X-Treme Audio MISI - Manual (Page 7)

LINE ARRAYS
fig. 9
As a result of this property of arc sources, taking into account the
lower semi-arc only and adding a linear source, one can see (fig.
10) that the J source model is suitable to describe the sound field
represented in fig. 6.
fig. 10
The J source model can be generalized in the progressive source
(fig. 11), where the curvature is no longer null (or, better, infinite) and
then constant such as in the J source, but it is parametrized in rela-
tion to a coefficient
σ. The analytical formulation is even more com-
plex than the arc source but it is clear that a progres sive source can
achieve complete control of the emission lobes.
fig. 11
7. Line arrays: “the state-of-the-art”
The term “ line array” (also called “sound columns”) applies to a
sound reproduction system made up of a variable number of verti-
cally arranged units (also called modules), which can achieve the
effect of a single acoustic source having the dimen sions of all the
component units and whose performance provides a coherent re-
production, that is the result of the sum of its various compo nents.
The vertical alignment allows narrowing of the reception zone to be
achived as well as greater directivity and sound pressure compared
to traditional systems.
The idea is to create columns made up of low, middle and high fre-
quency speakers; the systems consist of small, light modules joined
into a wide acoustic source - the “line array”. The main advantage of
this type of system is the energy saving deriving from narrowing the
vertical directivity and a higher directivity of the sources which can
also produce sound waves decreasing by 3 dB only for each dou-
bling of distance instead of 6 dB as happens in traditional systems.
These types of waves are defined as
cylindrical and are generated
while respecting certain parameters relating to the elements making
up the array within a certain distance from the source (near field),
which depends on the frequency of the reproduced wave and on
the lenght of the source itself. Having only two dispersion dimen-
sions instead of three as in traditional spherical waves, the sound
transmitted by the cylindrical waves decreases much more gradu-
ally in relation to the distance from the source. As a result, the listen-
ing experience does not change significantly in terms of sound level
from a position far from the line array source to a position very near
to it. Moreover, the vertical radiation for this type of system decays
rapidly above and below the line array. As a result, less reverbera-
tion is generated in case of indoor use because no wave is radi-
ated towards any reflecting surfaces existing in the upper part of the
room. Consequently, clarity and sound intelligibility are remarkably
improved.
8. X-Treme Vertical Line Array: product range
Created in 2001, the X-Treme brand identifies all the products man-
ufactured by the Sound Corporation group business unit which
produces “concert, touring and portable sound systems”, that is
professional audio systems for concer ts, open air “live” events or
any other indoor installation where music is played live.
The X-Treme SBU (Strategic Business Unit) catalogue presents 3
different lines of
vertical line array (VLA), all consisting of a 3-way
module (the bi or tri-amplification mode can be selected by switch-
ing the high current handling terminals in the crossover) and its cor-
responding stacked or flying subwoofer, available in both active and
passive versions.
The
Linear Source Array (LSA) system is the top solution of the
range: in particular, the XTLSA module features high performances
in terms of acoustic pressure as well as an innovative horn-loaded
midrange configuration; the
MISI TM ( Middle-Sized Line Array)
system has been designed to achieve an acoustic pressure similar
to that of the above-mentioned “big” system, but with a higher re-
sponse speed. Finally, the
Mini Line Array (MLA) system stands
out for its exceptional sonic accuracy with extremely reduced bulk
and weight.
Line source Arc source
J source
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