decoud wrote:

It seems there is broad agreement here with what I take to be Romy's position, which is that one cannot have a sophisticated understanding of music reproduction if one does not have a sophisticated knowledge of music.

It never was my position, sorry. I never stressed any “knowledge of music”, not a lot of the reason is that I do not have this knowledge. So, what you said is your perception not my expression.

decoud wrote:

Now all of this would be easier if one had some better measures by which the fidelity of reproduction could be gauged - not as a substitute for listening but as an adjunct. The various functions of frequency commonly quoted are not very useful because they assume that the sound is stationary, which of course it is not. The only non-stationary test one tends to see - the response to a step function - is of course a very artifical thing. So, what we need is a method for analysing non-stationary, non-linear, time-varying signals. The best of these is probably empirical mode decomposition.  Romy, would you be persuaded to give it a try? (there is a version for MATLAB here http://perso.ens-lyon.fr/patrick.flandrin/emd.html) I do not for a minute believe it would be as good as a human ear, but it may be interesting to show that it can capture aspects of "reality" missed by crude things such as bandwidth and distortion values.

Sounds interesting or at least entertaining. I have no personal experience with EMD, and even if I had I doubt that I have expertise to enterprise the result into some kind of useful conclusions. I generally do not use any of the contemporary speakers design and evaluation techniques. All those TEF analyses and maximum length sequence system analyses are good but I do not do it. It is not that I am against any time-domain metrics but I never had needed it and my thinking about sound does not incorporate any time-domain analyses. You probably found someone more intelligent on the subject even to support this conversation…

Do not forget, decoud, that no of the methods of mathematic approximation of realty measure the actual Reality. The time-domain metrics, the decomposition method and anything else measure juts reflection of Reality in term of language of Reality description, nothing more. It is a powerful tool… for those who need it. However, the adoption of this language to describe Reality has some intrinsic problems in my view a person do not deal with Realty anymore but with semi-scientific surrogate of Reality.

decoud wrote:

I suspect wavelets would be much better than a fourier transform and rather less good than emd. The reason is that since we do not know what features of the signal are decisive in perceiving it as real, a signal-adaptive technique such as emd is more likely to capture them than a decomposition based on a set of arbitrarily chosen functions such as wavelet analysis. The beauty of emd is that the decomposition is determined by the signal itself and so is highly efficient at extracting its essential features.

el`Ol wrote:

I don´t know whether the audio industry`s products are so sophisticatet that they need mathematical steam hammers to improve them. In a German forum there is a discussion about a diploma work from the TU Berlin where the student found out in psychoacoustic tests that the subtraction frequency of the intermodulation products is the non-linearity that interferes most with the perceived sound quality, and built a valve anplifier that is optimized in this respect. Quote: "Der "BLACK CAT 2" hat einen Dfferenztonfaktor von 0,002% und einen Klirrfaktor von 0,033 %, während der Telefunken HA990, als Beispiel eines handelsüblichen HiFi-Transistorverstärkers, einen Differenztonfaktor von 0,366 ( das 183-fache des BC2 ) und einen Klirrfaktor von 0,0048 hat." What can be critizised is that he compares his amp with a quite old mass product, but he says it is representative for what average people have in their living rooms. However, finding out that the subtraction frequency factor of this mass product is two orders of magnitude above its THD, where in his amp it is one magnitude below, is quite shocking.

Andy Simpson wrote:

This type of test is more commonly called DFD (difference frequency distortion) and is sometimes used in microphone measurement to measure acoustic/mechanical non-linearity.

Andy Simpson wrote:

If anybody is interested in listening, I am interested in perception of differences - dynamics, clarity, TUNING (ie. audible presence of inharmonic products), etc.

drdna wrote:

Andy Simpson wrote: This type of test is more commonly called DFD (difference frequency distortion) and is sometimes used in microphone measurement to measure acoustic/mechanical non-linearity. This is interesting. What physical methods are employed to minimize the distortion?

Andy Simpson wrote: If anybody is interested in listening, I am interested in perception of differences - dynamics, clarity, TUNING (ie. audible presence of inharmonic products), etc. Well I listened to these files. There was an obvious difference. It did not seem to be blinded: the "A" files seem to have more distortion. I perceived the distortion as a loss of some of the correct sound which was then made into noise. The analogy: taking a fine wood carving, sanding it lightly and sprinkling the surface with the resulting sawdust. The noise floor and hence clarity and dynamics suffer, as well as correct timbre of sound. In general, my impressions of distortion are: harmonic distortion: usually too slight to be heard intermodulation distortion: affects timbre, focus, presence frequency response: affects "connection", emotional color SO far... Adrian