Understanding speaker dispersion
Every loudspeaker has a coverage pattern: the horizontal and vertical angles within which it delivers even sound, typically defined by the points where the level falls 6 dB below the on-axis level. A 90° × 50° speaker spreads sound across a wide horizontal arc but a narrower vertical one. Outside that pattern, listeners hear lower level and dull treble.
Coverage width = 2 × distance × tan(horizontal angle ÷ 2)
A 90° speaker covers a width of about twice the distance: 4 m wide at 2 m, 20 m wide at 10 m. That's why front rows often fall into gaps when speakers are mounted at the sides of a stage.
Choosing the dispersion
| Pattern | Typical use |
|---|
| 40° – 60° horizontal | Long, narrow rooms; long throws; outdoor events |
| 75° – 90° | General-purpose PA, bars, halls |
| 100° – 120° | Wide, shallow rooms; front fills; under-balcony |
| Column / line arrays | Very narrow vertical coverage, even level front to back |
Aiming the speakers
- Mount speakers above the audience's heads so the front rows don't block the back.
- Aim the on-axis point at about two-thirds of the audience depth to balance near and far levels.
- Avoid aiming at hard back walls and ceilings, which cause echoes and feedback.
- Splay left and right speakers slightly outward in wide rooms so their patterns don't overlap too much in the middle.
Fills and delays
When one pair of speakers can't cover the whole area evenly, add front-fill speakers along the stage lip, out-fill speakers for wide side seating, and delay speakers further back – time-aligned to the main system so sound appears to come from the stage.
Level from front to back
With a single point-source speaker, the level falls about 6 dB every time distance doubles. If the back row is four times as far as the front row, it's 12 dB quieter. Line arrays and column speakers reduce that difference by controlling vertical dispersion; distributed systems put speakers closer to every listener.
Frequently asked questions
How wide does a 90 degree speaker cover?
About twice the distance from the speaker – roughly 20 m wide at 10 m.
How high should PA speakers be?
High enough that the bottom of the speaker clears the audience's heads – often 2 – 3 m (7 – 10 ft) above the floor for standing crowds.
Where should I aim my speakers?
Aim at about two-thirds of the way back into the audience and tilt down to reduce reflections from the back wall.
What does −6 dB coverage angle mean?
At the edges of the stated angle the sound is 6 dB quieter than on-axis – noticeably softer and less bright.
When do I need front fill speakers?
When the main speakers are wide apart or high up and the front rows fall outside their coverage.
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