X-Treme Audio MISI - Manual (Page 8)

User’s manual
Self-powered systems
The Linear Source Array
XTLSA/A, MISI TM XTMISI/A and Mini Line
Array XTMLA/A active modules have been designed with the pur-
pose of offering highly professional products combining the X-Treme
audio system quality with new digital electronics technologies for
the audio sector: in fact, both the power stage and the power sup-
ply unit have been entirely designed with switching technology to
achieve high performance with very reduced weight.
The signal quality, in terms of distortion, is the same of that of the
traditional professional amplification systems, while the pre-ampli-
fication stage uses a powerful
DSP (Digital Signal Processor)
which allows extremely accurate processing of the signa l as well
as the implementation of complex algorithms in infinitesimal times.
In particular, the system management is innovative and accurate
thanks to the remote connection thus enabling the creation of
speaker system networks which can be controlled by a single sta-
tion. The X-Treme designers’ efforts have led to the development of
very interesting products for those working in the professional audio
sector and appreciating continuous technological improvements.
9. X-Treme Vertical Line Array: system design
The X-Treme vertical line array (VLA) acoustic speaker systems
have been designed to achieve broad horizontal and vertical cov-
erage. This has been obtained thanks to a new waveguide for
high range selection capable of producing a 120° coverage on a
horizontal plane. Starting from an array made up of side-by-side
X-Treme speakers, the cabinets can be progressively opened by
using the rear bars and by selecting the hole that ensures correct
positioning, to obtain an array with different curvatures. A linear
array can be created by using the hole corresponding to the low-
est position in the rear of the cabinet handles. All X-Treme VLA
loudspeaker systems have been designed as systems composed
of identical elements in a vertical array configuration.
When different loudspeaker systems (often called ‘
line array mod-
ules’) are configured in a line array, the electro-acoustic transducers
are placed inside the cabinets in order to meet the Wavefront Sculp-
ture Technology
© criteria for each frequency band (1. the wave fronts
generated by the electro-acoustic transducers for high frequencies
are planar, 2. the “step”, that is the distance between acoustic cen-
tres of the individual mid-low frequencies sources is smaller than half
the wavelength correspon ding to the highest reproduced frequency
= cut-off freq.).
Therefore, each element generates a
linear wave-front with
a constant phase which enables several elements to be as-
sembled together creating a single broad sound source. Since
the separation angle between the elements is adjustable, the
wave-front can be modelled by changing the shape of the array.
Thanks to a successful coupling right across the audible spec-
trum, the X-Treme VLAs generate a
coherent wave-front on a
large area with tiny variations in frequency response and sound
pressure level. Therefore, these products are broadband sound
reinforcement systems which ensure coherence up to the high-
est frequencies. In terferences may occur as in all loudspeakers
systems, but what makes X-Treme different is that interferences
are constructive in the declared coverage area, and destructive
outside this area. In a line array configuration, the bulk of the en-
closures is smaller because all the array elements are coherently
coupled, and fewer cabinets are required compared with conven-
tional systems.
This means that the VLAs are highly competitive in case of touring
applications in which transport, space availability and assembling can
be very expensive. These properties make these systems very con-
venient even for fixed installations where compact dimensions and
coverage predictability are essential factors. In fact, one of the key
benefits of the line arrays is predictability of the wave-front shape.
Besides coverage accuracy, another important advantage resulting
from using X-Treme array systems is their ability to extend the near
field at high frequencies.
In linear arrays, this leads to SPL reduction by 3 dB for each doubling
of the distance versus 6 dB in the traditional systems. This property
results from the physical features of cylindrical waves and spherical
waves. This also means that these systems should not be evaluated
on the basis of the classic “
cost/kilowatt” ratio — since they gener-
ate flat wave-fronts, they follow different attenuation laws compared
with traditional systems. Determining the SPL value according to
standard calculations is not meaningful because VLAs generate a
combination of cylindrical and spherical wave-fronts which must be
evaluated according to specific models (as shown in paragraph 4).
X-Treme curved arrays
When
curved arrays are used, a combination of cylindrical and
spherical propagations is obtained. Although the propagation of
pure cylindrical waves does not always occur, reduction by 3 dB
in relation to distance can be achieved through the extension of
the near field and correct orientation of the system on the listening
area. From a psycho-acoustic perspective, the near field extension
allows the listener to be at a great distance from the systems and
to perceive just a small difference in SPL terms due to the non con-
ventional attenuation. In practice, the result is a high fidelity listening
expe rience, a better stereophonic image and exceptional clarity. At
a subjective level, listeners feel that the speaker systems are closer
to them and that the sound is “right on your face”. The sound image
localization is towards the stage, rather than towards the speaker
systems. The near-field extension implies that not very high sound
pressure levels are required near the system in order to obtain suit-
able SPLs at the back of the listening area. Moreover, this property
reduces the potential hearing loss for the audience and technicians
alike. The near-field extension, combined with the coverage ac-
curacy and predictability, can also effectively increase the
critical
distance in highly reverberating spaces (critical distance can be
defined as the distance to which the direct sound energy equals
that of the reflected sound). In many situations it is very important to
prevent signals from reaching the ceiling, which means preventing
energy from reaching any reflecting surfaces which have no relation
with the sound event, such as in sports halls, arenas or amphithea-
tres. Having less reverberation resulting from the sound acting on
empty rooms or reflecting surfaces and by directing more energy
to the listening area, critical distance can be increased in a specific
room. Finally, another benefit of X-Treme VLA systems is the high
decaying SPL level outside a well-defined wave field. This allows
installation of the arrays behind or on top of the microphones with
an exceptional resistance to feedback. Basically, if the bottom of the
last module is visible, it means that one is outside the system cov-
erage field. The FOH technicians too will prefer working with these
loudspeaker systems for their low back-propagation, even at low
frequencies, as the woofers will be positioned in a vertical array.
The high SPL attenuation levels outside the coverage area make
X-Treme VLAs an excellent solution for situations in which environ-
mental noise should be avoided, such as, for example, in open air
amphitheatres located near residential areas.
8/21