Sound Quality Vs. Measurements

[a.wayne]

Originally Posted by tvrgeek

Originally Posted by ThorstenL
However my experience is that certain types of replay systems appear to handle what is on the recording in a way that aggravates the audibility, often severely so, while others appear to not cause such aggravation and if such a thing is even possible seem to "fix" the problem.

EXACTLY, but in my wife's case it is horns and some violins. So, what objective measurement can we make in the amp/driver system that quantifies this problem? It would be easy to just say pony up for well designed above average equipment, except her favorite amp is a mid-fi, but well executed, Rotel 840! I am sure my mid-fi speakers "allow" this more than decent ones will.

One gentleman who did some recording engineering in his time suggested it was common to boost the 4K range a bit to make the recording "pop". Maybe true, but I tried a gentle broad dip (via my DCX) and it did not seem to help. Of course adding that monster in the mix might have done more harm than good. I should build a passive notch filter for a better test.

I would bet as much speaker related as the electronics ..... The problem with studio monitoring is the poor speakers used in monitoring, where most changes are not noticiable until a fair amount of lift is used.



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[SY]

Originally Posted by Johnny2Bad

When the job is creating the sound, fidelity may or may not be relevant. When the job is reproducing the sound, fidelity is paramount. Two distinct objectives that happen to use similar technology.

And the third- when archiving the sound (the goal of some types of recordings), fidelity is paramount. That's an aspect of recording that many producers/engineers don't get.

[vacuphile]

Originally Posted by john curl

Switching supplies IM garbage back, and, as well, the HIGH frequency garbage MUST be 'nulled', if possible, by power supply rejection, which REQUIRES the feedback loop to work extra hard, OR it becomes part of the output signal.
Wow, do our 'critics' actually think anything through?

I am not a critic of persons, just critical towards ideas that don't fit into my conceptual framework and/or hands on experience with the matter at hand. Since I am here to learn, I am more than prepared to modify my ideas, given proof of my errors in thinking. In this instance, this has yet to occur.

There are a number of reasons for that. The first is my observation, mentioned before, that the supply rails of an amplifier under load fed by a linear ps look much nastier to me than the same fed by a SMPS. The second are the size and composition of the nasties; with a linear ps the deviations are larger and more inside the audio band than with a SMPS, where they typically are way above the audio band and relatively small. This makes filtering them out not that hard. In short, with a well regulated and well designed SMPS, less work will be required from the feedback loop to reject power supply irregularities.

vac

[vacuphile]

Originally Posted by DF96

A high Q resonance (either peak or null) could cause problems, but might not show up in measurements unless one of the test frequencies happened to hit it spot on. Music, where the higher frequencies could be mainly percussive noise, might excite the resonance because noise hits all frequencies within its bandwidth.

You might be right in the case of a stepped sine sweep, but it should show up in MLS, since the impulse to excite the driver contains all frequencies without discontinuities.

My take on sibilance is that diffraction might be a primary cause. The FR at the top end may flip flop around a great deal when a loudspeakers is measured at different angles off-axis, even taking very small angle steps, diffraction being the cause of this. Different wavefronts alternatively combining constructively and destructively will lead to much higher local peaks than any mechanical form of resonance in a driver can cause.

The ribons as mentioned by Thorsten and DBMandrake may suffer a bit less from this as long as the listener stays within the beam.

vac

[DF96]

Originally Posted by vacuphile

it should show up in MLS, since the impulse to excite the driver contains all frequencies without discontinuities.

Almost, but not quite. All frequencies will be a harmonic of the sequence repetition rate, so this must be low enough that the harmonic spacing is sufficiently narrow.

[tvrgeek]

Is it a valid concept to look not directly at the rails, but at the amp output in evaluating the effect of the supply, be it SMPS or linear? This looks at it as a system for the case at hand, not as a general rule. One amp may be far more tolerant of issues from one or the other so there may not be a simple answer for which is best. "it depends"

[DF96]

Its only the amp output which connects to the speakers (apart from any induction between cables).

There is more to a PSU than output voltage - output impedance will vary with frequency too. A regulated supply, including SMPS, is likely to have a rising impedance with frequency because of the need to stabilise the feedback loop. A conventional unregulated supply will have a mainly falling impedance.

[vacuphile]

Originally Posted by DF96

Almost, but not quite. All frequencies will be a harmonic of the sequence repetition rate, so this must be low enough that the harmonic spacing is sufficiently narrow.

sure, and you must have enough bins in the subsequent fft to analyze the response, but my point is that even narrow peaks will show up, given the right methodology.

[DBMandrake]

Originally Posted by vacuphile

My take on sibilance is that diffraction might be a primary cause. The FR at the top end may flip flop around a great deal when a loudspeakers is measured at different angles off-axis, even taking very small angle steps, diffraction being the cause of this. Different wavefronts alternatively combining constructively and destructively will lead to much higher local peaks than any mechanical form of resonance in a driver can cause.

Although I agree that diffraction at high frequencies is bad (quite bad in fact) and can be a source of "harshness", I'm not sure that I would pin it as the sole culprit for sibilance.

What you're saying implies that it's the perturbations in the frequency response caused by diffraction that are to blame - yet EQ, even accurate narrow band EQ doesn't seem to eliminate it on drivers which have it.

My take is that it's a time domain phenomenon, whether that be one or more high Q resonances that ring for a long time, or perhaps the time delayed signal from a diffractive edge - both stretch out the original signal in time.

Significant diffraction which is centered in the sibilance range could indeed be a contributor, but I think not the only culprit.

The ribons as mentioned by Thorsten and DBMandrake may suffer a bit less from this as long as the listener stays within the beam.

With the ribbon you have both a very clean CSD, as well as greatly reduced diffraction effects, assuming its a wave-guide type with directivity control. Whatever the reason, sibilance isn't an issue, even if the treble is turned up.

[DF96]

Yes. (to post 1028)