The main point was about the tools used to takes measurement, all applications of Fourier theory and his fundamental linear nature and his time independant basic nature...
The ears did not work in a linear manner at all and live in a time dyssimetric dimension for our fundamental perception...
All the measures taken about amplifiers and dac are tools of a linear nature in the frequencies domain basically... But How to use them to serve the non linear nature of our hearing abilities an his time dependant nature ?
We must not use Fourier analysis then with a naive idea about distortions coming from components and complete ignorance about the way human hearing perceive them...I cannot cite him about distortions it will be too long post...
Dr. Hans Van Maanen explain it better that i can here...
Here is a gist of his ideas :
«The temporal resolution of human hearing is at least an order of magnitude better than derived
from its frequency response, so it is very likely that especially metal percussion instruments
show a clear difference between ‘live’ and recorded sound...
Several instruments have a strong contribution above 20
kHz
• Several instruments have a strong attack, rapid change of
signal at start, with very clear high-frequency content
Learnings from literature
• Attack is essential part of the specific sound of the
instrument
• Instruments with a strong attack are the toughest to
reproduce in a “natural sounding” way
• Specific instruments: Turkish drum, percussion, (grand)
piano, cymbals, triangles
• But also human voices.
• The Fourier theory is one of the fundamental basics on
which the whole sound reproduction building rests
• It says that any signal can be separated in an infinite series
of (co)sine waves of increasing frequency
• It is known that humans cannot hear continuous sine waves
above 20 kHz and the upper limit decreases with age
(I know!)
• Tests have shown that human hearing is insensitive to the
phase of continuous sine wave sound signals
• The common conclusion is that reproduction of sound from
20 Hz – 20 kHz with only the correct amplitude is completely
sufficient for sound reproduction, indistinguishable from the
original, but quite in conflict with the above mentioned
anecdotal findings and with what I hear.
• Theory learns that to reconstruct the original signal from
the Fourier components also requires the correct use of
the phase
• Ignoring the phase response means that the reproduced
signal can, in time domain, be different from the original,
even if the amplitudes are identical
• As is shown, ignoring the phase leads to a change in the
temporal properties of the signal, which is clearly seen
from its envelope
• This has consequences for e.g. the attack of percussion
instruments and the grand piano
So is the change of the signal in time domain really inaudible?
• The anecdotes indicate that the temporal properties are of
importance for the perceived quality of reproduced sound
• Tests of Kunchur indicate temporal resolution of human
hearing of 5 – 6 μs (which is rather surprising with 20 kHz
upper limit of hearing)
• The Fourier theory has several conditions, like a.o.:
- the system should be linear
- the system should be time-invariant
• Human hearing is neither
So is the Fourier theory directly applicable to human hearing?
Although the Fourier theory has been well established since the second half of the 19th century, it is surprising that so little attention is given nowadays to the conditions, required to apply the linear theory. It has been applied unreluctantly to electronics and human hearing, even though neither fulfil either of these requirements. Therefore, it should not come as a surprise that the
results are inconsistent with listening experiences.
It should be clear that when the conditions of linearity and time-invariance are not fulfilled, results, based on the Fourier theory, can be thrown straight into the wastepaper basket.
Regretfully, these conditions are rarely respected and without hesitation, the frequency response, determined with continuous sinewaves, is interpreted as if it were from a linear and time-invariant system. Which explains why the behaviour of the amplifier with dynamic signals (like music) differs from the (expected) behaviour, based on results obtained with steady,
continuous signals. To reproduce complex and dynamic signals like music well, the amplifier needs to be -next to a large number of other conditions- also as much as possible time-invariant and all its amplification stages should be as linear as possible. If not, artefacts will show up which manifest themselves mostly in the time domain and lead to a degradation of the sound stage and thus of the perceived quality. It is banging on an open door that the less an amplifier (also internally!) fulfils the requirements for a linear and time invariant system, the
larger the contribution of artefacts to its output signal will be. As several of these cannot be detected using continuous sine waves, these differences may not show up in the specifications.
This can explain why amplifiers with similar specifications give significant differences in the perceived quality.
The Fourier theory is very powerful and useful for audio, but it can only be applied correctly when the conditions imposed are fulfilled. The major requirements are linearity and time-invariance, but these are often not fulfilled, leading to incorrect results and conclusions. When the Fourier theory is used to predict the temporal properties of an audio system, one should realize that these conditions can only be approximately fulfilled. It should be verified to which extent the approximations will introduce deviations from the ideal, desired condition.
Then Any ASR review of amplifiers will not be a warrant of "musicality"... Then Keep your ears open... Measures and especially some limited set of measures dont tell all the story there is to tell....
Thanks Amir for the falsification of the Gear market specs ...
Keep for yourself your theory that all there is to say about sound qualities is relative to your limited set of measures...
Subjectivist are not in the obligation to stay ignorant about measures and hearing theories and fact...
Objectivist must learn psycho-acoustic science behind technology and develop humility....
By the way i am perhaps the only one posting deep scientific reason why Amir ideology about hearings and all perceptive "musical" qualities correlated by him to a narrow set of linear measures is just that : a marketing ploy, an ideology but not science...
Amir do a great sercvice by informing us , i thank him for that many times, the problem is that he really think the information given is absolute truth about perceived experiences musical qualities...They are not... And there is no more and no less deluded subjectivists than there is deluded objectivists... Psycho-acoustic is a too deep matter to be reduced to a limited set of linear measure on the gear based on Fourier theory or to be based only on gear fetichism ...
