ATC SCM20ASL Owner's Handbook Manual page 14

C4 SUB MK2 LE
P r o d u c t D e s c r i p t i o n enable connection to mono or stereo sources.
A pair of buffered, un-filtered balanced Outputs provide
The ATC C4 Sub Mk2 is a high-performance 12"/300mm
connection to partnering active monitor loudspeakers,
active subwoofer, designed from the ground up to
amplifiers or to daisy chain multiple subs. 21dB range
deliver the exceptional levels of performance required to
of gain control, three low pass frequency settings, polarity
partner ATC ' s active and passive loudspeaker range.
switch and a 180 degree continuously variable Phase
Its performance and features make it ideally suited to
setting allow the user to optimise the subwoofer for
use within stereo, multi-channel surround and
use with a very wide range of partnering loudspeakers.
immersive audio systems.
The low pass filter can also be set to 'Off' (320Hz)
The sub features a sealed-box (infinite baffle) design, should the user wish to use the C4 Sub Mk2
chosen for its balance of sub-bass extension and driver with external processing.
control. The cabinet is heavy and inert to minimise
The amplifier features fault monitoring of amp panel
cabinet colouration.
temperature and power amplifier DC offset:- either fault
The SS75-314SC driver employed has been meticulously condition is indicated via illumination of a single red
optimised to reproduce the lowest 3 octaves of the LED mounted on the amp panel.
audio band within the design of the C4 Sub Mk2
When in use, the subwoofer Output can be muted using
subwoofer system. It employs a short-coil operating in
a single latching footswitch connected via a ¼"/6.35mm
an exceptionally long magnetic gap to deliver high
jack. The mute function does not affect the Outputs to
sound pressure levels with very low levels of distortion.
the primary loudspeakers, only the Output from the sub
The C4 Sub Mk2's convection cooled amplifier is itself. Additional subs can be muted using the same
mounted in the rear of the cabinet. Two balanced Inputs single footswitch via connection to the mute 'Thru' jack.
membrane traps are effective at treating the low bass,
typically below 80Hz and the porous absorbers
frequencies above this. Porous absorbers such as those
made from foams, fibreglass or rockwool are not
effective at absorbing low bass energy without a very
large air space between them and the wall behind.
For this reason, they are a poor choice of absorber
for the subwoofer bandwidth.
To minimise problems a free-standing subwoofer should
be kept away from corners where possible. Avoid placing
the subwoofer mid-way between any two parallel walls.
R o o m I n t e r a c t i o n S u b w o o f e r P l a c e m e n t
The room in which a loudspeaker is placed can The C4 Sub Mk2 is supplied with 4 x steel spikes which
be thought of as a filter, altering the acoustic response can be fitted to the threaded holes in the base of the
at the listening position from that of the loudspeaker. subwoofer. The spikes are optional and can be fitted to
ensure the subwoofer is seated firmly when positioned
The position of the loudspeaker in a room will influence
on a soft carpeted floor. Without the spikes fitted,
how it interacts with the space making it critical to
achieving the best performance at the listening position. the subwoofer will sit on the 4 x fixed rubber feet, which
is ideal for hardwood/concrete flooring.
Positioning is particularly relevant to subwoofers because
at low frequencies the room will have a strong influence Start with the subwoofer positioned next to one of
due to room modes/resonances. Room modes manifest the stereo monitors and at the same distance from the
themselves in an uneven distribution of acoustic energy listening position. When installing two subwoofers, start
within the room, which can lead to either too much with one by each of the stereo monitors. In most cases
these guidelines will give the best results, however all
or too little bass at the listening position. A room with a
rooms vary, and it is a good idea to experiment with both
well-controlled low frequency response (reverb time)
will have a far smaller influence on the performance listening and speaker positions until a good compromise
of the subwoofer and will be less sensitive to subwoofer is reached. When working on optimising the positioning,
positioning. Applying acoustic treatment in a domestic only change one variable at a time. Positioning the
setting is not always possible or desirable but if subwoofer in the centre of the room, equidistant from the
two side walls and between the left and right stereo pair
considered it should be noted that typically, a combination
must be avoided. In the majority of cases, this position will
of resonant membrane traps and porous absorbers
are needed to control the low frequency. The resonant result in large irregularities in the frequency response.
Multiple subs will excite the room from multiple locations comply with local statutory safety requirements and
and will often give a more even in-room response. alternatives should not be substituted. If you intend to use
Also, a pair of subs can be placed with the same physical your subwoofer in an alternative territory, please contact
relationship to the pair of main speakers and the ATC for advice. Always earth the mains connection.
listener. Please see page 30 for recommendations on
The signal cable(s) and plug(s) should be of a good
how to set the amplifier filters and level.
quality and XLR terminated. Poor cable and plug quality
will compromise the performance of your subwoofer.
The signal Input pin configuration is shown in Diagram 5.
C o n n e c t i o n
If two signal connections are made to the subwoofer
Two or three cable connections are required for each (i.e. a stereo pair) the left and right signals will be summed
subwoofer: one for mains power and one or two for the by the amplifier, increasing the effective input level to
audio signal. The mains cable is specifically supplied to the amplifier stage by 6dB.
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