L-Acoustics V-DOSC, Operator'S Manual

Page: 153 / 158

L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 153 of 158
APPENDIX 7: WST Criteria Number 5
In the AES Journal paper ''Wavefront Sculpture Technology'', Vol. 51, No. 10, October 2003 it is
shown that the maximum angle allowed between enclosures is given by the following
expression:
According to WST Condition 1, the Active Radiating Factor (ARF) should be higher than 80%.
The STEP distance is the separation between acoustic centres and d
min
is the minimum distance
to the closest members of the audience.
For front-loaded systems such as V-DOSC or dV-DOSC it is basically the size of the component
that determines the vertical height of the enclosure and, in turn, the separation between
acoustic centres. Taking the nominal component diameters for 8”, 12”, 15” and 18” speakers
and adding two thicknesses of wood for the top and bottom enclosure walls therefore
determines the STEP distances given in the table below. ARF is set to 80% since this is the limit
for satisfying WST Condition 1 and the maximum angles are calculated for two minimum listener
distances: d
min =
10 or 20 metres.
Table 22: WST Criteria Number 5
For front-loaded 15” systems such as V-DOSC, it is seen that the maximum allowed angle is 4.8
degrees for d
min
= 10 m and 6.0 degrees for d
min
= 20 m. This explains why the maximum
ANGLE STRAP value for V-DOSC is 5.5 degrees.
For front-loaded 8” systems (dV-DOSC) it is seen that the maximum allowed angle is 11
degrees for d
min
= 10 m and 11.7 degrees for d
min
= 20 m. Although the maximum value for dV-
DOSC may seem conservative at 7.5 degrees, this value corresponds to a minimum listener
distance of 3 metres, allowing listeners to be closer to the system for downfill or shorter throw
applications.
COMPONENT Nominal Diameter Enclosure Height Max Interelement Angle Max Interelement Angle
(mm) (m) (degrees) (degrees)
18'' 460 0,496 3,2 4,6
15'' 380 0,416 4,8 6,0
12'' 300 0,336 7,0 7,9
8'' 205 0,241 11,0 11,7
dmin = 10 m dmin = 20 m
π
α 180
24
1
min
max








− =
d
STEP
STEP ARF