L-Acoustics V-DOSC, Operator'S Manual

Page: 127 / 158

L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 127 of 158
Step-By-Step Tuning Procedure
In general terms, installation and tuning proceeds as follows:
Room Dimensions
⇒
ARRAY or SOUNDVISION
⇒
Sound Design
⇒
Installation Parameters
System Install
⇒
System Focus
Preset Selection
⇒
FOH Drive Rack/CO24 Channel Assignment
⇒
Configure Amp Racks
System Check
⇒
Coverage Check
⇒
Time Align
⇒
Balance
⇒
Tune
1) With reference to the installation parameters calculated in ARRAY or SOUNDVISION, install the
system and perform trim and site angle adjustments according to the procedures outlined in
Section 4.2.
2) Configure your signal distribution system by selecting the appropriate preset for your
configuration and refer to the Preset Setup sheets (tables 11-14) while patching your signal
distribution system. Configure COMB connectors for all amplifiers racks accordingly (and
remember the old saying: “amps on last, amps off first”).
3) Send pink noise to each array (one array at a time, band by band) and spin up amplifier channels
individually and sequentially in pairs. For all bands, turn up amp channel 1 to make sure it’s
working and then amp channel 2 to confirm that there is acoustic summation with channel 1.
Then turn down amp channel 1 to confirm that 2 is working. Then turn up amp channel 3 to
check acoustic summation with channel 2, etc. Repeat the process (i.e., 1; 1 and 2; 2; 2 and 3; 3;
3 and 4 etc) until you have checked all amp channels and all bands for each array. If you
encounter a polarity problem, use a polarity checker to isolate the problem.
4) Verify coverage by running low level pink noise through the system (excluding subwoofers) and
walking the room. Check the coverage down front and at the back of the venue. Perform any
required trim and angle adjustments if necessary.
5) Using your measurement system, at the mix position, compare Left versus Right polarity and
frequency response, channel by channel, as a final system check. All responses should be identical
within 1 dB, except for the high band where larger deviations are acceptable (2 to 3 dB). Beware
of wind effects which can affect HF measurement stability and repeatability.
6) Typically, the subwoofers act as an overall time reference for the complete system so the next
step is to time align the subwoofers to the main arrays.
If a time domain measurement system (WinMLS, MLSSA, TDS) is not available, use a laser
rangefinder to measure the geometric difference between the main array and the subs (at your
reference point of choice). Adjust the subwoofer delay by adding the geometrically-determined
delay to the pre-aligned subwoofer delay that is included in the OEM preset as a starting point.
♦
Place a microphone on the floor (at your reference point of choice) on-axis or equidistant
between the left V-DOSC and left subwoofer arrays (alternatively, time alignment measurements
can be conducted on FOH R). For LCR subwoofer arrays, refer to Section 3.5.3 for
recommendations concerning measurement microphone locations for time alignment
♦
Mute the highs and mids
♦
Individually feed the low channel of the main L arrays then the L subwoofers with pink noise and
adjust the crossover output levels to obtain the same measured level (and/or change the
measurement microphone reference distance to obtain the same measured level)
♦
Invert the sub polarity from it’s OEM starting point
4W, INFRA or X presets: change from +ve to –ve
X AUX preset: change from –ve to +ve
♦
Feed L subs and L lows with pink noise and fine tune the delay adjustment by up to +/- 3 msec
(from the geo pre-aligned delay) to obtain maximum cancellation