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Designer Notebook: MLA Compact, A Lower Profile Approach From Martin Audio

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By Jason Baird May 10, 2012

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In 2010, Martin Audio brought a radical new approach to touring sound with the Multi-cellular Loudspeaker Array (MLA), an integrated system that is self-powered with six channels of amplification and DSP, networked with both audio and control on the same cable.

Furthering the package is a combination of cellular drive and fast, automated optimization software. Cellular technology helps achieve phase-coherent summation across the respective coverage area, holding both frequency response and SPL within a very tight, user-specified window.

The new MLA Compact widens the scope of applications, designed for situations not requiring the full power and throw of the full-size MLA, or where a smaller, lighter system is called for. It is scalable, and can meet the needs medium-scale touring and fixed installations such as concert halls, theatres and churches.

The footprint of an individual cabinet is 31 (w) x 11 (h) x 19.7 (d) inches, and weight is 109 pounds. As a point of comparison, a full-size MLA box measures 44.7 (w) x 14.6 (h) x 26.5 (d) inches and weighs 193 pounds.

In The Box
Compact loudspeakers often use direct radiators for the lows and mids because more efficient acoustic technologies are hard to adapt to small cabinet volumes. The 3-way MLA Compact, however, applies new slot and horn-loading techniques to the low and mid sections.

Like it’s bigger brother, MLA Compact presents an integrated approach. (click to enlarge)

Further, it deliberately avoids the use of coaxial, co-entrant or cross-firing midrange/HF driver arrangements. which introduce acoustic discontinuities that can affect the on- and off-axis frequency response of both MF and HF sections. In MLA Compact, the MF and HF horns are completely separate in order to produce consistent, true 100-degree horizontal constant directivity coverage.

The LF section utilizes 2 x 10-inch (2.5-inch voice coil) neodymium drive units in a unique Hybrid configuration that fosters acoustic efficiency and enhances “punch.” Each driver is slot-loaded into a truncated horn with a low flare rate, to give a high sensitivity of 103 dB @ 1m/2.83V. The slot-loading allows the twin LF drivers to be optimally spaced within the enclosure.

A look at the slot- and horn-loading approaches inside MLA Compact. (click to enlarge)

This double-source arrangement significantly improves the directivity control of the LF section maintaining the 100-degree beamwidth down to 250 Hz and reducing mid-bass output at the sides and rear of the array. The LF drivers are very high excursion with vented poles to reduce power compression and eliminate turbulent air noise.

MLA Compact has separate MF and HF horns with horizontal constant directivity characteristics, so the horizontal off-axis response tracks the on-axis response exactly.

The MF horn utilizes 2 x 5-inch (1.5-inch voice coil) neodymium drivers to produce 109 dB @ 1m/2.83V, which represents a significant gain on the typical efficiency of 102 dB found in cross-firing direct radiator designs in comparably sized systems. It’s possible due to acoustic and thermal designs that utilize forced-air cooling and a thermally conductive aluminum housing.

The I/O capability on the back of each cabinet. (click to enlarge)

The HF section includes 4 x 0.7-inch-exit neodymium compression drivers that feed separate horns providing 100-degree horizontal constant directivity. The driver combination replaces the more traditionally used large-format compression driver and has less distortion, as well as having a more extended HF response.

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