Text:/ Derek Powell
Images:/ Courtesy of the SAFC
Photography by Peter Barnes

DOING IT ON THE QUIET

After previous incarnations in adapted and refurbished spaces, the new build provided the opportunity for the architectural and acoustical team to finally apply a rigorous approach to two vital objectives for the Premier theatre – keeping out extraneous noise and building-in perfectly-tailored acoustics.

Very low levels of external noise in the studio are crucial to the Dolby Premier specification, so SAFC engaged Swift to assess the level of noise from aircraft, passing trains and ground-borne vibrations at a number of potential sites before Glenside was chosen. However, from a noise point of view, a quiet location is just the start.

Peter Swift explained that the mixing studio itself is essentially a separate structure within the studio building. “…there are actually structural breaks all around,” he noted. “So where services cross, there are flexible connections”. Making certain of the structural separation was a key challenge, as he described. “Whenever the slabs were poured, with the appropriate isolating material between them, you’ve got to make sure that pieces don’t fall down the cracks and cause little transmission bridges. Because once you start building walls up inside – if you haven’t found them, then it’s too late. You’ll never find them.”

‘Hold points’ were built into the construction schedule to allow the AECOM team to measure the relative vibration levels between the isolated slabs to make sure nothing was amiss. It was exacting work, but the pay-off was extremely low levels of airborne and structure-borne noise in the mixing theatre.

THEN KEEPING IT HUSH HUSH

Designing the frequency response of the space was a step-by-step process, relying heavily on physics and mathematics, but also on some simple geometry, Swift explained – launching into what was virtually a master-class in studio acoustics. The first stage, once the volume and the basic proportions of the theatre were established by the Architect, was for Swift to use the raw dimensions to calculate the ‘modes’ or standing-wave frequencies that would exist in the space. He then set to smoothing out the potential resonances by tweaking the dimensions of the walls slightly and running all the calculations again until he had the proper distribution of modes across the audio spectrum.

Next, using some simple ray-tracing diagrams, he adjusted the angles of the walls, ensuring that the first reflections from each speaker would be directed away from the mixing position. “Any reflections that you do get need to be a little bit late and at least 10 and preferably 20 dB down which means you’ve got to really look at the relationship of the side walls and the absorption on them,” Swift pointed out.

From there, a key part of the process is designing the right mix of absorption in each frequency band to meet the crucial reverb time versus frequency parameters. “You can’t just put soft, wide-band absorption across the whole theatre – it gets too one-sided, so you’ve got to mix wide-band and low frequency with a bit of reflective stuff”, he said.

There’s heaps of maths involved so that the right absorption gets installed, but at the end of the build Swift still allowed for time to do the crucial final measurement and tuning of the absorbers by hand.

STRUCTURALLY SOUND

The architects worked closely with Swift, adjusting their structural design to each iteration of his calculations. I asked architect Steve Grieve if he found the process unduly constraining. “Not at all”, he replied. “If you understand the Dolby specifications well enough from the point of view of performance requirements, then you can work with the acoustic engineers to develop the identity of the space itself. In the case of the screening theatre and the mixing theatres in particular – often the absorption panels have a particular pattern and texture. The actual materials have to be exposed so they work acoustically, so if you work with them, you can use them as a design feature.” The end result, highlighted by well-placed lighting, is simply stunning and the theatre looks every bit as spectacular as it sounds.

Meanwhile, working with AECOM AV consultant Mike Comiskey, Mike Rowan set about assembling the equipment side of the equation. For speakers, Rowan turned to their established supplier Krix, whose SA-manufactured and THX-certified cinema speakers are exported around the world. He settled on three identical KX-5920 3-way boxes from their commercial cinema range for left, centre and right, with each driver powered by one QSC 3422 or QSC 1644 amplifier channel. Subs were a pair of massive twin-18inch KX-4610s, while 12 KX-1870 two-way boxes, each driven by a QSC 1622 channel, took care of surround. To minimize losses across the speaker cables, the QSC amps driving the front speakers were located adjacent to the enclosures, behind the micro-perforated screen.

An upgrade to the existing Harrison console was next on the agenda. Rowan chose the Harrison MPC4-D console, optionally working in concert with a ProTools D-Command 16-channel control surface. The Harrison console is attractive because it is in wide use for film, enabling interstate and overseas mixers to familiarise themselves with the room easily. For different projects, a sound engineer may to elect to mix from the Harrison console or from the ProTools interface. This would be an issue in most facilities as only one control surface could be positioned in the “sweet spot” at the centre of the room. However Mike Rowan devised an ingenious solution that allows the console to be reconfigured in less than ten minutes, so that either the ProTools or the Harrison can assume “centre stage”. He built an extended metal framework that spans the full width of the combined consoles. When required, the ProTools surface can be lifted out, then using a system of slides, the Harrison left console can simply move across making space for the ProTools to be placed in the centre

As befits a team with such impeccable local credentials (and the patience to spend 30 years perfecting their ideas), the Premier Studio is an absolute triumph. It looks spectacular, operates immaculately and has now been certified by Dolby as sounding absolutely flawless.