Fir Crossovers - Martin Audio MLA User Manual

MLA System
USER GUIDE
Instead of adopting flat wavefronts as advocated by early proponents of touring line arrays, our sophisticated in-house BEM
(Boundary Element Method) modelling techniques have shown that slightly curved wavefronts deliver much more consistent
SPL's to the audience where the array is curved — as in most practical, real-world applications.
Placing a kite shaped "wedge"part-way down the horn* enables a specific, desired curvature to be achieved — depending on
the shape of this wedge. In the case of MLA Compact, the HF wavefront is curved to provide a balance between optimal
summation over distance and summation at the maximum inter-cabinet splay angle of 10°;-
Conventional horn, curved wavefront With wedge: curvature is ideally optimised

FIR Crossovers

Like all three-way systems, MLA Compact's low, mid and high frequency sections are combined by a crossover. Up to now,
Linkwitz-Riley, 4th order filters have been the industry standard. With traditional filters like these, overlap at crossover can result
in a non-symmetrical horizontal polar pattern if the devices being crossed-over are side by side.
In the theoretical opposite extreme, a brick-wall filter would completely eliminate overlap, and the polar pattern would be
unaffected and symmetrical.
MLA's practical implementation uses very steep, VanishingPointTM, FIR filters. They are not actually brick-wall, because of the
effects of brick-wall filters on transient response. Listening tests confirm that the two devices are impossible to locate separately,
but sound like a single acoustic source, located at the point in space at which we have optimised the FIR filter.
MLA System User Guide V2.1
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