L-Acoustics A15 Focus — SPL & coverage in a 30 × 18 m hall

The A15 Focus is rated 140 dB @ 1 m, but that figure only means something once distance is applied. SPL falls with the inverse square of distance: at 15 m and full output the same cabinet delivers around 116 dB, and at the planner's 60 % drive setting — the realistic operating point that leaves headroom for programme peaks rather than running a cabinet at its ceiling — the figure at the listener comes down to roughly 114 dB. Reading the 140 dB spec sheet number as the number a listener will hear is the most common sizing mistake with this class of cabinet.

The cabinet's 100° × 10° (H × V) dispersion is what sets the planner's coverage-radius answer of approximately 17.9 m on the horizontal axis. The wide horizontal pattern is built for spreading across a seating plan from a single hang point; the narrow 10° vertical pattern is what keeps the wavefront off the ceiling and off the side walls, controlling throw and cutting the reflection energy that would otherwise blur speech intelligibility at the rear rows. Being passive, the A15 Focus has no onboard amplification — it needs a matched external amplifier channel sized to its stated power handling before any of these figures apply in the field.

Inside the planner, drag the listener-distance slider outward and the drive-level slider up or down to watch SPL move against the 140 dB @ 1 m rating in real time. The box-count figure the tool reports is a front-coverage estimate only — it divides the room footprint by the cabinet's usable coverage area to suggest a starting element count. SPL adequacy at the listener is checked separately from that count, because a room can pass on coverage area and still fail on SPL headroom, or the reverse.

The planner does not model room reverberation or RT60, so a hard-surfaced hall will show higher effective SPL at the listener than a treated one for the same input. It does not zone coverage across different seating areas, size a subwoofer pairing for programme material below the cabinet's stated range, assess the mechanical rigging a line-array hang requires, or configure the DSP delay and EQ settings that a real install tunes after the cabinets are hung.