Any good references for calculation of Speaker & Amplifier current / Voltage / Power matching ?

[availlyrics]

Driving a 2-ohm speaker with a 4 or 6-ohm stable amplifier is risky and likely to cause overheating, distortion, or permanent damage to the amplifier due to excess current draw. While it might work at low volumes, the output stage of the amp will struggle to maintain proper output voltage, overheat , the amp's output impedance will limit current or likely enter into the "protect mode". of
Its like a driving a 2-wheeler. like a scooty (unless its an old school Bullet) with more than two riders. Yes, it will run, but the engine would be over heating , control , steep climb & acceleration would be severely limited, the suspension would sag and so on.

 

[Ravindra Desai]

I have shared some calculations. I hope it will be useful for some.

Simplified definitions:
- Prms is output voltage x output current when amplifier output is a single frequency. Say: 1kHz.
- Pave, as applied to audio application, is ave of output voltages of different frequencies and different amplitudes x ave of output currents of different frequencies and different amplitudes
- Peak power is a measure of an amplifier to handle very large power for a very very small amount of time or an instance of time.
- Kindly note that considerations such as crest factor of 3 used for audio application, signal processing such as compression can skew the interpretation of calculations or the definitions

 

[availlyrics]

Prms is output voltage x output current when amplifier output is a single frequency. Say: 1kHz.

https://www.analog.com/en/resources/analog-dialogue/raqs/raq-issue-177.html

RMS Power vs. Average Power​

Question:​

Should I use units of root mean square (rms) power to specify or describe the ac power associated with my signal, system, or device?

Answer:​

It depends on how you define rms power.

You do not want to calculate the rms value of the ac power waveform. This produces a result that is not physically meaningful.

You do use the rms values of voltage and/or current to calculate average power, which does produce meaningful results.

Pave, as applied to audio application, is ave of output voltages of different frequencies and different amplitudes x ave of output currents of different frequencies and different amplitudes

Within its specs limits, it doesn't matter to an amplifier, whether the input signal is a complex musical piece or a sine wave test signal
The average power (Pavg) of a sine wave is the time-averaged value of instantaneous power over one full cycle. It represents the constant DC component of AC power, often termed active or real power. For a purely sinusoidal load, it equals half the maximum or peak power

Peak power is a measure of an amplifier to handle very large power for a very very small amount of time or an instance of time.

For a pure sine wave, the Average Power is exactly half of the Peak Power
Attch shows Sine wave vs music signal, pls note that the value of average power is closer to peak power in a sine wave .
That's why during sine wave testing , volume should be kept low



For more detailed information, please read the application notes by Rane Audio & Audio Precision

 

[arj]

I have not really read all of this hence maybe someone has covered this

While you can look at it electrically in terms of power and impedances there are a lot of other things also which come into play when you want to drive a speaker with sufficient power

1. Room. the larger the room the more the power needed to pressurize the room. Roughty every 1 m you are away from the speaker you lose 3dB ie you need double the power to get the same SPL. hence a 30W at 3m is equal to 60W power needed at 4m. this is very rough ..more like a thumb-rule ) some say dubling the distance needs 4 tomes the power as well)
2. two speakers rated at 4 ohms can still be very different loads for an amplifier because impedance and phase vary with frequency. Around low frequencies such as 40 Hz, a speaker with a more severe impedance or phase angle may need more current from the amp to achieve the same output
3. the amplifier topology. Constant current, SET, Push pull, Class A .. each of these can mean that the rated 30W can be very different in the real world


Hence you cannot match a speaker and amp by specs. you can shortlist but in the end there are too many factors..and ar better off going with 3-4 times the power if in doubt.