RCF Revamps the Audio System Inside the Mosta Rotunda Church

Mosta, Malta - The Mosta Rotunda is a circular neoclassical church located in the Maltese town of Mosta. The RCF Engineering Support Group collaborated with RCF’s local distributor, "The Sound System Co Ltd," which was tasked with installing and optimizing the renewed sound system of the church. The installation consisted of eight microphones connected to an RCF M18 digital mixer, two RCF VSA active steerable columns, and infill speakers, as part of the renovation of the church's internal audio system. The team worked to ensure even and optimized intelligibility across the entire seating area, despite the persistent reverberation caused by the church's architecture.

Designed by Giorgio Grognet de Vassé and built in the 19th century, the Mosta Rotunda boasts a dome that is 37 meters in diameter, inspired by the Pantheon in Rome. It's the 3rd largest unsupported dome Church in the world. During World War II, the church was struck by a bomb that pierced the dome and fell among the 300 worshipers in prayer but did not explode, an event known as the Miracle of Mosta. Today, the Mosta Rotunda is not only a place of worship but also a popular tourist attraction with its stunning architecture and rich history.

To reduce reflections that could negatively impact speech intelligibility, the optimal solution was to install a single line source using the digitally controlled VSA column array. This system relies on powerful digital signal processors (DSPs) to direct the audio signal of each speaker towards the listening area. The VSA column array is a multi-amplified vertically steerable array, which means that each individual speaker is separately amplified and digitally controlled, so the sound can be vertically tilted without inclining the cabinet. Additionally, it is fully compatible with RDNet, the proprietary RCF speaker management software. The installation includes a main VSA 2050 II aimed far-field, mounted on top of a VSA 1250 II used as a downfill. Both arrays are fixed to the wall.

Francesco Venturi, system engineer of the RCF ESG, illustrates the optimization workflow: “We started by acquiring far-field STIPA measurements and optimized VSA 2050 II beaming and tilting by accessing the speaker configuration, using an RCF Control2 interface and RDNet software,” said Venturi.

Once the beaming preset was optimized, the team performed FFT measurements to acquire transfer functions magnitude plots to tune VSA 2050 II frequency response upon Church acoustics. Venturi continues, “We shaped VSA 2050 II response by acting on the DSP parametric equalizer, using RDNet software. The process was then repeated for the near-field VSA 1250 II steerable array, first configuring the beaming preset, then optimizing the response”.

After tuning, the speaker system was able to provide rich and accurate voice reproduction with an even intelligibility figure above 0.50 (inside the empty church). The RCF M18 digital mixer allowed optimization for each microphone for gain, gate, and EQ settings.

“The improvement in intelligibility with the new RCF steerable array audio system is truly remarkable!” exclaimed Jon Vella Zarb of The Sound System Co Ltd. Locally, the church is notorious for its poor acoustics, RCF rose to the challenge and the VSA system truly exceeded my expectations, providing excellent audio to the Mosta's congregation!"