The
history of the cathedral goes back as far as the fourteenth
century. Construction began in 1386 and several parts of the
building have been added or restored in the following centuries.
It was declared a National Monument in 1878. Its richness and
vastness can be expressed by sheer number. The external length
is 158 m, the highest point 108 m, and the internal height
in the central part of the church is 45 m. The cathedral contains
3.600 statues of different sizes and 164 decorated windows.
The total area covered is 12.000 m2, the total volume 440.000
m3. Whilst it is an overwhelming place artistically speaking,
the Duomo above all is still the place where the people of
Milan gather for their prayers, and to participate in services,
up until the present day. For this reason, speech intelligibility
is crucial, and in 2000, it was decided that the existing sound
system would be replaced by a new Intellivox system.
 For Prase Engineering, to be involved
in this process was both an honour and a challenge. Ennio
Prase, with his colleague Marco Cappelotto, was responsible
for supplying, testing, programming and supervising the system.
The engineering work was done by Prase’s client, the ‘Fabbrica dell Duomo di Milano’,
an independent contracting
company working exclusively for the Dome of Milan. Chief Engineer
of the Fabbrica is Dr. Ir. Benigno Mörlin Visconti
Castiglione. “All in all,” Ennio Prase said, “it
took two years before the final decision was made by the Fabbrica
that Intellivox definitely was the right technology for them.
We invited our client to several projects where Intellivox
has been employed, and we have done two demonstrations in the
Dome itself”. Finally, the work started in the last months
of 2000 and was completed in spring 2001.
 The sound system
The installed sound system consists of six AXYS Intellivox-6c
(now known as the DC500) columns and five Intellivox-2c (DC
280) columns, as shown in fig. 1. The cathedral is shaped
like a cross, with the altar in the center. The main areas
to be addressed are the central nave and the two side naves,
where people will be sitting or standing over a total length
of approximately 60 meters while attending services. Because
of 36 massive pillars, as shown in fig.1, there is a large
shadowing effect in the central and side nave. For this reason,
two Intellivox-6c (DC 500) columns are mounted on the same
pillar on each side of this area, shooting slightly to the
left and right to compensate for the shadowing effect. Two
more 6c (DC 500) columns are aimed at the second side naves,
both on the left and right side of the cathedral. These six
columns together provide all the coverage and the SPL necessary
in the central part of the church.
However, after final evaluation under
real life conditions, two Intellivox-2c’s (DC280) were
added to cover the last part of the central nave. Covering
a full 80 m including the area where tourists are walking
in and out of the cathedral proved to be too much, even for
the Intellivox-6c (DC 500) loudspeakers. Ennio Prase explains: “It
turned out that tourists are generating a lot of noise in
this entrance area, even while services are going on. This
background noise was too much to keep intelligibility up
to the specified standard, therefore, two 2c (DC 280) loudspeakers
have been installed and time aligned with the main system.” In
the front of the church, three more Intellivox-2c (DC 280)
columns have been used.
One is aimed at the altar area and two are aimed at the left
and right arm of the cross, where people will be seated on
special occasions. These three columns are shooting in the
opposite direction from the central nave to prevent interference
with the main system. Because the lobes of all Intellivox columns
are electronically aimed at their specific area with great
precision, interference and unwanted reflections are reduced
to a minimum.
 After completing the installation,
the STI (Speech Transmission Index) value with all loudspeakers
active was measured between 0,50 and 0,60 - which according
to international standards stands for “good speech intelligibility”.
Under the given circumstances, this is an excellent result.
In the Milan cathedral, Prase Engineering
was not only involved in supplying the Intellivox system,
but also designed the system for automated sound reinforcement
of the daily services. In the old situation, during each
service two sound engineers manually operated a Siemens console
with 24 inputs and 6 outputs, that was installed in 1984
by Milan company IRMIL. The console, according to Ennio Prase,
is “a real piece of art”.
Because it was specifically designed for this cathedral and
its services, the Fabbrica dell Duomo wanted to keep and automate
it, but still be able to operate it manually. “We completely
rewired the console. All the faders are now VCA controlled,
on each bus there is DSP-processing available with dynamics,
EQ, delay, etcetera. The console is now fully automated, every
fader is visible and can be operated from the screen.” During
the daily services the automation is used, on special occasions
the console will still be operated manually.
Prase Engineering and AXYS Intellivox
There are approximately 25.000 Catholic churches in Italy,
of which most are old to very old. Ennio Prase estimates that
85 % of them can be described as acoustically very difficult,
because of their large volume and the hard surfaces of walls,
ceilings and floors. Prase Engineering has been the Italian
distributor of AXYS for four years now, and in this relatively
short period, hundreds of churches have been supplied with
Intellivox
systems, including the St. Pauls Basilic in Rome. The systems
are not installed by Prase Engineering itself, but via its
network of Class A Contractors specialised in church installations.
Ennio Prase: “In Italy AXYS is definitely not a new product
but proven technology!”
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