Amplifier power scandal
You’ll often have the manufacturers twist the formulas around to calculate the power output differently in an effort to make their amplifiers sound more impressive than other ones. When speaking about AC, Voltage peak (VP) power= VRMS x square root of 2 or 1.414 for a pure sine wave which is close to what a perfect amplifier would be with no dc component. For example the mains voltage in the USA is 120 volts RMS, x the square root of 2 or 1.414 would give us 170 volts peak. Now the peak to peak (VP-P) is affectively the difference between the lowest and the highest point which in the case of our sine wave is double peak power or about 340 volts.
Now let’s say we have an amplifier that is listed at 500 watts with some certain impedance load. If that 500 is peak power then it’s likely only about 350 rms power. If that 500 is peak to peak power then it’s affectively double peak power in which case we would take 250 divided by the square root of 2 which would give us 177 rms. If the manufacture doesn’t list the specifics then it will leave you guessing as to how much power it really is. Also keep in mind some of the variables such as the AC waveform not being a pure sine wave, peaks or troughs significantly higher at some points will affect the power calculations. Also not all speakers are the exact impedance rating either so keep that in mind. For instance a 2 own subwoofer may be 1.8-2.2 ohms and a 4 ohm speaker may be 3.2-4+ ohms. Usually if you look on the data sheet you can get the precise figure. All these things can make the output slightly different than calculated.