Solutions: LSS loudspeakers lower reverb times in four chapel-install19 January 2016
High reverberation times had to be tackled, as well as the right audio equipment selected and installed, to optimise intelligibility throughout the four chapels in this sanctuary, writes Mike Clark.
A challenging audio installation was recently completed and inaugurated in the sanctuary of The Immaculate Heart of Mary, Refuge of Souls, built in the small southern Italian town of Paravati. The sanctuary is centred around the tomb of Natuzza Evolo, who was widely regarded as a mystic, believed to have received the stigmata and to be able to speak directly with the Virgin Mary. An idea of the important role played by Evolo, founder of the Cenacles of Prayer, can be had by the fact that six Italian bishops and more than 100 priests celebrated her funeral mass in 2009, which was attended by 30,000 mourners.
The sanctuary includes four chapels, in which the majority of the equipment was installed; Toni Soddu, founder and CEO of Grand Acoustics, was responsible for the design, choice of the necessary material and equipment and the supervision of all the installation work.
An Italian audio industry veteran, Soddu explains: “This is the largest installation I’ve worked on to date, but other projects of this type have included and auditorium and rehearsal room of the Centro Giovani in the Tuscan town of Piombino and the acoustic treatment of the Val di Cornia parks conference hall. Giuseppe Laruffa of LSS Advanced Loudspeakers, whom I have known for many years, introduced me to the client and my ‘interface’ with the Natuzza Evolo Foundation for the installation work was Father Michele Gordiano.”
Soddu’s brief was to provide a set-up with the most modern technologies available that was user-friendly and would last through time. The first step was to run a series of meticulous on-site equipment tests to ensure high-quality speech intelligibity.
All the loudspeakers in the various areas are by Italian manufacturer LSS Advanced Speakers Systems, based in Polistena (Reggio Calabria), and were chosen to for correct speech reproduction in environments with medium reverberation times.
During audio prediction and simulation work, Soddu used Ivie Technologies’ IE-45 audio analysis system, for its Real Time Analyzer (RTA) and Sound Pressure Level (SPL) functionality, with RTA and RT-60 software.
The most urgent acoustic problems to be addressed were those of the cupolas. In the two small chapels (Confessions and Almighty), reverberation time (RT) at 1,000Hz was 7s with a long decay in the centre part of the rooms.
To solve this, a circular panel with a diameter of approximately 6m was installed with the upper side, positioned approximately 1.2m below the cupola’s surface, covered completely with 2m x 1m x 100mm sheets of sound-absorbing material with a density of 30kg/m3. The entire surface of the cupolas got the same acoustic treatment, and was covered with a design reproducing the wood of the original structure. Thanks to this stratagem, the final RT was 2.6s at 1,000 Hz with optimum speech reproduction.
The same procedure was carried out in the Main Chapel and Natuzza’s tomb. In the latter, before treatment, RT was around 12s at 1,000 Hz and there was noticeable turbulence between 100 and 350Hz. Using the same system as in the small chapels, but increasing the diameter of the flown centre panels to 20m and covering the entire cupola with the same material, the RT obtained was just 2.4s, with a great improvement in the mid-low frequency range. In the Tomb, the ORV sound-absorbing material was mounted with a false ceiling to match the sanctuary’s all-white design.
A total of approximately 2,000sqm of the sound-absorbing material were installed: ORV Manufacturing’s Fiberform 62T 2SL 100% thermo-bonded polyester fibre (PET) sheets were installed. Completely recyclable and with Class 1A flammability, Fiberform was the first polyester product used for insulation and soundproofing on Italian and European railway carriages.
As far as the loudspeakers are concerned, the main chapel features a micro vertical line array with 12 LSS ST17 modules, divided into three sections of four elements each, powered by a Lab.gruppen PLM 12K44/SP 4-in, 4-out powered loudspeaker management system with the latest (version 6.3) Lake Controller release; and two LSS custom polypropylene front fill speakers, driven by a Lab.gruppen IPD 2400. This two-channel digital amplifier is widely deployed throughout the Sanctuary’s chapels and features 2 x 1,200W/4 ohms, internal DSP with 40 real-time parametric EQs, high- and low-pass filter, input delay, output delay, crossover and limiter. The main chapel also has a delay system, consisting of eight LSS MIL 130 compact 2-way speakers. There are four more MIL 130 enclosures on monitor duties on the altar and both delay speakers and monitors are driven by more IPD 2400 (two and four units respectively).
The Sanctuary’s smaller Confession and Almighty Chapels have identical sound systems, comprising an LSS J16 mini line array divided into two sections of six modules and another pair of LSS 4x4in custom polypropylene enclosures (400W each) recessed in the altar steps.
Sound in the room hosting Natuzza’s tomb has a set-up with two PP4-10 line source column enclosures, each divided into two sections of five loudspeakers, driven by an IPD 2400, plus a delay system featuring eight PP4 compact wide-range point source speakers, driven by two more IPD 2400.
The Sanctuary’s internal walkways are covered by 14 more PP4 enclosures, driven by a pair of IPD 2400, whereas the porticos are covered by 32 recessed LSS 100V ceiling speakers driven by a Lab.gruppen C28:4 four-channel amplifier.
The majority of the LSS speakers installed are off-the-shelf models, but two (the J16 and the delay speaker recessed in the steps) were designed and built specifically for the project and will soon be added to the manufacturer’s catalogue.
As well as the Lab.gruppen units’ Lake Contour on-board EQ-delay, signal processing is courtesy of four Soundweb London BSS BLU-806 8×8 units.
The Sanctuary’s stock of microphones includes eight AKG DHT 800 D7 BD1 handheld digital transmitter microphones and 24 DPA models: eight DPA d:vote goosenecks; eight DPA d:fine headsets and eight d:screet miniature models. Eight VDL Studio microphone preamplifiers complement the set-up.
Regarding the work prior to the choice of power amps, microphones and signal control units, Soddu explains: “Comparison tests were run using various brands. Soundweb’s BLU-808 was immediately seen to be the best, with the software most suited to this type of use. After testing four other leading microphone brands, DPA gave me what I was looking for, and A:B tests were also run between the Lab.gruppen amplifiers and another world-famous brand.”
Soddu concludes: “This was a really unique experience. Normally, on this type of installation, the project starts out with a design, after which a cost limit is established before the actual installation work is carried out, the entire system fine-tuned and with some final tweaking the result is achieved. In the case of the sanctuary, and its large spaces, I had the rare opportunity of testing the equipment under real working situations, thanks to the monthly meetings held with the Foundation. Microphones, amplifiers, digital controllers and wireless systems were run in a real dynamic situation. Tests were initially run without any acoustic treatment and, thanks to the acoustic treatment and the correct calibration and fine-tuning of the hardware chosen, I managed to achieve the results I’d hoped for.”