Hybrid Flown/Ground Stacked Subwoofers (4-Way System Operation); Figure 67: Hybrid Flown/Stacked Subwoofer Configurations - L-Acoustics dV-DOSC Operator's Manual

3.4.3 Hybrid Flown/Ground Stacked Subwoofers (4-way system operation)

(a) Flown dV-SUB, ground stacked centre SB218 line array
(b) Flown dV-SUB, ground stacked L/R SB218 arrays
(c) Flown and ground stacked dV-DOSC/dV-SUB,
ground stacked L/R SB218 arrays
(d) Flown dV-SUB, ground stacked LCR SB218 arrays

Figure 67: Hybrid flown/stacked subwoofer configurations

As seen in Figure 67, dV-SUB enclosures can be flown offstage beside L/R dV-DOSC arrays or as part
of the array to provide low frequency extension and ground stacked subwoofers added to provide
additional low end impact.
Figure 67 shows several options for the ground stacked subwoofers – SB218 enclosures are standing
vertically (on their side) or stacked in columns. This orientation is beneficial for two reasons: 1) all of
the central ports are aligned - this provides optimum port coupling and low frequency output at the 32
Hz port tuning frequency; 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 seen in Fig. 67a, 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
an audience tribune gradient. Horizontal coverage of the central line array can be adjusted with
electronic delay processing (see Section 3.5.2) and experiments are also ongoing into the use of
additional rear channel subwoofers (located at the focal point of the delay processed central line array)
to provide improved flexibility and control.
Note: As an alternative to the central line configuration shown in Fig. 67a, individual SB218s can be spaced
apart and used as part of a distributed front fill system.
The stacked L/R subwoofer configuration shown in Fig. 67b proves a convenient location for stereo
front fill enclosures (for example, dV-DOSC, ARCS or MTD/XT coaxial enclosures). 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 also Section 3.5.3). 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 67c shows a hybrid/flown stacked subwoofer configuration suitable for theatrical sound
reinforcement – particularly for touring applications.
Figure 67d shows a ground stacked LCR subwoofer configuration that also provides locations for
stereo infill and/or stacked centre fill enclosures (see also Section 3.5.3).
Overall, the flown L/R plus ground stacked subwoofer configurations of Figs 67 a,b and d create an
LCR configuration with the potential for improved low frequency coverage in both horizontal and
vertical planes. Figure 67c is acceptable in narrower venues where centre build up is less problematic.
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dV-DOSC dV-SUB Manual V3.0 June 2005