We evoke musical inspiration
through natural acoustic transformation


FlexAcoustics was founded by Niels Werner Adelman-Larsen in 2005 and has pioneered research and development within acoustics for amplified music and multipurpose venues for two decades. The company specializes in inventing and developing reliable, state-of-the-art variable acoustic technologies. They are all unique to other solutions, and are based on what research shows must be done, to overcome the challenge of truly adapting the acoustics of a hall to fit different basic types of music.

The first invention, aQflex™/aQtube™, was based on Niels’ discovery of the - under certain conditions - surprisingly high sound absorption properties of inflated flexible membrane structures and the possibilities derived from these.

Later, the groundbreaking evoke™ series was added to the product range. All evoke solutions also build on research and hence the notion, that when ON, variable acoustics systems must absorb more bass sound than treble. In fact, evoke1 is used in cutting-edge acoustic research in several sound labs across the world.

Common to all FlexAcoustics solutions is that they verifiably create the optimal audio quality throughout the hall - including the stage – regardless of music genre. This allows musicians to evoke truly great music while the audience have the concert experience of their lives. This is achieved by adapting the hall to the ideal reverberation time curve for each basic type of music.

“I have been fortunate to have played with some of the most excellent musicians, creating experiences I'll cherish forever. Jamming with Pat Metheny, Joshua Redman, and Jorge Rossy and performing with world-class artists like Doug Raney, Esbjörn Svensson, Jacob Fischer, Josefine Cronholm etc. Art created at such a level deserves to be met by the acoustics of the performance spaces.
That is what I strive for and what has become my fuel”.
- Niels Werner Adelman-Larsen


Niels Werner Adelman-Larsen holds an M.Sc. in acoustic engineering from the Technical University of Denmark, as well as a Ph.D. in acoustics from Aalborg University. Before pursuing his professional career as a musician, he studied music and sound engineering at Berklee College of Music on a scholarship, and took a B.Sc. completed with a thesis on room-acoustics for sound studios.

So far, he has played more than 1,200 jazz, pop and rock concerts around the world, which has given him a unique insight into acoustic music venue design. Throughout those concerts, Niels learned that most halls are, in fact, unsuitable for amplified music such as pop and rock. This hands-on experience led him in 2004 to initiate the first profound scientific research projects within acoustics for amplified music venues ever conducted. A field he has since almost solely developed.

Niels’ investigations led to peer-reviewed research articles, as well as the only scientific book about acoustics suitable for amplified music (Springer Verlag) and to the ISO:23591 standard. His research and ideas are widely applied by acousticians around the world on a daily basis.


It was scientifically proven in Niels' studies that long low-frequency reverberation makes a hall unsuitable for amplified music. When a room does not absorb these sound waves, they bounce between surfaces for a long time. This causes a long reverberation time - the time it takes for the sound to fade out in a room. So, room acoustics is indeed happening in the time domain.

Longer reverberation also means louder reverberation. Quiet, un-amplified music - for instance chamber music - needs longer reverberation to become loud enough. But that may, in turn, make other audio material unintelligible. For instance, we know this from churches: the priest is hard to understand unless you sit right at the front or close to a loudspeaker.

The same happens with music - especially when a lot of rhythm and syncopation is present. The intelligibility of the music becomes low since one sound continues at a loud level while the next starts. The music becomes muddy.

However, choir or legato-types music often sounds great with a very long reverberation time. Hence, the need for natural acoustic transformation. Low-frequency sounds are typically loud at amplified music performances. The challenge is that while higher frequencies are directed by the PA towards the audience, who absorbs 5-6 times less LF-sound than MF and HF, LF is emitted almost omni-directionally from the speakers to surfaces that probably don't absorb LF sound, creating a many reflections and thus long reverberation time.


Most contemporary music such as pop, rock, electronica, etc. is percussive and loud at lower frequencies, caused by bass, keyboards, drums, etc. This is not ideal in most halls, as they have long reverberation time in the 63 and 125Hz bands but not above 250Hz. In short, MF and HF are absorbed by the audience and the air - the lows are not.

At very low frequencies, the 63 Hz band and below, only the bass and bass drum are present, and the level is lower than in the 125Hz band where many instruments are rhythmically active. Therefore, the masking by sounds in the 63 Hz band is less of an issue than sounds in the 125Hz band. In fact, the reverberation time can be longer in the 63Hz band than in the 125Hz band without being disturbing.

Consequently, the critical frequency band that needs special attention is the 125Hz octave band.


Apart from the technology aspect where we offer evoke and aQseries solutions, it is key that in a wider perspective, venue owners, sound engineers, acousticians, designers and architects start focusing on a common understanding of the issue - and a common standard for what the goal should be.

Niels Werner Adelman-Larsen has put a focused effort into increasing awareness of these challenges through research and lectures around the world. He authored the first ever scientific book on this topic and is a member of the ISO TC43/SC2 standardization group that incorporates his and others’ research findings into the ISO 23591 standard.

The ultimate solution is evoke or aQflex. They make sure that a venue's acoustics stays within the ISO standard recommendations. An acoustic measurement - in combination with geometrical data - will reveal the true potential of a hall. In fact, part of the studies included a questionnaire in which a third of the musicians responded that they actively avoid concert halls with poor acoustics for amplified music.

The result: natural acoustic transformation.



Frequently asked questions


Want to know more about what FlexAcoustics can do for your case?
Give us a call or fill out the form and we will get back to you as soon as possible.
© 2023 FlexAcoustics. All rights reserved.
f [Hz]
α max / ON
α max / ON
α max / OFF