Fig. 14 Details of XTDS15/A and XTDS18/A rear panel
The two switches on amplified subwoofer modules XTDS15/A and
XTDS18/A make possible the following operations:
two different low
pass cuts
and
polarity inversion
.
The lowest frequency cut (90 Hz) is adapted correctly to the use
with the respective main modules in the Deflector line, which must
be set to “
sub
” mode by choosing the correct preset; the other cut
(120 Hz) can be useful if used with the respective Deflector Line main
modules, in order to create a boost wherever necessary in the 100
Hz zone, or to use the subwoofers with smaller main modules, which
are not extended so well at low frequencies. The figure shows the
subwoofer model XTDS18/A frequency response
2
as an example,
with the two different low pass cuts available.
Fig. 15 Subwoofer XTDS18/A presets
2
measured on the ground with reflective floor and microphone along the axis of 2 m in
virtually anechoic conditions (measurement of impulse response and partial separation
of reflections, the first obstacle at 4 m). Input signal – 20 dBu.
In standard insulation conditions (with the main speakers resting on
the subwoofers, directly or with a stand holder), the polarity must be
rigorously set to
direct mode
, therefore with the switch turned off.
For this reason, the position with inverted polarity (switch down) is
marked in red on the panel in this particular case. Otherwise there
will be a pressure cancellation effect, that will lead the device to loose
efficiency in the crossover band (100 Hz zone). Polarity inversion can
only allow for a better subwoofer and upper module coupling only, if
the two cabinets are placed between them. “Better coupling” means
that in the crossover band (100 Hz zone) the system is able to supply
more sound power in the environment, which depends on the rela-
tive position between the subwoofers, upper modules and the walls
or large obstacles. Whether or not polarity inversion brings about this
improvement can be understood by listening, through direct meas-
urements or simply “by ear”.
Fig. 16 Standard configuration of
subwoofer-upper module coupling (direct polarity).
10. SYSTEM CONFIGURATIONS
The following are the standard Deflector range configurations. In
each case it is also possible to use the “
halved
” version, with just
one satellite and one subwoofer on each side (consequently halv-
ing the sound power supplied). The connections of two loudspeaker
systems to the same amplification channel should be in parallel. The
amplifier supply remains unchanged when going from one to two
speakers at each side, because halving the acoustic impedance
from 8 Ohm to 4 Ohm allows the amplifier to generate about twice
as much power, in other words its rated power.
Fig. 17 System configuration with XTD88
and XTDT amplifiers
8/12