Dortmund Stadium goes active with RCF

The planning and design of the system was a joint venture between RCF’s 10-strong Engineering Support Group, led by Product Market Manager (Install Sound), Antonio Ferrari, and RCF Group German Subsidiary, led by Georg Hofmann and Norbert Wessel, working in conjunction with integrators fulfil engineering GmbH, headed by Norbert Labudda. It is fulfil engineering’s planning department that initiated, coordinated and supervised the project. The EASE 4.3 predictions provided the design architecture to develop a fully optimised system, setting the splay angles and placements of the hangs — which are spaced equidistant, some 20 metres apart. Four clusters each are mounted down the East and West tribunes (firing into the upper and lower tribunes) and three each cover the South and North stand.

All 196 active line array elements have been especially weatherised and the cone drivers coated, as is the wooden enclosure, which is is painted with polyurea both inside and out. All metallic items are fabricated in stainless steel. The decision to completely overhaul the system had been taken after complaints about intelligibility and coverage — particularly the insufficiency of the low frequency response.

Wessel recalls, “Once we had floated the idea of an active approach we needed to select the ideal system. We knew the TTL33-A was a workhorse in live audio and had 100% confidence in the TTL33-A system. We know it has an amazing touring pedigree — with six drivers, 3-way amping and powerful DSP built in. Although the idea of having an extended low frequency performance was derived from the live concert business, it was the best possible solution.”

The wizardry was clearly in the RDNet Control 8 network, which had not been present in earlier versions of RCF’s premium TT+ series. And it was the real-time monitor and control attributes — allowing it to manage a maximum of 256 devices per hub and 32 per bus in in a ring topology — that convinced Mr. Creydt (although in Dortmund fewer are used — one per grandstand plus another four as a hardware backup). Since everyone was aware that system checks in the past had taken a long time to implement and rectify, errors could now be flagged and addressed immediately. “We knew this would save both time and money — and that we had the technology to do the impedance control,” Wessel continued. Fulfil had stressed the necessity of meeting all regulations for the evac as a result of which RCF made modifications to the cabinet and mounting facility, enabling coverage to be provided from a single array.

The decision to specify the 2 x 15” subs, powered by 3400 watts of digital amplification, was something of a masterstroke, with a frequency response of 35 Hz - 120 Hz, and RDNet boosting the pattern control. Says Norbert Wessel, “The TTS26-A is able to be operated up to 160Hz so we were able to overlap the frequency range of the TTS26-A and the TTL33-A from 60Hz-160Hz. Therefore we used the TTS26-A firstly to extend the overall frequency range down to 40Hz, and secondly to create directional behaviour in conjunction with the TTL33-A, in the range from 60Hz up to a little over 120Hz.” The network technology between the stands’ alarm systems is fully redundant with its fibre optic ring feature. RDNet, has been specially programmed to ensure the entire signal path is monitored — the result of a permanent pilot tone generated from the PAVA system hub which is supervised by the input modules of the TTL33-As and allows cross communication. In fact two pilot tones are used: one at 19 kHz for cable testing and one at 10 Hz for transducers monitoring.

One special feature of RCF’s new amplifier modules is the full monitoring option on all chassis that are integrated in the speaker, with reporting carried out via bus systems. The entire transmission system is on a redundant optical multi-mode fibre ring with open standard architecture, communicating via TCP/IP, USB and RS-485.

“We have managed to integrate the complete monitor facility into TTL33-A so we can detect and measure the impedance of the speaker at the input stage and feed back to a network link using GPIO and so on,” he says. “We carry out LF and HF checks, as well as transducers and cable connections; if there is a fault we see it in RDNet and have direct contact with the PA/VA system.” In addition, the RDNet allows the venue to supervise the output stage status with a preset single structure, that takes into account temperature, delay etc.

To create an unusual array design with a vertical angle of approx. 140°, firing into the back of the upper and lower tribunes (and outwards to the edge of the pitch, including security and ‘technical’ coaching areas), some bespoke engineering was required. Georg Hofmann admits that weight had been a key factor in their considerations. “We started to think about a solution that would be easy to install and maintain. We needed a sub-bracket mounted on the beam with a motor hoist. We could have used standard fixing but instead we sought a dedicated solution.”

Norbert Wessel explains that although it is function of the TTL33-A acoustic design to be able to EQ and level the pattern control via DSP, in Dortmund the optimisation is only carried out by the mechanical curving of the array. “As a result, we maintain maximum audio output and constant behaviour over the whole array up to highest levels.”

Both Norbert Wessel and Georg Hofmann are impressed by the results. “The use of active speakers has certainly enhanced the frequency range. I was impressed how constant the audio is ±2dB in the special voice range between 400Hz-4-5K. You barely hear the crossover at all.” fulfil themselves had wanted more control in the frequency range, rather than sheer PA levels, according to project engineer, Lars Bendfeldt. With bases in Gelsenkirchen and Dortmund, his company has been responsible for installation, such as intercom and power supplies, since the last system was installed 13 years ago.

It was in 2000, that Germany won the FIFA World Cup bid, as a result of which the stands were further extended. In a stadium originally built in 1974 (to hold 54,000 people) four new stands were built to fill the corners between the existing grandstands bringing the capacity up to its present 80,720 (standing and seated.

Wessel summarises, “With the old system the voice was high-passed at 400Hz but this did not deliver a natural sound and when musical content was played it was not satisfactory. With the RCF solution the bass drum provides high impact as demonstrated at the first live show broadcast through the system, and there are fewer reflections due to the way in which it was configured.”

It is unlikely that the TTL33-A will ever reinforce a rock concert at this stadium — a celebrity football match is the biggest event outside football that would class as entertainment. On match days it will be switched on typically an hour before kick off as background music beckons the crowds in. Inputs include the standard radio mics, MP3 and line devices, with a DJ and celebrity announcer Norbert Dickel — a former player back in the 1980’s — who also operates a live internet stream so that fans can chat to him online.

In fact Dickel was so anxious about the quality of the new sound system that he flew in from vacation and took a taxi direct from the airport to the ground just to hear it. Both he and the resident DJ were instantly impressed with the improved sound, confirms Wessel. fulfil engineering has been retained to maintain and healthcheck the technical infrastructure at the stadium which fans refer to as ‘The Temple’. The final word comes from Norbert Labudda himself. “This acoustic distribution system is the most advanced you will find in any German stadium and we expect it to set a benchmark for others to emulate. It is the first system that corresponds to all norms and facilitates universal control and monitoring — from a single component right up to the loudspeaker chassis.”