What are the Mains in a Sound System?

The mains (also called the main PA or main speakers) are the main loudspeakers of a sound system, usually left and right of the stage, that carry the full mix from the front of house desk to the audience. Everything the audience hears comes mainly from the mains.

How the mains work

Setting up the mains follows a standard order:

  1. Placement: speakers are flown above each side of the stage, often as a line array, or stacked on the ground in smaller venues.
  2. Subwoofers: separate bass cabinets are added, usually on the ground in front of or under the stage.
  3. Processing: a system processor splits the signal between the mains, subs and any fills, and protects the speakers.
  4. Tuning: the system engineer measures the room and adjusts EQ, delay and levels.
  5. Mixing: the sound engineer mixes the show through the mains from the front of house position.

Visiting acts check what mains a venue has in its technical specification during the advance. Venues often share that specification through documents in Crescat.

Mains vs monitors

The mains point at the audience and carry the full mix. Monitors, such as wedges or in-ear systems, point at the performers and carry their own mixes so they can hear themselves. The two are mixed separately, often by different engineers.

Parts of a main PA system

  • Left and right main speakers or arrays
  • Subwoofers for the low bass
  • Front fills for the first rows
  • Out fills or side fills for wide rooms
  • Delay speakers for long rooms and outdoor sites
  • Amplifiers and a system processor

Frequently asked questions

Why are they called the mains?

Because they are the main speakers that the audience hears. The name separates them from monitors, fills and delays, which support the mains in particular areas.

What is the difference between flown and ground-stacked mains?

Flown mains hang above the stage on motors, giving even coverage and clear sightlines. Ground-stacked mains sit on the floor or stage, which is simpler but can be too loud for the front rows and quieter at the back.

Is the PA the same as the mains?

Often, yes. People use "PA" for the whole sound system the audience hears, and "mains" for its main speakers. In everyday use, the two words are often swapped.

Related terms