L-Acoustics V-DOSC, Руководство оператора

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L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 96 of 158
3.4.3 Hybrid Flown/Stacked Subwoofers
Flown SB218 with ground stacked centre SB218 line array
Flown dV-SUB with ground stacked L/R SB218 arrays
Figure 73: Hybrid flown/stacked subwoofer configurations
As seen in Figure 73, SB218 or dV-SUB enclosures can be flown beside L/R V-DOSC arrays as a low
frequency extension of the system and additional ground stacked subwoofers added to provide
sufficient low end impact for the first 15-20 metres. As discussed in Section 3.4.2, flown subwoofers
provide improved low frequency summation, impact and throw along with the important benefit of
improved time alignment throughout the audience. Typically, flown SB218s are operated in X mode
while ground stacked SB218s are processed in X AUX mode. For flown dV-SUB / ground stacked
SB218 configurations, dedicated X and INFRA presets are available (see Section 1.15).
Figure 73 shows two options for the ground stacked subwoofers – in both cases, SB218 enclosures
are standing vertically (on their side). This orientation is beneficial for two reasons: 1) all of the central
ports are aligned horizontally - this provides optimum port coupling plus low frequency output at the
port tuning frequency (approx 30 Hz); 2) when oriented in this manner, the SB218 is at a convenient
height to serve as a stacking platform for front fill or stereo in fill enclosures. As an alternative to the
central line configuration, individual SB218s can also be spaced apart and used as part of a distributed
front fill system (see Fig 78f).
A central line array of SB218s will radiate omnidirectionally (into half space) vertically - this is of
interest for indoor venues in order to obtain low frequency impact throughout the tribune section of
the audience. Horizontal coverage of the central line array can be improved with additional electronic
delay processing (see Section 3.5.2) and overall, flown L/R plus ground stacked subwoofers form an
LCR configuration with the potential for improved low frequency coverage in the horizontal plane.
The stacked L/R subwoofer configuration shown in Figure 73 proves a convenient location for stereo
infill enclosures (for example, dV-DOSC or ARCS). Provided that the separation between the stacked
L/R subwoofer arrays is approximately 4.5-6 metres, they will also act as a centre channel in
conjunction with the flown L/R subwoofers to create an LCR configuration with the accompanying
benefits of more even horizontal coverage (see 3.5.2). As a time alignment reference (for FOH L, for
example), the measurement microphone should be located between the flown L and stacked L
subwoofers and at a distance where the energy from the flown and stacked subwoofers is identical.
Such a time alignment reference provides the most even horizontal coverage combined with a smooth
transition between flown versus ground stacked subwoofers with distance.
Figure 74: Hybrid flown/stacked subwoofer example : L/R = 14 V-DOSC + 3 dV-DOSC (per side); flown dV-SUB
(6 per side); ground stacked SB218 (6 per side); LL/RR = 4 V-DOSC + 6 dV-DOSC (per side); stereo infill = 2
dV-DOSC (per side); distributed front fill = 4 dV-DOSC (Bjork, POPB Paris 2003 – sound design M Malki)