QUAD ESL-989 - Manual (Page 6)

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Each loudspeaker should be connected to its appropriate amplifier output so that the
two pairs of wires are connected in the same way, to ensure that the speakers
operate in phase.
Switching On and Off
The on/off switch has a rocker action; press the bottom to switch the ESL on and the
top to switch it off. A red LED next to the on/off switch indicates that the speaker is
on.
Amplifier Requirements
The ESL loudspeaker should be used with an amplifier of output capability between
20V and 30V rms (40-100W into 8 Ohms). The impedance characteristic is
essentially resistive and presents no problems to the amplifier. The ESL protection
circuits limit the maximum input voltage to 40V and there is no volume benefit from
using an amplifier with an output greater than 30V rms (100W into 8 Ohms).
Amplifiers with an output capability in excess of 35V rms (150W into 8 Ohms
approx) may be used but with caution – see Loudspeaker Protection.
If the Quad 405/2 power amplifier is used, the amplifier voltage limiters should not
be fitted.
Loudspeaker Protection
The ESL loudspeaker is fitted with a protection circuit, incorporating a special device
called a multifuse, which prevents damage from excessive programme input signals.
Should the loudspeaker be severely overdriven, for any length of time, the circuit will
operate and effectively reduce the drive to the loudspeaker, causing a reduction in
the volume level with some loss of quality. If this occurs, then the volume control of
the amplifier should be turned down. After a delay of a few seconds to allow the
circuit to reset, the volume can be increased, but only to a point below which the
protection circuit initially functioned, otherwise the circuit may operate again.
Persistently overdriving the loudspeaker will cause the multifuse to completely fail,
necessitating its replacement by a qualified engineer.
The above conditions are unlikely to occur in normal use or with amplifiers with a
power output rating of less then 100W. Steady state signals in excess of 10V rms
should not be fed to the loudspeaker.
When the AC power to the loudspeaker is switched off or disconnected, the signal
input protection circuit operates to prevent excessive signals being fed to the
loudspeaker elements – though care should be taken to ensure that the
loudspeakers are not driven for long periods (minutes) with no AC power applied.
Positioning the Loudspeakers
However good the loudspeaker, the final results will depend very largely on the
acoustic characteristics of the listening room and the position of the loudspeakers in
it. Do not be afraid to experiment with both position and orientation and make a point
of trying some of the less obvious as well as the more obvious positions. The
benefits obtained from the time spent doing this can be very rewarding. The subject
of room acoustics is complex and beyond the scope of this manual. It is assumed
that the loudspeakers will be used in a room with moderate reverberation, neither
too bright nor over damped. Furnishings can alter the acoustic characteristics of the
listening room, and here common sense is the best guide.
The loudspeakers have constant directivity over a wide angle in both horizontal and
vertical planes, so the response does not vary with the height of the listener’s ears
from the floor.
ESLmanual Feb02 11/02/04 9:14 AM Page 6