Martin Audio MLA User Manual page 147

MLA System
USER GUIDE
achieving this, 3D graphs for example but they don't really meet the brief of being quick and easy to interpret. The Index plot
solves this problem.
As we will see when we look at the application in more detail, we draw a two dimensional slice of the venue in which we are
deploying our array. It then gets presented in Display like so;-
The colours represent the three types of plane; the audience area are green, non-audience, areas around the venue which we
are not concerned about are red, and finally areas where we would like the system to actively steer sound away from known as
hard avoid are blue. By default the hard avoid is the stage but this could also be reflective back walls or balcony fronts, or noise
sensitive areas beyond an arena at an outdoor event. The planes are represented by a series of dots. These are spaced closer
together in the audience region where we need the most detail. Ideally we would like to be able to view the frequency response
at each of these dots so each becomes a sort of virtual measurement mic.
The normal way to present a graph of frequency response is of course for the horizontal 'x' axis to be frequency, usually from
20Hz to 20KHz, and for the vertical 'y' axis to display magnitude, usually in dB. If however we display magnitude with colours we
can easily show many response plots simultaneously. If we make red the highest magnitude- the loudest- and blue the quietest,
by running through the colours in the spectrum we can very easily identify the peaks and troughs in a response. This frees up the
vertical axis which we can use for all of our "virtual mics";-
This is the Index plot of a completely un-optimised system. The horizontal axis as mentioned is frequency. As we cannot optimise
very low frequencies the graph starts at 50Hz going all the way up to 20KHz. The vertical axis is now the 2D slice of the venue
MLA System User Guide V2.1
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