Someone had to say it, RMS power makes no sense at all. I think all this relates to the crest factor of the signals for an intended application. Purpose built power amps will have different real world capabilities depending on the peak to average (or RMS) ratio of the signals in that application.
This is most evident in telecom with very data efficient QUAM signals, the crest factors can be very high and occasional clipping can not be tolerated. If a full scale single frequency sine wave gets to the input the magic smoke comes out very quickly. For audio the same thing is true on a smaller scale.
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When did power become wattage. Thanks Jan.
Somehow units have replaced what it is they represent.
Power by wattage,
Potential by voltage.
Current by amperage.
Also there is no such thing as RMS power.
That would be the same a saying RMS Joules per second.
Energy is not measured in root mean square.
There is no such thing as capacity in reference to capacitors. The word is capacitance.
Aren't semantics fun?
Somehow units have replaced what it is they represent.
Power by wattage,
Potential by voltage.
Current by amperage.
Also there is no such thing as RMS power.
That would be the same a saying RMS Joules per second.
Energy is not measured in root mean square.
There is no such thing as capacity in reference to capacitors. The word is capacitance.
Aren't semantics fun?
I learned quickly there is no such thing as a gravity wave, it's gravitational wave.
Standardized tests done properly provide a yardstick for comparison. Some standards (like some of the ones alluded to) are meaningless in every way.
That is why I do two tests for evaluation. Continuous sine wave power both channels driven into load without clipping, and transient power into load without clipping. These are two tests that tell you a lot about an amplifier, and provides a useful yardstick for comparison.
These results can be used to accurately set up a sound system with required sound pressure level. They provide an accurate, convenient, repeatable metric.
Semantics is BS,especially when applied to science and technology.
These parameters that you think are nonsensical are used by technicians and engineers every day to obtain predictable and repeatable results. They work when applied properly.
However, terms like "Watts" "RMS" "Hi Fidelity" "Music Power" ad nauseum are meaningless and even overtly deceptive when used by marketing departments. Did you see where I did actual measurements on cheap consumer "hi-fi" equipment? Electrons don't lie.
They also defined it for their purposes in DIN45500/DIN EN61305 and agree that it has next to nothing to do with the actual meaning of RMS but in a world of PMPO, Music Power, Total System Power etc RMS was known to the public and closest in value to what they came up with so they just used that term.
In the world of the Deutsche Industrie Norm RMS power is defined as the maximum an amp can deliver for 10 minutes using pink noise as input signal.
I posed the same argument to an MSci of Electrical engineering 40 years ago who promptly corrected me. I argued it is valid term used in audio.
He replied that audio is full of _______. I'll let you will in the blanks.
Used by technicians and engineers. I can assure you it is not what they were taught.
You're missing the point it's not about semantics but clarity of thought. RMS gives the equivalent heating power of an arbitrary signal it IS the power. RMS of power is nonsense and denotes a lack of understanding on a fundamental level. The extension from pure real to complex loads is easily done with complex algebra. BTW the use of the term RMS power is probably the most common brain fart in the EE world.
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Yes if a fresh grad looks at you funny after saying it in an interview you hire them immediately.
Yes if a fresh grad looks at you funny after saying it in an interview you hire them immediately.
Although it's probably far too late for me. I'll keep that in mind for a word of advice.
Well I use the term Watts RMS over in my speaker voltage thread because it's the way that most people think about it, amps are advertised like that and to avoid it being mistaken for peak power. Telling people about how much voltage they need from their amp output doesn't give them a scale they are familiar with.
I've advocated for amps to be rated in volts, only to be shot down again and again in this very forum, where people should know better. It's not going to change, but a voltage rating would be so much better.
I agree with Kevin and some others that this is nothing new. If anything, it seems that the wattage claims are not as bad as they used to be, except maybe in car audio.
I've advocated for amps to be rated in volts, only to be shot down again and again in this very forum, where people should know better. It's not going to change, but a voltage rating would be so much better.
I agree with Kevin and some others that this is nothing new. If anything, it seems that the wattage claims are not as bad as they used to be, except maybe in car audio.
On this we agree. However the term RMS has a real meaning to engineers and technicians. It is used in other electrical engineering applications than audio.
It's exactly what I was taught in electrical engineering school. It is used in designing power distribution systems and to calculate heat dissipation in a load among other things.
The true meaning of RMS is simply the area under the curve (an integral). For DC the RMS voltage is the DC voltage. For a sine wave it's 70.7% of the peak voltage. For a square wave it's 100% of the peak voltage.
For a musical program RMS calculations are complex and constantly changing. For test purposes we use sine waves. The results of these tests give us reliable data that can be applied in a uniform manner.
It works.
That's because when we design we think in volts. We think about power after we calculate voltages.
If I say I need X amount of watts, I calculate the required voltage and take it from there. After hashing it out I go back and think about power and SOA. How about you?
Voltage specifications would be very meaningful to most people here. They would only serve to further confuse the hapless public, who have been lied to, double talked to death, and hoodwinked since the first caveman discovered flint.
Little wonder the public looks at engineers like they're devious shamans. IT'S NOT US FOLKS! IT'S THE LYING (insert your favorite swear word) IN MARKETING!On this we agree. However the term RMS has a real meaning to engineers and technicians. It is used in other electrical engineering applications than audio.
It's exactly what I was taught in electrical engineering school. It is used in designing power distribution systems and to calculate heat dissipation in a load among other things.
The true meaning of RMS is simply the area under the curve (an integral). For DC the RMS voltage is the DC voltage. For a sine wave it's 70.7% of the peak voltage. For a square wave it's 100% of the peak voltage.
For a musical program RMS calculations are complex and constantly changing. For test purposes we use sine waves. The results of these tests give us reliable data that can be applied in a uniform manner.
It works.
RMS voltage yes, RMS current yes, but not RMS power. The product of these two measures is just power. Check your text.
If you were taught otherwise then it was brain fart.
OK on this we agree. I work with voltages anyway in my designs and then go back and calculate power.
Is it any wonder that the consuming public is confused? This is a marketing department's dream!
Still, when they say "RMS power" I think "RMS voltage into a load." I'm not even sure what the public thinks.
BS terms sure are confusing. Good for sales too.
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