11
Array Design
Background
Creating an effective array with the MTS-4 requires a
precise understanding of how to combine the coverage
area and SPL of the individual speaker with those of
adjacent speakers. Array design is a trade-off between
increasing on-axis power and creating smooth transitions
between the coverage areas of adjacent speakers.
As the splay angle (the angle between adjacent cabinet
faces) decreases below the coverage angle of the individual
speaker, the on-axis power increases, but the coverage
overlap between adjacent speakers causes comb filtering
and other frequency response variations.
As the splay angle increases toward the coverage angle,
the on-axis power decreases, but the variations in fre-
quency response diminish. As the splay angle increases
beyond the coverage angle, noticeable gaps begin to
form in the array’s coverage area.
NOTE: The trapezoidal shape of the MTS-4 does not
represent the horizontal coverage area of the speaker.
Tight-packing MTS-4s results in the
minimum
recom-
mended splay angle (15
°
) for horizontal arrays.
Array Design for Low Frequencies
Since the MTS-4 contains sub and low frequency drivers,
in addition to mid and high drivers, array design for the
MTS-4 must incorporate the different array response of
high and low frequencies. The beam width for a single
speaker widens as the frequency decreases. Frequencies
below 125 Hz are mostly omnidirectional while higher
frequencies are more directional.
NOTE:
H
and
V
are abbreviations for
horizontal
and
vertical
.
The low frequencies of adjacent arrayed speakers exhibit
on-axis addition and off-axis cancellation, resulting in a
narrowing of coverage in the dimension in which they
are arrayed. A H array of two MTS-4s narrows the H
coverage without affecting the V coverage. A V array
of two MTS-4s narrows the V, without affecting the H
coverage. In both cases, there is 3 to 6 dB SPL of on-axis
low frequency (LF) addition compared to a single
MTS-4. Due to the larger distance between LF drivers in
V, compared to H arrays, the V coverage narrows at a
faster rate than does the H coverage for H arrays, given
the same array size and adjacent speaker placement.
Increasing the number of MTS-4s in the array increases
the LF directional control. A properly designed V array
steers low frequencies to include balconies and upper
tiers, while a H array focuses low frequencies for longer
throw distances without interacting with the walls.
Loading
One of the most important factors governing LF response
is speaker placement with respect to adjacent surfaces.
The MTS-4 gains significant LF power by coupling with
nearby floors and walls. Half-space loading describes a
speaker coupling with one surface. Speakers placed on
the floor benefit from half-space loading, while flown
speakers in free-space (without a nearby wall or ceiling)
do not. In general, subwoofers in half-space generate
twice the SPL (+6 dB) compared to the same number in
free-space.
NOTE: SPL values refer to an on-axis measurement
position. The actual SPL addition and narrowing of coverage
varies with frequency and depends on the physical
displacement between cabinets, loading conditions, and
room acoustics.
MTS-4 Coverage and Maximum SPL
A series of outdoor tests was conducted at Meyer Sound
to determine the coverage angle and on-axis SPL for
arrays with one and two horizontal rows of up to five
speakers each, at numerous splay angles. The measure-
ments were conducted at a distance of 8 m with half-space
loading; on-axis SPL values were interpolated from 8 to
1 m. The coverage angle for the array is the result of
averaging the –6 dB points from 125 Hz to 8 kHz.
The horizontal angles in the tables below represent the
optimal narrow (15
°
), middle (30
°
), and wide (45
°
) orienta-
tions for the MTS-4. The vertical splay angles represent
the optimal narrow and wide configurations. 2@0
°
LT
denotes long throw: the two horns are coupled directly
together (top speaker upside down/bottom speaker up-
right) to form a single narrow horn.
The table on the following page shows the SPL and
coverage angles that result from grouping the MTS-4 in
arrays of up to five units horizontally and two rows
vertically. All splay angles refer to the angle between
cabinet centers.
If this information does not address your application
requirements, contact Meyer Sound to obtain additional
information on array design.
