Specifications

22
(3) Configurations of Multiple Units
When the APL-10/12 is used in multiples, certain techniques can be applied
to help achieve the desired results. To start with, the enclosures should be
placed touching one another. Separating them, even a little, limits their power
summation and can generate lobes and unwanted response anomalies.
Multiple units configured in a line will exhibit increased directionality in the
axis of the line. For example, placing four or more APL-10/12 speakers hor-
izontally end-to-end narrows their horizontal coverage pattern without
changing the vertical pattern (NOTE: dispersion is essentially omni-direc-
tional for a single unit). Such a configuration can be used to increase the cov-
erage distance in a large venue, such as a deep shed. Conversely, stacking four
APL-10/12 speakers in a vertical line will narrow their vertical coverage angle
without changing their horizontal dispersion. This configuration could be use-
ful to penetrate long distances in a flat outdoor space, such as a soccer field.
RULE OF THUMB: Whenever the coverage angle is narrowed, on-axis power
is also increased. The greater the number of enclosures placed in a line, the
narrower the dispersion angle will be, with a corresponding increase in sum-
mation and forward-radiated power. The lowest frequency that will exhibit
such behavior is directly a function of the array size.
The length of the array must be at least a 1/4 wavelength of the frequency of
interest for any semblance of directional control to occur. At 1/2 wavelength,
directional control starts to become effective. As the length of the line grows,
directional control (i.e., narrowing of the dispersion pattern) increases con-
tinually, becoming more and more effective.
Chart 4 depicts wavelength vs. frequency (at ISO preferred frequencies)
throughout the operating range of the APL-10/12, in relation to the number
of APL-10/12 speakers that would approximate a 1/2 wavelength of the fre-
quency of interest when arrayed end-to-end and top-to-bottom.
No. end-to-end/
No. top to bottom
No. end-to-end/
No. top to bottom
Wavelength
feet / meters
25
44.8 / 13.7
9 / 12
7 / 9.5
5 / 7.5
4 / 6
3.5 / 5
3 / 4
2 / 3
6 / 9
5 / 7
4 / 6
3 / 4.5
2 / 3.5
2 / 3
2 / 2
31.6 35.6 / 10.9
40 28.3 / 8.6
50 22.5 / 6.9
63
17.9 / 5.4
80
14.2 / 4.3
100 11.3 / 3.4
Chart 4
Frequency
in Hz
APL-10 APL-12