Index Plots - Martin Audio MLA User Manual

MLA System
USER GUIDE
the four below have on the response. Ignoring this effect will clearly compromise the ability to accurately predict how the array
will perform, in fact measurements show that ignoring the boundary effect can result in inaccuracies of up to 8dB which fairly
obviously would make the system unusable.
Martin Audio have perfected the computer model for our Multicellular systems to such a degree that the predicted performance
can reach accuracy of as close as 1dB of measured results which has made the whole system not only possible but extremely
accurate.
Numerical optimisation uses the computer model to check the performance for a given mechanical orientation or DSP
configuration, and compares the result on the venue slice to what you have asked the system to achieve. It will then try an
alternative option to see if it is getting closer or further from the desired result. If it is further from what you want it to achieve
it will ignore that configuration and pursue the more successful angles or EQ curves, trying configuration after configuration
before it has attempted close to every possible combination and has got as close as possible to the desired result.
If you consider the first optimisation which calculates the splay angles, for an MLA system there are eight possible angles available
between each cabinet; 0.5, 1, 2, 3, 4, 5, 6 and 7.5⁰ If you have a reasonable size array of say 16 enclosures that means a total of
8 x 8 x 8 x....8, (fifteen 8's!) or 35,184,372,088,832 possible combinations of angles between all cabinets. Clearly analysing each
of these combinations involves a substantial amount of processing but pales into insignificance compared to the hundreds of
thousands of calculations required when running numerical optimisation for the DSP; every band of EQ frequency, bandwidth
and gain, phase and FIR filters for every one of the cells of every cabinet. This is why a powerful PC is required and the EQ
optimisation can take up to fifteen minutes or so for a large array in a complex arena. Even the most powerful PC available today
couldn't try every possible combination in a reasonable time scale so complex algorithms are used so that when a certain
sequence of filter parameters are consistently demonstrating results further from the goals that have been set, the system will
abandon those avenues and try others. With this system highly accurate parameters can be produced that are as close as possible
to the desired goals in a reasonable time frame. This is a very basic explanation, in fact it is Martin Audio's development of the
revolutionary but phenomenally complex digital algorithm that the application uses to refine the optimisation which give the
best possible results in a reasonable time frame. Not only that but key parts of the optimisation process are multithreaded which
means that the system is able to exploit the latest 64-bit, quad core processors to speed up the entire process.
Whilst this system is processor hungry clearly it is a very realistic and practical method to obtain the best possible results from
an array where so many variables are at your disposal. Trying to manually adjust several thousand DSP parameters is obviously
not going to be realistic however good a system technician believes his ears might be.

Index Plots

The other concept which Martin Audio developed as part of the MLA system is the index plot. We needed a method to display
the results of the system optimisation that was clear and easy to interpret. Because the whole basis of the system is that the
radiated signal is coherent where it arrives at all parts of the audience as opposed to when it leaves the array we needed a
method of displaying the frequency response at dozens of positions simultaneously. There are a few methods in existence for
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