Shure M615as Schematic

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TWX:

910- 231-004s

3121866-2200

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TELEX:

72.4381

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I

SiiEET

M615AS-2E EQUALIZATION

ANMYzEn SYSTEM

I

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

Copyright
27A1350 (RB)

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

dB

ATTENUATOR PRESSURE USING In

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

(8

-

92 d BV (25 pV)

-

62

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.

15

d~

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

m

+I0

z

W

V)

5

%

0

Y

W

E

-10

Y

-20

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

dB

50

100

FREQUENCY IN

HERTZ

500

ES615/M615 SYSTEM LOW

FREQUENCY RESPONSE

FIGURE 1

Switch

per octave above 1 kHz (see Figure

2)

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**

dB**

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,

5W

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

3

Weight

M615 M615AS

2.2

kg

(4 Ib

13

5

5.6

oz)

kg

kg

(11

(12

Ib)

Ib 4 02)

Net

Combined Net

Packaged

2.3

2.9

kg
kg

(4
(6 Ib

Ib

15

oz)

7

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

dB

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

3.

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

4

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.)

2.

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.

4.

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.

1.

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

2,

and the PINK NOISE LEVEL

M615 is operating satis-

Level

section.

low-

HIILO

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

a

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-

A

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.

2.

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.

3.

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.

4.

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

dB

0, turn the INPUT LEVEL control slowly

4

or less, the

3

dB per octave rolloff starting at

ATTENUATOR switch to OUT, the

0. Place the ES615 or other equal-

3.

This assures that the input sensitiv-

15

ROLLOFF position

rolloff. The FLAT

warmup time.

dB ATTENUATOR switch

HI/

can cause power amplifier overloading and possible readjustment of speaker positions, or physical
speaker damage. Figure 5 shows a typical room changes such as the addition or removal of

response prior to equalization, with initial peaks absorbing material. It is important to note that major
occurring around
adjustments for this condition would be a reduction main listening area should not be made.

of the 125 and
these HI LEDs off. (For clarity, the high-frequency

rolloff is not depicted.)

TYPICAL ROOM RESPONSE

BEFORE EQUALIZATION

5.

Observe which HI LEDs have turned on and slowly

adjust the corresponding equalizer frequency filter

control in the "cut" direction until those LEDs just

turn off. Do not adjust the equalization control any

more than necessary to turn the LED off. Note that
in the process of reducing an equalizer control to
turn a HI LED off, the LO LEDs of one or both ad­jacent octave bands may turn on as a result of
normal filter interaction. Simply slightly readjust the
equalizer controls of the affected octave bands until
the LO LEDs again go out.

6. When both HI and LO LEDs are off, slowly reduce
the

HI/LO ENVELOPE control. Some HI LEDs will

begin to turn on, indicating relative peaks in re­sponse. Repeat step
Figure 6 shows the room response of Figure 5 after
initial equalization of the low frequencies. Note that
as the

the 500,

velope and these HI LEDs have turned on. Equalizer
adjustments would now be made to turn these LEDs
off.

Continue reducing the

eliminating peaks that appear. When a satisfactory

envelope has been obtained, move the equalization
microphone to other positions in the listening area
and note which HI or LO LEDs turn on. It may be
necessary to readjust the INPUT LEVEL control for

a minimum number of lit LEDs due to level differ­ences between locations. The

control setting may be increased to determine the
extent of response changes at the new location. At
this point, corrective action may be taken by either
slight adjustment of the equalizer frequency filters,

HIILO ENVELOPE control has been reduced,

1K and

125.

and 250 Hz. Initial equalizer changes to the equalizer settings obtained in the

250

Hz filter control settings to turn

FIGURE

4K

5

5

to eliminate these peaks.

peaks are now outside the en-

HI/LO ENVELOPE control and

HI/LO ENVELOPE

TYPICAL ROOM RESPONSE AFTER

LOW-FREQUENCY EQUALIZATION

FIGURE 6

7.

The sound system has now been equalized to pro­vide a smooth, controlled-rolloff frequency response,
free of major irregularities. Figure
room response after equalization, with the
ENVELOPE control at 2 (&I) dB. Note that no at­tempt has been made to "boost" the frequencies
beyond the bandwidth limits of the system.

At this point, feed the system with program-type
material (live or recorded) and make slight adjust-

ments to brighten or otherwise modify equalized
response using the system's tone controls.

TYPICAL ROOM RESPONSE

AFTER EQUALIZATION

FIGURE

Stage

former with an intelligible source of the sound required
for the performance.

Monitor

Equalization of stage monitor systems is performed

principally to eliminate feedback while providing the per-

1.

Connect the performer's microphone to the sound
system and adjust the levels to a point just below
feedback. Place the

crophone at the performer's ear level (facing forward

Systems

7

ES615 or other equalization mi-

7

shows the final

sound-

HI/LO

toward the monitor speaker), and connect the ES615
to the M615. Make certain someone is standing in
the performer's position to simulate performance

conditions.

2. It is advisable to roll off the low-frequency response
of the system by reducing the settings of the equal­izer frequency controls below 250 Hz. Attenuation of

frequencies in this range reduces low-frequency

noise pickup without affecting intelligibility.
Set the ABOVE 1 kHz switch to FLAT. This position

3.

is used for near-field conditions such as are en-

countered in stage monitor setups.

4.

Set the 15 dB ATTENUATOR switch to OUT, and HI/
LO ENVELOPE control to 12, and the PlNK NOISE
LEVEL control to
and allow one minute

turn the INPUT LEVEL control slowly up until the

first LO LED goes out or flickers. Note the INPUT

LEVEL control setting and reduce it by approximate-

3.

This assures that the input sensitivity is low

ly
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

4

or less, the 15 dB ATTENUATOR switch should be
set to IN and the process repeated. If the INPUT
OVERLOAD LED comes on during adjustment 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 in-

terfere with measurements and adjustments.

5. 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 spec-

trum indicate the bandwidth limits of the monitor

system. It is important to note that any attempts to
equalize at these bandwidth limits must be done

judiciously. Excessive boosting of these frequencies

can reduce intelligibility, and cause power amplifier
overloading and possible speaker damage.

6. Observe which LEDs have turned on and slowly ad­just the corresponding equalizer frequency filter
control in the "cut" direction until those LEDs just
turn off. Do not adjust the equalization control any

more than necessary to turn the LED off. Note that

the process of reducing an equalizer control to

in

HI

turn a

jacent octave bands may turn on as a result of

normal filter interaction. Simply slightly readjust the
equalizer controls of the affected octave bands until

the LO LEDs again go out.

7.

When both HI and LO LEDs are off, slowly reduce
the

begin to turn on, indicating relative peaks in re­sponse. Repeat step 6 to eliminate these peaks.

Continue reducing the
eliminating peaks that appear. When a satisfactory
envelope has been obtained, set the audio console
or mixer volume control for the performer's micro-

phone to a stable point slightly below the feedback
threshold. Gradually increase the monitor master

LED off, the LO LEDs of one or both ad-

HI/LO ENVELOPE control. Some HI LEDs will

0. Turn on all units in the system
warmup time. Starting at 0,

HI/LO ENVELOPE control and

gain control until an obvious increase in amplitude

in a particular frequency band is noted on the
This is the onset of feedback; adjust the appropriate
equalizer filter control to reduce the system response

in this area. Continue this process until satisfactory
gain before feedback and the desired response is
achieved. Make a voice test of each performer mi­crophone position to determine if an adequate feed­back threshold is attainable. Final adjustment of the
equalizer and/or individual channel tone controls
(if available) may then be made to improve quality

or intelligibility of the sound presented to the per­formers.

Home Entertainment Systems

Home entertainment (hi-fi) systems incorporating an
equalizer may be properly equalized using the M615 as
follows.

1. Set all controls on the hi-fi system to flat. Set the
volume control to maximum or, if a loudness com-

pensation switch is provided, turn the loudness

switch off. Place the

sired listening area, at approximately listening height

and facing the normal listening direction (front center).

2. Set the ABOVE 1 kHz switch as required. Although
the FLAT position is applicable to most home enter-

tainment system (near-field) setups, in large or "live"

rooms a far- or reverberant-field condition may

sometimes be encountered in which the

position could be used. This position provides a

3

smooth
to be most pleasing to audiences in larger listening
areas.

3.

Connect the pink noise generator output to the re-

ceiver or amplifier auxiliary input of one channel.

4.

Set the 15 dB ATTENUATOR switch to OUT, the

HI/LO ENVELOPE control to 12, and the PlNK NOISE
LEVEL control to

and allow one minute

turn the INPUT LEVEL control slowly up until the

first LO LED goes out or flickers. Note the INPUT

LEVEL control setting and reduce it by approximate­ly
enough to prevent the ambient noise level from af-

fecting equalization results. With the MIC input in

use, if the initial INPUT LEVEL control setting is

4

or less, the 15 dB ATTENUATOR switch should be

set to IN and the process repeated. If the INPUT

OVERLOAD LED comes on during adjustment of the

INPUT LEVEL control, the control setting is too high
and must be reduced for proper LED indications.
IMPORTANT: The equalization procedure requires
a stable ambient noise level. Extraneous noise such
as TV, air conditioners, or loud conversation will in­terfere with measurements and adjustments.

5. 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 spec-

trum indicate the bandwidth limits of the system. It

is important to note that any attempts to equalize at

these bandwidth limits must be done judiciously. Ex-

cessive boosting of these frequencies can cause
amplifier overloading and possible speaker damage.

dB per octave rolloff which has been found

3.

This assures that the input sensitivity is low

ES615 microphone in the de-

0. Turn on all units in the system
warmup time. Starting at

M615.

ROLLOFF

0,

CAUTION:

Excessively high signal levels for long

periods of time may damage many hi-fi speakers.

Equalization analysis should be performed at as low

a signal level as possible.

observe which HI LEDs have turned on and slowly
adjust the corresponding equalizer frequency filter
control in the "cut" direction until those LEDs just
turn off. Do not adjust the equalization control any

more than necessary to turn the LED off. Note that in
the process of reducing an equalizer control to
turn a HI LED off, the LO LEDs of one or both ad­jacent octave bands may turn on as a result of nor­mal filter interaction. Simply slightly readjust the
eaualizer controls of the affected octave bands until
thk LO LEDs again go out.

7.

When both HI and LO LEDs are off, slowly reduce

HI/LO ENVELOPE control. Some HI LEDs will

the
begin to turn on, indicating relative peaks in re­sponse. Repeat step 6 to eliminate these peaks.
Continue reducing the

HIILO ENVELOPE control
and eliminating peaks that appear until a satisfac­tory envelope has been obtained.

8. Connect the pink noise generator output to the re­ceiver or amplifier auxiliary input of the other channel

and repeat steps

9.

Once equalization of the hi-fi system has been

4

through 7 for the other channel.

achieved, the system equalization or tone controls
can be adjusted slightly to satisfy personal prefer­ence.

SERVICING

WARNING

Voltages in this equipment are hazardous to life.
Refer servicing to qualified service personnel.

Disassembly

Disconnect ac power. The M615 cover may be removed
by removing one screw at the top center of the front and
rear panels and one screw at each side of the chassis

bottom.

Printed circuit assembly
connecting connectors J7 and J8 from the board (see

Parts Placement diagram), and removing the board from
the nylon fasteners by squeezing the upper protruding
tabs on the circuit board side inward and sliding the
baard outward and off the fasteners.

Printed circuit assembly A9 may be removed by first
removing two screws on the bottom of the chassis which
secure the metal shield associated with Assembly

Lift the shield and circuit assembly upward and out of

the chassis. Remove the circuit assembly from the shield

by squeezing the upper protruding tabs of the nylon

fasteners on the circuit board side, and sliding the board

outward and off the fasteners.

The multiple printed circuit assembly consisting of A2
through A8 may be removed by first removing four
screws on the bottom of the chassis. Carefully lift the
assembly upward and out of the chassis. As the as-

sembly becomes clear of the chassis, remove connectors
J9, J10, J11 and J901. Remove the top support bracket
and metal bracket from the LED end of the boards.

A1 may be removed by dis-

A9.

Printed circuit assemblies

A3

through

A8

may now be re­moved from motherboard A2 by pulling outward. Always
pull boards and connectors straight to avoid bending
male pins.

Filter/Rectifier/Comparator

When replacing one of the

Replacement

FiIter/Rectifier/Comparator
printed circuit assemblies (A3 through A7), the filter cen­ter frequency (TUNE: RX03, RX15)* and rectifier (LEVEL:
RXOI, RX16)* potentiometers must be calibrated as fol­lows. Note that TUNE and LEVEL potentiometers for two
filter frequencies are present on each assembly. The
TUNE adjustment for each frequency must be performed
before the LEVEL adjustment.

Calibration: Filter Center Frequency

To calibrate the filter center frequency, set INPUT LEV-

EL control to

10 and apply a -40 dBV (10 mV) sinusoidal
input signal at the desired frequency to the analyzer aux
input. Connect the signal from test point TP201 to the
horizontal input of an oscilloscope. Connect the signal
from the filter test point

(TPX02) to the vertical input of
the oscilloscope. (The signals must be obtained using a
probe with a

1

k resistor in series with and as close to
the tip of the probe as possible.) Adjust the oscilloscope
to produce a circular or elliptical Lissajous pattern.

Ad-

just the TUNE potentiometer (RX03) until a straight line

denoting 0" phase shift is observed on the oscilloscope.
Repeat this procedure for the other filter frequency on
the assembly using test point

TPX03 and TUNE poten-

tiometer RX15.
Calibration: Rectifier Level

If the

Filter/Rectifier/Comparator

assembly has been
replaced, make certain the TUNE potentiometers have
been adjusted prior to LEVEL potentiometer adjustment.

If, during the Analyzer Checkout procedure, one or more
LEDs remain on, the LEVEL potentiometer for that fre­quency may be readjusted slightly as follows.

To calibrate the rectifier level, set the ABOVE 1 kHz
switch to the FLAT position and apply the AUX LEVEL
output of the pink noise generator to the analyzer AUX
INPUT. Set the

PINK NOISE LEVEL control to 5 and care­fully adjust the INPUT LEVEL control until all 10 LO LEDs
blink randomly on and off except for the frequencies re­quiring calibration. Adjust the LEVEL potentiometer

(RXOI
or RX16) until the associated LO LED blinks randomly.
Repeat this procedure for any other frequency requiring
adjustment.

Printed Circuit Assembly Connectors

Printed circuit assembly connectors J7 through J11,

J201 through J206, and J901 use the AMP Incorporated

Commercial Interconnect System. To replace a lead and
its associated connector contact, proceed as follows.
Using a scribe or other pointed instrument, depress the
contact through the slots at both sides of the connector

housing. This will free the contact and allow it to be re-

moved from the rear of the connector housing. Trim a

YE

new lead so that
trimmed lead in a new contact (Shure Part No.

inch of wire appears. Insert the

56A225).
Crimp the wire and the lead insulation to the contact.
Solder the wire to the crimped connection. lnsert the new
contact (with attached lead) in the connector housing,
pushing firmly to lock the contact.

*

For reference designat~ons containing "X" (RX03, TPXOP, etc.), substitute

the appropriate board number (3 through

7)

for the board being adjusted.

MODEL M615 REPLACEMENT PARTS LIST

Reference

Designation

Replacement

No.

Kit

*

Replacement Kit Consists

aty-.

I

Printed Circuit
Assembly, Preamplifier

Printed Circuit
Assembly, Overload Detector
and Mother Board

Printed Circuit
Assembly, 32

Printed Circuit
Assembly, 125

Printed Circuit
Assembly, 500

Printed Circuit
Assembly,

Printed Circuit
Assembly,

Printed Circuit
Assembly, Noise Generator

Printed Circuit

Assembly, Power Supply

Diode, Silicon, Computer,

75v

Description

2

8

&

63

&

&

&

4

&

16 kHz

Of:

Hz

250

1,000

kHz

1
1

I

Hz

Hz

I

Commercial

Alternate

None

None

None

None

None

None

None

None

None

56A225

Diode, Light-Emitting

Silicon Rectifier,

V2

A

Zener Diode,

Fuse,

Slo-Blo %A, 250V

(M615-2E only)

Connector, Female 3-Pin
Audio

Connector, Phono Jack,
Grounded Shell

Connector, Phone Jack,
Shorting

Connector, Male, 3-Pin
Audio

Connector, Phone Jack,
Shorting

Connector, Phono Jack,
Grounded Shell

1

Connector Contact (only)

100V,

SilLcon, 27V

1

Monsanto MV5075C

I

Motorola 1 N4002

Motorola 1 N4750A
Littelfuse

31 5.125
Switchcraft

D3F
Switchcraft

351 2A
Switchcraft

11

2A

Switchcraft
D3M

Switchcraft
11 1

Switchcraft
3511A

None

Ac

95A689
90A1715A

*

Parts listed as RKC Kits should be ordered by that kit number. Any orders received for piece parts where RKC Kit number
shown will be shipped in

RKC

quantities.

Receptacle

Knob, INPUT LEVEL

9

(M615-2E

only)

None
None

is

MODEL M615 REPLACEMENT PARTS

LIST

(Continued)

Reference

Designation

M

P2
M P3
P Ll

Q101, Q103,
Q105, (2802­803, Q805-807

Q102, Q104,
Q106, Q801,
Q804, Q808

Q107
Q108
Q809

(2901

R4/ R6

R5

R301, R316,
R401, R416,
R501, R516,
R601, R616,
R701, R716

R303, R315,
R403, R415,
R503, R515,
R603, R615,
R703, R715

S1-5

S6

S6

S7

TI-2

T3
T3

U201, U302

U301

W1

W1

Replacement

Kit No.

*

-

-

RKC45

R KC89

RKC65
RKC66

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Qty.

-

-

1

4

-

1
1

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Part No.

65B931A
90E1662

80A79

86A350

86A348

86A334
86A335
86A373

86A374

46A064

46A065

46A062

468062

55B83

5591 03

55A126

55A116

90F2150

51A269
51 A274

86A806

86A805

95A632

90A1888

Replacement

Knob, PINK NOISE LEVEL

Knob,

Lamp, Indicator, Neon

Transistor, Silicon, NPN

Transistor, Silicon, PNP

Transistor, Silicon, NPN
Transistor, Silicon, PNP

Transistor, Field

Effect, N-Channel
Transistor, Silicon, NPN

Potentiometer, Dual,
Audio Taper,

Potentiometer, Modified
Log Taper, 5k

Trimmer Potentiometer,

2.5k

Trimmer Potentiometer,

30k

Switch, Slide, DPDT

Switch, Slide, DPDT
(M615)

Switch, Slide, DPDT
(M615-2E)

Switch, Slide, DPDT

(M615-2E only)

Transformer
Assembly

Transformer, Power
Transformer, Power

(M615-2E)
Integrated Circuit, Quad

Comparator

Integrated Circuit, Quad

Operational Amplifier

Cable and Plug Assembly, Ac
(M615)

Cable and Plug Assembly, Ac
(M615-2E)

Kit Consists

Description

HI/LO ENVELOPE

Of:

50k/50k

&

Shield

(M615)

Commercial

Alternate

None
None
Leecraft

36N1311-6

Motorola
2N5210

Motorola
2N5087

TI TIS92
TI TIS93
Siliconix or

lntersil E230
Motorola

2N4922

None

None

V101 S252B

CTS

CTS V1 OlS253B

Switchcraft

46206LR

Switchcraft

46206LR

Marquardt

4021.01 01
Marquardt

4021.0201
None

None

None

Raytheon
LM339DB, RCA
CA339G, TI
SN72339N

Raytheon
RC3403ADB

None

None

*

Parts listed as RKC
shown will be

shipped in RKC quantities.

Kits should be

ordered

by

that

k~t

number.

Any orders received

10

for

piece parts

where RKC Kit number

is

PRINTED CIRCUIT ASSEMBLY

A1

2430-1

1629-1

PRINTED CIRCUIT ASSEMBLY A2

PRINTED CIRCUIT ASSEMBLIES A3-A7

2432-1 /631-2

NOTCH

NOTCH

PRINTED CIRCUIT ASSEMBLY A8

2667-4/812-2

PRINTED CIRCUIT ASSEMBLY A9

FURNISHED ACCESSORIES

Tilt Bracket 47A100
Carrying Case .65A1130B
Test/lnterconnecting Cable .95A844

M615 parts readily available through local electronics
parts distributors are not shown on the accompanying
parts list. Values are shown on the circuit diagram. Com­mercial parts not readily available and unique parts are
shown on the parts list and may be ordered directly from

the factory. The commercial alternates shown on the
parts list are not necessarily equivalent, but may be used
in the event that direct factory replacements are not im-

mediately available. To maintain the highest possible per-

formance and reliability, Shure factory replacement parts
should be used.

In addition to the parts list and circuit diagram, a parts

placement diagram and printed wiring assembly layouts
are provided to assist in parts location and identification.

This Shure product is guaranteed in normal use to be

free from electrical and mechanical defects for a period
of one year from date of purchase. Please retain proof
of purchase date. This guarantee includes all parts and

labor. This guarantee is in lieu of any and all other guar-

antees or warranties, express or implied, and there
shall be no recovery for any consequential or incidental

damages.

Carefully repack the unit and return it prepaid to:

If outside the United States, return the unit to your dealer

or Authorized Shure Service Center for repair. The unit
will be returned to you prepaid.

.................................

...........................

..................

REPLACEMENT PARTS

GUARANTEE

SHIPPING INSTRUCTIONS

Shure Brothers Incorporated
Attention: Service Department
1501 West Shure Drive
Arlington Heights, Illinois 60004

PRINTED

PREAMPLlFl

CIRCUIT

ER

r--

ASSEMBLY

BOARD

--

A1

--7

I

OVER

CIRCUIT

LORD

DETECTOR

ASSEMBLYAZ

AND

MOTHER

BObRD

I

(PRINTEDNRcuIT

I

I

FILTER, RECTIFIER

I

i

ASSEMBLIE~A~-A~

AND

COMPARATOR

TYP.

(PRINTED

BOARDS

CIRCUIT

ASSEMBLY

A3

SHOWN)

--1

ALL CAPACITORS EXCEPT CXOI

*REFERENCE

ARE
AND

NOTES:

I. ALL ClPAClTORS IN

2.

3.

DESIGNATIONS

SHOWN

FOR

r

;HRzi;

ASSEMBLY

X"

VOLTS.

REPLACE

OTHERWldE SHOWN. ELECTROLYTIC CAPACITORS SHOWN

IN

,AF

ALL RESISTORS 1/4W, 10%

SHOWN.

THE FOLLOWING SVMBOLS DENOTES

d-7

WITH

#

CX07

AND ALL RESISTORS

FOR

RESISTORS

A3.

FOR

PC

ASSEMBLY

pF

AND 50V OR MORE UNLES5

P.C.

GROUND

OTHER

UNLESS

BOARD

AND

NO.

OTHERWISE

(3-7).

CAPACITOR5

ASSEMBLIES

IN

TABLE

WITH

A4-A7,

r)RE

57.

ASTERISKS

SEE

TABLE

MODEL

M615

CIRCUIT DIAGRAM

I

PRINTED

I

PINK

I

CIRCUIT

NOISE

-

GLNERATOR

r4SSEMBLY

-

-

A6

BOARD

-

- -

-

--

-

-

-

-

--

1

I

I

120

50160

5

VAC

HER

WATTS

72

PRINTED CIRCUIT

POWER

SUPPLY

r--

ASSEMBLY

BOARD

A9

--7

I

I

(MIINSI
POWER

YO-BLD

POWER

BLU

BU(/RED

M615-2E

POWER

SUPPLY

MODEL M615 CIRCUIT DIAGRAM