Having installed an Alcons QR36 pro ribbon line-source column loudspeaker in 2007 for its predominantly spoken word performances, an expanding programme of events saw Hamburg’s Thalia Theater adding bass extension in 2021, and now complete a more comprehensive upgrade.

The first Alcons installation revealed acoustic challenges in the theatre auditorium, as it has a very high ceiling very little floor space. In addition, there are the usual problems of getting sound under the galleries. The first installation of Alcons QR18 pro ribbon column loudspeakers, QR36 pro ribbon line source column loudspeakers and small-format LR7 pro ribbon line array systems provided initial relief to that situation.

‘At the time, we were looking for something compact and extremely precise that would only cover the audience and nothing else,’ says Thalia Theater sound engineer, Ben Schröder. ‘That works perfectly with the installed Alcons systems up to this day. Since then, we have been able to project significantly more direct sound into the last rows without long arrays or too many reflections. What we lacked over the years, however, was headroom in the low mids and high lows. We wanted to be able to perceive the low ends as a direct impulse. And this is where the trouble began…

‘In 2021, we tried to expand the front basses by adding a small BF121 MkII sub to each top, while at the same time revamping the upper tier sound reinforcement. This worked quite well from a sonic perspective and also provided the desired increase in headroom for live music. But there was another problem – we were always in conflict with the lighting, specifically the follow spots, because the PA was just hanging too low.’

Four Alcons LR7 pro ribbon line array systems were added, allowing to split the centre array and provide more flexibility in collaboration with the lighting. To achieve better low-frequency imaging, a new sub-bass system was installed next, comprising four Alcons BF151 MkII single 15-inch subwoofers, installed as a 2x2 cardioid pair above the gantry, two more under the upper tier sound truss and a further two units above the upper tier sound truss, with all eight woofers calibrated in two positions as one mono system. After 15 years in operation, the existing amplifiers were also replaced, with six Sentinel10 amplified loudspeaker controllers replacing the earlier four analogue ALC2 and ALC4 controllers.

‘We chose Alcons’ small 15-inch woofers because we didn’t have a lot of space available and could only add limited weight to the roof. It was a long evaluation process,’ says sound engineer, Stefan Flad. ‘But, in the end, it became clear that there were hardly any other alternatives to achieve the desired low frequency imaging and more headroom in our particular situation.’

The new bass cluster is installed in an end-fire configuration. This allows variable configuration of eight 15-inch BF151 MkII woofers, each of which can take on different tasks as a pair. This approach still required sensitivity with regard to the lighting. So an additional loudspeaker was added to the centre cluster, to be used only in those situations when the lighting would hang so low that it obstructs parts of the centre cluster.

‘We came up with the idea of building a cluster made of small woofers,’ Schröder says. ‘The BF151 MkII are doing a fantastic job here! Such a deep, rich bass response with lots of dynamics from such a compact system – that totally blew us away. After all, a 15-inch is never enough for a subwoofer system, right? Except with Alcons. Even the 12-inch BF121 is a sufficient woofer and incredibly loud with no audible distortion. With the whole system up and running, you can actually hear the difference quite clearly when you turn that BF121 on. That’s remarkable.’

Schröder says that the new central upper bass allowed the other woofers to be turned down by 5dB while maintaining the same level in the stalls. ‘Now we not only have more bass from the ceiling, but the overall distribution in the house is fantastic, and we’re really having fun at the mixing desk. The musicians are also thrilled,’ adds Flad.

‘If you like ribbon tweeters, Alcons is certainly the top choice,’ Schröder continues. ‘For us, this technology has advantages because we need a lot of low end. And the Alcons woofers are simply outstanding. Alcons really knows what deep bass is. The small, deep-sounding BF151s and the sophisticated woofer system designed by Stefan Flad and Heiko von Wallis made this extraordinary sound reinforcement concept possible in the first place.

‘With the addition of BF121s for the high bass and the new amps, we were able to turn a speech PA with deep bass into an inherently more balanced sounding musical PA with enough headroom from the lowest ends all the way up to the high-resolution highs, without having to design a whole new PA system.’

The result is a remarkable improvement in the theatre’s sound reproduction. ‘Early 2023, we hosted the Lessingtage [Lessing Days] with a wide range of performances,’ Schröder reports. ‘The visiting artists were consistently enthusiastic and kept asking us about our great sound system. That really feels good after the very delicate system planning phase.’

Industrial Arts from Glinde, Germany, installed the system, with Heiko von Wallis in charge of calibration and offering input throughout the planning phase, which also required some custom solutions.

‘It was only thanks to the dedicated efforts of everyone involved that a very convincing solution could be achieved and the requirements of the lighting department could be balanced with a modern bass reproduction for the audience,’ concludes Flad.

More: www.alconsaudio.com