Outdoor Amphitheater Calculator

Design outdoor venue acoustics with SPL propagation, delay speakers, shell gain, and power requirements.

Inputs

Seating capacity

Max distance to stage (ft)

Stage width (ft)

Acoustic shell depth (ft)

Ambient noise (dB)

Tab to move between fields

Results

SPL at back row (dB)

74

SNR at back row (dB)29

Amplifier power (watts)500

Delay speaker zones1

Shell gain (dB)8

Seating area (sq ft)12,000

Good Intelligibility1

How to Use This Calculator

Enter Seating capacity, Max distance to stage (ft), and Stage width (ft).
Set Acoustic shell depth (ft) and Ambient noise (dB).
Review the SPL at back row (dB) result.
Use SNR at back row (dB) and Amplifier power (watts) to inform your decision.

How the result changes with Max distance to stage (ft)

Max distance to stage (ft)	SPL at back row (dB)
145	77
383	69
668	64
905	61

What each input means

Seating capacity: Total audience capacity.
Max distance to stage (ft): Distance from stage to furthest seat.
Stage width (ft): Performance stage width.
Acoustic shell depth (ft): Depth of sound-reflecting shell behind stage.
Ambient noise (dB): Background noise level (quiet rural ~35, suburban ~45, urban ~55).

What each result means

SPL at back row (dB): Natural sound level at furthest seat.
SNR at back row (dB): Signal-to-noise ratio (need >15 for speech).
Amplifier power (watts): Total PA system power needed.
Delay speaker zones: Additional delay towers for even coverage.
Shell gain (dB): SPL increase from acoustic shell.
Seating area (sq ft): Total audience area needed.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Seating capacity = 2000, Max distance to stage (ft) = 200, Stage width (ft) = 50, Acoustic shell depth (ft) = 20 = 5 input(s) provided
Calculate SPL at back row
SPL at back row = sourceSPL - 20 * log10(distanceMeters)
74 = 74
Calculate SNR at back row
SNR at back row = round(splAtMaxDistance - ambientNoisedB)
29 = 29
Calculate Amplifier power
Amplifier power = round(max(500, powerNeeded))
500 = 500

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