Line ‘Em Up: The Expanding World Of Column Loudspeakers

Mention column loudspeakers to grumpy old sound guys and the Shure Vocal Master immediately springs to mind, as it seemed that every ’70s band used it.

Actually, line sources have been around for well over a half-century, but they’ve gained in popularity of late because they offer a solution for those who need efficiency in the vocal range combined with even coverage and a very slim, unobtrusive profile.

The characteristics of line source columns – wide horizontal coverage, minimal vertical coverage above and below the enclosure and coherent sound in the vocal range – are all attractive features, particularly in highly reverberant environments.

Driver spacing determines the highest frequency at which a column of identical drivers acts as a line source, while the height of the column determines the lowest frequency with directivity. As with modular line arrays, a short system might efficiently throw the midrange but leave a puddle of low-frequency mud behind the enclosure. Line source coupling behavior and pattern control tell us that loudspeaker cones exhibit coupling behavior up to a frequency whose wavelength is half the distance between adjacent acoustic centers.

Column loudspeakers with 6.5-inch diameter cones, when tightly-spaced, will couple up to about 1,000 Hz. Four-inch cones couple to about 1,600 Hz, and 2-inch cones to 3,300 Hz. Above these frequencies, top and bottom lobes appear in the polar response; however, restricting the high-frequency response of some of the cones can reduce lobing. This can be achieved with passive filters in the cabinet or with active filters.

It’s common for columns to be combined as multiple cabinets to achieve better performance as taller systems for bigger rooms. Longer columns provide pattern control reaching to lower frequencies. A 9-foot column can provide control to 125 Hz, so combining three 3-foot columns can increase low-frequency performance.

A specialized version of the line source column is called “digitally steerable,” with individual amplification, delay and equalization for each driver, allowing the column’s vertical coverage to be tilted down (or up) and focused for short or long throws, though its horizontal coverage remains fixed.

The advantage is that the loudspeaker can be placed flat on a wall while its coverage can be tailored to a specific listening area. One advantage to digital steering is that the entire coverage pattern can be oriented downwards. Mechanically tilting a passive array adjusts the farthest coverage while leaving the coverage towards its sides near the original height.

Applications requiring additional bandwidth and dynamic range have lead to 2-way designs that incorporate separate high-frequency transducers in addition to the column of tightly spaced loudspeaker cones.

As with miniature line arrays, some systems have companion LF columns that employ long-excursion small-format woofers to extend pattern control to lower frequencies. Alternately, traditional subwoofers can supplement a column’s LF response.

Enjoy our Real World Gear Photo Gallery Tour at the latest available column loudspeaker models.

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