User manual

5-2 P1200A User Manual
Vertically stacking the cabinets, rather than horizontally arraying them is
particularly useful in deep rooms where more than one cabinet has to
be used because a single cabinet has insufficient throw for the level
needed at the back of the room. This helps reduce interference in the
horizontal plane and gives more vertical directivity.
Coupling subwoofers
Regardless of the type and operating principles of the subwoofer
systems, the basic relationships of coverage and array directivity at bass
frequencies apply.
− Vertical arrays of subwoofers carry bass further since they have
higher vertical directivity, and hence dissipate less energy in the
vertical direction.
− Horizontal arrays have greater horizontal directivity and can
therefore be used more effectively to influence level distribution in
the horizontal plane, e.g. between the middle and sides of the stage.
The typical effect of bass over-accentuation on the central axis
between the two front stacks can be reduced by rotating the two
subwoofer arrays in an outward direction. The broader the SUB
array, the greater the effect.
If a large number of systems are available, an L-shape configuration
can combine the advantages of the two variants.
The arrangement of subwoofers in flown arrays (C4 system) is often
determined by the position of the TOP cabinets, i.e. the coverage
requirements of the array. However, it is important to ensure that the
subwoofer systems are also arranged in groups (blocks, rows or
columns) in order to benefit from the coupling effects described above.
5.2. Wiring
In order to keep losses in tone and power low the length of cable run
between mainframe and loudspeaker should be kept as short as
possible. A conductor size of 1.5 mm
2
(16 AWG) is necessary, 2.5 mm
2
(12 AWG) is preferable.
When full range loudspeakers and actively driven subwoofers are
operated together, then - due to the different pin assignments of the
systems - four-core cables have to be used.
We recommend the use of d&b MC4 cable (4 x 2.5 mm
2
/ 4 conductor
12 AWG). MC4 cables retain their flexibility even at low temperatures
and can be supplied in various lengths.
If very long cable runs are unavoidable in an installation, a conductor
size greater than 2.5 mm
2
(12 AWG) may be needed to reduce power
loss and to achieve an acceptable damping factor (relation of load
impedance to cable impedance). If the individual conductor size in a
cable is insufficient, then it’s permissible to use two or more of the
conductors.
The following ‘rule of thumb’ formula allows you to estimate the
maximum cable length with an acceptable damping factor (>10):
maximum (single) length of cable [m] =
3 x load impedance [ohms] x cross-section [mm
2
]