Published
in April 2006
DSP: The Common
Denominator
By Bob Pelepako and Steve Minozzi
Digital technology crosses disparate venues.
One wouldn’t think
that a “nave” and an outdoor athletic field,
such as Fordham University’s Jack Coffee, would have
similar audio solutions.
Digital signal processing
(DSP) rapidly is becoming the common denominator for sound
system design/build contractors. The technology allows maximizing
of assets and expanding of the client base.
DSP processors have multiple analog
audio inputs and outputs (I/O) that interface directly with
microphones, line-level audio devices and amplifiers. The
original analog signal is sent into analog to digital (A
to D) converters that sample and transform the analog audio
signals into a digital bitstream. Once the signal is in
the digital realm, numerous functions can be applied, without
signal loss, to reshape the original signal. These manipulated
bitstreams are then output to digital to analog (D to A)
converters, where they are transformed back into analog
audio signals.
The algorithms and codecs used
to manipulate the digital signals are contained within firmware,
which acts like an operating system for the DSP processor.
Manufacturer-supplied design software is used to put different
signal-processing blocks into place. The software provides
a variety of “drag and drop” DSP blocks that
become “virtual” sound-system components, such
as automixers, matrix mixers and routers, parametric equalizers,
delays, comp/limiters, etc. “Virtual cables”
connect the various DSP blocks, forming a digital signal
path. The signal path is saved as a file that is uploaded
to the processor via its Ethernet port. The parameters of
the DSP blocks can be adjusted and manipulated via a computer
or with various remote-control devices.
When the Archdiocese of Newark
Property Management Division commissioned Monte Bros. to
design and install a new sound system in the Cathedral Basilica
of the Sacred Heart in Newark NJ, we arranged a series of
site meetings with Msgr. Richard F. Gronki, Cathedral Rector;
John J. Miller, director of Music Ministries; and James
Goodness, director of communications, define the acoustical
and logistical parameters.
DSP processing has increased the
ability to tailor sound to spaces with difficult acoustics.
The requirements for the new sound
system in this premier worship space were attainable only
with the implementation of DSP processing:
• Intelligibility of
the spoken word, liturgical singing and music, with even
coverage in all of
the listening
areas.
• Automatic performance of
all “voice lift” sanctuary and wireless microphones,
with the
availability of temporary
user adjustments via an intuitive and user-friendly control
panel.
• Control of all choir microphones
via a remote-control panel, which would return to a “default”
setting automatically upon powering up the sound system.
• Remote control of all choir
microphones and line-level audio inputs with
password-protected
“surface control software” installed on the
Cathedral’s laptop computers.
• Automatic presets for the
configuration of the choir microphones, to accommodate a
variety of Cathedral
and “guest” choirs.
• Independent “broadcast
audio feeds” to media mult box audio outputs at various
strategic locations
in the worship space.
• Remote control of the independent
broadcast audio mix with password-protected surface control
software that can be operated simultaneously on multiple
computers.
• A failsafe analog
back-up system that would activate automatically in the
event of a failure of
the primary DSP processor, and provide uninterrupted audio
from the “voice lift” sanctuary
and wireless microphones to the main listening areas of
the worship space, and also
to the independent broadcast audio mix.
• Remote access to the sound
system’s DSP processor via the internet, to enable
firmware updates and
the ability to remotely perform technical adjustments to
the sound system.
|
Both of these environments—
Cathedral of the Sacred Heart’s narthex and
the New York City Real Time Crime Center—are
protected by the same DSP failsafe analog backup system.
|
The usual requests for dependable
and functional multiple wireless microphone systems, along
with the implementation of voice lift and choir microphones
with generous polar patterns, and the ability to replicate
and remotely control pre-recorded music from the worship
space, were also thrown into the mix.
The initial design process produced
interesting similarities with other seemingly unrelated
projects in our repertoire of installations!
The sanctuary, which is the main
focal point of this worship space, and frequently accommodates
as many as 200 people, along with the adjacent surrounding
ambulatory, has a total of 15 loudspeakers in the chandeliers,
which require independent digital parametric equalization
and signal processing. The ability to treat this area as
a separate entity allows the local use of multiple microphones
during liturgies and special events such as ordinations
and concerts.
The pulpit, cathedra, lectern and
cantor’s microphone locations were managed by a virtual
auto-mixer, and assigned individual parametric equalization
and comp/limiters to increase intelligibility and establish
an automatic dynamic range for each individual microphone
location. This processing is required to reduce the effect
of the cavernous reverberation present in the worship space.
We suspended four hyper-cardioid
overhead choir microphones on custom tubing over the sanctuary,
along with two super-cardioid music microphones in the adjacent
ambulatory, and four additional hyper-cardioid choir microphones
on stands, for use by choirs and musicians in the sanctuary.
Because choir microphones do not
require noise gate technology, digital presets were programmed
to independently mute and un-mute the overhead choir microphones,
the ambulatory music microphones and the choir microphones
on stands, using a digital control panel installed into
the organ console.
An additional digital control panel
was installed at the electronics console, to provide temporary
adjustments to the volume of the “voice lift”
microphones in the sanctuary, along with digital presets
to reset the entire sound system, and to alter the default
parametric-digital equalization, to accommodate the increase
in ambient noise from the air-conditioning system.
The DSP processors were programmed with a “power-up”
master preset that automatically returns the sound system
to the default settings when it is energized.
Other Environments
As examples of audio problems at
other environments that are seemingly different from the
Cathedral setting, automatic presets with similar programming
were implemented to manage 20 different room combinations
in the 10,000-square-foot main banquet room of the Hilton
Garden Inn Hotel in Staten Island NY, as well as Fordham
University’s Jack Coffee combination Football and
Baseball athletic field in the Bronx NY.
Enhanced individual signal processing
for microphones in analog sound systems, such as parametric
equalization, comp/limiters and noise gates, usually require
additional, separate, analog devices that significantly
increase the cost of the sound system, and are limited to
the range of adjustment provided by the manufacturer.
The two wireless lavaliere microphone
systems in the Cathedral are programmed to activate logic
output nodes from the digital auto-mixer that control a
“virtual ducker,” to lower the volume of the
altar microphone automatically, if either of the two wireless
lavaliere microphones is in use.
This feature is extremely popular
in houses of worship with altar microphones, because it
eliminates the need to turn off the wireless lavaliere microphones
when speaking in the vicinity of the altar.
The DSP programming that enables
the wireless lavaliere microphones to control the altar
microphone in Sacred Heart Cathedral is similar to the programming
employed at Roman Catholic Archdiocese of New York boardroom,
at St. Joseph’s Seminary in Dunwoodie NY, in which
the Card-inal’s microphone has “chairman”
status and takes priority over any of the remaining 23 boardroom
table microphones.
The “number of open microphones” (NOM) feature
that was employed in the Seminary Boardroom sound system
is a standard feature of the DSP processor in Sacred Heart
Cathedral.
|
DSP signal processing technology
was used to manage the automatic functions of multiple
mics in both the Cathedral of the Sacred Heart pulpit
and seminary boardroom environments.
|
The auditorium sound system at
CUNY Law School in Flushing NY, which features 160 table
microphones and four wireless microphone systems, surrounded
by a distributed speaker system, has similar DSP programming
and “virtual” sound-system components.
One of the more challenging tasks
was the implementation of the automatic analog back-up system,
which we originally developed for New York Police Department
Headquarters Real Time Crime Center and Emergency Operations
Center. An 8x16 microphone splitter for the eight main sanctuary
and wireless microphones is connected to the main DSP processor
and also to an analog backup mixer.
If any of the DSP processors fail,
a digital “logic box” connected to the DSP processors,
and to the analog backup mixer, would close a contact that
activates a preset in the digitally controlled analog backup
mixer. The audio from the main sanctuary microphones would
then be allowed to pass through the analog backup mixer,
through an equalizer and distribution amplifier, and finally
through a 16x8 combiner that transfers audio to the amplifiers
for the main speaker zones in the Cathedral.
If the DSP processor re-activates,
the logic box sends a preset that mutes the analog backup
mixer, automatically returning the sound system to its original
operation.
“Surface control software”
is offered by some manufacturers and allows for replicating
and graphically redesigning selected DSP processing blocks
into a user-friendly interface, with password protection
and the ability to control the sound system simultaneously
on multiple computers, for limited control of the performance
of assigned microphones and presets.
A VPN router and high-speed internet
access can be used to control these processors remotely,
directly from the internet, for adjustments and firmware
upgrades to the sound system.
DSP processing provided the freedom
to design and install a truly integrated sound system in
this Cathedral and the other mentioned locations, without
compromises, and for a competitive price.
Although DSP processing involves
investments in computer technology, along with training
and certification of technicians, the benefits of an expanded
client base and a homogenous inventory are well worth the
investment for design/build contractors.
Bob Pelepako and Steve Minozzi founded Monte Bros. Sound
systems, Inc., Ardsley NY, in 1966.
|
