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KV2 delivers tailor-made audio solution for Prague’s most prestigious concert hall

Conceived as a multi-purpose cultural centre combining exhibition rooms with concert halls, the Rudolfinum is one of the most architecturally remarkable buildings in Prague. It is also the home of the Czech Philharmonic Orchestra, which first performed in the Rudolfinum’s world-famous concert hall in 1896 under the baton of Antonín Dvořák. Today it is still the most prestigious concert hall in Prague and offers a dense and varied program of exceptional classical music concerts. The 1,100-capacity Dvořák Hall, named after the famous Czech composer, is renowned for its remarkable acoustics and is sought after for its unique atmosphere and for recording classical works.

Ahren Prohmann, world-renowned producer, music director, and winner of several Grammy Awards, remarked after making a complete recording of Dvořák's symphonies in 2014 that none of the world's famous old halls, such as the Musikverein in Vienna, the Concertgebouw in Amsterdam or the Symphony Hall in Boston, have such a highly recognizable sound as the Dvořák Hall. The acoustics are characterized by a very long reverberation, most notably in the mid frequencies and the distinctiveness of the sound in the Dvořák Hall is enhanced by other unique elements, such as the construction of the auditorium.

For many years, however, sound masters have struggled with the reproduction of amplified speech, especially with intelligibility and even coverage of the entire space. Efforts to resolve this have always run up against limitations in technology and the very strict requirements of the Rudolfinum’s listed building status, which do not allow technical installations that are not in keeping with the architectural aesthetics. "We have been struggling for a long time with insufficient intelligibility of the spoken word in the Dvořák Hall; it was never ideal due to the particular nature of the acoustics," admits Radomír Stöhr, technical administrator of Rudolfinum.

George Krampera, the world-famous designer of sound systems and the founder of the Czech company KV2 Audio, undertook the task of resolving these issues with his team. His career spans over five decades in the development of professional audio technologies, many of which have become industry standards. His company's philosophy is built on a unique technological approach, which is focused on achieving the highest possible dynamic range and the lowest possible losses caused by distortion and signal change when passing through individual parts of the sound chain. "Our technology respects many factors that are important for sound quality, whether we are talking about electronic integrity, sampling of digital systems, pulse response, dynamic range or acoustic design," says Krampera.

David Mareček, CEO of the Czech Philharmonic, also welcomed the cooperation with KV2 Audio: “We have excellent experience with KV2 sound systems, in particular with the annual Open Air concert, which heralds the end of the Czech Philharmonic’s concert season in June. It is traditionally broadcast live on Czech Television."

The physical constraints of the building meant that the spaces available for loudspeaker placement were not optimal for standard loudspeaker coverage patterns, so a bespoke solution had to be developed. The team, led by George Krampera, designed and built a fully customized system, not available in the KV2 catalogue, with custom horns designed to meet the unique dispersion requirements of the room. Equal emphasis was placed on both controlled dispersion and minimizing the effects of reverberation from above, by designing the system in such a way that it would not disperse towards the ceiling, but play directly towards the audience.

Utilising KV2’s SLA ethos they were able to solve many of the timing issues that would have been present if installing one of today’s third party DSP based solutions, solutions which are often extremely sensitive to feedback, and a problem that would have only been compounded by the extremely challenging acoustics of the room.

Technological advances through KV2’s Super Live Audio (SLA) research, such as a newly developed 5” low inductance midrange driver, meant the fastest and most accurate midrange was available as a critical part of the system design. This ensured clarity of vocal reproduction and extreme resolution, even in the most reverberant areas of the Hall. Should digital processing have been necessary, KV2’s industry leading DSD based 20MHz system was of course on hand, but on this occasion a pure analog signal path was the chosen solution.

Built into the fabric of the building where possible the stalls are covered by two three-way custom install passive column systems with very high resolution and controlled dispersion, equipped with six 10” speakers for low-mid frequencies, two 5” for midrange and one 1” speaker for highs. The balcony is served by a similarly designed three-way system with additional custom sidefills comprising four 6" speakers for low-mids, one 5" speaker for mid-high frequencies and one 1 "for highs.

Two ESP4000 amplifiers provide amplification for the passive full-range speakers in the Dvořák Hall, and two analog SAC2 analog controllers provide sound processing.

“At KV2, we try to minimize the distortion of the entire electroacoustic chain, which is why we have maintained the complete signal path in the highest possible, fully analog quality. We completely avoid any digital processing here, which really helps” emphasizes Krampera.

The sound booth for the Dvořák Hall is equipped with a pair of active EX6 speakers from the standard KV2 production portfolio and a Soundcraft analog mixing console, which has been specially modified in KV2’s labs for high-resolution sound. The choir benefit from a pair of passive ESD10 monitors, as well as a pair of ESD6s in the backstage area, all powered by ESP amplifiers.

The sound project also included the Suk Hall, which is historically the youngest hall in the Rudolfinum building. Completed in 1942 and decorated in a style inspired by the Rudolfinum’s original architects, the 190-capacity Suk Hall is ideal for chamber performances.

In 2015, the hall was completely refurbished with the aim of improving the acoustic properties. George Krampera's team also equipped this space with a pair of specially designed three-way active speakers with very high resolution and controlled dispersion (4x 6” low-mids, 1x 6” mid, 1x 1.75” high). An important characteristic of this system is the full-range frequency response of the system coupled with its optimised coverage. Another interesting detail to aid aesthetics is the incorporation of the slim amplifier, with passive cooling, built into the wall of the hall itself.

“I am very proud of the work of my team who faced difficult conditions with this assignment, necessitating a majority of tailor-made, unique solutions. We were able to capitalize upon our many years of experience in building sound systems and fully respect the technological principles on which our company stands in order to deliver the audio experience they have been dreaming of for so long,” adds George Krampera.

In the vast majority of cases, the new sound system is used to reproduce the spoken word. Audiences and technicians alike are thrilled with the results, especially for televised broadcasts.