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The two-minute guide to digital line array loudspeaker columns

Andrew Brister 24 May 2010
The two-minute guide to digital line array loudspeaker columns

Line array columns have been developed as an alternative to using many more speakers in a ceiling grid or projecting from a wall. Neil Voce of Ateis looks at the design options

What is a digital line array column?
It is a column loudspeaker, ie tall and thin, that has been developed to deal with intelligibility issues in areas with higher reverberation times, or to cover larger areas where ceiling speakers would be impractical. It uses digital signal processing (DSP) to shape the output coverage of the loudspeaker to fill the required area with an even and intelligible sound field. It is mounted vertically and is therefore easy to disguise on existing building surfaces.
Line array columns can be used for both vocal sound reinforcement eg in a lecture theatre or church and for voice alarm applications such as stations, atria and shopping malls.

How visually obtrusive are they?
The key advantage of digital line arrays is that they are vertically mounted and steer their sound down. Therefore they can be readily integrated into the lines of the building design. The units themselves are only 150mm wide and 150mm deep so, although they are quite long, they really aren’t obtrusive.

How crucial is the positioning?
The height is not that crucial since the amount of angle can be varied. Typically, the base of the unit would be between 2.8m and 4m above finished floor level, but they can be 10m above if that’s what’s needed. They can steer their field of coverage down up to 45 degrees. Obviously, there shouldn’t be obstructions between the speaker and the area you wish to cover.

How easy are they to hide away?
Although they are white as standard, they can be finished in any RAL colour or otherwise decorated as required. As they are quite long (2m up to 5m), that has to be considered, but they can also be flushed in the right surface or placed behind acoustically transparent grilles.

What, if any, alternatives are available ? Relative pros and cons? 
Line array columns have been developed as an alternative to using many more speakers in a ceiling grid or projecting from a wall. They are individually quite expensive but cheaper to install and wire than a solution using many speakers. This can make the overall solution cost effective.
In a ‘live’ space such as a church they give a very natural sound with a focus that is hard to achieve with multiple smaller speakers – they are also ideal for listed interiors where the minimum of additional equipment is wanted.
In the end, particularly if you are doing a voice alarm system, there are spaces in which achieving the intelligibility you require for the system to be signed off is only really achievable using this type of solution.

How can you avoid a poor installation?
Planning! Get the manufacturer to run you up a predictive model that will show the quality of coverage. There are acoustic modelling programmes such as EASE and CATT. In these, you can input a model of the space you need to cover and then ‘install’ the loudspeaker in that model. This will allow you to experiment with placing and model types before you begin. If, for example, visually the speaker would be better in position ‘A’ but the installer says it will sound better in position ‘B’ you can model the performance in those two positions and then see how each position will perform and then make your decision on placement.

Neil Voce is director at Ateis

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