absorb low frequency sound
short bass reverb is crucial for rock
absorb evenly from 63 Hz to 1kHz
the fundamental frequencies of music
audiences absorb higher frequencies
high Q directs HF at audience
Far the greatest share of concerts are within the ideom of amplified music; pop, rock, latin, electro etc. Since these genres are rhythmically active and loud at bass frequencies, they need first and foremost a hall with controlled low frequency reverberation to work well. Many halls are actually the opposite: very reverberant at low frequencies. Both these facts are documented in the scientific literature.
On the other hand, classical music needs a longer reverberation time, also at low frequencies, to carry out and support the sound and respond to all tones in the orchestra somewhat equally.
So the challenge in multi-purpose concert halls is to vary the reverberation time especially for bass tones. Mid- to high frequencies are often over-absorbed since an audience absorbs them by 100% – and also the air absorbs treble.
But high frequency reverberation is needed for an orchestra to express dynamics; this is true for many instruments within all musical styles. Without high frequency response from the hall, the music becomes dull.
Pop- and rock halls can also have a longer reverberation at higher frequencies – this gives audience and musicians a feeling of being enveloped in sound; being inside the music – surrounded by it. The audience, orchestra and hall becomes one unity – a social event.
The directivity of PA loudspeakers is high at high frequencies, so that sound is aimed at the audience who absorbs it. A result of a longer RT at MF-HF is that a lower degree of artificial reverb will be employed by the sound engineer engaging the halls’ own, beautiful natural reverberation.
The aQflex and aQtube do just that: barely affect the reverberation when inactive while absorbing the fundamental frequencies of musical instruments equally much when active.
In some halls it may be advantageous to adjust the acoustics to whether there is an audience or not. This is easily done with retractable drapes, banners, curtains since these have a very similar absorption curve at various frequencies as an audience: they usually absorb little bass and lots of high frequencies. This is an ideal solution also for music education institutions.
Recommended RT in various octave bands etc. for pop & rock concerts can be found under Research papers.