What a speaker’s coverage angle means in a real room

A datasheet says “90° × 50°”. Here is what that covers in metres, and what it does not tell you.

Included angle

A coverage angle is the total angle between the two edges of the speaker’s beam, measured from the front of the speaker. A speaker listed as 90° horizontal covers 45° to each side of its axis. The vertical angle works the same way up and down.

Width covered = 2 × distance × tan(angle ÷ 2). For horizontal coverage:

A 90° speaker covers a strip as wide as twice your distance from it. At 10 m that is 20 m, wider than most function rooms. The same speaker with 50° vertical coverage covers 9.3 m of height at 10 m, which is why aiming (tilt) matters more than it looks: aim too high and the back of the audience falls outside the beam.

Where the edge is

The edge of the beam is the point where the level has dropped by a stated amount, usually 6 dB, sometimes 3 dB, and sometimes the page gives no definition at all. The planner treats the stated angle as the point 6 dB below the on-axis level and lowers the level smoothly towards the edge. A speaker whose angle was measured at 3 dB will cover somewhat more than the planner shows, and the planner’s figures for such a model will be on the cautious side. Each speaker page records the definition when the source gives one.

What the angle does not tell you

• Real speakers narrow at high frequencies and widen at low ones. A single angle is an average over a band.
• Some horns can be rotated, so “horizontal” and “vertical” can swap. Check how the speaker is standing.
• Beyond the edge the level keeps falling, and it does not drop to zero.

Measured data (polar files published by manufacturers) is more accurate than a nominal angle. The planner uses the datasheet angle today.

Next: placing speakers on stands.