L-Acoustics dV-DOSC Operator's Manual page 12

The configuration of transducers in a dV-DOSC element 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
(spherical) 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 (Left / Right) 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. For flat dV-DOSC
arrays, this 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. This property arises due to the physics of cylindrical
waves versus spherical waves (see the figure below).
This means that dV-DOSC should not be evaluated in terms of the classical "$ / kilowatt"-ratio, i.e.,
due to it's ability to perform Wavefront Sculpture, dV-DOSC has different attenuation properties
than conventional systems. Comparing SPL predictions according to standard calculations is not
meaningful since dV-DOSC produces a combination of cylindrical and spherical wavefront
propagation that must be evaluated using specific calculations.
Aside: This is one of the reasons why EASE and CATT-Acoustic modelling data was not available for dV-
DOSC, V-DOSC and ARCS in the past (whereas data was provided for the coaxial MTD products
manufactured by L-ACOUSTICS). Custom modelling for WST-based system simulation has recently been
completed for the EASE and CATT-Acoustic room acoustics modelling packages.
When curved dV-DOSC arrays are employed there is a combination of cylindrical and spherical
propagation. This combined propagation, together with the actual shape of the audience geometry
allows the wavefield to be focused so that tonal balance and sound pressure levels are evenly
distributed throughout the listening area. Although pure cylindrical wave propagation is not always in
effect, 3 dB reduction with distance can still be obtained along with extension of the nearfield by
dV-DOSC dV-SUB Manual V2.0 Nov 2001 12