Sound Design; Stacked Or Flown - L-Acoustics dV-DOSC Operator's Manual

3. SOUND DESIGN

3.1 STACKED OR FLOWN?

Although flown systems are generally preferred, there are good arguments to support both solutions
and, in some cases, the choice is dictated by the venue itself, i.e., sometimes it isn't possible to fly the
system since rigging points are not available or weight restrictions apply.
Stacked Systems improve image localization for the audience since the perceived sound image is
lowered to stage level. This is beneficial in small venues and stacking also offers more low frequency
energy due to enhanced ground coupling. Since dV-DOSC has less SPL attenuation from front-to-rear
of the audience than conventional systems, this allows a stacked system to project further and provide
better underbalcony penetration in theatres and clubs, for example. In addition, for geometric reasons
a stacked system can provide more extended vertical coverage than a flown system - this can be seen
using ARRAY 2004 or SOUNDVISION and is simply related to the geometry of the audience to be
covered. For example, distributed field level stacked systems are an excellent solution for stadium
sound reinforcement – fewer enclosures are required to obtain the necessary audience coverage
vertically and, as an additional benefit, the subjective image is lowered to field level.
Stacking is a good solution for applications where up to 12 dV-DOSC enclosures can optimize audience
coverage, low frequency response and image localization.
Flown Systems are the best solution to achieve uniform sound pressure level and even tonal balance
over the audience provided that the number of arrayed enclosures is sufficient to provide the
necessary front-to-rear coverage and that WST Condition 4 is respected (i.e., inter-enclosure angles
are selected to obtain equal spacing between enclosure site angle impacts over the audience). Flying is
also an excellent solution for sightline problems that commonly occur. Typically, system trim height
should be selected to provide a 4:1 ratio between the throw distances to the furthest and closest
members of the audience. Such a trim height tends to make it easier to satisfy WST Condition 4 and
thus obtain optimum SPL distribution. Offstage coverage is another consideration when selecting array
trim height – in general, the best results are obtained when the top dV-DOSC enclosure has a zero
degree site angle and is flown at the same height as the highest audience elevation.
For flown systems, additional speakers are typically necessary to cover center fill, front fill or offstage fill
requirements. Good candidates include ARCS, KUDO or additional dV-DOSC arrays (see Multiple Arrays).
Other distributed front fill or stereo infill enclosures include: L-ACOUSTICS MTD108a, MTD112b,
MTD115b, 112XT, 115XT or 115XT HiQ loudspeakers.
Hybrid Stacked/Flown Systems are a good solution for theatrical installations where the flown system
provides balcony (circle) and upper balcony (upper circle) coverage and the stacked system provides
floor (orchestra level) coverage. Most theatres have significant vertical coverage requirements due to a
relatively short throw distance of 20-35 metres combined with a high audience elevation of 12-15
metres in the upper circle. In addition, many theatres have rigging points with weight load restrictions
that limit the number of loudspeakers that can be flown. For these reasons, the hybrid stacked/flown
sound design approach is practical in reducing the number of enclosures required and at the same
time this sound design approach can help improve image localization (especially with the addition of
centre cluster, front fill and underbalcony delay systems combined with judicious time alignment and
relative level adjustment between all elements of the sound design).
Note: For hybrid stacked/flown systems, the trim height of the flown system should be selected so that the
bottom dV-DOSC cabinet has a zero degree site angle and is at the same height as the listening level for the
first row of the balcony audience. This helps avoid reflections from the balcony face while providing more
even off-axis coverage for the first row of the balcony.
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dV-DOSC dV-SUB Manual V3.0 June 2005