Stacked Or Flown; Stacking Guidelines - L-Acoustics dV-DOSC Operator's Manual

3.2 STACKED OR FLOWN?

Although flown systems are generally preferred by most sound engineers, there are good arguments
to support both solutions. In many cases the answer is dictated by logistics that are venue-specific,
i.e., sometimes it simply isn't possible to fly PA.
"Stacking" onstage lowers the perceived sound image to stage level which is beneficial in small
venues. Stacking also offers more low frequency SPL due to enhanced floor coupling and since dV-
DOSC has less SPL attenuation from the front to the back of the audience than traditional systems,
this allows a stacked system to project further. In addition, for geometric reasons a stacked array
can provide more extended vertical coverage than a flown one - this can be seen using the ARRAY
2000 spreadsheet. For these reasons, stacking makes sense in small configurations where only a few
elements can optimize audience coverage.
"Flying" is the best solution to achieve uniform sound pressure level and even tonal balance over the
entire audience provided that the number of elements arrayed is sufficient to provide the necessary
front to rear coverage. Flying is also an excellent solution for sightline problems that commonly
occur and provides better high frequency penetration into the audience with reduced shadowing
effects. For flown configurations, additional speakers are added to cover center- or front-fill
requirements and to help pull the localization image down towards the stage for the first 10-20 rows
of the audience. Good candidates for this include ARCS stereo infill, distributed dV-DOSC apron fill
or other front fill enclosures such as: MTD115a, MTD112, MTD108a or EX112 loudspeakers.

Stacking Guidelines

The stacking system is rated for a maximum of 12 dV-DOSC elements.
For this type of installation, the precise nature of dV-DOSC vertical coverage allows little margin for
error. The designer must know if the audience is standing or seated - the bottom of the array should
always be higher than the ears of the first rows of the audience and the lowest element tilted
downwards. Note: for extended bandwidth applications, a vertical stack of 4 SB218 subwoofers
provides a convenient stacking platform at a height of 2.2 m above ground level. Alternatively, 3 dV-
SUBs provide a good stacking height (2.1 m above ground level).
If the bottom of the array is too low, the first rows receive too much SPL and audience members
directly in front of the system behave as an acoustic screen for the following rows (shadowing).
Ideally, the bottom of the array should be slightly above the audience (not lower than 2 m or 6.5 ft
above floor level), with the lowest element tilted downwards as necessary.
130 140 150 160 170 180 190 200 2
A distributed, field level stacked system for stadium sound reinforcement.
dV-DOSC dV-SUB Manual V2.0 Nov 2001 64