ARX Early ISC User Manual

Early ISC Control Unit/Speaker Processor

Information Sheet

IMPORTANT - PLEASE READ THIS FIRST

Apart from very early units with fixed power cables, these are dual voltage
units. It is essential that you check that the voltage on the fuseholder cover

below the AC connector on the rear of the chassis is set correctly before

connecting it to AC power.

THIS IS SET FOR 100 V AC TO

120 V AC OPERATION

To change, pull fuseholder out and rotate 180o, then push in again. Do not insert
power cable into unit until voltage has been correctly set. Do not plug power
cable into AC power until voltage has been correctly set

THIS IS SET FOR 220 V AC TO

240 V AC OPERATION

INTERNATIONAL LIMITED WARRANTY DISCLAIMER

All these products are out of warranty. The information contained in these notes is given in good faith to
the best of our knowledge, and believed to be accurate, BUT NO GUARANTEE OF ITS ACCURACY IS
EITHER EXPRESSED OR IMPLIED. Many units may also have been modified by their owners over the

years from their original specifications, and that should be kept in mind when using these products.

You’re on your own.

!!! Check carefully at each stage for correctness of wiring and function before powering up !!!

ARXARX

ARX Systems Pty Ltd, PO Box 15,

ARXARX

Moorabbin, Victoria 3189, Australia

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Phone: [phone]

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On the Web: www.arx.com.au

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Early ISC Speaker Processor Owner's Information - all models ©2004 ARX®

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Introduction

These notes have been compiled for the benefit of owners of older ART/ARX speaker processors. Please pay close
attention to the section on connecting the I.S.C. leads to the processor. The colour code and channel selection is
particularly critical when putting the system together for the first time. Severe speaker damage can be caused by
incorrect wiring. So please, take it easy and check things as you go.

What is I.S.C?

I.S.C stands for Interactive System Control, ARX’s innovative Speaker and Electronics Interface.
ISC monitors the output of the power amplifier driving each set of Loudspeaker components and compares this signal

with an internal model of the SOA (safe operating area) of the driver. When the signal applied to the driver tries to
exceed that SOA, the signal is limited or held at a level which is safe for the driver to reproduce. As the driver signal
forms part of a feedback style loop this SOA can never be exceeded.

Why monitor the outputs of the amplifiers?

What interests us is the actual power being applied to loudspeaker components,
not the signal being applied to the input of the Power Amplifier. To measure this
accurately and allow the user their personal choice in Power Amplifiers we have
to access the outputs of the amplifier. This is used as the reference.

What size amplifier do I need?

ARX quote a “recommended minimum amplifier size” - we don’t quote power
handling. The ISC processor determines the amount of power supplied to each
speaker, ensuring this remains within the SOA of the driver. By recommending the minimum amplifier size we are
indicating that this is the least amount of available power required for ISC to operate in the way it was designed by ARX
engineers.

For example: If you operated a system from, say, a 100 watt per channel amplifier, and the ISC processor was designed
to begin operation at around the 200 watt level you would find the 100 watt amplifier completely squared off into
clipping (gross overload distortion) before the ISC processor was aware that any action was required, thus for all intents
and purposes cancelling out the system protection.

Where do I put the processor?

The processor is mounted with the Amplifiers in the amp rack. In most applications once the main frequency response
balance is set, system equalization is achieved by a Graphic or Parametric Equalizer, so there is no need to constantly
access the processor.

Part A - Two Way Systems

TYPICAL FRONT PANEL CONTROLS

Channel A level trim

These controls let you adjust the input level to the unit. During normal operation it is set at the maximum (10) position.
Note: this is an attenuator only, not a gain control. Setting this level too low may reduce the headroom in the preceding
equipment.All remaining controls are recessed behind an acrylic security cover. Unscrew the knurled nut at each end of
the cover and lift off to make adjustments.

Low control

This control determines the Low Frequency output of your system. During normal operation it is set at the 0dB (unity)
position (12 o’clock). It also provides up to +6 dB of gain past unity.

Low ISC LED

This LED indicates that the ISC protection circuitry is operating on the Low output. During normal operation this LED
will light up on transients or peaks if the system is being used to achieve high SPL. This is normal, and should not be
taken as an indication that the system is being overdriven. However, if this LED is on for the majority of the time, then
the Low level is too high and should be reduced.

High control and High ISC LED

Same as for Low but applicable to High

VHF level trim control

This control determines the Very High Frequency energy output of your system. It provides control from -12 dB (Hard
LEFT) through to 0 dB/unity (Hard RIGHT). It should be set in the 0 dB position for a flat response, but for a more
musical response you can rotate it anti-clockwise until the desired roll off is achieved.

Early ISC Speaker Processor Owner's Information - all models ©2004 ARX®

Connecting the ISC leads

--- Early Models with Red and Black leads

The Red and Black ISC leads, on 4 pin XLR connectors, plug into the corresponding sockets on the rear of the Control
Unit. The RED leads connect to the OUTPUTS of the LOW amplifiers, in parallel with the leads going to the LOW
speakers. The BLACK leads connect to the Outputs of the HIGH amplifier, in parallel with the leads going to the HIGH
speakers.

Pin configuration is Pins 1 and 2 - Red (Low), Pins 3 and 4 Black (High)

• Connect both RED leads to the LOW amp outputs, and both BLACK leads to the HIGH amp outputs. They are
not polarity sensitive and don’t mind whether they are connected to + or –.

• Make sure you don’t get these mixed up as you will end up with the LOW ISC controlling the HIGHs, and vice
versa, which can cause major speaker damage to the HIGH drivers.

• Make sure that the Channel A ISC leads are connected to the Channel A amplifiers, and Channel B leads to the
Channel B amplifiers, or you will end up with the Channel A ISC controlling Channel B and vice versa, which
can give very strange results AND CAN OVERDRIVE THE SYSTEM.

NOTE: If your amplifier has Black and Red output terminals, don’t attach one Black ISC lead to a Black
terminal and a Red one to a Red terminal. It won’t work and may cause damage.

• Work slowly and carefully, and take the time to get it right. It’s a good idea to mark all leads as you go, so you can
visually check all connections before powering up.

Also note that inputs and outputs on early processors, in keeping with the accepted standards of the time, were wired Pin
3 + (Hot), Pin 2 – (Cold), and Pin 1 Audio Ground

--- Later Models with White and Blue leads

The White and Blue ISC leads, on 6 pin XLR connectors, plug into the corresponding sockets on the rear of the Control
Unit. The WHITE leads connect to the OUTPUTS of the LOW amplifiers, in parallel with the leads going to the LOW
speakers. The BLUE leads connect to the Outputs of the HIGH amplifier, in parallel with the leads going to the HIGH
speakers.

These leads allow the Control Unit/Processor to monitor the output of the amplifiers, and to activate the protection
circuits if the power exceeds the maximum safe operating area of the speaker.

these connections!

The White and Blue ISC leads, on 6 pin XLR connectors, plug into the corresponding sockets on the rear of the Control
Unit. The WHITE leads connect to the OUTPUTS of the LOW amplifiers, in parallel with the leads going to the LOW
speakers. The BLUE leads connect to the Outputs of the HIGH amplifier, in parallel with the leads going to the HIGH
speakers.

Pin configuration is Pins 1 and 2 - White (Low), Pins 3 and 4 Blue (High), Pins 5 and 6 trigger a relay to activate the
Control Unit, and to turn it off if the leads are removed

• Connect both WHITE leads to the LOW amp outputs, and both BLUE leads to the HIGH amp outputs. They are
not polarity sensitive and don’t mind whether they are connected to + or –.

• Make sure you don’t get these mixed up as you will end up with the LOW ISC controlling the HIGHs, and vice
versa, which can cause major speaker damage to the HIGH drivers.

• Make sure that the Channel A ISC leads are connected to the Channel A amplifiers, and Channel B leads to the
Channel B amplifiers, or you will end up with the Channel A ISC controlling Channel B and vice versa, which
can give very strange results AND CAN OVERDRIVE THE SYSTEM.

NOTE: If your amplifier only has Neutrik Speakon output terminals, you will need to connect the ISC
leads to the speaker cables by splicing them into the speaker cable after the connector, or by making up a
Y connector, so that one Speakon goes to the ISC leads, and the other goes to the speaker cable.

These units won’t turn on until you make

• Work slowly and carefully, and take the time to get it right. It’s a good idea to mark all leads as you go, so you can
visually check all connections before powering up.

Early ISC Speaker Processor Owner's Information - all models ©2004 ARX®

Rear Panel Configurations

CHANNEL A ISC RETURNSCHANNEL B

AC POWER

INPUT AND FUSE.

CHECK FOR

CORRECT
VOLTAGE

CU 215S REAR PANEL

AC POWER

INPUT AND FUSE.

CHECK FOR

CORRECT

VOLTAGE

AC POWER

INPUT AND FUSE.

CHECK FOR

CORRECT

VOLTAGE

IN

FROM

CONSOLE

OUT TO

LOW AMP

IN CH. A

OUT TO

HIGH AMP

IN CH. A

IN

FROM

CONSOLE

CHANNEL A CHANNEL B

OUT TO

IN

FROM

CONSOLE

LOW

AMP IN

CH. A

OUT TO

MID/HIGH

AMP IN

CH. A

CHANNEL A ISC RETURNSCHANNEL B

IN

FROM

CU118S

OUT TO

MID

AMP IN

CH. A

OUT TO

HIGH

AMP IN

CH. A

IN

FROM

CU118S

OUT TO

LOW

AMP IN

CH. B

OUT TO

LOW

AMP IN

CH. B

OUT TO

MID

AMP IN

CH. B

OUT TO

HIGH AMP

IN CH. B

OUT TO

MID/HIGH

AMP IN

CH. B

OUT TO

HIGH

AMP IN

CH. B

ISC

LEADS

FROM

CH. A

ISC

LEADS

FROM

CH. B

ISC RETURNS

ISC

LEADS

FROM

CH. A

LEADS

FROM

CH. A

ISC

ISC

LEADS

FROM

CH. B

ISC

LEADS

FROM

CH. B

CU 912/922S REAR PANEL

CU 212S REAR PANEL

Part B - Sub Bass Systems
Channel A level trim

This control lets you adjust the input level to the Channel A circuitry. During normal operation it is set at the maximum
(10) position. This is an attenuator only, not a gain control. Setting this level too low may reduce the headroom in the
preceding equipment.

Normal/Reverse LEDs

These LEDs indicate the status of the Phase Reverse switch. Also, either one lit up indicates that the Control Unit is
connected to the AC power.

Phase Reverse switch This switch changes the Low Frequency output phase of the CU 118s by 180

o

Normal/Sub switch

In the Normal position, the CU 118s covers Low frequencies from 250 Hz downwards. In the Sub posiion, it covers Low
frequencies from 90 Hz downwards. Use Normal position when using it in conjunction with the CU 212s control unit,
and Sub position when using it for Low frequency enhancement of other systems.

Level control

This control determines the Low Frequency output of your system. During normal operation it is set at UNITY,the 0 dB
nominal operating position (12 o’clock). It also provides up to +6 dB of gain past unity.

ISC LED

This LED indicates that the Interactive System Control protection circuitry is operating on the Channel A output. During
normal operation this LED will light up on transients or peaks if the system is being used to achieve high SPL. However,
if this LED is on for the majority of the time, then the Low level is too high and should be reduced accordingly.

Early ISC Speaker Processor Owner's Information - all models ©2004 ARX®

Connecting the ISC leads

The White and Blue Interactive System Control leads, on 6 pin XLR connectors, plug into the corresponding sockets on
the rear of the Control Unit. The WHITE leads connect to the OUTPUTS of the LOWamplifier Channel A, in parallel
with the leads going to the speakers. The BLUE leads connect to the Outputs of the LOW amplifier Channel B, in
parallel with the leads going to the speakers.

These leads allow the Control unit to monitor the output of the amplifiers, and to activate the speaker protection circuits
if the power exceeds the maximum safe operating area of the speaker. The Control Unit won’t turn on until you make
these connections.

CHANNEL A CHANNEL B ISC RETURNS

AC POWER

INPUT AND FUSE.

CHECK FOR

CORRECT

VOLTAGE

IN

FROM

CONSOLE

OUT TO

CESSOR

MID/HI

PRO­CH. A

OUT TO

LOW

AMP IN

CH. A

IN

FROM

CONSOLE

OUT TO

MID/HI

PRO-

CESSOR

CH. B

OUT TO

LOW

AMP IN

CH. B

ISC LEADS
FROM CH.

A&B

Pin configuration is Pins 1 and 2 - White (Channel A), Pins 3 and 4 Blue (Channel B), Pins 5 and 6 trigger a relay to
activate the Control Unit, and to turn it off if the leads are removed

• Connect both WHITE leads to the LOW amp Channel A outputs, and both BLUE leads to the LOW amp Channel
B outputs.

• Make sure you don’t get these mixed up - make sure that the Channel A ISC leads are connected to the Channel A
amplifiers, and Channel B leads to the Channel B amplifiers, or you will end up with the Channel A ISC
controlling Channel B and vice versa, which can give very strange results.

• Work slowly and carefully, and take the time to get it right. It’s a good idea to mark all leads as you go, so you can
visually check all connections before powering up.

NOTE: If your amplifier only has Neutrik Speakon output terminals, you will need to connect the ISC leads

to the speaker cables by splicing them into the speaker cable after the connector, or by making up a Y
connector, so thet one speakon goes to the ISC leads, and the other goes to the speaker cable.

Special Note for Early units

Early 118 processors used a 4 Pin XLR connector with different colour ISC leads: RED for Channel A, BLACK
for Channel B. So in the above instructions, substitute RED for WHITE, and BLACK for BLUE.

Also note that that inputs and outputs on early processors, in keeping with the accepted standards of the time,
were wired Pin 3 + (Hot), Pin 2 – (Cold), and Pin 1 Audio Ground

Pin configuration is Pins 1 and 2 - Red (Channel A), Pins 3 and 4 Black (Channel B)

Early ISC Speaker Processor Owner's Information - all models ©2004 ARX®

Part C - Passive Systems - CU303s, CU306, PowerPro, MicroPro

These systems use a passive crossover inside the speaker cabinet, and a single pair of ISC leads control each channel.
These leads allow the Control unit to monitor the output of the amplifiers, and to activate the speaker protection circuits

if the power exceeds the maximum safe operating area of the speaker.

Early Systems - Red and Black ISC leads

Both RED leads connect to the OUTPUT of Amp Channel A, in parallel with the speaker leads.
Both BLACK leads connect to the OUTPUT of Amp Channel B, in parallel with the speaker leads.
Both YELLOW leads connect to the OUTPUT of the SUB Amp, in parallel with the speaker leads.
Very early models had 4 Pin XLR connectors; later models had the ISC leads hard wired to the rear of the Control/Unit/

Processor
Note that early processors, in keeping with the accepted standards of the time, were wired Pin 3 + (Hot), Pin 2 – (Cold),

and Pin 1 Audio Ground

Later Systems - White and Blue ISC leads

Both WHITE leads connect to the OUTPUT of Amp Channel A, in parallel with the speaker leads.
Both BLUE leads connect to the OUTPUT of Amp Channel B, in parallel with the speaker leads.
Both YELLOW leads connect to the OUTPUT of the SUB Amp, in parallel with the speaker leads. The ISC leads are

hard wired to the rear of the Control/Unit/Processor

Check this wiring very carefully. Don’t get them mixed up, otherwise you will have the output of Channel A controlling
the input level of Channel B and vice versa.

NOTE: If your amplifier only has Neutrik Speakon output terminals, you will need to connect the ISC leads

to the speaker cables by splicing them into the speaker cable after the connector, or by making up a Y
connector, so that one Speakon goes to the ISC leads, and the other goes to the speaker cable.

System connection diagram

Early ISC Speaker Processor Owner's Information - all models ©2004 ARX®

Typical Specifications

CU212s

Input Impedance

Balanced 20 Kohms
Unbalanced 10 Kohms

Input Headroom

+21 dB

CMRR

>50dB, 20 Hz - 20 KHz

Output Impedance

150 ohms

Output Level (Max)

+20 dB

Filter Type

Linkwitz-Riley state variable
24dB per Octave

Frequency Response

20 Hz to 20 KHz.
Note: RFI filter -6dB 100KHz

Signal to Noise Ratio

-90dB Unweighted

-93dB A weighted

Distortion

.004% @ 0dB, 1 KHz

Dynamic Range

111dB

Input Connectors

Female XLR; Pin 1 Ground,
Pin 2 + (Hot) Pin 3 - (Cold)

Output Connectors

Male XLR; Pin 1 Ground,
Pin 2 + (Hot) Pin 3 - (Cold)

Power Requirements

220/240 - 100/120 V AC 50/60
Hz, 8 watts (8 VA)

Weight

5 lb/2.2 Kg

Dimensions

19"W x 1¾"H x 6"D
482 x 44 x 155 mm

CU118s

Input Impedance

Balanced 20 Kohms
Unbalanced 10 Kohms

Input Headroom

+21 dB

CMRR

>50dB, 20 Hz - 20 KHz

Output Impedance

150 ohms

Output Level (Max)

+20 dB

Filter Type

Linkwitz-Riley state variable
24dB per Octave

Frequency Response

200 Hz to 20 KHz.
Note: RFI filter -6dB 100KHz

Signal to Noise Ratio

-90dB Unweighted

-93dB A weighted

Distortion

.004% @ 0dB, 1 KHz

Dynamic Range

111dB

Input Connectors

Female XLR; Pin 1 Ground,
Pin 2 + (Hot) Pin 3 - (Cold)

Output Connectors

Male XLR; Pin 1 Ground,
Pin 2 + (Hot) Pin 3 - (Cold)

Power Requirements

220/240 - 100/120 V AC 50/60
Hz, 8 watts (8 VA)

Weight

5 lb/2.2 Kg

Dimensions

19"W x 1¾"H x 6"D
482 x 44 x 155 mm

PowerPro

Input Impedance

20 Kohms electronically balanced

Maximum Input Level

+20dB

CMRR

>50 dB, @ 1 KHz

Output Impedance

300 ohms electronically balanced

Maximum Output Level +22dB
Signal to Noise ratio

90 dB, unweighted

Dynamic Range

110 dB

Distortion (THD)

.008% @ +4 dB, 1 KHz

Crossover Frequency

-3dB @100Hz (to SUB out)

HighPass Filters (-3dB point)

35 Hz SUB output
60 Hz A/B outputs

ISC Returns

Differential Inputs,
22 KOhms impedance,
hard wired to chassis

Input Connector type

Balanced 3 pin XLR

Output Connector type

Balanced 3 pin XLR

Power Requirements

100/120 - 220/240 V AC, 50/60
Hz, 8VA (8 watts)

Weight

5 lbs/2.2 Kg

Dimensions

19"W x 1¾"H x 6"D
482 x 44 x 155mm

CU912/9222s Specifications

Input Impedance

Balanced 20 Kohms
Unbalanced 10 Kohms

Input Headroom

+21 dB

CMRR

>50dB, 20 Hz - 20 KHz

Output Impedance 150

ohms

Output Level (Max)

+20 dB

Filter Type

Linkwitz-Riley state variable
24dB per Octave

Frequency Response

20 Hz to 20 KHz.
Note: RFI filter -6dB 100KHz

Signal to Noise Ratio

-90dB Unweighted

-93dB A weighted

Early ISC Speaker Processor Owner's Information - all models ©2004 ARX®

Distortion

.004% @ 0dB, 1 KHz

Dynamic Range

111dB

Input Connectors

Female XLR; Pin 1 Ground,
Pin 2 + (Hot) Pin 3 - (Cold)

Output Connectors

Male XLR; Pin 1 Ground,
Pin 2 + (Hot) Pin 3 - (Cold)

Power Requirements

220/240 - 100/120 V AC 50/60
Hz, 8 watts (8 VA)

Weight

5 lb/2.2 Kg

Dimensions

19"W x 1¾"H x 6"D
482 x 44 x 155 mm

It’s worthwhile noting that early
processors, in keeping with the
accepted standards of the time,
were wired Pin 3 + (Hot), Pin 2
– (Cold), and Pin 1 Audio Ground

However, older units may have
been modified by users to the
current Pin 2 + Hot standard as
listed here