Here are the steps to calculate the power output of an amplifier when connecting a 4-ohm speaker:
- Find the amplifier’s rated power output at 4 ohms. This is usually specified on the amplifier’s datasheet or manual. Let’s assume it’s 100W at 4 ohms for this example.
- Calculate the peak voltage output using:
Peak Voltage = √(Power x Impedance)
For 100W at 4 ohms:
Peak Voltage = √(100 x 4) = 20V
- Calculate the RMS voltage output by dividing the peak voltage by √2:
RMS Voltage = Peak Voltage / √2
RMS Voltage = 20V / √2 = 14.14V
- Calculate power using:
Power = (RMS Voltage)2 / Impedance
Power = (14.14V)2 / 4Ω
Power = 100W
So for a 100W @ 4 ohm amplifier connected to a 4 ohm speaker, the expected power output is 100W.
The key is knowing the amplifier’s rated power at the impedance of the speaker you’re connecting. This gives the peak voltage, and the rest is calculating RMS voltage and power from that. Always verify the amplifier’s rating at the speaker impedance to avoid overloading.
Citations:
[1] https://geoffthegreygeek.com/speaker-impedance-changes-amplifier-power/
[2] https://www.crownaudio.com/how-much-amplifier-power
[3] https://www.diyaudio.com/community/threads/calculating-output-power-of-amp.5660/
[4] https://electronics.stackexchange.com/questions/542888/how-to-calculate-the-expected-output-current-being-drawn-by-a-speaker
[5] http://www.sengpielaudio.com/calculator-AmplifierLoudspeakerAndOhm.htm
[6] https://youtube.com/watch?v=YDnZ9We3QpQ