Line Source
A
R
2R
2A
34
This 100° coverage angle also defines the recommended limit for the relative angle between TTL33-A/ TTL31-A arrays,
for example, when main L/R FOH TTL33-A/ TTL31-A arrays are oriented at zero degrees, offstage LL/RR arrays can be
oriented at up to 100° relative to the main L/R arrays while maintaining a 6-7 metre separation between arrays in order
to maximize overall system coverage while reducing the audible effects of interference.
For the mid to low frequencies, line arrays must be coupled together to narrow their vertical coverage and project mid
and low energy to the far field. The directional control of the array is achieved when the length of the array is similar or
larger than the wavelength of the frequencies being reproduced by the array. As frequencies get lower and wavelengths
get longer, the number of cabinets has a critical effect but the splay angle between cabinets has little effect since the to-
tal length is not modified substantially. The number of array elements, however, is important: the more TTL33-A/ TTL31-A
loudspeakers used, the more directional the vertical beamwidth becomes at the lower frequencies.
Apart from coverage precision and predictability, another sig-
nificant benefit of TTL33-A/ TTL31-A is the fact that the system
effectively extends the near field region at higher frequencies. For
flat TTL33-A/ TTL31-A arrays, this results in a 3 dB reduction in
SPL with doubling of distance as opposed to the 6 dB reduction
that is typical of conventional systems. This property arises due to
the physics of cylindrical waves versus spherical waves. Due to its
ability to perform planar wave front, TTL33-A/ TTL31-A has differ-
ent attenuation properties than conventional systems. Comparing
SPL predictions according to standard calculations is not meaning-
ful since TTL33-A/ TTL31-A produces a combination of cylindrical
and spherical wave front propagation that must be evaluated using
specific calculations. When curved TTL33-A/ TTL31-A arrays are
employed, there is a combination of cylindrical and spherical propa-
gation. Although pure cylindrical wave propagation is not always in
effect, 3 dB reduction with distance can still be obtained along with
extension of the near field by correctly focusing the system on the
audience. Psycho acoustically, near field extension allows one to
walk a considerable distance from a TTL33-A/ TTL31-A system with
only a small difference in SPL due to the system’s unconventional
attenuation rate
0° between adjacent enclosures 15° between adjacent enclosures
Cylindrical wave expands in horizontal dimension
only at 2R surface area increase 2 times -> 3 dB
attenuation
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