Shure SR-107 Service manual

222 HARTREY AVE.. EVANSTON. IL. 60204 U.S.A.

AREA CODE 312/866.2200 CABLE: SHUREMICRO

TWX:

910-231-0048 TELEX: 72.4381

OPERATION AND SERVICE MANUAL

MODEL SR107

AUDIO EQUALIZER

The Shure SR107 Audio Equalizer is a compact, versatile unit designed to provide adjustment of tonal balance on an octave-by-octave basis across the audio frequency range. The for the purposes of feedback control in live performances, playback equalization (correcting for equipment response and/or room acoustics in prerecorded performances), and improvement in the sound quality of live performances. Equipment response correction includes the elimination of such problems as transducer incompatibility, overload at low frequencies (rumble), tape hiss and disc surface

noise. The device, designed primarily for installation between the audio console or mixer and the power amplifier of the sound system.

SR107 is used in sound system applications

SR107 is a balanced input and output line level

DESCRIPTION

The SR107 has ten octave band, minimum phase, com-

bining type filters centered on from 31 Hz to 16 kHz. Each filter is adjustable for ap-

proximately 15 dB of boost or attenuation. The equalized output is adjustable over a

gain of up to 20 dB may be introduced to compensate for

low input signals. A peak-responding overload emitting diode (LED) is provided on the front panel. The SR107 contains both professional three-pin and phone jack input and output connectors, and a phone jack auxiliary output.

The

SR107 is designed for maximum simplicity of operation and maintenance. All components are of the highest quality and are operated well within their respective ratings to assure maximum reliability under normal use conditions.

The

SR107 and SR107-2E are identical except that the

SR107 operates from 108-132 Vac, 50/60 Hz and the SR107-2E operates from either 105-125 or 210-250 Vac, 50/60 Hz (switch-selectable). The SR107-2E is supplied with a detachable ac line cord (without power plug). The SR107 (only) is listed by Underwriters' Laboratories, Inc., and is listed by Canadian Standards Association as

certified.

All

SR107 units are supplied with four rack-mounting screws for mounting in standard 19-inch (483 mm) audio equipment racks or in optional Shure

Carrying Cases. An optional protective cover, Shure Model A107A, is also available.

International

Organization

for

Standardization

ISO? preferred frequencies

215 dB range, and overall

light-

A30A or A105A

SPECIFICATIONS

Equipment Type Voltage Gain:

GAlN Control at UNITY

GAlN Control at +20 dB

LEVEL Control

Frequency Response Signal to Noise Ratio

(20 Hz-20 kHz) .Typically 99 dB at maximum out-

Output Noise,

Maximum (300 HZ-20 at LINE OUTPUT) -84 dBV (63 pV)

Output Hum and Noise,

Maximum (20 HZ-20

at LINE OUTPUT)

lnput Common Mode

Rejection

Clipping Level

(30 HZ-20

Input

'See

Page

.......

kHz

.........

kHz):

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

.....

.All transistor inductorless active

equalizer

dB LINE INPUT to LINE OUTPUT

-27

dB LlNE INPUT to AUX

OUTPUT

-50 dB LlNE INPUT to MIC OUTPUT

.......

+20 dB LINE INPUT to LINE

OUTPUT

-7 dB LlNE INPUT PUT

-30 dB LlNE INPUT

OUTPUT

...

.Provides additional gain adjust-

ment of k15 dB over values given above, EQUALIZER IN

mode only.

.%2 dB from 30 Hz to 20 kHz,

EQUALIZER IN or BYPASS

.....

put with Filter Controls and LEVEL Control at zero and

GAlN Control at UNITY in

EQUALIZER IN mode.

...

69 dBV (0.50 mV), LEVEL Control at

-91

Switch in BYPASS

...

83 dBV (71 pV)

67 dBV (0.56 mV), LEVEL Control at +15, Filter Controls at

-15

-88

Switch in BYPASS

.90 dB minimum at 100 Hz

+18 dBm minimum (+15.8 dBV,

6.2V) GAlN Control at UNITY

-2

0.62V) GAlN Control at + 20dB

+15, Filter Controls at

dBV (28 pV), EQUALIZER

dBV (40 pV), EQUALIZER

dBm minimum (-4.2 dBV,

to AUX OUT-

to MIC

27Al089

1979,

(SF)

Shure

Brothers

Inc.

Printed

U.S.A.

FIGURE

Output

Overload Indicator Input Impedance

Output Impedance: mum

MIC OUTPUT LINE OUTPUT AUX OUTPUT

Distortion: Weight .3.5 kg

lntermodulation

Harmonic

Phase

Equalization Filters:

Center Frequencies

Characteristics

...........

.......

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

+18 dBm minimum (+15.8 dBV,

-10.2

-34.2

....

Illuminates 3 dB 21.5 dB before

.....

.70 kilohms actual, balanced Hz; 6 watts maximum

....

...

.I15 ohms actual, balanced (for

...

.630 ohms actual, unbalanced Storage -29°C to 71°C (-2O0Fto 160°F)

.0.25% max. at 12.2 dBm (3.2V)

.I% max. total harmonic distor-

Pin 3 and tip contacts of

.....

.Octave spaced from 31 Hz to 16

.15.5 f 2 dB boost or attenuation

6.5

6.2V) at LINE OUTPUT dBV minimum (0.31V) at

AUX OUTPUT Filters are minimum phase,

dBV minimum (19.5 mV)

at MIC OUTPUT ly isolated. output clipping occurs

bridging (for use with line level source, 10 kilohms or less.)

ohm actual, balanced (for use with 25- to 600-ohm inputs)

use with 600-ohm lines)

(for use with auxiliary circuits

of 600 ohms or more

ance)

(LINE OUTPUT) with a 60 Hz Installation and 7.0 kHz input at a

tion at 12.2 OUTPUT), 30 Hz-20 kHz with

Filter Controls at +15, GAIN Certifications .Listed by Underwriters' LaboraControl +20 dB and LEVEL tories, Inc.; listed by Canadian Control at +15

INPUT Connectors are in

phase OUTPUT and tip contacts of

LlNE and AUX OUTPUT Con-

nectors

kHz. Accurate to within

of labeled value

at center frequency

t2 dB at maximum boost or attenuation at one-half octave above or below center frequency

dBm (3.2V) (LINE

with

4:l ratio

MIC/L'NE

SR107 FRONT PANEL

imped-

LINE

t10%

Operating Voltage

and Power

Accessory Power Temperature

Operating

.........

SR107: 120 Vac t lo%, 50/60 SR107-2E: 105-125 or 210-250

...a

-31 Vdc open circuit, 27 Vdc at

........

Typical filter frequency response characteristics are shown in Figures 5A and

combining type and electrical-

Vac, 50/60 Hz; 6 watts maxi-

-7°C to 57°C (20°F to 135°F)

..........

Dimensions

.........

.44.4 mm height x 483 mm width

x 218 mm depth (1-314 in. x 19 in. x 8-9/16 in.) (Figure 3)

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

Finish

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

..........

Matte black

.Equipped for standard 19 in.

(483 mm) audio rack mount-

ing; may be operated in optional Case (with other equipment)

........

Standards Association as certified (SR107 only)

Measurement conditions unless otherwise specified: Operating voltage 60

(SR107). 230V 60 tion (~~107-2i). LI~E INPUT 7 volt at 1 OUTPUT nated in control at zero;

and

A'UX

150 ohms;

OPERATING INSTRUCTIONS

TO reduce the risk of fire or electric shock, do not

expose this appliance to rain or extreme moisture.

Functional Description (Refer to Figures 1 and 2)

31 Hz to 16 kHz Filter Controls- Provide _+I5 dB

level adjustment at center frequency of each of ten

octave band filters.

with VOLTAGE SELECTOR Switch in 220V posi-

OUTPUT terminated in 600

GAlN Control at UNITY:

EQUALIZER

Switch set to

WARNING

mA, maximum

Ib, 12 oz)

A30A or A105A Carrying

kHz

through 600 ohms. LlNE

ohms, MIC

Filter Controls and LEVEL

IN.

OUTPUT'

58.

I~OV,

termi-

SO/M

WLlTS

SR107-2E

ONLY

FIGURE

SR107 REAR PANEL

EQUALIZER IN/BYPASS Slide Switch - Disables

filters and LEVEL Control in BYPASS position and

returns gain of Equalizer (LINE INPUT to LlNE OUT-

PUT) to value determined by rear-panel GAlN Control. LEVEL Control -Operative only in EQUALIZER IN mode. Provides adjustment of Equalizer output level

+I5 dB to compensate for changes in gain re-

of sulting from Filter adjustments.

OVERLOAD LED dication when peaks in output signal approach actual clipping level of output amplifier. POWER unit. Power-On lndicator Lamp being applied to unit. 30 VDC Accessory Power Jacks open circuit (27 Vdc at 10 equipment. AUX OUTPUT Phone Jack- Provides unbalanced low-impedance output for connection to audio console or amplifier-mixer link input. LlNE OUTPUT Phone Jack unbalanced line level output to power amplifier. MIC/LINE Slide Switch - Connects line level or low-impedance microphone level signal to 3-pin OUTPUT Connector. OUTPUT 3-Pin Male Connector anced output at either line level or low-impedance microphone level as selected by May be unbalanced externally. GAlN Control

from UNITY to +20 dB to accommodate various

input and output requirements. Operates in both EQUALIZER IN and BYPASS modes. LlNE INPUT 3-Pin Female Connector balanced bridging, high-impedance input connec-

tion from audio console or mixer-preamplifier. May be unbalanced externally.

LlNE INPUT Phone Jack unbalanced bridging, high-impedance input con-

nection from audio console or mixer-preamplifier. Ac Grounded Line Cord -Connects unit to ac

power source

VOLTAGE SELECTOR Slide Switch

lection of 105-125 or 210-250

tion AC (MAINS) POWER 3-Pin Connector unit to ac (mains) power source via supplied line cord

General Operating Instructions

The

SR107 Audio Equalizer is primarily intended for connection in a sound system between the output of an audio console or mixer-preamplifier and the input to the power level input to the Equalizer and utilizes its line level output to drive the power amplifier. In a system using a limiter or compressor between the mixer and power amplifier, the limiter or compressor and power amplifier to achieve best signal-to-noise performance.

Out and Link In jacks of a console or mixer equipped with these jacks. The operation at the lower signal levels characteristic of this location and is equipped with an auxiliary output of appropriate level for the Link In connection. In the follow-

amplifier(s). A typical installation provides a line

An alternate location for the

ON/OFF Switch - Controls ac power to

(SR107-2E only).

SR107 should be connected between the

Provides peak signal visual in-

Indicates ac power is

Provide 31 Vdc

mA max.) for accessory

Provides balanced or

Provides bal-

MIC/LINE switch.

Provides gain adjustment range

Provides

Provides balanced or

(SR107 only).

SR107 is between the Link

SR107 can provide satisfactory

Vac 50/60

Permits se-

Connects

opera-

ing general operating procedure, variations in connec-

tion for Link operation are indicated where applicable.

1. Using hardware provided, install Equalizer securely in standard 19 in. (483 mm) rack or optional making electrical connections.

2. Connect audio console or mixer-preamplifier line level output to or phone jack (13. 14). (For Link use, connect link

output of console or mixer to either

INPUT Connector.)

3. Connect OUTPUT Connector (9, 11) to power amplifier input. If 3-pin connector is used, place in LlNE position. (For Link use, connect

OUTPUT (8) to link input of console or mixer.)

4. Place all Filter Controls (1) and LEVEL Control (3)

in zero position. Move EQUALIZER Switch (2) to BYPASS. Set GAlN Control (12) to

UNITY. (For Link use, set GAlN Control to

SR107: Connect ac line cord (15) to grounded 108-

132V, 50/60 Hz ac source. SR107-2E: Move VOLTAGE SELECTOR Switch (16) to 115V or 220V position as appropriate. Attach suitable insert chassis connector into AC (MAINS) POWER Connector (17). Connect ac line cord to grounded 105-125V or 210-250V, 50/60 Hz ac source.

6. Position speakers in desired operating locations

and aim for uniform coverage of audience area.

Position microphones (if used) as required by per-

formance or application involved. Basic precautions

relative to microphone and speaker locations

should be observed to reduce feedback potential. Set all tone controls in audio console or mixer to their zero or flat position. Set output phase switch (if any) to

7. Apply power to sound system. Place POWER ON/

OFF Switch (5) in ON position. Power-On lndicator Lamp (6) will go on, indicating operation of unit.

8. Using voice, program material or tone generator

(such as Shure Model system, increase console or mixer output level until SR107 OVERLOAD lndicator (4) flickers. Increase volume control on power amplifier until amplifier clipping distortion is evident. OVERLOAD lndicator now indicates onset of clipping in both power amplifier. NOTE: This step does not apply to Link operation.

9. Using voice or program material as source, adjust

console or mixer output to provide desired sound

level in room. (For Link use, adjust individual channel volume controls for desired mix and set to level

that will cause only occasional flickering of OVERLOAD lndicator on peaks of high level program material.) If microphones are used as sound

source, satisfactory sound level may not be possible

due to feedback. In this case, set volume to stable

point just below feedback level.

10. Operation of flickers slightly, on only the loudest program peaks, is recommended. This will maximize signal-to-noise ratio, but will generally not result in audible distortion since lndicator threshold is 3 dB below actual clipping level. Operating with OVERLOAD lndicator always off may result in less than optimum signal-to-noise per-

formance.

A30A or A105A Carrying Case prior to

SR107 LlNE INPUT 3-pin connector

SR107 LlNE OUTPUT phone jack or 3-pin

&pin male power plug to ac line cord and

0" or in-phase condition.

A15TG) for input to sound

SR107 such that OVERLOAD lndicator

SR107 Audio

SR107 LlNE

MIC/LINE Switch

SR107 AUX

IN/BYPASS

$20 dB.)

SR107 and

SR107

If OVERLOAD Indicator is flashing brightly or on constantly, operating level is too high and will cause distortion, and may result in less than full power output from the sound system.

11. Set EQUALIZER Switch to IN position. Adjust Filter Controls for particular equalization objective. See

procedures for feedback control, and playback and live performance equalization in following sections.

While adjusting Equalizer Filter Controls, use

LEVEL Control to maintain desired volume in room. Do not attempt equalization beyond bandwidth limits of sound system. For best results, keep

number of Filter Controls used to a minimum, and adjust each control no more than required.

12. After equalization, perform listening check of audience area to be sure that sound quality is satisfactory throughout room.

Mounting and Ventilation

The SR107 Audio Equalizer is designed for rack-mount-

ing in a 483 mm (standard 19 in.) audio equipment rack and is supplied with the necessary mounting hardware (see Figure 3).

SR107 may also be operated while mounted in a

The

Shure

A30A or A105A Carrying Case. The A30A has a

panel height capacity of 88.9 mm

(3% in.) for two SR107s or one SR107 and one other unit of 44.4 mm (1% in.) height. The

A105A has a panel height of 178 mm (7 in.)

and will accommodate up to four units with panel heights

equal to that of the

SR107.

No special precautions are required for ventilation. The

SR107 may be operated over a temperature range of - 7"

to 57°C (20" to 135°F) in continuous duty without

derating.

Power Supply

The SR107 is furnished with a three-conductor power cable and three-prong grounded plug (15). Connect the SR107 to an outlet which supplies 108 to 132 volts ac, 50/60

power. The maximum power consumption at 120 volts under normal operating conditions is 6 watts (0.05 amperes at 120 volts).

If extension cords are re-

quired, a high-quality, 18 gauge or larger cord should

be used.

18-9/16 IN]

197

mm'

483

443

mrn

IN]-

rnm

117

7/16

17-314 IN)

"NOT INCLUDING CABLE/CONNECTOR CLEARIWCE DEPTH

FIGURE

OVERALL DIMENSIONS

The SR107-2E is furnished with a three-conductor detachable line cord without a power plug. Obtain a suitable 3-pin male power plug and attach it to the line cord. The plug should be installed by qualified service personnel. (Brown lead goes to "hot" or "live" terminal, blue lead to neutral terminal, and

green/yellow lead to ground or earth terminal.) Connect the equipment end of the line cord to the AC (MAINS) POWER Connector (17) on the

rear panel of the SR107-2E. Select the proper operating voltage (1 15V for 105-125V supply or 220V for 210-250V supply). Maximum power consumption at either operating voltage is 6 watts.

A POWER ON-OFF toggle switch (5) on the front panel

controls the application of ac power to the

red indicator lamp (6) indicates the power-on condition.

Functional Circuit Description

Input connections to the SR107 Audio Equalizer are

made through either a three-conductor (stereo type)

phone jack (14) or

three-pin female audio connector

(13) (see Figure 4). The connectors are wired in parallel to provide a balanced line level input with either connector. Inserting a two-conductor phone plug into the

phone jack will automatically unbalance the input. The

input signal is passed through a 6 dB transformer to an attenuator. The attenuator provides an

additional 11 to 26 dB of loss depending upon the setting of the LEVEL Control (3) described later.

I44

11-314 IN)

SR107 and a

stepdown input

FIGURE

SR107 BLOCK DIAGRAM

The next stage is an input amplifier which has a gain of 14 to 34 dB depending on the setting of the rear panel GAlN Control (12). The output of the amplifier is fed to

two cascaded differential amplifier stages which com-

prise the equalizer boost and cut circuitry. The individual active gyrator resonators for 31 Hz, 125 Hz, 500 Hz, 2 kHz

and 8 kHz are connected to the first of the differential amplifiers and provide control of these frequency bands.

The second amplifier is connected to the 63 Hz, 250 Hz,

1 kHz,

kHz, and 16 kHz active resonators for control of

the remaining five frequency bands. Each of the ten

octave-spaced filters is equipped with a front panel Filter Control (1) which may be adjusted for up to 15 dB boost

or cut relative to its zero or flat position (see Figure 5). This configuration of minimum-phase networks assures correct filter characteristic combinations, minimum am-

plitude ripple, and minimum phase shift.

The output of the second Equalizer differential ampli-

fier is fed to the EQUALIZER

IN/BYPASS Switch (2) which selects the input to the line output stage from either the equalizer amplifier in the IN position, or from the output of the input amplifier stage in the BYPASS

position.

(3)

The Equalizer LEVEL Control

of the Equalizer output level over the range of

provides adjustment

215 dB relative to its zero setting. Reduction in output is accomplished by attenuating the signal input to the input ampli-

fier. An increase in output is produced by changing the gain in the output amplifier. The LEVEL Control operates only when the EQUALIZER

INIBYPASS switch is set to

the IN position.

-10

-5

-10

20 100 KO0 IOPOO 20,000

FIGURE 5A-

FREWENCY IN HERTZ

Em FILTER AT

7.5 dB

BOOST

CUT

work at the output of the output amplifier. The AUX OUT-

PUT can be used to feed the link input of an audio

console or mixer so equipped.

An LED driver stage connected to the output amplifier

illuminates the front panel OVERLOAD LED (4) when the

audio signal approaches the output clipping level. The

OVERLOAD Indicator operates in both the EQUALIZER IN and BYPASS modes.

Input and Output Connections

Two LlNE INPUT Connectors are located on the rear

panel of the

SR107. A professional, three-pin female audio connector (13) provides a balanced connection from the audio console or mixer-preamplifier. A standard

1/4

in. three-conductor (stereo) phone jack (14) provides either a balanced or unbalanced input connection depending upon the phone plug (three-conductor or

two-

conductor) used.

The gain of the

the back panel

SR107 can be adjusted by means of

GAlN Control from UNITY to +20 dB in either the EQUALIZER IN or BYPASS modes. The 20 dB gain capability may be used in hi-fi or Link applications to maintain desired signal-to-noise performance through

SR107. It also allows the Equalizer to accommodate a

the variety of normal input and output levels while maintain-

ing an adequate operating signal-to-noise ratio.

Three output connectors are provided on the rear

panel. A professional three-pin male audio OUTPUT con-

nector provides

balanced low-impedance output at either microphone or line level depending upon the setting of the associated

LlNE OUTPUT Connector is a standard

MIC/LINE Slide Switch. The

1/4

in. three-

conductor (stereo) phone jack which provides a low-

impedance line level output that can be either balanced

or unbalanced. The AUX OUTPUT Connector is

1/4

ard

in. two-conductor phone jack providing a low-

stand-

impedance unbalanced output suitable for connection to

a hi-fi power amplifier or the link input of a mixer or audio console. The LINE, microphone level and AUX outputs are isolated and may be used simultaneously.

t20

+I5

t10

-5

-I0

-I5

-20 4

20 100 1000 IO.WO 20.000

681

FIGURE50 -EACH FILTER AT MAXIMUM BOOST OR

FREWENCV IN HERTZ

CUT

681

FIGURE 5.

TYPICAL FILTER CHARACTERISTICS

The output amplifier has a gain of 5 to 20 dB depend-

ing on the setting of the LEVEL Control, and is capable

of delivering

18 dBm through the output transformer to

a 600-ohm load at either of the balanced LlNE OUTPUT

(9,

Connectors nector may be switched from balanced line level to

11). The three-pin male OUTPUT Conlow-

impedance microphone level output (50 dB below line

level) by means of the

MIC/LINE Slide Switch (10) which

selects one of two secondary windings on the output

(8)

transformer. The AUX OUTPUT Phone Jack

is sup-

plied with an output signal that is 20 dB below that of the

LlNE OUTPUT. This is obtained from an attenuator net-

APPLICATIONS

The primary applications for the SR107 Audio Equal-

izer are as follows:

1. Feedback Control -Adjustment of sound system frequency response to provide maximum gain before feedback and improved sound quality in a variety of live performance situations. The

is equally adaptable to feedback control functions in either a house sound system or stage monitor (foldback) system.

2. Playback Equalization -Adjustment of audio play-

back system frequency response to compensate for any variations in electrical or acoustical response that may alter the natural sound of the recorded

material.

Live Performance Equalization - Adjustment of sound system frequency response to provide a tonal balance appropriate to the performance and to reduce the tendency for feedback.

The following sections present procedures and recom-

mendations for the use of the

SR107 in each of these

applications. Also included is a section discussing acous-

tic measurement instrumentation and its use with the

SR107.

Feedback Control

In many live performance sound reinforcement applica-

tions, feedback is often the limiting factor in achieving

SR107

satisfactory sound amplification and coverage. The SR107

Audio Equalizer provides the means for selective sup-

pression of those octave frequency bands in the audio

spectrum where feedback is likely to occur. These fre-

quency bands differ from one installation to another

depending upon the acoustics of the room, equipment

used, and speaker and microphone placement. The range

of control of both frequency and amplitude provided in

SR107 is sufficient to accomplish significant feedback

the suppression without noticeable loss of program material.

Proper adjustment of the Equalizer for feedback control is a matter of some experimentation; a general procedure is described here. These procedures for both house and stage monitor live performance sound reinforcement sys-

tems assume that the system speakers have a consistent

phase relationship and that all microphones used are also wired for consistent phase operation. If necessary, the phase of any balanced microphone line equipped with professional 3-pin connectors can be reversed using

a plug-in Shure Model

House System

1. Refer to General Operating Instructions for initial connections and setup.

Adjust individual mixer volume control for each performer's microphone to level slightly below feedback threshold. If console or mixer is equipped with output phase reversal switch, set to position giving highest gain without feedback. If necessary,

reduce setting of master volume control slightly and

return to feedback point for each switch position to evaluate switch effect. Operation of this switch will usually affect only low-frequency feedback.

3, Increase LEVEL setting until feedback squeal or

ringing is heard. If feedback appears to be pitched, one of five mid-to high-frequency Filter Controls eliminating feedback. Each Filter Control should be turned down (counterclockwise) and back to

position slowly to determine which is most effective. Control which stops feedback with the least rotation should be turned down only so far as necessary to eliminate feedback.

If feedback frequency happens to fall between

bands covered by two adjacent controls, it may be necessary to turn down both controls slightly to obtain desired feedback suppression. If feedback sound first noted in step 3 was

5. pitched, adjustment procedure should be started using low-frequency (31 to 500 Hz) Filter Controls.

6. Having eliminated first feedback condition, increase gain by clockwise rotation of LEVEL Control until feedback is again noted. Repeat steps 3, to eliminate new feedback condition. This may require adjustment of different Filter Control or a further decrease in control or controls previously turned down.

7. Repeat step system before feedback is sufficient for perform-

ance involved, (b) feedback becomes a combination

of sounds of various frequencies, or (c) any one

Filter Control has been turned all the way down

(-15). Adjust LEVEL Control to slightly below

point at which final feedback sound occurred.

Conduct voice test using each live microphone in

sequence. As each microphone is used, listen for

ringing. If ringing is noted, attempt to eliminate it by further decrease in appropriate Filter Control or slight decrease in LEVEL Control setting.

Al5PR Phase Reverser.

high-

thru 16 kHz) will be most effective in

"0"

low-

and 5

6 until either: (a) volume level of sound

9. Perform critical listening check in audience area

during talk test or live performance to determine if additional equalization adjustments are necessary to improve sound quality (boost of frequency bands

in the and intelligibility, etc.). Refer to Live Performance Equalization for additional information.

Stage Monitor System

In a stage monitor system the

tween the audio console monitor line output (line level)

or the line level output of a monitor mixer and the line

level input of the power amplifier used to drive the stage monitor loudspeakers. With this exception the initial setup of the stage monitor system is the same as that given in General Operating Instructions. The number, type and arrangement of microphones and speakers should be the

same as used in the performance.

If more than one performer's microphone is involved, select lead performer or center stage microphone for use in feedback equalization procedure. NOTE: During this procedure a person must stand in front of or hold the microphone being equalized in a manner similar to that of the performer.

Roll off low frequency response of system by adjusting 31 Hz Filter Control to 125 Hz to -5. This will reduce low frequency noise

pickup without affecting intelligibility.

3. Equalize stage monitor system following House System procedure, Steps

4. Conduct voice test for each of remaining micro-

phone positions in sequence using same channel gain setting as for first microphone. (This assumes that all microphones used have essentially the same sensitivity and response.) If feedback or ringing is encountered at any microphone location, try elim-

inating it by adjustment of nearest speaker position or microphone distance. While performing voice test, check intelligibility of sound from monitor speakers. Intelligibility can usually be improved by boosting frequencies in vided that the feedback threshold is not affected.

5. Check operation of stage monitor system with all performer microphones on (preferably with someone standing in front of or holding each microphone) to determine maximum gain settings before feedback for individual channel and master volume controls.

Operate stage monitor system and house system simultaneously at desired volume levels to verify satisfactory performance. If house system console or mixer is equipped with output phase reversal switch, operate switch and check for any improvement in gain before feedback in either house or stage monitor system.

Playback Equalization

SR107 Equalizer may be used to adjust the overall

The frequency response, octave by octave, of an audio playback system to compensate for any electrical or acoustical response deficiencies of the system and to provide more natural sound reproduction.

Assuming that good engineering practice has been followed in selecting and installing the loudspeakers for uniform sound coverage, it is necessary to subjectively evaluate the sound quality and to equalize for reasonable audio spectral balance. While no specific procedure can be offered for this type of equalization, the following recommendations should be helpful:

kHz to 4 kHz region to improve presence

SR107 is connected be-

15, 63 Hz to

through 7.

kHz to 4 kHz range, pro-

10,

+ 14 hidden pages