d&b's eminent C-Series for Hamburg's Congress Centre
The Congress Centre Hamburg (CCH) has always staged a wide variety of events since it opened in the late 1970s. Besides the obvious conferences that form its mainstay, the largest hall, Hall One, with a capacity of three thousand seats, has over the years hosted many performances including orchestral, choral, rock and pop. A wide fan shaped auditorium with deep sloping stalls and balcony, CCH Hall One is an ideal venue for such a variety of events; visually there isn't a bad seat in the house, with open unrestricted views of the stage. Although it is forty-six metres from the front stage edge to the back wall, this large auditorium still manages to engender a fair degree of intimacy between performer and audience thanks to creative architecture and careful choices of materials. Unfortunately this benign state has not been reflected in the acoustics, which is why CCH has continuously sought to avail itself of technological advances to address such shortcomings. The very latest electroacoustic update has achieved some remarkable results. Amongst others the prestigious Sinus Award in the Venue category, which went to Rüdiger Aue, Project Manager of Hamburg based service providers Amptown Sound & Communication, for planning and installing the new PA system for the Main Hall.
"There are a few problems with the acoustics of the hall," began Rüdiger Aue. "The room has a reverb time of around 2 seconds, 3.5 around 100 Hz, shortening to 1.0 at the high end above 10 kHz. But the main problem is reflections, particularly from the back wall; the front row seats could hear a very clear echo. These also create difficulties for the performers on stage."
"Keeping loudspeaker energy off the side walls to prevent further exciting the reverberation of the room is a well-known solution to the first problem," said Aue. "We have established d&b loudspeaker systems in all the halls of CCH for exactly that reason, the well defined pattern control over a wide bandwidth makes this operation simple. The latest installation uses a line array of d&b C3s left and right with C4-TOPs and SUBs and Q7 fills, flown left and right. There is also a centre cluster of Q1s. But it's with a second system of subwoofers, an Endfire array, where we have been able to address the problems of the back wall reflections and the fluctuations in level across the seating area that have plagued previous installations."
Aue's design works as follows: for the front area of the auditorium d&b C7-SUB bass clusters were installed left and right, filtered specifically to propagate just 40-90 Hz. For the rear half of the hall, two of the so-called Endfire arrays were installed, again using C7-SUBs. "These four subwoofers are in a row," explained Aue. "Mechanically separated by a quarter wavelength at 60 Hz to which they are tuned, they are also time aligned to produce a super-cardioid propagation pattern. This achieves two things: the main system low end doesn't have to be so loud to reach the back of the hall that it blows away the front row audience; attenuation from the Endfire array is –20 dB directly below the main cluster and at the back it cancels bass energy returning toward the stage; those troublesome echoes."
Amptown has installed a complex solution to a complex acoustic, eight Soundwebs and twenty-eight d&b D12 amplifiers, (utilising Soundweb Designer and d&b ROPE C software) controllable from PC via WLAN enabling operation from anywhere in the hall. Perhaps the biggest problem remaining for CCH is to persuade visiting production engineers to use the installed PA system, but Hofmann's technical team are well versed in pointing out the difficult idiosyncrasies of this room and have years of experience to back this up. Woe betides any engineer that doesn't listen.