Shure M615as Schematic

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M615AS-2E EQUALIZATION

ANMYzEn SYSTEM

The Shure Model M615AS Equalization Analyzer System is designed to permit rapid and accurate adjustment of the frequency response of a sound reinforcement, monitoring, or playback system incorporating an equalizer such as the Shure Model M610 Feedback Controller. The

M615 Equalization Analyzer,

their various accessories, and a portable case. (The M615

ES615 are also available separately.)

and

The M615 provides two major functions. First, it is a source of equal-energy-per-octave random noise ("pink noise"), available at microphone and auxiliary levels with adjustable output, to serve as a test signal source. Second, the M615 accepts the output of the Microphone (or other microphone) or an auxiliary-level signal, and indicates the relative energy in each of 10 octave bands. Two light-emitting diodes (LEDs) for each octave indicate whether the energy is below a given LO (reference) level, above an adjustable HI level, or (if both

LEDs are off) between the two levels (within the enve-

lope). The object is to adjust the sound system equalizer to turn off the LEDs of the system response which is within the envelope. With minimum envelope size (2 dB) and all LEDs off, the resultant octave-energy frequency response curve will be smooth within approximately curves may be selected: flat, or the 3 dB per octave

rolloff above 1 kHz typical of most desired "house curve" responses. Two overload LEDs, a microphone input tenuator, and an input level control are also provided. A switch provides either microphone input low-frequency response compensation for the phone or a flat frequency response characteristic.

ES615 Analyzer Microphone is an omnidirectional,

The dynamic, measurement microphone. Its broad, flat frequency response with controlled low-frequency designed specifically for use with the M615 Analyzer.

M615AS includes a microphone cable, swivel

The adapter, tilt bracket, tem carrying case.

The Model is identical to the Model the Model M615-2E Equalization Analyzer instead of the Model

the

(switch-selectable).

M615. The M615 operates from 108-132 Vac and

M615-2E operates from 90-125 or 180-250 Vac

M615AS-2E Equalization Analyzer System

GENERAL

SR107 Audio Equalizer or

M615AS consists of the

ES615 Analyzer Microphone,

ES615 Analyzer

M615, thereby producing a

k1 dB. Two resultant

at-

ES615 Analyzer Micro-

rolloff is

test/interconnecting cable and sys-

M615AS, except that it contains

The M615 (only) is listed by Underwriters' Laboratories, Inc., and listed by Canadian Standards Association as certified.

Model

M615AS Features:

Permits rapid and accurate adjustment of octave band equalizers in sound systems

Pink noise generator with microphone- or aux-level

output Ten octave bands from 32 Hz to 16 kHz Rugged LED High and Low indicators Selectable resultant octave-energy curve: flat for near

field equalization or 3 dB per octave 1 kHz for reverberant field equalization

LED microphone and input overload indicators to as-

sure accurate equalization Adjustable input and pink noise output levels

Microphone input with 15 dB attenuator and selector switches

Adjustable envelope from 2 to 12 Aux output jack for monitoring or connection to ac-

cessory instrumentation Tilt bracket permits positioning Analyzer at con-

venient viewing angle Sturdy carrying case for all System components

high/low impedance selectors,

flat/ES615 frequency response

rolloff above

(+I to 26) dB

SPECIFICATIONS

All signal levels referred to are pink noise levels.

Inputs

IMPEDANCE LEVEL CONNECTOR High or Low MIC 3-pin professional female* High

Outputs

IMPEDANCE LEVEL CONNECTOR Pink Noise Generator

High or Low MIC 3-pin professional male' Pink Noise Generator

High AUX phone and phono pin jacks Analyzer

High AUX phono pin jack

Designed to mate with Cannon XL series, Switchcraft A3 (Q.G.) series or equivalent connector

EQUALIZATION ANALYZER

AUX phone and phono pin jacks

1978, Shure Brothers Inc.

Printed in

U.S.A.

PINK NOISE GENERATOR Output Level

AUX LEVEL HI-Z MIC LEVEL

1 dBV (890 mV)

(Level control at 10)

LO-Z

-29 dBV (35 mV) -49 dBV (3.5 mV)

MIC LEVEL

Spectrum

Equal energy per octave pink noise, flat %I dB, 32 Hz to 16 kHz

lmpedance

OUTPUT DESIGNED FOR USE WITH ACTUAL

Lo-Imp.

Mic Level 25- to 600-ohm microphone 110 ohms Hi-Imp.

Mic Level 33-kilohm microphone circuits 2.3 kilohms Aux Level High-impedance (10 kilohms 1.5 kilohms

circuits balanced

unbalanced

or more) unbalanced aux unbalanced circuits

ANALYZER Sensitivity

(Pink noise levels to turn off LO LEDs; INPUT LEVEL control fully clockwise)

INPUT 15

Lo-Imp. Mic. Out -117

Hi-Imp. Mic. Out

AUX

ATTENUATOR PRESSURE USING In

In -77 dBV (0.14 mV)

INPUT VOLTAGE SOUND Hi-Imp. Mic. Out -17 dBV (0.14V)

ES615 MICROPHONE

dBV (1.4 pV) 45 dB SPL

102 dBV

92 d BV (25 pV)

pV) 60 dB SPL

dBV (0.79 mV)

ABOVE 1 kHz ROLLOFF FREQUENCY RESPONSE

FIGURE 2

Mic Overload

(Pink noise levels to turn on MIC OVERLOAD LED)

INPUT

LO-imp.

ATTENUATOR PRESSURE USING

Mic. out -40

In -25

INPUT

VOLTAGE

~BV

(10 mv) 122 d~ SPL

dBV (56 mV) 137 dB SPL

2 dBV (0.79V)

SOUND

~~615

MICROPHONE

lnput Overload

(Pink noise aux input level to turn on INPUT OVERLOAD LED; INPUT LEVEL control fully clockwise)

dBV (56 mV)

-25

FlatlES615 Switch

In ES615 position, complements low-frequency rolloff

characteristic of ES615 Microphone (see Figure 1)

t20

+I0

-10

-20

Above 1

kHz

FLAT: Used for near-field measurements; produces

flat resultant frequency response. ROLLOFF: Used for reverberant and far-field meas-

urements; produces resultant frequency response rolled off at 3

100

FREQUENCY IN

HERTZ

500

ES615/M615 SYSTEM LOW

FREQUENCY RESPONSE

FIGURE 1

Switch

per octave above 1 kHz (see Figure

HiILo Envelope

2 to 12 dB (-+I to k6 dB), adjustable

Aux Output Voltage Gain

INPUT GAIN Lo-Imp. Mic

Hi-Imp. Mic +31

AUX

lnput attenuator out

+54

-4

dB**

Impedance

INPUT DESIGNED FOR USE WITH ACTUAL

Lo-Imp. Mic.

Hi-Imp. Mic.

Aux 100-ohm to 10

OUTPUT DESIGNED FOR USE

Aux High-impedance (10 kilohms 4.7 kilohms unbalanced

25- to 600-ohm microphones 950 ohms balanced 33-kilohm microphones 140 kilohms unbalanced

level sources

or more) unbalanced aux (with MIC input in use) circuits

kilohms high

WITH ACTUAL

42 kilohms unbalanced

Operating Voltage

M615: 108-132 Vac, 50/60 Hz, 5W M615-2E: 90-125 or 180-250 Vac, 50/60

Hz,

Temperature Range

Operating: Storage:

-7" to 57°C (20" to 135°F)

-29" to 71°C (-20" to 160°F)

Dimensions

See Figure 3

OVERALL DIMENSIONS

FIGURE

Weight

M615 M615AS

2.2

(4 Ib

5.6

oz)

(11

(12

Ib)

Ib 4 02)

Net

Combined Net

Packaged

2.3

2.9

kg kg

(4 (6 Ib

oz)

CONTROLS AND CONNECTORS

PlNK NOISE LEVEL Control:

Sets pink noise generator

output level.

INPUT LEVEL Control:

Sets input signal level and LO

LED threshold to the analyzer.

ABOVE 1

high-frequency response or a smooth resultant

KHz Switch: Selects either a flat resultant

high-

frequency 3 dB per octave rolloff above 1 kHz.

INPUT OVERLOAD LED:

Lights if INPUT LEVEL control

is set too high for input signal level, causing erroneous

M615 LED indications.

MIC OVERLOAD LED: Lights with excessive micro-

phone input levels, indicating need to switch in 15 dB attenuator or reduce pink noise level.

HI/LO ENVELOPE Control: Adjusts the HI LED threshold

relative to the LO LED threshold. The resultant frequency response envelope may be varied from 2 to 12

(%I

HIILO LEDs:

to +6 dB).

The LO LED for each octave lights if the

input signal within its octave is below the lower threshold set by the INPUT LEVEL control. The HI LED for each octave lights if the input signal is above the upper

threshold set by the

PlNK NOISE GENERATOR OUTPUT

nector:

Provides pink noise generator output connec-

HI/LO ENVELOPE control.

AUX LEVEL Con-

tion to aux-level inputs.

PlNK NOISE GENERATOR OUTPUT

nector:

Provides pink noise generator output connec-

MIC LEVEL Con-

tion to microphone-level inputs.

PlNK NOISE GENERATOR OUTPUT

MICROPHONE MI-

PEDANCE Switch: Selects low- or high-impedance pink noise generator microphone-level output.

MICROPHONE INPUT

15 dB ATTENUATOR Switch: Reduces microphone input sensitivity to avoid microphone preamplifier overload. Affects microphone input only.

MICROPHONE INPUT

FLATlES615 Switch: Selects either flat response or low-frequency boost complementing the response characteristics of the

ES615

Analyzer Microphone, making the system response flat.

Affects microphone input only.

MICROPHONE INPUT Connector: Provides microphone

input to analyzer.

MICROPHONE INPUT

IMPEDANCE Switch: Selects

low- or high-impedance microphone input to analyzer.

AUX INPUT Connectors: Provides input to analyzer from

mixers, amplifiers or other aux level input signals. In addition, accepts aux level output of pink noise generator (using the supplied cable) for self-testing purposes. Automatically disables MICROPHONE INPUT

if plug is inserted.

AUX OUTPUT Connector: Provides for monitoring or

connection to accessory instrumentation. This con-

nector is in parallel with the analyzer AUX LEVEL input connectors, or monitors the equalized microphone preamplifier output if the AUX INPUT connectors are not

in use.

PRELIMINARY SETUP

The following should be performed prior to using the

M615AS Equalization Analyzer System:

1. Remove the protective cap from the grille assembly of the

ES615 Analyzer Microphone. This cap should

be used during transit and storage only.

2. Install the tilt bracket assembly on the M615 Equalization Analyzer as follows: Attach the No. 6-32 machine screws and

capnuts in the two lower holes at the front of the M615 cover. Make certain the capnuts are on the outside of the cover. Insert the ends of the tilt bracket through the two upper holes at the front of the M615 cover. Slip the plastic caps over each end of the tilt bracket. Swing the tilt bracket downward against the front panel so that the machine screw heads provide a detent to stop the

4).

bracket from sliding (see Figure

Note that the M615 can be replaced in its carrying case with the tilt bracket in place and extending straight outward from the front panel.

M615

WITH TILT BRACKET

FIGURE

Model M615-2E: The Model M615-2E is supplied

with a detachable line cord without a three-pin male power connector. Obtain a suitable three-pin male plug and attach it to the line cord. The plug should be installed by qualified service personnel. The brown lead goes to the "hot" or "live" terminal, the blue lead to the neutral terminal, and the

green/yellow lead to the ground or earth terminal. Select the proper voltage range (90-125 or 180-250 Vac) using the rear-panel VOLTAGE SELECTOR switch.

SETUP AND OPERATION

In the following setup and operation procedures, the

objective is to produce a smooth acoustical frequency

response in the audience listening area. This condition is indicated by both LO and HI LEDs being off. However, due to the nature of random noise, a signal near thres-

hold will cause flickering of the LED, rather than a positive on-off indication. It is generally sufficient if one or

several LEDs are blinking, but not off completely.

The time required to allow the analyzer to respond to a change and sample sufficient noise to give an accurate indication depends on the octave band observed and the amount of change made. The low-frequency octave bands require more time to stabilize, and major changes in

equalization require more time to provide LED indications. Up to 20 seconds may be required for large frequency changes, while 1 second is sufficient for midand high-frequency changes. Note that when the M615

is turned on, at least one minute is required for the circuits to stabilize and provide proper LED indications.

ANALYZER CHECKOUT

M615 Analyzer may be checked for proper func-

The

tion prior to use as follows:

1. Connect the line cord to a 108-132 Vac (M615), or 90-125 or 180-250 source. (Select the proper operating voltage using the VOLTAGE SELECTOR switch.)

Connect the supplied test/interconnecting cable be-

tween the pink noise generator AUX LEVEL output

and the analyzer AUX INPUT.

3. Set the ABOVE 1 kHz switch to FLAT, the

ENVELOPE control to control to approximately 5.

Turn on the ONIOFF switch and allow the unit to stabilize for one minute.

5. Slowly adjust the INPUT LEVEL control until all LEDs are off. Note that the low-frequency LEDs (below 500 Hz) will respond more slowly to INPUT LEVEL

control adjustment.

This check indicates that the

factorily and is ready for use.

While the output to AUX INPUT checkout as described above, a similar checkout using the MICROPHONE LEVEL output to MICROPHONE INPUT may be performed. To account for normal slight variations in response between the auxiliary and microphone connections, set the

ENVELOPE control to 3 for this checkout.

Connect the testlinterconnecting cable supplied with the cable with male and female professional three-pin connectors between the pink noise generator MICROPHONE LEVEL output and the analyzer MICRO-

PHONE INPUT.

2. Set the 15 dB ATTENUATOR switch to OUT, the FLAT/ES615 switch to FLAT, and both IMPEDANCE

switches to either HI or LO.

3. Perform the checkout procedure as described above. If one or more LEDs remain on, an adjustment may be

performed (by qualified service personnel only) as described in the Calibration: Rectifier

M615 is factory-calibrated for AUX LEVEL

ES615 Analyzer Microphone or a similar

Vac (M615-2E), 50160 Hz power

and the PINK NOISE LEVEL

M615 is operating satis-

Level

section.

low-

HIILO

EQUALIZATION: GENERAL

While the final measure of any equalization effort is a

subjective judgement of the quality of the sound delivered to the audience, acoustic measurement instrumentation such as the

be of considerable assistance in more efficient and consistent equalization procedures.

The energy per octave), an equalization analyzer and an omnidirectional analyzer microphone with a flat response compatible with the analyzer. The analyzer indicates the relative signal amplitude of each octave band for the complete audio spectrum.

In general, equalization analyzer equipment is used to allow equalizer adjustment by measuring sound system performance instead of by subjective evaluation. Connection, setup and operation of the equalizer remains the same. Recommendations regarding various equalization objectives are also generally applicable.

Analyzer equipment usually is used first to establish the desired house curve, which is the sound system response characteristic preferred for that particular application. For playback equalization the analyzer microphone is located in the main audience area and connected to the equalization analyzer input. The noise

generator is connected to the audio console or mixer

input and the volume adjusted to provide a sound level

at least such an arrangement the analyzer is placed in close

proximity to the equalizer so that, as equalizer adjustments are made, the results are easily observed. Adjustment for a flat response in the audience area of a large room will usually result in an overly bright sound. Common practice is to adjust for 3 dB per octave

the high frequencies starting at about 1 kHz for reverberant-field equalization. Frequency response is then

checked in other locations in the audience area and, if necessary, the equalizer is readjusted slightly to improve the average response for the entire audience area. Final equalization adjustments are based on listening tests using typical program material.

Home entertainment system equalization using mentatioy is similar to playback equalization, except that

amHifier (or amplifier portion of a receiver) is used

an insteyl of a mixer, the analyzer microphone is placed in

,desired listening location instead of the main audi-

the

ewe area and the system is equalized flat for near-field eqdalization.

Equatization of a sound reinforcement system using instrumentation is the same as for playback equalization.

The sound system is equalized

desired house curve with all microphones turned off. The

individual microphone volume controls are then increased

equally (assuming microphones have similar character-

istics) or to the approximate use settings, below the

feedback threshold. The mixer master gain control is then

increased slowly while observing the equalization analyzer. As the feedback threshold is approached, the

analyzer will show the frequency band where feedback is about to, or does, occur. This band is then suppressed

priate equalizer filter control. This process is repeated

until the major feedback tendencies have been

M615AS Equalization Analyzer System can

M615AS consists of a pink noise generator (equal

10 dB above the room ambient noise level. In

rolloff of

instru-

initially to produce the

prominent increase in amplitude of

using the appro-

sup-

pressed and a reasonable sound volume level can be produced. A talk or other performance test of each open microphone is then conducted and the quality of the sound produced is sampled by listening in various locations throughout the audience area. Additional equalization adjustments are made based on the listening evaluation, while taking care to avoid any significant reduction in the feedback threshold previously achieved.

Equalization of a stage monitor system using analyzer equipment is similar to playback or house system equalization except that measurements and evaluation are confined to the performer's stage area. The pink noise generator is connected to the mixer input and the audio console or mixer volume adjusted to provide an output from the monitor speakers at least 10 dB above the ambient noise level. A person is placed in front of the lead performer's microphone (to simulate performance conditions) and the analyzer microphone is placed next to the

person at ear level to sample the sound field in that area. The analyzer microphone output is viewed on the equalization analyzer and initial response adjustments, such as low-frequency sole or mixer volume control for the performer's microphone is then set to a stable point slightly below the feedback threshold. The monitor master gain control is gradually increased until an obvious increase in amplitude in a particular frequency band is noted on the equalization analyzer. This is the onset of feedback and the appropriate equalizer filter control is used to reduce the system response in this area. This process is continued until satisfactory gain before feedback and the desired response is achieved. former microphone position is made to determine if an adequate feedback threshold is attainable. Final adjustment of the equalizer and/or individual channel tone controls (if available) is made to improve quality or intelligibility of the sound presented to the performers.

rolloff, are made. The audio con-

voice test of each per-

OPERATION

This section contains basic instructions for connecting

and operating the

It should be noted that individual room acoustics, equipment characteristics, and increasing operator proficiency will all contribute to the development of equalization analysis techniques which may differ somewhat from the guidelines described here.

M615AS Equalization Analyzer System.

Connections

Interconnect the units of the sound system as for normal operation. Connect the M615 pink noise generator output to the input of the console, (either microphone, or aux level using the supplied test/ interconnecting cable), amplifier or receiver, and, if the M615 microphone-level output is used, set the MICROPHONE IMPEDANCE switch as required. Connect the ES615 Analyzer Microphone to the M615 microphone input. Set the phone input IMPEDANCE switch to LO. If a flat-response equalization microphone rather than the used, set the PEDANCE switch as required.

FLAT/ES615 switch to ES615 and the micro-

FLAT/ES615 switch to FLAT and the IM-

mi~er, preamplifier

ES615 is to be

Sound Reinforcement Systems

1. Place the speakers of the sound reinforcement sys-

tem in listening area locations to provide optimum

audience coverage. Maximum coverage in many installations is obtained with the speakers on each

side of the sound source and as far forward as possible. Assuming a single speaker to either side of the sound source, the speakers should be positioned so that an imaginary line from the center of each speaker runs to the back row of the audience area.

For "clustered" speaker installations covering a wide area, each speaker should be positioned so that its angle of coverage slightly overlaps that of the speaker next to it as their sound output enters the audience area. The pink noise generator output

of the M615 may be used (at low system power levels) to provide an audible signal source for speaker placement checkout. A listening test of the audience area may be made for dead zones, frequency response variations, or other symptoms of

improper coverage. Avoid listening to speaker pattern overlap areas, as these are apt to be erratic.

Set the front-panel ABOVE 1 kHz switch as required. A system equalized using the

provides a smooth 1 kHz, which usually results in the most pleasing audience reaction. Research has shown that a per-

fectly flat frequency response curve generally yields

an overly bright sound that is made more natural by

using this gradual high-frequency

position is normally used only for near-field equal-

ization particularly in small or acoustically "dead"

rooms, or for electrical equalization of preamplifiers, tape recorders, and amplifiers.

Set the 15

LO ENVELOPE control to 12, and the PlNK NOISE

LEVEL control to ization microphone on a microphone stand at a seated listening height, approximately on-axis to one

of the speakers and mid-way between the speaker

and the rear of the audience area. Turn on all units in the system and allow one minute Starting at up until the first LO LED goes out or flickers. Note the INPUT LEVEL control setting and reduce it by approximately ity is low enough to prevent the ambient noise level

from affecting equalization results. If the MIC input

is being used and the initial INPUT LEVEL control setting is should be set to IN and the process repeated. If the

INPUT OVERLOAD LED comes on during adjust-

ment of the INPUT LEVEL control, the control setting

is too high and must be reduced for proper LO LED indications. IMPORTANT: The equalization procedure requires a stable ambient noise level. Extraneous noise such as construction, rehearsal, or loud conversation will interfere with measurements and

adjustments.

Slowly increase the PlNK NOISE LEVEL control until one to three HI LEDs go on. Most LO LEDs will go

out; those remaining on at either end of the spectrum

indicate the bandwidth limits of the sound reinforce-

ment system. It is important to note that any attempts to equalize at these bandwidth limits must be done judiciously. Excessive boosting of these frequencies

0, turn the INPUT LEVEL control slowly

or less, the

dB per octave rolloff starting at

ATTENUATOR switch to OUT, the

0. Place the ES615 or other equal-

This assures that the input sensitiv-

ROLLOFF position

rolloff. The FLAT

warmup time.

dB ATTENUATOR switch

HI/

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