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
The aQflex has an absorption coefficient of app. 0,5 (63-1k Hz) in the densest configuration when mounted directly on the ceiling. This alpha works in the entire ceiling area. When in-active it is close to zero.
Certified measurements in reverberation chamber
Certified measurement on discrete object
Certified measurements in real hall
The closer the baffle-lines the higher an alpha. Preferably the uninflated baffles are app. 80 cm apart (center-to-center) for an alpha of app. 0,5 63 – 1k Hz. As the baffles are 70 cm thick when inflated they cannot be much closer than 80 cm; center-to-center. So ideally the baffle-lines should be close. In some cases there may be other things placed in the ceiling obstructing the placement of absorbers. This would reduce the alpha somewhat. The absorbers must be mounted directly to the ceiling to get these coefficients.
The above diagram shows the best estimate of the abosption coefficient of a 80 cm spacing (center-to-center) of baffles in a hall.
Here below is a certified measurement from a US reverberation chamber with baffles spaced app. 80 cm center-to-center:
Below is the certified measurement, baffles in a thin, wooden well, from a Danish reverberation chamber. Baffle spacing 75 cm center-to-center: (Download full report above)
With a distance of app. 130 cm center-to-center, not evenly spaced, the alpha in a real hall was measured to app. 0,37 (see full report above). This is enough though, to obtain a very audible difference of RT if the room is not very high compared to ceiling area. The reason is that absorbers work in the bass frequencies too. The 3 different, certified measurements are not comparable, and the best estimate of what alpha will be a result of an aQflex in it’s closest configuration is seen in the upper of the three tables above.
If the aQflex cannot be mounted direct on the ceiling it is probably better to mount aQtubes mid-air and connect them to the aQflex system of air-ducts and controlunit etc. The reason is that the alpha of the aQflex drops especially in the 125 Hz octave band when it is away from a sound-reflective surface.