Text:/ Derek Powell

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 significant. 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 coffered 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 specified 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 coffered 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 fit 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 for speech reinforcement.

The three speaker pairs allow for functions to be set with the stage or lectern in different positions — at the front, on the left, or the right side of Kings Hall. Only one pair will generally be in use at any one time with configuration handled by a Q-Sys DSP which takes care of all the audio routing in the installation. The correct speaker pair for each orientation is selected using a Crestron control system, accessed by a discreet wall-mounted touch panel or an iPad running Crestron’s XPanel software.

ACOUSTICS: LET THAT SOAK IN

However, the active electronics and speakers could only ever be part of the solution. The initial brief acknowledged the existing acoustic problems and Luis’ preliminary measurements had confirmed that some absorption would be needed to tame the acoustics. The reverberation time was around four seconds and during the museum’s daily opening times, noise from the tour groups in the wings to either side echoed right across the space. But what could be done without impacting the heritage values and distinctive architectural features of this space?

“That was a little bit tricky,” Luis admitted. “We did the required calculations and then tried to find a product that looked right — could be colour matched, and performed as well as possible for what we were permitted to do”.

Luis’ solution was ingenious and virtually invisible. He had broad-band fabric-covered absorber panels made up to the precise dimensions of the decorative plaster panels on the walls. Colour matched to the plaster, they are visually indistinguishable from the architecture but have a valuable effect on acoustics.

“It has had a really good impact on intelligibility in the room,” Luis noted. “It shaved about a second off the reverberation time. At 1kHz, the measured reverberation has come down from four seconds to 2.7s, which is much more manageable.”

ECHO CHAMBERS

With Kings Hall tamed, attention turned to the Parliamentary chambers. The old House of Representatives chamber, once the scene of many fiery debates across the dispatch boxes, was now regularly filled by visiting school groups learning about parliamentary procedures and processes. The first requirement here was for a sound reinforcement and hearing assistance system for the use of teachers and museum guides. In addition, because the space was heavily used for functions and commercial presentations, it needed a lectern, dual video projection flanking the Speaker’s chair and a full-range program sound system.

The audio, projection and hearing assistance arrangements had to cover every one of the 128 green leather members’ seats as well as the 50-seat public gallery while making the absolute minimum impact on the fabric of the space and remaining discreet to the point of near-invisibility.

Perhaps surprisingly, although the chamber had been fitted with microphones for Parliamentary broadcasts, there had never been a PA system, so Luis needed to start from scratch with no ready-made cabling conduits, nor any established speaker recesses where new infrastructure might be hidden. Once again, the ideal solution was the narrow, low-profile Fohhn column arrays, this time using the larger DLI-230s mounted to either side of the old Press Gallery.

Luis created presets that allowed each speaker system to deliver two different beams at once. One beam covers the floor of the chamber while the second directs sound only to the public gallery which can be switched on whenever that area is in use. To allow full-range sound, two matching Fohhn subwoofers are floor mounted behind the railing of the Press Gallery, adjacent to the columns but out of sight. Because the gallery is not open to the public, the speakers did not need any fixings so there was no effect on the heritage woodwork.

VOTE FOR PROJECTION

The projection system was required for use with visiting school groups and also for occasional corporate presentations. Again, any equipment added to the space needed to be as unobtrusive as possible and to be removable without damaging the fabric of the chamber. Integrators, Sound Advice, responded with some innovative mounting solutions to meet this demanding brief. They concealed twin Panasonic RZ670 laser projectors in the public gallery and devised a discreet mirror system to project across the chamber. On the opposite wall, twin retractable screens were suspended from the Press Gallery balcony. The screen cases were colour matched to the woodwork so they virtually disappeared when not in use.

For functions, HDMI inputs to the projectors are available at the lectern positions with signal transport provided by Crestron’s DM-NVX-350 video-over-IP solution. A Shure ULXD series lectern mic and dedicated receiver keeps cabling to an absolute minimum, providing functionality without intruding on the unique character of the chamber. Once again, a Crestron TSW-760 touch panel allows function staff to set-up and control the presentation facilities.

GUIDING HAND

The guides who take the regular school tours through the museum take control of each space they enter using an iPad running Crestron XPanel. In each room, the system allows the guides to tune the radio mic receiver to their own Shure lapel mic transmitter and to trigger educational video content on the projection system. Behind the scenes, BrightSign video players provide content via the network to the projectors in each space. Out in Kings Hall, other automated BrightSign players provide interpretive video content to projectors that use the acoustic panels as a screen surface.

Of particular importance in the project was the comprehensive hearing assistance system, which is used for both tour groups and functions across the Kings Hall and the chambers. Two separate systems provide flexible options for any patron who enter the spaces. First, all audio (microphones and video program sound) is directed to a Williams AV hearing hotspot. Patrons can use an app downloaded to their own smartphone to tune in to sound in each space via wi-fi and then use their own earbuds, headphones or Bluetooth system. For patrons who don’t use a smartphone, pre-configured iPods with personal neck loops or headphones are available from the museum staff.

The second system installed in the spaces uses the ‘Roger’ protocol devised by hearing aid manufacturer Phonak which is already popular in a number of schools. An RF beacon located at the entrance to each room alerts users of certain Phonak hearing aids that a direct connection is available. It allows the aids to automatically tune in to the audio from a local Phonak base station connected to a feed from the room sound system.

ANSWER TIME

Many seasoned AV practitioners would rather avoid jobs that combine poor acoustics with the constraints of working in heritage listed buildings. Luis, though, enjoys putting his years of university study in audio and acoustics to good use.

“Solving acoustic problems in difficult spaces is something I like to do,” he confided. “Whether I am working in Kings Hall or Bankwest Stadium, I’m trying to provide the best clarity in a challenging environment. So understanding not only loudspeakers but acoustics helps a lot.”