Key Takeaways
- Line arrays are correct for rooms deeper than 15 metres and audiences above 300 pax — the SPL consistency across the room depth justifies the cost premium
- Point-source systems are correct for rooms shallower than 12 metres, audiences below 200 pax, and budget-sensitive events where the SPL consistency advantage of line arrays is not relevant
- The 6 dB per doubling of distance rule (point-source) versus 3 dB (line array) means that at 30 metres, a point-source system produces 6 dB less SPL than at 15 metres; a line array produces only 3 dB less
- Rental cost difference: a line array system for 500 pax costs approximately 2–2.5× the rental cost of an equivalent point-source system
- Hybrid systems (line arrays for main coverage, point-source for fill positions) are the most common professional production choice
How line arrays work
A line array is a speaker system consisting of multiple small speaker elements stacked vertically and driven together as a coherent source. The vertical arrangement creates a narrow vertical dispersion pattern (which reduces reflections from the floor and ceiling) and a wide horizontal pattern (which covers the full audience width). The coherent addition of all elements produces an SPL roll-off of approximately 3 dB per doubling of distance — half the 6 dB roll-off of a conventional point-source speaker. In a 30-metre-deep room, the back row of a line array-served audience receives approximately 6 dB less SPL than the front row; a point-source-served audience receives 12 dB less. In terms of perceived loudness, this is the difference between a consistent and an inconsistent listening experience.
When point-source is correct
A point-source speaker (a single enclosure with a high-frequency horn and low-frequency cone, producing a conventional dispersed pattern) is correct for: rooms shallower than 12 metres (the SPL consistency advantage of line arrays is not relevant at this depth); audiences of fewer than 200 (the budget premium for line arrays is not recovered in perceptible quality improvement); and some rooms where the ceiling height limits the line array's ability to be properly angled (a 4-metre ceiling provides insufficient distance for a line array to develop its controlled directional pattern). A well-chosen point-source system in the correct room produces excellent results. A line array in a room it was not designed for produces the same mediocre results as a poorly-chosen point-source.