‘Very impressed’: Event Acoustics on the new Martin Audio MLA loudspeaker system

03 march 2011

Being focussed on tackling noise spill at live events and sound quality issues in highly reverberant spaces, we were delighted to receive an invitation from Martin Audio's Belgium distributor, Face, to do measurements at an open air MLA demo. The things we had read in advance about the system were hard to believe, and if true would make it the sound system we all dream of.

To put it simply, according to the specs the system could deliver sound where you want it and no sound where you don’t want it – and can accurately predict this. The MLA system was set up at a festival field close to the Face headquarters. The site measures 80 meters wide by 160 meters deep.

Two PA wings were set up 24 meters apart (with 12-box hangs per side trimmed at a 10 meter height). A further 12 MLX subs were stacked adjacent to each other—forming a single broadside array—along the front. To measure it we set up our class 1 EA event monitoring system with measuring points at 20, 60, 95 and 130 meters. Additional measurements where done with class 1 Svantek handheld meters.

The system setup

For the audience we set up two big display screens in the best FOH tent we’ve ever seen – the dream of every engineer: a bar with service at FOH. As the EA event monitoring system is internet-based, even read-out facilities for smartphones and tablets were provided for the audience.

The Event Acoustics event measurement system has the following components:

Measurement stations

Fully weatherproof class 1 measurements stations with integrated Svantek 957/959 sound level meters for local data storage, and an industrial PC and modem for data handling and transport. Rugged screen for the sound engineer with all the required readings.

Internet based monitoring software

Per web page the status of 15 field stations can be seen in real time and with history. Parameters like dB(A), LAeq, dB(C), LCeq or one third of octaves can be graphical presented.

EA correlation module

Unmanned sound monitoring is a very challenging job. Are you measuring passing cars or the event? Which stage is causing the sound levels at the monitoring point and is spectral information available? To answer those questions we developed our EA correlation module and the ability to listen in real time at a monitoring point. Within minutes the EA correlation module can answer all those questions.

The Results

The results were impressive: behind the arrays we measured an unbelievable drop of more than 27 dB(A). I had a nice chat with Jason Baird, the leading designer of the system. Were talking just two meters from the back of an MLA array, without needing to raise our voices. According to the predictions of Martyn ‘Ferrit’ Rowe the system should have a flat sound level to 80 meters then drop by 5 dB(A) at 95 meters and more than 10 dB(A) at 130 meters. To our surprise, this happened when we were allowed, for a couple of minutes, to put on our favourite track “Pink Noise” from various artists, as the following graph shows.
Apart of the controlled sound coverage, the system has a very equal frequency response at every listening position. A second thing we were surprised by is the spatial coverage of each array – it seems like the horizontal opening angle is even at each frequency, something I’ve never experienced, creating a great stereo sound. This is really the tool we are looking for and hope to use soon, to tackle event noise spill and other acoustical problems with events in the highly reverberant spaces of our clients.

Peter van der Geer,

Senior consultant Event Acoustics