Loudspeaker Processor Configuration - Lab.gruppen PLM Series Operation Manual

8 sIGNAL FLOW AND PROCEssING
The sophisticated output section monitors faults
and generates warnings when appropriate; warnings
are displayed on the front panel of the PLM and
also sent as messages over the control network.
These indications allow the operator to adjust system
settings if necessary. In the rare event that maximum
ratings are grossly exceeded, the PLM will shut down
until the condition has been rectified or the incorrect
setting has been readjusted. Sensing circuits also
transmit local output power stage temperature,
processor card temperature, and PSU temperature
to the appropriate protection circuits. Refer to section
7.3 – Amplifier and Load Protection Systems for
more details.
Table 8-1 lists analog input sensitivity in dBu and Vrms
for an example PLM 10000Q with a 4 ohm load for
various Amp Gain settings and maximum/minimum
ISVPL settings. Analog input headroom is set at 26
dBu (see section 9.12.3.1).
INPUT
sENsITIVITY
WITH IsVPL sET
TO 153 V
GAIN sETTING dbu
(db)
+44 -1.1
+41 +1.9
+38 +4.9
+35 +7.9
+32 +10.9
+29 +13.9
+26 +16.9
+22 +20.9
Table 8-1
8.2 Loudspeaker processor
configuration
The PLM includes a dedicated Dolby Lake processing
system configured with two inputs and six outputs.
The relationship between inputs and outputs can be
defined by the user via the DLC PLM Edition software
package. The simplest configuration (the default)
is that each input feeds its own set of processing
elements, including a two-way crossover. The set
24 PLM Series Operation Manual
INPUT
sENsITIVITY
WITH IsVPL sET
TO 17.8 V
Vrms dbu Vrms
0.68 -19.8 79mV
0.96 -16.8 0.11
1.36 -13.8 0.16
1.92 -10.8 0.22
2.71 -7.8 0.32
3.84 -4.8 0.45
5.42 -1.8 0.63
8.59 +2.2 0.99
of per-channel processing elements is referred to
as a Module, which in this case has a 1-in/2-out
configuration.
Figure 8-2: DLC PLM Edition screenshot showing module and
signal flow of a 2-way crossover.
The processor can be configured in a variety
of other ways, e.g. as a 3-way crossover
with dedicated auxiliary processing for a
Sub output. (This would be ideal for a 3-way
main or side-fill hang plus a subwoofer). In this case,
the PLM is configured as 1-in/4-out, utilizing the
system as a single set of processing elements, or
Module.
Figure 8-3: Module screenshot showing signal flow of a 3-way
crossover plus 1 aux.
The Dolby Lake processing system provides two
distinct categories of crossovers:
▸ Infinite Impulse Response filters (IIR) such as
the classic Bessel, Butterworth or Linkwitz-Riley
types; these are available with slopes ranging
from 6 dB/octave to 48 dB/octave.
▸ Finite Impulse Response filters (FIR) providing
zero phase shift with steep transition slopes
at the crossover frequencies. These are also
referred to as Linear Phase Crossovers.
Each set of processing elements is referred to as
a Module and can be configured as crossovers,
full-bandwidth auxiliary outputs, or a combination
of the two.
Details of how to configure the Dolby Lake processing
system can be found in the Dolby Lake Controller
User Manual.