Introduction; Wavefront Sculpture Technology™ Fundamentals; The Sound Reinforcement Problem - L-Acoustics dV-DOSC Operator's Manual

INTRODUCTION

The small ''d'' in dV-DOSC refers to the mathematical terminology for the derivative function since dV-
DOSC can be considered as a derivative of V-DOSC. dV-DOSC provides the same benefits of
Wavefront Sculpture Technology as V-DOSC except in a much smaller format.
We hope this manual will help you to understand the basic theoretical principles behind how the dV-
DOSC system works. Understanding these principles will help you to optimally use dV-DOSC and dV-
SUB in sound design – whether for touring or fixed installation. Understanding the concepts behind
dV-DOSC and Wavefront Sculpture Technology are just as important as learning the many operational
details related in this manual – the more you understand the big picture, the more effectively you will
use the system.
dV-DOSC is a complete system approach – starting from the basic scientific question of how to
effectively couple sound sources then including all aspects of performance prediction, sound design,
system installation, rigging, cabling, signal distribution, digital signal processing and system tuning. This
turnkey system approach allows for accurate and predictable results, however, in order to achieve the
best results you need to understand the theoretical concepts behind how the system works and adopt
a methodical approach to sound design and installation. For these reasons, specialized training is
necessary to obtain the best results with the system. Some people think that working with dV-DOSC
is complicated but once you understand the procedures involved, you save time and - more
importantly - obtain better, more predictable results.
Apart from sound quality and the turnkey system approach, there are many other benefits to
dV-DOSC. Many readers are already aware of these – if not, hopefully they will become apparent
throughout the course of this manual.
WAVEFRONT SCULPTURE TECHNOLOGY™ FUNDAMENTALS

The Sound Reinforcement Problem

The first task of sound engineers and audio consultants is to design sound reinforcement systems for a
given audience area. Performance expectations in terms of sound quality, sound pressure level (SPL)
and coverage consistency have progressively increased over the years while at the same time the size
of the audience has grown, inevitably leading to an increase in the number of loudspeakers.
In the past, conventional horn-loaded trapezoidal loudspeakers were typically assembled in fan-shaped
arrays according to the nominal horizontal coverage angle of each enclosure in an attempt to reduce
coverage overlap that causes chaotic interference. With this type of arrangement, the optimum clarity
available in one direction could only be provided by the individual enclosure facing in this direction.
Attempts at "flattening the array" to achieve greater throw and higher SPLs resulted in severe
interference in an uncontrolled way, affecting coverage, pattern control, intelligibility and overall sound
quality. Even when arrayed according to specification (always an ''optimum'' compromise since the
polar response of individual horns varies with frequency), the sound waves radiated by individual horn-
loaded loudspeakers do not couple coherently thus the conventional system approach is fundamentally
flawed. Furthermore, the chaotic sound fields created by interfering sound sources waste acoustic
energy, thus requiring more power than a single, coherent source would in order to obtain the same
SPL.
As an illustration of this, imagine throwing some pebbles into a pool of water. If one pebble is thrown
into the water, a circular wave will expand concentrically from the point where it entered. If a handful
of pebbles are thrown into the water, we observe the equivalent of a chaotic wavefront. If we throw
in a single larger stone, having total size and weight equal to the handful of pebbles, then we again see
a coherent circular wave as for the case of the single pebble — only now with a much larger
amplitude. If all of the individual pebbles could be glued together, this would provide the same effect
as the larger stone...
This illustrates the thinking behind dV-DOSC and V-DOSC: if we can build a single sound source from
a number of individual speakers that can be separated for transport and handling, then we have
achieved our goal, i.e., to provide a totally coherent, predictable wavefield.
9
dV-DOSC dV-SUB Manual V3.0 June 2005