L-Acoustics dV-DOSC, Operator'S Manual

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dV-DOSC dV-SUB Manual V3.0 June 2005
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The internationally patented
1
DOSC waveguide is the core technology contained in dV-DOSC.
Essentially, the DOSC waveguide allows fulfilment of the first WST condition for frequencies higher
than 800 Hz, i.e., the wavefronts generated by individual DOSC waveguides are planar and their
combined radiating surface area accounts for at least 80% of the total surface area. For conventional
horn-loaded systems, coherent summation is simply not possible at higher frequencies since the
wavelength becomes progressively smaller than the physical separation between horn and driver
assemblies and neither of the two WST criteria can be satisfied. As a result, interference occurs
throughout most of the high frequency section's operating bandwidth for a conventional system.
By comparison, a dV-DOSC array is a full-spectrum, coherent loudspeaker system even for the
highest frequencies. As with any speaker system, interference does occur, however, the main
difference for dV-DOSC is that within the defined coverage region the interference is constructive,
while outside of the defined wavefield it is destructive.
One of the key benefits of WST is the predictability of the wavefront's shape. Horizontally, the entire
dV-DOSC array has the same directivity as a single enclosure (120°). Vertically, the coverage is
determined by the number of arrayed enclosures and the angle of separation between them. Given
this predictability, vertical coverage can be quickly optimized to match the audience geometry using
either L-ACOUSTICS ARRAY2004 or SOUNDVISION software. These convenient, user-friendly
programs help the operator determine how to focus the wavefront so that tonal balance and sound
pressure levels are evenly distributed throughout the audience (WST rule #4). Using either of these
programs, sound design can be performed and installation parameters determined on a case-by-case
basis to optimize coverage for each venue according to the audience geometry.
The configuration of transducers in a dV-DOSC enclosure is symmetrical with respect to the plane of
propagation of the wave, i.e., the plane bisecting the horizontal coverage angle. High frequency
transducers are located in the middle and low frequency transducers are located on both sides of the
high section. Such a configuration is described as having coplanar symmetry.
Coplanar symmetry is the cylindrical domain equivalent of the coaxial arrangement
*
for individual
sound sources. Essentially, coplanar symmetry allows for homogeneous coverage of the sound field at
any listening angle over the dV-DOSC array’s 120° horizontal coverage window. Coplanar symmetry
also eliminates off-axis acoustic cancellations at crossover points so that polar lobing is not an issue.
Psychoacoustically, coplanar symmetry is largely responsible for the exceptional imaging properties
that are characteristic of dV-DOSC when used in stereo (L/R) configurations.
Apart from coverage precision and predictability, another significant benefit of dV-DOSC is the fact
that the system effectively extends the near field region at higher frequencies (the nearfield is defined
as the region where cylindrical wavefront propagation applies and the farfield is the region where
spherical wavefront propagation occurs). As pictured in Figure 3, cylindrical wave propagation results
in a 3 dB reduction in SPL with doubling of distance as opposed to the 6 dB reduction that is typical of
conventional systems that radiate spherical wavefronts.
Due to it’s ability to generate cylindrical wavefronts, dV-DOSC has different attenuation properties
than conventional systems and should not be evaluated in terms of the classical "$ / kilowatt"-ratio.
Comparing SPL predictions according to standard calculations is also not meaningful since dV-DOSC
produces a combination of cylindrical and spherical wavefront propagation that must be evaluated
using specific calculations.
*
Distributed sound reinforcement using coaxial loudspeaker technology is L-ACOUSTICS’ other approach to sound
reinforcement. Either we respect WST criteria to obtain coherent coupling between individual sources and create a
single coherent line source (as for V-DOSC, dV-DOSC, KUDO, ARCS) or we separate individual, coherent sources
(MTD or XT coaxial loudspeakers) in a manner so that desired audience coverage is achieved while the effects of
audible interference are reduced. For more details on the benefits of coaxial loudspeaker technology and distributed
sound design techniques, please refer to the MTD or XT User Manuals (available for download on:
www.l-
acoustics.com ).
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The DOSC waveguide is registered under European patent n°0331566 and North American patent n°5163167
Please see Appendix 2 for a description of the DOSC waveguide