All change

All change

Published: MEA

A combination of skill, knowledge and software was the solution when commissioning the system at the Souk Okaz public theatre in Saudi Arabia became designing a new PA. James Ling reports.

Picture the situation. You’ve just arrived on-site at a plateau 2,000m up in the mountains ready to commission the system you have been simulating and adapting on and off for the last 18 months. There have been good lines of communication with the client and the partner on-site fitting the system, so it should be a relatively simple job of tuning the PA to the room. Then you find out everything has changed. The simple task of tuning has become one of redesigning the entire system in a limited timeframe. What do you do?

The option taken at the Souk Okaz public theatre in Taif was to get simulating. ‘The initial simulation worked on an L-C-R configuration with 10 left, 10 right and five down the centre. The left and right hangs were quite wide out from each other, hence why we needed the extra centre,’ recalls Sennheiser Middle East technical sales manager Ryan Burr. ‘When we got to site, we found that the hanging points had been moved about 5m forward and about 10m inwards.’

Even before the team arrived onsite at the 3,000-seat tent-style venue to discover this latest challenge, there had been plenty of changes to the design. ‘We had initial designs where we did some simulations and so on. But all of that had to change when we got information on all the materials being used,’ says Mr Burr. ‘For example the absorption coefficient of the seats and the tent material itself changed a couple of times. That had an impact on reflections so the absorption coefficient of the material had to be changed in the simulation, thus providing us with different results.’

The venue is used for the poetry and storytelling competitions which are the highlight of the Souk Okaz cultural event. With intelligibility a priority for the project, these small changes made a large difference. However, the importance of the intelligibility also meant that the client had extremely high expectations of the system. ‘The client kept asking us to change things and then to come up with intelligibility figures that were unattainable,’ explains Mr Burr. ‘We even looked at putting in some acoustic materials in the room itself in order to try and dampen some of the reflections. The cost implication of that was just too much. Because it is such a vast chasm of a space, it would have been so difficult and so costly to do that,’ he reasons. ‘It took us a fair bit of time to convince the client that this was the case.’

And so, as the team from Sennheiser joined its local partner Modern Lifestyles to find the DAS Audio Aero 8-A line array system flown to the original specification from its new hanging points, it became clear that some revision was going to be needed. ‘We had to recalculate our simulation in order to make sure we got the same minimum 100dB level that we were asked to get throughout,’ explains Mr Burr.

The team needed to come up with a new system based on the existing components with the new hang points. Mr Burr is quick to declare how pleased he was not to be alone in taking on this challenge. He was joined onsite for the commissioning by Sennheiser UK sound reinforcement specialist and touring front of house engineer for Leona Lewis, Dave Wooster. ‘Having someone there with that level of knowledge really does help. Being able to do that repositioning of the PA on the fly in such a short period of time wouldn’t have been possible without him onsite,’ beams Mr Burr. ‘It would have taken us a day, maybe two to do a full simulation again, and then have the positions changed and angles of the boxes all changed. Because he was onsite, he just fired through it and got it done really quickly. We were finished within half a day for the repositioning.’

The new position for the hangs meant the room no longer needed the L-C-R configuration. ‘With us having to pull the outer hangs inwards, it meant that there was no real need for a centre hang. The entire area was still being covered with maybe the exception of the back three rows on the outer sections of the audience area, which wasn’t really a major issue,’ says Mr Burr. ‘We decided to dispense with the centre hang and extend the left and right arrays down further. That meant we could have more boxes projecting into the outer areas thus increasing the SPL in those areas. That meant that instead of having a hang of 10 per side, we had 12 per side.

‘The remaining box, we put on top of the subs, just as a front fill for the front two rows, which are historically the VIP rows,’ continues the technical sales manager. ‘We EQ’d that front fill box so it was mainly just high frequency that was coming out of it, just so the intelligibility in the front rows was better.’

With speech being the primary focus of the system, low-end support was only a minor consideration. Six double 15-inch LX-215 subs have been placed along the front of the stage, but again this was not the original plan. ‘These were initially arrayed in a staggered V shape in order to accommodate some of the lobing effects we were getting from the low frequencies. But in hindsight, after listening to that and looking at how it was laid out on the floor, we decided that it wasn’t really necessary, it was much easier just to have a single straight line of centre subs,’ reasons Mr Burr. ‘We had difficulties hearing the dramatic effects of the lobing, it wasn’t until you used an analyser and went round the room that you could actually notice it,’ he explains.

‘Visually it made a huge impact having that staggered setup for the subs as it impacted on the floor space that was required to accommodate it. That was a large part of the decision to put it right up against the stage anyway. That helped the profile from a visual perspective as the subs look much neater. It made the whole project look neater to be honest,’ continues Mr Burr. ‘Based on how often the subs were going to be used and how much low frequency was ever going to be coming out of it, it seemed like the fairer thing to do.’

While the new system may be more visually appealing than the original design, Mr Burr will not be drawn on whether it sounds better than the original planned system. ‘It’s difficult to tell if it sounds better than the one originally designed. Definitely they have had an increase in SPL in the majority of the audience area – whether or not that makes it sound better I don’t know,’ he reasons. ‘Moving the hangs closer to the audience area also improved the intelligibility because the higher the SPL of the direct sound, the easier it is to drown out the reflections, thus not having an effect on the intelligibility.’

Combining experience and knowledge with software on the ground was a tactic used for the second part of this project, the wireless microphone setup. This was a particular challenge due to the size of the stage area that needed to be covered. With a history dating back 12 centuries, the venue is steeped in tradition – the theatre itself is built on the site of the historic marketplace – and the designers wanted to emphasise that with a stage area that includes elements of the natural terrain. While this offers many more creative avenues for performers to explore, it also challenges the Sennheiser G3 wireless solution.

‘From a wireless microphone point of view we needed to ensure that coverage in all of those areas is uninterrupted. We achieved this with antenna positioning,’ explains Mr Burr. ‘We used our Wireless Systems Manager (WSM) software and there is a section on that which allows you to do a walkthrough of the stage area. It shows you where you are getting drop outs so you can reposition antennas based on the fact that you want to cover a particular area, ensuring that the drop outs don’t actually happen.

‘We positioned the antennas in strategic locations, allowing us to be able to cover the whole of the auditorium as well,’ he continues. ‘It took a little bit of doing, a couple of walkthroughs and then just getting the positioning right, but once we’d finished you could go to the back row of the auditorium with a wireless mic and have no problem, you were still getting full coverage there.’ Again for commissioning this portion of the project, Mr Burr directs a lot of the credit towards Mr Wooster.

‘To be able to commission it the way we did, we had to get Dave Wooster,’ he states. ‘He comes with good credence, good experience – he’s worked in small auditoria right up to big stadium-sized venues. He anticipated some of the pitfalls we might encounter, especially when it came to coverage of RF. He ensured that the positioning was right with the antennas so that we could cover everything.’

The final result is an installation that has exceeded the expectations of the client. This is something that Mr Burr is justifiably proud of. ‘Seeing the way the client has reacted and the ideas they have had for increased use that the system could get is really satisfying. It took a little bit of time to get the system right for the room, but it was totally worth it.’

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