Central Location, Ground Stacked; 3-Way Presets For Dv-Dosc And Sb218 Subwoofers; 3-Way Presets For Dv-Dosc And Dv-Sub Subwoofers - L-Acoustics dV-DOSC Operator's Manual

Central Location, Ground Stacked

This configuration optimizes the radiated energy. All subwoofers are acoustically coupled and the
floor acts as a mirror that virtually doubles the number of subs. Given the same number of subs, the
overall pressure obtained by ground stacking in this manner is simply not achievable in any other
configuration.
The central ground stack solution is not devoid of shortcomings. Typically the problems are:
Tonal balance has an exaggerated low boost for the closest members of the audience. Front fill
speakers are necessary to compensate for this local buildup of low frequency energy.
Low end can spill back onstage and cause feedback problems for the stage monitoring system
Restricted projection due to audience absorption and modified thermal conditions (this problem
is likely to occur with any ground stacked configuration)
Mutual radiation pressure may wear the drivers located at the center of the array
For the central ground stacked configuration, the subwoofers are not acoustically coupled with the
main dV-DOSC arrays. They are processed separately and fed with an independent signal from an
auxiliary output.
NOTE: For central ground stacked subwoofer configurations, typically an 80 Hz low pass filter is employed
along with aux sub drive. Presets for use with the SB218 are dV 3WX SB218 L0/HI (XTA) and DV 3WX SB
L/H (BSS). Presets for use with dV-SUB are dV 3W 80 dVS LO/HI (XTA) and DV 3W 80 L/H (BSS)
If a center line of subwoofers is installed, horizontal directivity will narrow while the subwoofers will
remain omnidirectional vertically. Electronic delay arc processing as described in the V-DOSC
manual can help broaden the narrowing of the central lobe and improve overall coverage
horizontally. Please consult the V-DOSC manual for further details.

3-WAY PRESETS FOR dV-DOSC AND SB218 SUBWOOFERS

Two types of presets are provided for the SB218: 3W (100 Hz HPF for dV-DOSC) and 3WX (80 Hz
HPF for dV-DOSC). The 3W preset is intended for applications where subwoofers are flown close to
the dV-DOSC array as an extension of the system or when SB218s are used as a stacking platform.
The 3WX preset is intended for applications where subwoofers are ground stacked, separate from
the flown dV-DOSC arrays. Both presets are optimized for a 2:1 dV-DOSC:SB218 cabinet ratio.
A dV-DOSC array is capable of radiating frequencies down to 100 Hz at high level with good
directivity control. As seen previously in the ''Powering dV-DOSC'' section, a dV-DOSC array is
typically high-pass filtered at 100 Hz and the limiter threshold set at 7 dBu for the low section in
order to provide excursion protection for the 8'' components. This is the case for 3W presets while
for 3WX presets, the dV-DOSC low section is high pass filtered at 80 Hz and the limiter is set at 5
dBu. For 3WX presets, since there is no overlap in the effective operating bandwidths of sub and dV-
DOSC low sections, the subwoofers can be operated with the same polarity in 3-way mode without
phase problems due to the overlap of crossover frequencies.

3-WAY PRESETS FOR dV-DOSC AND dV-SUB SUBWOOFERS

For dV-DOSC plus dV-SUB 3-way presets, a variety of crossover points between dV-SUB and the
dV-DOSC low section (80, 120 and 200 Hz) are provided for different configurations. The 80 Hz
crossover point is intended for applications where dV-SUB and dV-DOSC are physically separated
(eg. ground stacked subwoofers with flown dV-DOSC system). The 120 Hz crossover point is
considered optimal in terms of power bandwidth for both dV-SUB and the dV-DOSC low section
and is intended for all closely coupled applications (closely coupled flown subwoofers or ground
stacked systems). The 200 Hz crossover point allows the dV-SUB to function as a combination
dV-DOSC dV-SUB Manual V2.0 Nov 2001 68