San Juan de Dios is a colonial era church built around 1765 – long before sound systems were invented or acoustic design was understood. It is constructed entirely of “rubble stone” with a cement binder and plaster coating. The original sound system was installed around 1990. The building interior is acoustically reflective which results in a high reverberation. This means that at a normal rate of speaking, consonants will overlap and intelligibility suffers.
Beginning in 2019, sound measurements were taken, and an engineering analysis of the current and alternative sound systems, wall treatments, etc was made.. For those interested, there is a report available that can be downloaded.
The study showed that the amplifier needed to be replaced with a more modern digital type that provided zone control and better fidelity and power capability, and that the current speakers should be replaced with professional types that were more directional so as to keep the sound pointed at the audience and away from the reflective walls and ceiling.
The new amplifier was installed along with four HS1200 type speakers at the front and middle of the Nave. New wiring for the speakers was also installed. At this point, a test report was written which can also be downloaded.
This system provides much improved clarity for the front and middle of the church originally populated for the English Mass, but the rear was still relatively poor. In addition, attendance has grown from 25-35 at the beginning of this work to 50-75 now. So, two additional HS1200 speakers were installed at the rear which is the current configuration.
There are two important measures of sound system performance that were measured after each change. These are the direct sound uniformity (the uniformity of the early arriving sound intensity) and the clarity (the ratio of early arriving to later arriving sound intensity). Both were measured at 21 different locations in the Nave . Using the industry standard definitions for what is considered good, fair and poor for uniformity and clarity, the percentage of seating locations meeting these definitions can be calculated. The two bar charts below summarize the gradual improvements that have been made starting with the original sound system in September 2020 and ending with the current system measured in December 2021. The right most bar in both charts shows the performance with the rear wall absorption (not currently installed).
4 April 2022
