ATC SCM25A Pro User Manual page 4

I n s t a l l a t i o n
1 . D e s c r i p t i o n
The SCM25/45/50/100/110 and 150 are a range of three
way loudspeakers. All of the range, excluding the SCM25
and SCM45 are available as passive or active units.
The SCM25 and SCM45 are only available as active
units. The product name suffix denotes the technology
featured in the product.
"SL" denotes Super Linear Magnet technology and "A"
denotes that the Loudspeaker includes active amplification.
Passive monitors are equipped with a "tri-wire" connection
panel to enable separate amplification of the bass, mid
and high frequency drivers. Active units have a built in
three way Amplifier with frequency, gain and phase
correction which has been individually optimised at the
ATC manufacturing facility. Adjustment of input sensitivity
and bass boost are available to the user via controls
on the rear panel of the unit.
2 . U n p a c k i n g a n d H a n d l i n g
The SCM25, 45, 50, 100, 110 and 150 are large heavy items
and should be handled with care. Always employ a
second person to assist in moving them. Unpacking is best
carried out on the floor, with adequate open space
around the carton, preferably close to their final position.
• Open the carton and remove all loose items.
• Remove the upper Sratocell foam cap.
• Remove the polythene or cloth bag, leaving
the baffle protector in place.
• Carefully lift the loudspeaker out from the
lower Sratocell foam cap using the handles
and the port opening as lifting points.
• The speaker can now be positioned in the
listening/control room
• Remove the baffle protector.
Loudspeaker Positioning - Stereo
distance z
distance x = distance y = distance z
3 . M o n i t o r P l a c e m e n t
The subjective performance of any monitor loudspeaker will be 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
on appropriate stands 1 metre from the side walls and 2 metres from the back wall
In professional installations, try to avoid placing speakers on the console/desk meter
bridge. Typically, this compromises the balance of the loudspeaker especially in the
lower mid range. If the balance is bass light, the monitors can be moved towards the
back walls.
innapropriate positioning. For stereo listening, loudspeakers should be positioned
so they form an equilateral triangle with the listening position (See Fig.1).
Loudspeaker stand height should be chosen to position the loudspeaker
acoustic axis at, or close to ear level (See Fig.2). All rooms vary and it is a good idea
to experiment with both the listening and speaker position until a good compromise
is reached. For professional installations the requirements are often very specific.
Please consult with an experienced professional acoustician if necessary. Monitors
Monitors with an asymmetric (offset) driver array should be positioned such that the
midrange driver and tweeter are inboard. If the monitors are to be placed in any form
of cabinet, adequate side and top clearance for cooling airflow must be provided.
Alternatively, the Amplifiers should be removed and installed remotely. All ATC 3-way
loudspeakers are designed with the mid-range dome as the reference acoustic axis.
With this in mind, the loudspeakers should be positioned with the mid-range dome
at, or slightly below ear level (See Fig.3).
4 . L i s t e n i n g
The ear and brain tend to interpret distorted sound as loudness and thus
underestimate the actual level of undistorted sound. The SCM ,
and 150, like all ATC monitors, demonstrate 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
SCM , 25 45, 50,
Fig. 1
your ears
harsh, Any
overloaded and that the volume level should be reduced.
SCM 25/45/
Use the Bass Boost control for fine tuning rather than to compensate for
100 , 110 and 150 to produce
themselves to become a source of distortion and
audible distortion indicates that either the system
50/100/ 110/ 150
Fig.2
Reference acoustic axis
Position at ear level or up
to 5 degrees above ear level
25 45, 50, 100
sufficient sound pressure levels for
make the sound appear
or your ears are being
, 110
3