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.

The requirements of Cathedral of the Sacred Heart’s sanctuary, CUNY Law School auditorium and the Hilton Garden Inn’s 10,000-square-foot ballroom with 20 room combinations are handled with the same DSP automatic preset capability.

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.

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