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In Reply to: RE: This has nothing to do with acoustic power posted by Ralph on October 06, 2010 at 09:33:18
I see a serious efficiency problem and an 'out of control' ambient frequency response.
I a recent post of mine
http://www.audioasylum.com/forums/otl/messages/3/33624.html
I recalled the classical graph of (electrical) power transfer/efficiency vs. the relative amplitude of source and load impedance.
Assuming that source impedance is high (w.r.t. speaker load impedance) this means that the amplifier/speaker combination, when operating according to power paradigm, lies at the very left of the peak of the curve of electrical power transfer, close to the XY origin, where efficiency is extremely low.
If this is correct, power paradigm is basically negating the very purpose of audio power amplification.
What is even worst (in my opinion) is that the power paradigm portion of the power transfer characteristic is so steep to actually preventing any tonal balance with the vast majority of commercial speakers (that are designed for optimal performance when driven by a voltage source and whose electrical impedance varies quite a lot over the operating band).
Pushing to the limit your argument, if the source impedance were infinite we would even obtain a flat frequency response (irrespective of any variation of speaker load impedance), but with NO POWER TRANSFER at all to the speaker.
If this is the price of power paradigm I would rather stay with moderate feedback (and voltage source paradigm)!
I still do not know how to faithfully reproduce the orchestra dynamic range (more than 90 dB) without enough 'raw' power.
Best Regards
Luca
ecc230
Follow Ups:
to some sort of weird extreme. "high output impedance" refers to an amplifier that is perhaps more than 0.5ohms output impedance- some appreciable fraction of the load impedance...
IOW power production is the issue; look at all zero feedback SETs made, they are all part of this.
0.5 Ohm difference is nothing.
English/American is not my mother tongue but I understand very well the meaning of the words.
High source impedance in technical world means many, many times the load impedance.
If the difference of input and output impedance is so small (0.5 Ohm or the like) I see that 'power paradigm' is nothing different from common impedance matching (for almost maximum power transfer).
Nothing new, nothing particularly interesting, in a single word, 'moonlight'.
Good for advertisement, not for engineers.
Best Regards
Luca
ecc230
When you are referring to a conversation about the output impedance of amplifiers, in the US anyway, the engineering language is such that 4 ohms would be considered a 'high output impedance' and 0.5 ohms would be somewhere between low and high, as most amps that have a 'low output impedance' are often 0.1 ohms or less.
There is no such thing as a power amplifier that has an output impedance that is say, 100 ohms or more. That's not an amp that can make any appreciable power, so by definition its not in the conversation.
So it does appear that the mother language is playing a role here.
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