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User Manual: SCM20ASL Pro
MULTICHANNEL
ACOUSTICENGINEERS
®
SCM20ASL Pro
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Safety Warnings
SCM20ASL Pro
1. Read instructions – all the safety and operating instructions should be read
before the appliance is operated.
2. Retain these instructions – the safety and operating instructions should be
retained for future reference.
3. Heed warnings – all warnings on the appliance and in the operating
instructions should be adhered to.
4. Follow instructions – all operating and other instructions should be
followed.
5. Water and moisture – the appliance should not be used near water, for
example near a bathtub, washbowl, kitchen sink, laundry tub, in a wet
basement or near a swimming pool etc..
6. Ventilation – the appliance should be situated so that its location or
position does not interfere with its proper ventilation. For example, the
appliance should not be situated on a bed, sofa, rug or similar surface that
may block the ventilation openings. Similarly, the appliance should not be
built into an installation, such as a bookcase or cabinet, that may impede
the flow of air through the ventilation openings.
7. Heat – the appliance should be situated away from heat sources such as
radiators, stoves or other appliances that produce heat.
8. Power sources – the appliance should be connected to a power supply only
of the type described in the operating instructions or as marked on the
appliance.
9. Power cord protection – power supply cords should be routed so that they
are not likely to be walked on or pinched by items placed upon or against
them, paying particular attention to cords at plugs, convenience
receptacles and the point where they exit the appliance.
10. Cleaning – the appliance should be cleaned only as recommended by the
manufacturer.
11. Unattended periods – the power cord of the appliance should be
unplugged from the outlet when left unused for a long period of time.
12. Object and liquid entry – care should be taken so that objects and liquids
do not fall into the appliance.
13. Damage requiring service – the appliance should be serviced by qualified
service personnel when:
i. the power supply cord or the plug has been damaged
ii. objects have fallen or liquid has been spilled into the appliance
iii. the appliance has been exposed to rain or other serious liquid exposure
iv. the appliance does not appear to operate normally or exhibits a marked
change in performance
v. the appliance has been dropped or the cabinet damaged
14. Servicing – the user should not attempt to service the appliance beyond
those measures described in the operating instructions.All other servicing
should be referred to qualified service personnel.
15. Grounding or polarisation – precautions should be taken so that grounding
or polarisation means for the appliance are not defeated.
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Welcome. In selecting ATC you have chosen an
example of the finest audio engineering
available. ATC was founded on a principle of
engineering excellence, and that principle still
defines our products today. Given the right
opportunities, ATC products will deliver
exceptional audio performance, but the
opportunities will only arise from careful and
thoughtful installation and use. Please read the
following manual fully. It will help you
understand the product and to realise its full
potential. We are happy to answer questions
and offer advice on any issues that arise
through installation or use of ATC products.
Contact details can be found at the back of this
manual.
SCM20ASL Pro
ATC was founded in London in 1974 by Australian emigre Bill Woodman, who still
heads the company today. An enthusiastic pianist and engineer he was naturally
drawn to loudspeaker design and after a period working at Goodmans, where many
of the names that went on to found British loudspeaker companies began their
careers, he struck out on his own.The premise on which ATC began is a simple one,
and one that in many respects is still true today: hi-fi loudspeakers tend to be
detailed and accurate but of limited dynamic range, while professional monitor
speakers tend to express the opposite character. ATC products were designed from
the outset to offer the best of both. It’s an easy concept to describe, but surprisingly
difficult to engineer.
The difficulty inherent in designing such loudspeakers is one of scale. Hi-fi levels of
accuracy and detail call for lightweight moving parts and delicate engineering.
Professional monitor levels of performance however demand far more robust
components engineered to survive the rigours of high level use for extended
periods.The only way to combine the two is through precision engineering of a class
and scale more often associated with aerospace or motorsport. But the results are
worth the effort and the cost. ATC loudspeakers, with their unique in-house
designed drivers, combine the best of hi-fi and professional to devastating effect.
ATC has become synonymous with active systems. Choosing to offer active
loudspeakers (where the passive crossover network is replaced by active filters and
multiple power amplifiers) is simply a result of the uncompromising attitude to
loudspeaker design.While passive systems still have their place,and ATC engineering
skills can still bring remarkable results from them,“active” is a fundamentally better
solution to the problems posed by accurate, high level music reproduction.The ATC
instinct is always for the better solution. Not cheaper, not quicker, but better.
It was the development of active loudspeakers that first brought ATC into
electronics design and engineering. Active speakers demand multiple power
amplifiers so ATC from the mid 1980s became not just a loudspeaker manufacturing
company but an electronics manufacturer too. The further step from electronics for
active speakers to a range of stand-alone amplifier products was natural and now
means that ATC engineering is available from the recording desk or CD player
output to the ears.
From modest beginnings ATC has grown to become one of the very few
manufacturers successful across both domestic and professional audio. By selecting
ATC you join a group of music lovers, professional audio engineers, studios and
musicians across the World that understand and value the engineering that goes into
an ATC product - and the sound that comes out.
Introduction
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Contents
Page 1 Introduction
Page 2 Section 1 Monitor Placement
Section 2 Connection
Section 3 Signal Cable Options
Page 3 Section 4 Operation
Section 5 Listening
Page 4 Section 6 Care and Maintenance
Section 7 Warranty and Contact
Specifications
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1. Monitor Placement
The subjective performance of any monitor loudspeaker will be fundamentally
influenced by the acoustic character of the room in which it is used, and its position
within the room. Most often monitors are installed in rooms which are comfortable
to sit and talk in.A mixture of carpets, curtains and soft furnishings
will help ensure that middle and high frequencies are reasonably
well controlled. There may however be low frequency problems;
either too much or too little bass. To minimise low frequency
problems the monitors should be kept away from corners or walls.
Start with them positioned around 1 metre from the side walls and
2 metres from the back.If the balance is bass-light, the monitors can
be moved towards the back walls. Use the Bass Boost control (see
Section 4.5) for fine tuning rather than to compensate for
inappropriate positioning. All rooms vary and it is a good idea to
experiment with both the listening and speaker position until a
good compromise is reached. If the monitors are to be placed in
any form of cabinet, adequate side and top clearance for cooling
airflow must be provided. For professional installations the
requirements are often very specific. Please consult with an
experienced professional acoustician if necessary.
2. Connection
Two cable connections are required for each SCM20ASL Pro
monitor: one for mains power and one for the audio signal. The
mains cable is specifically supplied to comply with local statutory
safety approvals and alternatives should not be substituted. If you
intend to use your monitors in an alternative territory please
contact ATC for advice. The mains connection must always be
earthed.
The signal cable and plug (not necessarily supplied) should be of a
good quality and XLR terminated. Poor cable and plug quality will
compromise the performance of your monitors. The signal input
pin configuration is illustrated in Diagram 1.
3. Signal Cable Options
Balanced cable configuration is the preferred option, however unbalanced
connection is possible. Diagrams 2 and 3 illustrate the signal cable connections
required for each option.Balanced (XLR to XLR) connection offers lower noise and
better immunity to “hum” pick-up. Unbalanced (XLR to Phono or Two Pole Jack)
connection carries risk of hum caused by multiple signal earths.
Hum problems resulting from unbalanced connection may be reduced by making ONE
of the following modifications to the signal cable connections: If the driving preamplifier
(or desk) is “double insulated” (i.e. has no mains earth), disconnect the signal cable
screen at the RCA Phono plug end.Alternatively, disconnect the signal cable screen at
the XLR end.This second option will make the source the reference signal earth.
SCM20ASL Pro
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Diagram 1 - input connection pins
Diagram 2 - balanced cable
Diagram 3 - unbalanced cable
Pin 1, ScreenPin 2, Signal (hot)
Two Core Screened Cable
Pin 3, Signal (return)
3 Pin Male XLR
Connector
3 Pin Female XLR
Connector
To Monitor Input
Hot
Return
Screen
To Source Output
1
2
3
1
2
3
Two Core Screened Cable
3 Pin Male XLR
Connector
Phono (RCA)
Connector
To Monitor Input
Hot
Return
Screen
To Source Output
1
2
3
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4. Operation
Diagram 4 illustrates the SCM20ASL Pro connection and control panel.Each feature
is described below.
4.1 Mains Inlet: The supplied mains power lead (appropriate to the local territory)
should be connected here. Ensure that the mains voltage specified on the panel
corresponds with the local supply.
4.2 Power Switch: Switches on the SCM20ASL Pro. When switched on the indicator
on the panel will illuminate.
4.3 Fuseholder: Should a SCM20ASL Pro fail to switch on when the power switch is
operated the fuse should be inspected. Lift out the fuseholder cover using a small
flat-blade screwdriver, remove the fuse and inspect it for damage. If required, a
replacement fuse should be fitted. It should be stressed
however that fuses most often fail only because of a
serious electrical fault. If this is the case then simply
replacing the fuse will only result in another fuse failure.
The monitor should be returned to ATC for service if a
second fuse fails.
4.4 Input Socket:The audio signal cable should be connected
here. Balanced or unbalanced cables may be used (See
Section 3 above).
4.5 Bass Boost: Provides up to 6dB of gain in the region of
40Hz. Adds more warmth and energy to the lower
frequencies in music, at the expense of accurate transient
reproduction. The control is detented to allow fine
matching of the boost level with other speakers in the
system.
4.6 Level Trim: Provides access to an internal control that
enables adjustment of input sensitivity. Use a small flat blade screwdriver to
access the control. As supplied, SCM20ASL Pro is calibrated to an input
sensitivity of 1V. Note:Modifying the sensitivity without the ability to recalibrate
will leave a pair of SCM20ASL Pro monitors unmatched.
4.7 Voltage Selector: Ensure that the appropriate voltage is set before switching on
the monitors.
Due to the nature of the electronics in ATC active loudspeakers it is quite normal
for a sound to be heard from the speaker when the power is applied or
disconnected. The noise heard will not damage the speaker and is quite normal.
Although ATC uses the highest-grade components, a different noise may be heard
from each speaker due to slight tolarance variations in the amplifier components.
5. Listening
The ear and brain tend to interpret distorted sound as loudness and thus
underestimate the actual level of undistorted sound.The SCM20ASL Pro, like all ATC
monitors, demonstrates very much lower levels of distortion than conventional
systems of a similar size and it is therefore advisable to begin listening at an artificially
SCM20ASL Pro
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Diagram 4 - connection and control panel
low level and carefully increase the volume. It is
also possible for the SCM20ASL Pro to produce
sufficient sound pressure levels for your ears
themselves to become a source of distortion and
make the sound appear harsh. Any audible
distortion indicates that either the system or your
ears are being overloaded and that the volume
level should be reduced.
The SCM20ASL Pro front panel power indicator
also functions to indicate overload and operation
of the protection system. In normal use the
indicator shows GREEN but changes to RED on
overload.Anything but occasional overload should
be avoided by reducing the volume level.
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Specifications
Drivers:
HF 25mm (1")
LF/MF 150mm (6")
Amplitude Linearity ±2dB 70Hz – 12kHz
Cut-off Frequencies
(-6dB free standing) 60Hz & 20kHz
Dispersion:
Horizontal ±80° Coherent
Vertical ±10° Coherent
Max Continuous SPL 108dB SPL @ 1 metre
Crossover Frequency 2.8kHz via active crossover with time (phase) alignment
Input Connector Male XLR
Input Sensitivity 1.0V Balanced (±6dB trim available)
Input Impedance >10k Ohms
Amplifier Output:
LF/MF 250 Watts RMS
HF 50 Watts RMS
Overload Protection Active Momentary Gain Reduction (both amplifiers)
LF Equalisation 0 to +6dB @ 40Hz
Cabinet Dimensions (HxWxD) 448 x 270 x 310mm
Overall Weight 30.0kg (66lb)
Power Requirements:
Voltage 100, 115, 230V
Frequency 50/60Hz
Stands/Brackets Matching floor stands and wall brackets
are available at extra cost.
SCM20ASL
The above specifications comply with the following standards:Australian Standard Specification No 1127 "Sound System
Loudspeakers" Part 5, IEFE Specification Standard No 219-1975
ATC reserves the right to vary products and specifications without prior notice.Acoustic Transducer Co. is a trading name and ATC
is the registered trade mark of Loudspeaker Technology Ltd.
SCM20ASL Pro
6. Care and Maintenance
High technology material finishes are used in this
product.The surfaces are durable and with a little
care can be kept as good as new even under
conditions of heavy use. Normally a dry duster will
be all that is required to keep the finishes clean.
Heavy soiling can be cleaned using a cloth slightly
moistened with a non-abrasive household cleaner.
There are no components within the speaker that
can be considered expendable, or that would
benefit from regular maintenance. There is no
requirement for any kind of routine service work
and there is no schedule for preventative
maintenance.
There are no user replaceable parts within the
speaker and in the unfortunate event of any
malfunction, repair should be referred to either
the supplying dealer or consultant, the relevant
importer,or ATC. ATC has every confidence in the
quality of each product that it manufactures.
7. Warranty and Contact
All ATC products are guaranteed against any
defect in materials or workmanship for a period of
two years from the date of purchase. Within this
period we will supply replacement parts free of
charge provided that the failure was not caused by
misuse, accident or negligence.
Purchasers who complete and return the
Warranty Card will have their warranty period
extended up to a period of six years from the
date of purchase.This guarantee does not limit
statutory rights.
ATC can be contacted at:
Loudspeaker Technology Ltd, Gypsy Lane, Aston
Down, Stroud, Gloucestershire GL6 8HR, UK.
Telephone: 01285 760561
Fax: 01285 760683
Email: info@atc.gb.net
Website: www.atc.gb.net
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ACOUSTICENGINEERS
®
Loudspeaker Technology Ltd, Gypsy Lane, Aston Down, Stroud, Gloucestershire GL6 8HR, United Kingdom
Telephone 01285 760561 Fax 01285 760683
Email: info@atc.gb.net Website: www.atc.gb.net
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