L-Acoustics V-DOSC, Руководство оператора

Страница: 92 / 158

L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 92 of 158
3.4 SUBWOOFERS
Although V-DOSC is capable of radiating frequencies down to 40 Hz with good vertical directivity
control (the low frequency directivity control limit depends on the size of the array), SB218
subwoofers are normally added to the system to extend the frequency response down to 27 Hz and
increase the overall unweighted SPL. Techniques for maximizing the combined response of low and
sub sections are discussed in the following along with subwoofer arraying techniques and overall sound
design recommendations. For additional information, please refer to Section 1.15 for details on
sub/low preset processing.
General Guidelines for the Use of Subwoofers
The number of subwoofers required depends on 3 parameters:
Number of V-DOSC Enclosures: the standard subwoofer ratio is 1.5 V-DOSC : 1 SB218
(for example: 3:2, 6:4, 9:6, 12:8, 15:10)
Type of Program Material: the standard ratio is recommended for most rock and pop applications.
For intense heavy metal or rap a 1:1 ratio is desirable; a 2:1 ratio can be acceptable for some
applications (e.g., corporate/special events); and in some cases, V-DOSC can be used without
subwoofers (e.g., classical music or speech reinforcement).
Type of Installation: For open air applications, the recommended quantities remain standard when
subwoofers are ground stacked. When subwoofers are flown, additional ground stacked
subwoofers may be required (see below – hybrid flown/stacked subwoofers).
In terms of processing, two cases can be considered depending on FOH mix engineer preference and
the intended purpose of the subwoofers. For some applications, subwoofers are used as an effect and
are not driven with the same signal as the V-DOSC system (separate auxiliary send). The other option
is to use subwoofers as a low frequency extension of the V-DOSC array and drive subs with the same
signal (4-way mode). All presets (4W, INFRA, X, X AUX) will function with aux sub drive or in 4-way
mode, however, the user should be aware of the operating bandwidths and select the preset that is
most appropriate for the installed configuration and application. Please refer to Table 9 for a summary
of sub/low preset processing and the following for a discussion of preset selection issues.
Subwoofers as a Low Frequency Extension
In this case, subwoofers are driven in 4-way mode with the same signal that is sent to the V-DOSC
array. All 4+2 presets are optimized for this type of system drive (input A / outputs 1,2,3,4 = SB218,
V-DOSC LOW, MID, HIGH, respectively) and the same channel assignments apply to 5+1 format
presets when the system is operated in 4-way mode.
Subwoofers as an Effect
In this case, subwoofers are driven using a separate aux send that is different from the signal sent to
the V-DOSC array. All 5+1 format presets allow for aux sub drive using input B / output 6.
Note: Additional 5+1 presets are provided for Lake Contour and XTA 226 that allow for driving 2-
way enclosures (ARCS and dV-DOSC) in conjunction with V-DOSC and aux sub drive. For these
presets, channel assignments are different: Input A / outputs 1-5 = V-DOSC LOW, MID, HI, dV-
DOSC LOW, dV-DOSC HI, respectively, and input B / output 6 = SB218. This type of preset is not
required for BSS 366 since the input source for the SB218 can be selected independently (i.e., 4+2
format presets can also be used for aux sub drive).
Please refer to the preset setup sheets in Tables 11-14 when patching your signal distribution system.