Walls do half the work indoors
In a hall, sound bounces off the walls, the ceiling and the floor. That reflected sound keeps the room full, so the back of the hall stays loud and the bass feels solid even with a modest system. Outdoors there is nothing to bounce off. Sound travels away from the speakers and simply keeps going, so it gets quieter much faster with distance.
Why turning it up is the wrong fix
The instinct is to turn the system up until the back of the lawn can hear. The trouble is that the people near the speakers then get far too much, and still the far end sounds thin. The right fix is coverage: more speakers, placed and angled so the whole lawn sits at a similar level. That is why an outdoor quote often lists more equipment than an indoor one for the same guest count.
Bass disappears in the open
Low frequencies need something to push against. Indoors the room reinforces them; outdoors they spread out and fade. A dance floor on a lawn needs more subwoofer than the same dance floor in a banquet hall, or the music sounds thin however loud it is.
Wind, damp and power
Wind moves sound around and can make it come and go at a distance. Sea air and dew get into equipment over a long evening, so connections need covering and stands need weighting. And garden or lawn sockets rarely carry a full sound and lighting rig, so most open-air events need a generator, placed far enough away not to be heard.
Planning an outdoor event
Tell us the size of the space, where the stage or DJ will be, where guests will sit and dance, and what power is available. We will plan the coverage around the actual layout rather than a guest count. If the venue is by the sea or exposed, say so — it changes what we bring.