Manual

5
SCM20ASL/SCM20PSL Pro
6 . O p e r a t i o n - S C M 2 0 A S L P r o
WARNING
THIS EQUIPMENT
MUST BE EARTHED
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
MAINS INPUT
50/60Hz
POWER CONSUMPTION
335VA MAX
CHECK VOLTAGE
BEFORE USE
1V
2.2dBu
2V
8.2dBu
balanced input
input sensitivity
(for 200W out)
2
1
3
1:
2:
3:
+
-
fuse
230V - 2.5A
115V - 5A
on
off
+3
+2
+1
0
-1
-2
0
-3
-6
bass shelf:
cut/boost (dB)
trim(dB)
serial number
voltage
FAULT:
amplifier overtemp/
DC offset
Acoustic Transducer Co. is a trading name and is
the registered Trade Mark of Loudspeaker Technology Ltd.
input impedance
10k Ω/leg
00001
230V
Fig. 7. SCM20ASL Pro Front Baffle
power/limit
Fig. 8. SCM20ASL Pro Rear Panel
6.1 Power On/Limit LED
Situated on the lower-front baffle of the SCM20ASL Pro is the Power On/Limit indicator LED. When the monitor is powered ‘On’, the LED will illuminate
green. This feature is shown in Fig. 7 above.
When the monitor is driven hard and the amplifier FET limiter begins to act, the LED will turn red. The brighter and longer the duration the LED red
‘flash’, the more severe the limit event. The FET limiter is designed to stop the amplifier ‘hard clipping’. It is not a fail safe way to protect the
loudspeaker drive units. When not active, the FET limiter is not in circuit ie. it is a parallel part of the circuitry and it will not reduce sound quality. When
the limiter is active it reduces gain with a ‘soft clipping’ characteristic. Nonetheless, when the limiter is active it does have an affect on the sound quality
and the amplifier distortion will increase. At these levels, the loudspeaker drive units will also display much greater non-linearities and the sound
pressure level should be reduced if critical judgements made on the monitors are to be trusted.
It should also be noted that the sound pressure levels produced when the amplifier is at full output and the limiter is active are capable of
causing hearing damage, especially if the listener is exposed to these levels for sustained periods of time. Critical judgements made on the monitors at
full output are also likely to be inaccurate. With ANY studio monitoring system, use consistent and moderate listening levels if consistent and accurate
judgements are required.
Figure 8. illustrates the connection and control panels for the SCM20ASL Pro amplifier. Each feature is described below.
6.2 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 voltage.
7
SCM20ASL/SCM20PSL Pro
SCM20PSL Pro
7 . C o n n e c t i o n
The SCM20PSL Pro monitors are equipped with a “bi-wire” connection panel to enable separate amplification of the bass/mid driver and tweeter. The
connection panel is shown in Fig. 8 below. If not bi-wiring, connect your speaker cable to either the upper or lower horizontal pair of terminals. Remove the
linking bars, between vertical pairs of terminals should you wish to take advantage of the bi-wire facility. The upper horizontal pair of terminals are connected
to the tweeter. The lower horizontal pair are connected to the bass driver.
Terminals can accommodate either stripped bare cable ends, 4mm banana plugs or spade terminals. Do not use crimps on the bare wire ends as the difficulty
2
in compressing them can cause poor link bar connection. Always use a good quality speaker cable with 2.5mm minimum cross sectional area per conductor
(79 strand). For cable runs longer than 5m 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 to the corresponding positive and negative terminals on the
amplifier.
A lack of bass output and very wide unstable stereo imagine is most likely caused by the left and right loudspeakers being connected out of phase. If the
system displays these characteristics, please check the polarity of the wiring.
8. Amplification
The choice of partnering amplifier to power the SCM20PSL Pro monitors will have significant influence on the performance of the system. Consider the
following when selecting an amplifier:
Ÿ With any passive loudspeaker there is a trade off between low frequency extension and sensitivity. These monitor’s extended low frequency response
means the sensitivity is relatively low. It is therefore advisable to select a power amplifier of relatively high power output capabilities. Typically, best
performance comes with use of amplifiers capable of >150W continuous into 8 ohms.
Ÿ Use of an underpowered amplifier will result in the premature distortion of the system and increased risk of damage due to voice coil overheating
Ÿ Valve or solid state amplifiers with high output impedances should be auditioned carefully, to establish that their characteristic reduced damping factor at
low frequencies is acceptable.
Ÿ Thanks in part to Super Linear technology and the underhung voice coil construction, these monitors not only demonstrate extremely low distortion at all
levels, but also a greatly enhanced effective dynamic range. This exceptional distortion performance, combined with a very wide dispersion will ruthlessly
reveal deficiencies in ancillary equipment. It is advisable, therefore, to audition the monitors with your proposed amplifier and ancillary system.
Serial No.
Designed & manufactured by:
Acoustic Transducer Company, Gypsy Lane,
Aston Down, Stroud, Gloucestershire, GL6 8HR.
England.
Acoustic Transducer Co. is a trading name and
is the registered trademark of Loudspeaker Technology Ltd
140001
Return to manufacturer for disposal.
Bass
HF
Fig. 8. SCM20PSL Pro Passive Input Panel