Display V2.1; Introduction; Numerical Optimisation - Martin Audio MLA User Manual

MLA System
USER GUIDE

Display v2.1

Introduction

Display 2.1 is the application that is used in conjunction with Vu-Net and a Martin Audio Multicellular System, either MLA, MLA
Compact, MLA Mini or a combination of any of these systems to generate the inter-cabinet angles and the DSP optimisation
parameters which can then be quickly and easily uploaded to the hardware over the U-Net system network or in the case of MLA
Mini directly using a USB connection. It also shows accurate analysis of the system response in the venue.
The application has an entirely straightforward, logical workflow; in fact it does not allow jumping to advance stages of the
design, it is necessary to complete each stage in a logical order.
Display 2.1 uses numerical optimisation to arrive at the resulting cabinet angles and DSP coefficients. Taking the cabinet angles
as an example, to explain the process in slightly crude manner this means that it tries a great many combinations of possible
angles, checks the result using the computer model of the array response and compares it to the desired response. It continues
to check through a huge number of possible combinations until it arrives at the closest match to what has been asked of it. In
the case of the cabinet angles, it has the facility to "polish" the array which means it does a second pass having arrived at a set
of angles to fine tune the array angles. This process although highly complex, actually only takes a few minutes, certainly no
longer than a conventional line-array prediction application. Having specified the cabinet angles the array can be rigged and
whilst that is being done the second stage of the optimisation process is done. This also uses numerical optimisation but this
time addresses the EQ, FIR, gain and phase parameters available in the DSP, going through the hundreds of thousands of possible
combinations possible until the output is as close as possible to the desired response. With a large array and complex venue this
could take up to ten minutes to complete however this will be far quicker than the time it takes to rig all arrays so in no way
slows down the show build-up. To actually try every possible combination of DSP would take months even on the most powerful
computer- there are millions of possible combinations and that is where the unique digital algorithm comes into play, examining
batches of results to see if certain parameter changes are taking you closer or further from your desired performance
characteristics. It will reject a series of parameter changes that are heading towards a "dead end" and instead will focus on those
which get you closer to the desired result, gradually honing all parameters until it reaches a result which is a close as possible to
the specifications that the technician has requested. This method allows phenomenal accuracy in a highly realistic and practical
length of time. The accuracy of the resulting design hinges on the computer model which predicts how the array will perform for
a given set of cabinet angles and DSP coefficients. The computer model devised for Display 2.1 is one of the most sophisticated
and accurate ever devised for an audio system and is capable of achieving results to closer than 1dB of actual measured
parameters.
A Display design can easily be done prior to arriving at the venue in the comfort of your office. If you have drawings of the space
and details of the flying position and the trim height of the arrays you can complete the rigging and DSP design which makes set-
up on site extremely quick and efficient. It is possible to try several different DSP optimisations with priority given to a variety of
performance characteristics. These can be uploaded to the array and stored in snapshots to be recalled in a few seconds.

Numerical Optimisation

At this point it is worth taking a moment to explain in detail one of the concepts behind how Display operates; Numerical
Optimisation is an easily misunderstood concept, a few people make the incorrect assumption that it is some sort of "averaging"
system meaning that the result is a compromise which couldn't be further from the truth.
What made multicellular systems possible was the development of a phenomenally accurate computer model of the system
which works hand in hand with the precision acoustic design of the cabinets. There are a colossal number of factors that affect
an array performance; the performance of individual drivers, the horn design, the angle between enclosures, the number of
enclosures et cetera. Martin Audio have taken the analysis of array performance to the most advanced level ever attempted,
including boundary effect modelling which includes the effect that all other cabinets in an array have on a single driver; essentially
each individual cabinet has a baffle extending above and below it formed by the other enclosures in the array. For cabinets in
the middle of the array this is fairly symmetrical but for cabinets towards the top and bottom it becomes more and more
asymmetrical which has a highly significant effect on the individual module performance and therefore the overall array
performance.
The diagrams below show the response of a single array element which is the second box down in a six boy array. The first picture
ignores the effect of its neighbouring enclosures. The second picture shows the dramatic effect that the enclosure above and
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