HomeCalculatorsAmplifier, Speaker & SPL Calculator

Amplifier, Speaker & SPL Calculator

These calculators will find how loud an amplifier and speaker combination will be, or what size amplifier you need to make a speaker a certain loudness.

There are five factors which contribute to how loud a speaker will be:

1) The distance from the speaker. Sound drops off the further you are away from a speaker.

2) The SPL required. This is how loud you want the sound to be at the distance specified. Some general levels are:

  • 70-80dB  for speech only
  • 80-95dB for light music
  • 95-110dB for heavy music

3) The speaker sensitivity. This is not an indicator of how sensitive the main (human) speaker is, but rather a measurement of the sensitivity of the loudspeaker. It should be available in the specifications for the loudspeaker (see Understanding Speaker Sensitivity for more info).  It is normally stated as the SPL measured 1 metre in front of the speaker with 1 watt of power driving the speaker. Hence the specification will read something like:

Sensitivity (1W/1m) = 85dB

4) Amplifier headroom. This is an allowance for the amplifier to cope with peaks without distortion. At least 3dB headroom is generally recommended. Note that for every 3dB allowance, the power requirement doubles.

5) The power of the amplifier, measured in watts.

In the calculator below, first input the distance from the speaker (and select feet or meters). From this distance the Sound Pressure Level (SPL) loss over that distance is calculated in decibels (dB).

Then, fill in the input fields of either calculator depending on if you want to know the required power for a target SPL (use the first calculator), or if you want to know how loud a given amplifier will be (use the second calculator).

Download Calculator
as Excel File
Purchase
Prices in US$

Note: these calculations are for “open-air” where there are no reflections from walls, ceiling and/or floors. When reflections are present, the SPL losses can be reduced by up to 6dB.

For those who need to know, the formulas used for these calculations are:

\large{SPL\ loss = {20\times Log_{10}\left(\frac{Distance\, from\, Spkr\left(meters\right)}{1}\right)}

and

\large{ Amplifier\ power =  \large{10^\frac{required\,amp\,gain}{10}}

Further reading

Disclosure: If you buy through these Amazon links Geoff receives a small commission from each sale.
Please Note: Due to other commitments I'm currently unable to spare the time required to answer further questions in the way I'd like. Hopefully this is a temporary situation. I'm sorry for this inconvenience.
Geoff