HOLOPLOT was chosen to deliver the intelligible, but invisible audio solution for St Hedwig’s Cathedral in the heart of Berlin as part of a renovation project. Modelled after the Pantheon in Rome, the cathedral opened in 1773. Berlin’s archbishop Heiner Koch ceremoniously reopened St. Hedwig’s Cathedral in November after a renovation lasting around six years.
Circular in shape, with a 30m diameter, the central space rises to a dome that peaks at a total height of 33m. The huge parabolic space has renowned acoustics for music. For spoken word, however, the reverb times negatively impacted intelligibility and the echo bouncing back to the altar in the centre posed a considerable challenge.
Sichau & Walter Architects, who won the redesign contract back in 2014, required an invisible solution that would solve these issues while being flexible enough to adapt to the variety of choral, concert, and spoken word content.
To address the space’s positional challenges and 6.5-second reverberation time, Jakob Greif, HOLOPLOT applications engineer and technical lead for the project, and his team designed a system based on the X2 Matrix Array.
X2 is HOLOPLOT’s compact Matrix Array loudspeaker, equipped with power over ethernet, enabling it to receive audio and control signals, and power through a single cable, simplifying installation and, in combination with the unit’s slim profile, enabling flush mounting.
These features allow the arrays to disappear behind custom screens, in narrow, recessed wall cavities, so as to not interfere with the building’s smooth, mute coloured lines, something that was very important to the project.
X2’s size and rotation flexibility enabled the team to utilise the modules in a variety of positions, including fixed in portrait orientation behind the main columns. 3D Audio-Beamforning then solved the positional issues created by having the altar located centrally.
Thanks to increased sound control in both the horizontal and vertical axes, ensuring that sound energy does not hit the highly reverberant walls, the team was able to build on these positive results to offer the cathedral committee a range of functions.
Peter Sichau, founding partner, said: “Worship architecture fundamentally differs from secular architecture, because its primary purpose is to create a framework, so that the celebrant, in this case the priest, can deliver mass in a way that offers worshipers a religious experience. Our methodology required the architecture and the space to be recognisable solely by the atmosphere and the acoustic of the space, which is very complex and challenging in this case.”
He added: “We have hidden 22 MD30 units behind perforated panels. The arrays are fixed in only three locations and deliver unique coverage zones that disregard the highly reflective surfaces of the cathedral. 3D Audio-Beamforming and our optimisation algorithms not only allow us to create a circular, rounded beam but also to split the direct throw, avoiding the altar microphone in the center of the nave and raising the gain before feedback threshold.”
Johannes Rogge, technical and media integration lead for the St Hedwig project, added: “Our priests will finally be able to speak comfortably at the altar and that is possible thanks to the way HOLOPLOT has designed the active beams. I am really impressed by how that works; to be able to hear the difference just by moving a few meters, is amazing.”
