AV Asia Pacific published a fantastic story in Issue #63 about Luis Miranda's Fohhn installation in Canberra's Old House.
Luis Miranda is a man who enjoys his work: "I just love solving problems," he declares. Luis is an audio consultant with Auditoria, a specialist consultancy whose work covers everything from Live Events (think: Olympics opening ceremonies) to major venue sound systems (think: the renewal of the Joan Sutherland Theatre at the Sydney Opera House and Bankwest Stadium at Parramatta). Luis has a PhD in Acoustics and relishes the challenge of coaxing good sound out of difficult acoustical environments. Throw in a few extra constraints like a heritage-listed building and he'll happily rise to the challenge.
This particular challenge was three spaces within a building that most of us will instantly recognise Old Parliament House in Canberra, the most signifcant building in Australia's democratic history. Those three spaces are the most iconic in the building: The House of Representatives Chamber; the Senate Chamber; and Kings Hall, "the huge echoing crossroads that was the beating heart of the House".
The House has been transformed into the Museum of Australian Democracy (MoAD) that now daily hosts educational tours for school groups and tourists, interpreting the history of our democratic institutions while preserving the fabric of the wonderful old building that has been witness to the most pivotal moments in our history. MoAD's aim was to bring 21st century audiovisual capabilities to this near century-old building. As part of the process, the Museum's Head of Facilities Chris Grebert and Project Manager Warwick Bartlett sharpened that broad aim by bringing together the needs of the different stakeholders education, tour groups, events, and, of course, the heritage requirements for the installation. The most problematic area was Kings Hall, the splendid space that sits between the Senate chamber on one side and the House of Representatives chamber on the other. Its highcofered ceiling, plaster walls and highly polished parquet foor make a grand statement but those very features also create an acoustic that makes sound reinforcement extraordinarily challenging.
With the hall now heavily in demand for all manner of functions, the brief from the museum was to design and install a fexible sound reinforcement system that could provide clear, articulate speech, while remaining virtually invisible. Luis knew that the system would need to deliver even coverage across the 16m width of the room while keeping sound away from the multiple refective surfaces that could easily create a giant echo chamber. A distributed speaker system would be out of the question as multiple speakers would badly impact the heritage values. But there was one possibility that ticked the right boxes: a line array with digital beam steering.
STAYING ON BEAM
As Luis started the design exercise, he knew that digital beam steering would be a powerful tool but the architectural limitations were quite signifcant. From a heritage point of view, the speakers in Kings Hall needed to be unobtrusive and away from major sight lines. The museum's
heritage department would have to approve all installations and they provided support in identifying solutions that would have the least impact on the fabric of the building. The ideal position would be high up in the cofered ceiling area, but that location would require a speaker with exceptional beam steering capability. Luis whittled down the possible speaker systems to a choice of three. The contractor specifed that every part of the installation had to be demonstrated and approved to ensure the outcome would be adequate, so Luis set about trialling the speakers in situ. He brought in a portable high-reach pallet lifter which could position the speakers at the right height to closely simulate various options for the final speaker position. He then took a series of measurements in the space to determine the impulse response for each of the speakers in a number of positions. The result was a pleasant surprise: "When we tested using the Fohhn DLI-230 speaker, we found that its beam forming worked really well," Luis recalled. "It proved that locating a speaker high up in the cofered section could deliver the coverage we needed while also being more in line with the Heritage Conservation Guidelines."
The final installation used three pairs of the DLI-230's smaller brother, the DLI-130 which ft perfectly in the recessed ceiling area. The DLI-130's useful frequency response extends down to 60 Hz which is extraordinary for a box running eight, four-inch drivers. As a result, subs weren't
needed since the requirement in Kings Hall was primarily speech reinforcement.
Contact the CMI Audio team to talk all things Fohhn - [email protected]