Sound for
Outdoor Events

01 — The starting point

Why open air sounds different

Indoors, what reaches the audience is the sum of two things: what leaves the box directly and what bounces off walls, ceiling and floor. That second component does a lot of work for free. It fills the back of the room, gives a sense of body and lets a modest rig seem sufficient. Outdoors that gift does not exist: you only have direct sound, and direct sound follows one implacable rule.

Every time you double the distance from the box, the level drops by around 6 dB. If you have a comfortable level ten metres from the stage, at twenty metres you have lost half the sense of volume and at forty metres you are at a different event. Indoors that fall-off is much gentler because reverberation sustains the level at the back. Outdoors, the back gets nothing. That is why the classic mistake — two boxes at one end of the garden and hope — always produces the same outcome: the people at the front leave because it is too loud, and the people at the back cannot hear.

Add three phenomena that never show up inside. The first is air absorption: humidity and distance eat the high frequencies, so at thirty or forty metres the sound arrives dull even when it has level. You compensate with a touch of extra brightness in the distant boxes, not by pushing the master. The second is wind, which does more than put rumble in microphones: because it blows faster at height than at ground level, it bends the wavefront. Downwind the sound carries further than planned; upwind it lifts above the audience's heads and disappears.

The third causes the most trouble and almost nobody accounts for it: the night-time thermal inversion. By day the ground is warm and the air above it cooler, and sound tends to bend upwards. In the small hours the opposite happens — the ground cools faster than the air — and sound refracts downwards, skips off the terrain and travels much further. That is the physical reason why the level that disturbed nobody at ten in the evening can be heard across a whole village at two in the morning.

Each type of space on the island behaves in its own way: we break it down venue by venue in the guide to event venues in Mallorca.

03 — Where each box goes

Coverage and orientation

Placement is the cheapest decision and the one that changes the result the most. It costs nothing and is usually worth more than doubling the rig. The rule we apply in any outdoor space is simple: distribute across several positions at moderate level rather than concentrating everything in one loud position. Four small boxes around a cocktail area sound infinitely better — and disturb far less outside the site — than two big boxes shouting from one end.

Height is the second parameter. The axis of the box has to sit above the audience's heads: in practice, at least 2.2 to 2.5 metres when people are standing. A box at chest height achieves two bad things at once: the bodies in the front rows absorb most of the mids and highs, and the people at the front receive a level far above those behind. When the audience is seated at tables the criterion changes and it pays to go lower and spread wider.

Once the area to cover exceeds about thirty metres of depth, delay comes into play. Sound travels at roughly 343 metres per second, which is about 3 milliseconds per metre. If you place fill boxes twenty metres from the stage, they have to be delayed by around 58 milliseconds so their sound coincides with what arrives from the main system. Without that delay you get a clearly audible echo and intelligibility gets worse rather than better. It is a two-minute adjustment on any modern processor, and it is the difference between a fill that works and a fill that gets in the way.

Finally, think in zones rather than in "the event's sound". An outdoor event normally has three: the welcome and cocktail area, where music is background and people are talking; the dinner area, where the level has to allow conversation without raising your voice at any table; and the dance floor, which is the only one that needs real level. Treating all three with the same system at the same volume is why people end up shouting at so many outdoor dinners.

05 — What stops a whole event

Electrical power and generators

Electricity is the number one point of failure at outdoor events. Not the gear, not the engineer: the power. And almost always for the same reason — nobody asked in time how much there was, and catering, lighting and sound ended up sharing a board sized for a house.

The two figures to request in writing from the venue are how many amps the available board delivers and whether the supply is single or three phase. A 25 amp single-phase board is about 5.5 kW on paper; with the caterer's ovens and fridges plugged in, what is left for sound and lighting is little and unstable. A three-phase supply at 25 A per phase changes the picture completely, because loads can be split: sound on one phase, lighting on another, catering on the third.

If there is a generator, its position is an acoustic decision, not a logistical one. A modern silenced set runs at around 65 dBA at seven metres, which is unnoticeable on an open forecourt but ruins a ceremony twenty metres away. The rule we apply: at least thirty or forty metres from the guest area, behind a wall or dense vegetation, and downwind of the prevailing afternoon breeze so neither the noise nor the diesel smell drifts into the site. And always on firm ground: loose gravel transmits vibration and the set sinks over the hours.

Then comes distribution. Sound and lighting must run on separate circuits, because dimmers and moving heads inject noise into the line that later shows up as hum in the system. And the whole rig must have a single earth point: when part of the gear is plugged into the house board and part into the generator, you create an earth loop and with it a 50 Hz hum that no amount of fiddling at the desk will remove. It is one of the most common faults and one of the easiest to avoid if distribution is planned before the first cable is run.

The consumption of the lighting side — moving heads, LED, uplighting — is broken down in the guide to event lighting types.

07 — What the musicians hear

Monitors and stage foldback

Monitors are the part of the system that suffers most when it goes outside, and the part that gets budgeted least. The cause is the same as everywhere else in this guide: inside a venue the musician hears themselves through reflection — the sound bounces off the back wall and returns; outdoors nothing returns. A singer who hears themselves perfectly with one wedge in the rehearsal room hears nothing at all on a stage deck at a finca.

The practical consequence is that outdoors you have to give more monitor than the musician thinks they need, and that the monitor mix stops being an accessory and becomes half the engineer's job. When the band cannot hear itself, the tempo drifts, the singer pushes and raises the stage level, and the stage level ends up contaminating the front-of-house mix. The audience perceives that as "the band sounds messy", but the origin is in the foldback.

There is one advantage of the open air worth exploiting: the risk of feedback is noticeably lower. With no walls returning sound to the microphone, you can work with more gain before the system starts to ring. That gives room to provide the monitor level actually required without resorting to aggressive filtering that leaves the voice with no body.

The last point is about coordination rather than audio: distance. In a large outdoor site the control position can be thirty or forty metres from the stage, with audience, tables and catering in between. Shouting is not an option and hand signals are not either. Any rig with a band needs a communication channel between stage and control — intercom or, at minimum, a talkback and an agreed set of signals — because the moment you need it is always the worst possible moment.

09 — The real ceiling

Noise regulation in the Balearics

It is worth being clear about the order of things here, because clients almost always have it inverted. What decides how late and how loud your event can run is not the regional law in the abstract: it is, in this order, the venue's activity licence, then the by-law of the relevant town hall and, as a general framework, Balearic regulation. The licence can be — and often is — stricter than the by-law. None of the three is negotiable on the day.

The practical consequence of all this is a single question, and it has to be asked in writing and before signing anything: what exactly does this venue's licence say about amplified music outdoors, at what hours and with what limit? The answer changes the budget and sometimes changes the whole format of the event. A space with a one o'clock cut-off at low level and one with a three o'clock cut-off and no limiter do not allow the same party, however much both advertise themselves as a "wedding finca".