UPTURNED T
series
SOUND REINFORCEMENT
ACOUSTIC RESEARCH
CONTROLLED RADIATION
User’s Manual
UPTURNED T
series
SOUND REINFORCEMENT
ACOUSTIC RESEARCH
CONTROLLED RADIATION
4
3.2
Loudspeakers mixed orientation: a careful study
The 8 loudspeakers in
PSUT8xx
sound column can be arranged - two by two
- at
four
different angles (from the bottom: 30°, 20°, 10° and 0° as compared
to the front axle) in the PSUT8TE version and at
two
different angles (from the
bottom: 30°, 20°, 30°, 20°) in the PSUT8AE version.
The orientation of the transducers was tested by means of detailed simulations
starting from the measurements of the individual speaker polarity. These tests
were carried out in the R&D lab of Sound Corporation. The purpose of the
mixed loudspeakers orientation was to obtain the widest possible horizontal
dispersion angle whilst maintaining maximum timbre homogeneity within
this angle. This requires, for instance, that individual loudspeakers’ emission
beams should become as complementary as possible at high frequencies
in order to limit the spatial aliasing problem due to the interaction between
adjacent loudspeakers (see “
High frequencies and spatial aliasing
” – Section 4.4).
As the centre of rotation of each individual loudspeaker, the Sound Corporation
engineers selected the centre of the polar response measurement for which
the smallest phase variations occurred when changing the angle at medium-
high frequencies.
Due to the different orientation of the two versions (PSUT8AE and PSUT8TE),
most of the loudspeakers in a stack configuration will be directed in pairs at
alternating angles of 20° and 30° up to the last two sets whose angles are 10°
and 0° (figure 2). So, a more acute angle is formed for the loudspeakers at the
top only, as they are to generate the strongest pressure component (at high
frequencies > 5 kHz) on listeners standing at a distance, whose viewing angle
“on the source” is narrow.
Conversely, listeners standing close-by will have wider average “viewing angles”
and prevalently perceive the sound from the intermediate loudspeakers,
for which reason they are also set to a wider angle (figure 2). Focusing high
frequencies to reach audience at distance through a smaller angle will lessen
sound absorption and dissipation occurring over long distances.
The following pictures (figure 3 and 4) show a simulation of a PSUT8AE
model obtained from the directivity measurements of the individual
loudspeakers in the octave of the 6 kHz: the first curve represents a
hypothetical column with all the loudspeakers facing the front (in-line
arrangement), the second curve represents the PSUT8AE model with its
typical sound beam distribution. The latter also shows how the lobes of
the vertical polar pattern (blue line) are rounded and less intense while
the horizontal polar pattern (red line) is significantly wider and more
homogeneous.
Figure 2. The loudspeakers at the bottom have a wider horizontal sound beam (blue in the
figure) and thus ensure adequate coverage for both musicians and the first rows of the
audience. The loudspeakers at the top - more aligned - will cover listeners at the far end,
thanks to a narrower horizontal angle.
Figure 3. Horizontal (red line) and vertical (blue line) polar patterns of
a hypothetical PSUT8xx model with all the loudspeakers
directed towards the front (in-line arrangement, 0°)
Figure 4. Horizontal (red line) and vertical (blue line) polar pattern of
a PSUT8AE model with the real arrangement of the loudspeakers’ angles
as designed and set up by Peecker Sound engineers
