remem-ber the following:

> Talk across the microphone head.> Interestingly, pop noises are worst about 2 in. from the mic. So move either closer or further away.> Perhaps use an extra foam windscreen.

Polar PatternThe “polar pattern” of a microphone indicates its sensitivity to sounds arriving from different directions. Omnidirectional microphones “hear” equal ly well in all directions while all others prefer sound from one (unidirectional) or two (bidirectional) directions.The polar diagram

shows the three-dimensional “hearing performance” of a microphone as a single curve. It is sufficient to plot only one half of the curve (0° through 180°) since the other half (180° through 360°) is symmetrical. In this way, the directivity can be shown for several different frequencies (broken, dotted, solid lines).

glossary

CK 31

At 150° off-axis, the sensitivity is 17 db down (referenced to 0°) at 125 hz (solid line), and 10 db down at 8 khz (dashdotted line, righthand half). 150° means 150° left, right, up and down (see diagrams on the next page).

figure-eight

ultra-directional

Omnidirectional

cardioid

hypercardioid

Pressure Gradient MicrophoneIf both the front and rear of a diaphragm are exposed to a sound field, then the force that vibrates the diaphragm results from the diffe-rence between the sound pressures in front and to the rear of the diaphragm (called the pressure gradient). The magnitude of the dri-ving force depends on the distance between the front and rear sound entries, the frequency, and the angle of incidence and is therefore a directional variable which can be utilized to design directional microphones. cardioid, figure eight, or hypercardioid polar patterns can be achieved by incorporating appropriate sound paths.

Pressure MicrophoneIf only one side (front) of a microphone dia-phragm is exposed to a sound field and the other (rear) side sealed off by a soundproof case, the diaphragm will be vibrated by changes in sound pressure only. Sound pressure being a non-directional (scalar) variable, the micro-phone is equally sensitive in all directions. The resulting polar pattern is called omnidirectional 1.

Proximity EffectIn unidirectional microphones, as the working distance decreases, the output voltage rises more markedly at the low frequencies than throughout the rest of the frequency range. This is due to the fact that the diaphragm is vibrated by the pressure gradient between its front and rear surfaces and the pressure gradient is related to the curvature of the wave fronts. This effect, known as “proximity effect”, begins to

explaining technical terms – frOm n tO Z


become audible at a few hundred hz and at extremely close workingwor-king distances, the output level may be up to 15 db higher at 50 hz than at 1 khz. This corresponds to about 6 times the normal output voltage.

Reflectionwhen a signal wave hits an obstacle, it will be reflected, i.e., bounce off the obstacle’s surface at an angle equal to the angle of incidence.

Remote AntennaAntenna that is connected by a special antenna cable to the antenna input socket on a receiver rather than directly to the antenna input socket.

Room RadiusIn a room within which a sound is generated, e.g. by a loudspeaker, every point is characterized by its own unique ratio of direct sound and sound reflected from the walls. The distance from the sound source at which the direct and reflected sound energies are equal is called the “room radius”. Outside the room radius the overall sound pressure level is constant throughout the room in the form of a “diffuse sound field”.

TransientTemporary change in voltage or current occurring as a voltage or current source is switched on or off, e.g., a transistor controlled by a pulse signal.

SensitivityA microphone’s output voltage at any given sound pressure level. A more sensitive microphone will sound louder at the same gain setting (the feedback risk being proportionately higher). high sensitivity (condenser microphones) is needed to drive the mixer adequately when far miking quiet sound sources. Sensitivity is commonly given in mv/Pa or dbv (referenced to 1 v/Pa) and measured at 1 khz.here are some examples: D58 0.7 mv/Pa (-63 dbv)D190 1.6 mv/Pa (-56 dbv)c1000 S 6.0 mv/Pa (-44 dbv)c535 7.0 mv/Pa (-43 dbv)c451 Eb comb 9.5 mv/Pa (-40.5 dbv)c460 bcomb ulS/61 10.0 mv/Pa (-40 dbv)c562 bl 20.0 mv/Pa (-34 dbv)

Shadow lossSignal loss which occurs in wireless transmission if an obstacle blocks the line-of-sight transmission path between transmitter and receiver.

Signal LossSignal loss in a cable may be due to ohmic resistance, dielectric leakage or radiation loss.

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Signal-to-noise (S/N) RatioThe S/n ratio is the difference between the reference sound pressure level of 94 db (1 Pa sound pressure) and the equivalent noise level. contrary to the equivalent noise level, a lower S/n ratio means higher noise and therefore a narrower dynamic range.

SquelchElectronic circuit that switches the receiver off when the received signal is too weak so the associated extraneous noise and the self-noise resulting from the receiver being switched off will be inaudible. The squelch threshold is usually user adjustable within a preset range.

Tone squelchThese terms denote a circuit that will open the audio path only when it detects a system-specific tone within the demodulated sig-nal. This tone is higher than 20 khz, the upper end of the range of human hearing, and is added to the audio signal by the transmitter.

Total Harmonic Distortion (T.H.D.)A measure of the non-linear distortion of a signal (e.g. a sine wave) that occurs when a microphone or input is overloaded producing harmonics (overtones) at multiples of thefundamental frequency.

Transient ResponseThe ability of a microphone to follow sudden sound events immediately. Transient response depends on diaphragm mass, transducer damping factor, etc.

UHF VHFultra high frequency very high frequency

Vibrational NoiseIn addition to air-borne sound, microphones also pick up mecha-nical noise such as impact, footfall, handling, or cable noise. Such unwanted noise can be reduced by special design features (trans-ducer shock mount, compensation systems, bass cut).

Vocal MicrophoneA microphone specifically designed for vocal use on stage. It incorpo-rates a pop screen, a transducer shock mount to reduce handling and impact noise, and is particularly rugged so it will survive the occasional drop from the stand. many vocal microphones have an upper midrange (3 to 8 khz) peak to make the voice cut through. In the studio, vocals are ideally recorded from 30 cm (1 ft.) or even farther, usually with con-denser microphones.

WavelengthThe distance between two consecutive peaks (or troughs) of a sine wave.

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1. general conditionS • How many people normally attend the services?

• How many microphones will ultimately be needed?

• How many microphones will be permanently installed and how many should be available for mobile use?

• What sound/audio sources will be involved? (Speech, live music, CD players, etc.)

• Will extra seating be provided for some services?

• Will the sound system be operated by a sound engineer?

• For what rites will the sound system typically be used?

3. chooSing microphoneS• May the microphones, loudspeakers, and receivers be

visible or must they be hidden?

• Which microphone types with which polar patterns can be used?

• Does the client prefer a permanent or mobile installation?

• Will a wireless microphone system be needed (for a moving preacher or testimonials by worshippers)?

• How rugged must the microphones be?

• What visual requirements (if any) should the microphones meet?

• In which areas of the hall will microphones be used?

• Should the microphones incorporate any controls (on/off switch etc.)?

2. the hall and itS acouSticS• Which areas are active, which passive?

• Are architectural drawings of the hall available (hard copy, electronic files)?

• Are there any limitations as to where loudspeakers or wireless transmitters and receivers may be mounted?

• Are there any requirements or limitations regarding the shapes and colors of components?

• Where are existing loudspeakers mounted and what are their projection patterns?

• In which areas will microphones be needed?

• Have active and passive areas been definitely fixed or can they be varied if required?

• Has the hall been acoustically treated and if so, how?

• What noise sources are to be dealt with?

• What noise levels are to be expected from these noise sources?

• Are there any acoustically critical areas (due to reflections off hard walls, windows, smooth surfaces)?

• How long is the reverberation time?

• To what extent does the presence of worshippers reduce the reverberation time?

• Does the hall generate any unwanted reflections (flutter echoes etc.)?

• What amount of amplification (NAG – Needed Acoustical Gain) is required?

4. SyStem operation

• Will the system be operated by a sound engineer or controlled by an automatic mixer?

• What are the visual and hearing conditions at the engineer‘s position?

• Are there any problems with the existing system and what is their nature?

chEcklistsimpOrtant pOints fOr designing a sOund systemknowing what to expect and what is expected of you makes it easier to design a good sound system. below are some lists of questions you should ask before beginning to design a sound system.


5. connecting the microphoneS a) Hardwire microphones

• Does the mixer provide microphone inputs with phantom power?

b) Wireless microphones

• How many wireless microphones will be used at the same time?

• What transmitters (handheld or body-pack) are required?

• What devices (head-worn and/or lavalier microphones, electric instruments, etc.) will be connected to the body-pack transmitters?

• Where can antennas be mounted?

• Which room can be used as a control room where the wireless receiver(s) can be set up, too?

6. controlling the Sound SyStem

• Is the system to be controlled from a mixing desk or by an automixer?

• What functions should the mixing desk or automixer provide?

• How many wireless channels will be used simultaneously?

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www.akg.com

AKG Acoustics GmbH Lemböckgasse 21–25, 1230 Vienna /AUSTRIA phone: + 43 1 86654 0, e-mail: [email protected]

AKG Acoustics, U.S. 8400 Balboa Boulevard, Northridge, CA 91329, U.S.A. phone: + 1 818 920 3212, e-mail: [email protected]

For other products and distributors worldwide visit www.akg.com Specifications subject to change without notice. 01

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Documents

AKG Places of Worship Guide