User Manual: SCM20ASLT • SCM20SL
MULTICHANNEL
ACOUSTICENGINEERS
®
SCM20
SCM20SL
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 po w er suppl y 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 the y
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.
1
Safety Warnings
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.
SCM20
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 w er e 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 pr ecision 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
2
Contents
Page 2 Introduction
Page 3 SCM20ASLT
Section 1 Monitor Placement
Section 2 Connection
Section 3 Signal Cable Options
Page 4 Section 4 Operation
Section 5 Listening
Section 6 Care and Maintenance
Section 7 Warranty and Contact
Page 5 Specifications
Page 6 SCM20ASL
Section 1 Monitor Placement
Section 2 Amplification
Section 3 Connection
Page 7 Section 4 Listening
Section 5 Care and Maintenance
Section 6 Warranty and Contact
Page 8 Specifications
SCM20ASLT
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 ma y ho we ver be lo w 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 on appropriate
stands around 1 metre from the side walls and 2 metr es from the
back. If the balance is bass-light, the monitors can be moved
towards the back walls. All rooms vary and it is a good idea to
experiment with both the listening and speaker position until a
good compromise is reached.
Fit and level the monitors on the floor spikes when their location
in the room is confirmed.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 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.
3
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
Installation
4. Operation
The SCM20ASLT is connected to the mains and
signal cables via sockets on the rear panel.The rear
panel also carries the mains switch and fuseholder.
Each features 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 (above the input socket)
corresponds with the local supply.
4.2 Power Switch:Switches on the monitor.When
switched on the indicator on the panel will
illuminate.
4.3 Fuseholder: Should a monitor 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).
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 SCM20ASLT, 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
low level and carefully increase the volume.It is also possible for the SCM20ASLT 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.
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 prev entativ e maintenance.
There are no user replaceable parts within the speaker and in the unfortunate ev ent
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 f or
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 b y 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
Installation cont’d
4
SCM20ASLT
SCM20ASLT
5
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.
Drivers:
HF 25mm (1")
LF/MF 150mm (6")
Amplitude Linearity ±2dB 80Hz – 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
Input Connector Male XLR
Input Sensitivity 1.0V Balanced
Input Impedance >10k Ohms
Amplifier Output:
LF/MF 200 Watts RMS
HF 50 Watts RMS
Overload Protection Active Momentary Gain Reduction (both amplifiers)
Cabinet Dimensions (HxWxD) 1000 x 239 x 388mm
Overall W eight 40kg (88.2lb)
Power Requirements:
Voltage 100, 115, 230V (factory set)
Frequency 50/60Hz
Stands/Brackets Integral adjustable floor spikes
Cabinet Finishes Standard real wood veneers are available in Black Ash,
Mahogany, Cherry and Natural Oak. Other veneers and
finishes can also be supplied to special order.
SCM20ASLT
Specifications
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. All rooms vary and it is a
good idea to experiment with both the listening
and speaker position until a good compromise is
reached. Fit and level the monitors on the floor
spikes when their location in the room is
confirmed. For professional installations the
requirements are often very specific.Please consult
with an experienced professional acoustician if
necessary.
2. Amplification
The choice of partnering amplifier for the SCM20SL will have significant influence on
the performance of the system.Consider the following when selecting the amplifier:
• With any passive loudspeaker there is a trade-off between low frequency
extension and sensitivity. The SCM20SL’s extended low frequency response
means that its sensitivity is relatively low. It is advisable therefore to select an
amplifier of relatively high power capabilities. Use of an under specified amplifier
will result in the system sounding distorted at high levels and may risk damage.
Valve or solid state amplifiers with high output impedance should be auditioned
carefully to establish that their characteristic reduced damping at low frequencies
is acceptable.
• The SCM20SL bass/mid driver voice coil is an unusually large 75mm and operates
in an overhung gap. The result is that the SCM20SL not only demonstrates
extremely low distortion at all levels but also a greatl y enhanced eff ective dynamic
range. This exceptional distortion performance, also combined with very wide
dispersion, will ruthlessly reveal deficiencies in ancillary equipment. It is advisable
therefore to audition the SCM20SL with your proposed amplifier and ancillary
system.
3. Connection
The SCM20SL is equipped with a “bi-wire” connection panel that enables separate
amplification of the bass/mid driver and tweeter. Remove the linking bars between
the two pairs of terminals if you wish to take advantage of the bi-wire facility.
The terminals can accomodate either stripped cable ends or 4mm plugs.Always use
good quality speaker cable with a 2.5mm
2
minimum cross sectional area per
conductor (79 strand). Cable of a smaller cross sectional area or fewer strands is
unsuitable. For cable runs longer than 10m use a significantly heavier gauge cable.
Consult your dealer or consultant for specific cable recommendations.
Ensure that the positive and negative terminals on each connection panel are
connected back to the corresponding positive and negative terminals on the amplifier.
SCM20ASL
6
Installation
SCM20SL
4. Listening
The ear and brain tend to interpret distorted sound as loudness and thus
underestimate the actual level of undistorted sound. The SCM20SL, 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 low level and carefully increase the volume. It is also possible for the
SCM20SL 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.
5. 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 prev entativ e maintenance.
There are no user replaceable parts within the speaker and in the unfortunate ev ent
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.
6. Warranty and Contact
All ATC products are guaranteed against any defect in materials or workmanship f or
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 b y 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 Technolog y 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
7
Specifications
Drivers:
HF 25mm (1")
LF/MF 150mm (6")
Amplitude Linearity ±2dB 80Hz – 18kHz
Cut-off Frequencies
(-6dB free standing) 60Hz & >22kHz
Dispersion:
Horizontal ±80° Coherent
Vertical ±10° Coherent
Sensitivity (sine wave) 84dB @ 1W @ 1 metre
Max Continuous SPL 108dB SPL @ 1 metre
Recommended Power
Amplifier 50 to 300 Watts
Nominal Impedance 8 Ohms
Crossover Frequency 2.8kHz
Input Connections Binding Posts/4mm Sockets (Bi-Wire capable)
Cabinet Dimensions (HxWxD) 4400 x 240 x 280mm
Overall Weight 22.7kg
Cabinet Finishes Standard real wood veneers are available in Black Ash,
Mahogany, Cherry and Natural Oak. Other veneers and
finishes can also be supplied to special order.
SCM20SL
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.
SCM20SLT
8
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
Loading...