Specifications

Appendix: Acoustics
Dynaudio Professional AIR reference manual – 2014-08-28 116
Rear wall cancellation
When the monitor is set up at some distance in front of
a wall, reections from the wall may occur and inuence
the perceived frequency response. This could result in
comb ltering if all frequencies produced by the monitor
were radiated in all directions. But monitors are typically
only omnidirectional at low frequencies.
The result of the reection is a single or a few dips in the
frequency response perceived in front of the monitor.
Fig. 79: A frequency (F) that has a wavelength of four
times the distance to the rear wall is canceled because
of the oppositely phased reection.
The dip – or cancellation frequency – depends on the
distance to the wall. If the distance is 1 meter, the rst
dip frequency will occur at a frequency with a wave-
length of 4 meters.
l = c / f
where
►
l = wavelength [meters or feet)
►
c = speed of sound (meters/second or feet/second)
►
f = frequency [Hz]
Hence
►
4 = 344 / f
►
f = 86 Hz
A closer position will result in a cancellation at a higher
frequency. This is then limited by the frequency where
the monitor becomes directional and does rot radiate
sound to the rear.
A farther position will result in cancellation at a lower
frequency. This is limited by the distance being so long,
that the reected sound is attenuated due to the long
extra path travel.