How do you figure the .....

[flyboylr45]

I once read on this website either Tom or Andry or someone post an equation fo figuring out how many watts your amplifier is putting out. I think it took the distance from the speakers and the decibel reading at your position and did something to it. Does anyone remember this equation? Thanks

 

[businessjeff]

Watts = Volts x Amps...

They may have been talking about some other way, is that what u mean?

 

[10010011]

I once read on this website either Tom or Andry or someone post an equation fo figuring out how many watts your amplifier is putting out. I think it took the distance from the speakers and the decibel reading at your position and did something to it. Does anyone remember this equation? Thanks

I am not so sure this would be a accurate way of measuring watts. As there are too many variables. Things like the sensitivity of your speakers must be known as a more sensitive speaker will output the same SPL at a lower power than a less sensitive speaker. Also higher frequencies require less power to reach the same SPL as lower frequencies.

The basic power formula is Watts = Volts x Amps

A more useful one would be Watts = V^2 / R or in this case Watts = V^2 / Z

Now you can measure volts across your speaker and calculate, but this is where things get tough. The resistance (R) well actually Impedance (Z) of your speakers changes with frequency. So measuring volts and calculating is only a "ballpark" estimate but as close as you can probably get.

 

[dronezero]

Well if you accurately know the sensitivity of a speaker and you are measuring the loudness under the same conditions that the sensitivity measurement was taken then you can figure the watts with the formula below.

W=10^[(X-S)/3]

W = watts
X = measured loudness in db
S = sensitivity of speaker with 1 W at 1m in db

 

[highfigh]

Well if you accurately know the sensitivity of a speaker and you are measuring the loudness under the same conditions that the sensitivity measurement was taken then you can figure the watts with the formula below.

W=10^[(X-S)/3]

W = watts
X = measured loudness in db
S = sensitivity of speaker with 1 W at 1m in db

That doesn't take the acoustical gain from reflections, though.

 

[dronezero]

I was kind of throwing that in with the knowing accurately you sensitivity specs. But yes if the sensitivity wasn't measured under similar conditions to what you are measuring under than that will affect the results.