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 SCM50, 100 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
SCM50, 100 and 150 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.
SCM
50/100/
150
25/
110/
3
2 . U n p a c k i n g a n d H a n d l i n g
• Open the carton and remove all loose items.
• The speaker can now be positioned in the
• Remove the baffle protector.
• Carefully lift the loudspeaker out from the
lower Sratocell foam cap using the handles
The SCM25, 50, 100, 110 and 150 are large heavy items and
• Remove the upper Sratocell foam cap.
• Remove the polythene or cloth bag, leaving
the baffle protector in place.
and the port opening as lifting points.
listening/control room
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
back walls.
for fine tuning rather than to compensate for
Use the Bass Boost control
innapropriate positioning. For stereo listening, loudspeakers should be positioned
to experiment with both the listening and speaker position until a good compromise
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
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
is reached. For professional installations the requirements are often very specific.
Please consult with an experienced professional acoustician if necessary.
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.2).
1 . D e s c r i p t i o n
The SCM25/50/100/110 and 150 are a range of three way
loudspeakers. All of the range, excluding the SCM25 are
available as passive or active units, the SCM25 is only
available as an active unit. Passive units have an SL suffix
and active units an ASL suffix. 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.
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.
30°
30°
distance x
distance y
distance z
distance x = distance y = distance z
Loudspeaker Positioning - Stereo
Fig. 1
acoustic axis: mid point between
bass/mid and tweeter
2-way systems
3-way systems
acoustic axis: 5 below
º
mid-range driver
Reference acoustic axis
Position at ear level or up
to 5 degrees above ear level
Fig. 2
