Measurements & Sound Quality

[bluesman]

2 hours ago, Ralf11 said:

2 examples of euphonic distortions:

1. slight fall in SPL vs. freq. sounds better to most listeners based on tests by JBL, et al.
2. even order distortion in amp stages (tho it is not clear to me that this has been rigorously tested, nor that it sounds better than no distortion at all)

1. Could you please direct us to the source of that information?  Everything I've ever read says that minor differences in SPL when comparing playbacks favor the louder, even if it's only a fraction of a db.

 

2. Harmonics, which are generated by every acoustic musical instrument) are multiples of the fundamental frequency (f).  The first harmonic is 1f (which is the same note as is being played), the second is 2f (one octave above the fundamental), the 3rd is 3f (which is pitched above the second by a musical fifth), etc.  Each successive harmonic is lower in energy than the ones below it, assuming no external "interference" from the source.  That interference, a combination of resonance and attenuation that alters the balance of natural harmonics generated by an instrument, gives each one its unique sound. 

 

Even order harmonic distortion means generation of even numbered harmonics, i.e. 2nd, 4th, 6th etc).  Odd order harmonics become more and more dissonant with the fundamental note and the lower harmonic structure as the order ascends.  The first harmonic and the lowest even order harmonics reinforce the fundamental notes being played, i.e. the actual note sounds a bit louder because it's being reinforced by quieter tones at exact octave intervals above it.  This gives the reproduced sound a slight low end boost similar in effect to the low end of the switchable "loudness contour" found in the front end of almost every audio amplification device in the 20th century. Its purpose was to compensate for the increased natural nonlinearity of human hearing at lower SPLs, and it made music sound "better" to users who expected a more dramatic SQ than is found in live music. The "loudness" or "contour" switch has been replaced by DSP, which lets users add the same kind of EQ in digital systems.

 

Does this kind of boost actually sound better than none? That's purely subjective, but far more people prefer artificially inflated low ends than naturally lean ones in virtually every listening "test" ever done - and a casual survey of DSP settings wherever I go shows that most people do boost lows and highs.  This tends to reinforce the fact that even order harmonic boost (a polite term for distortion, since it's not in the source material) is thought to sound better by most people.

 

Playback at live listening levels renders such boost unnecessary. Whether listening at SPLs far short of that is improved by such boost is subjective.  But pianissimo passages heard live are also affected by our nonlinear hearing, so boosting quiet passages in playback also gives them an unnatural quality compared to live performance. Boost not for me, but it's apparently preferred by the majority of listeners - and this is why they also prefer even order harmonic distortion (which, functionally, is addition) to none at all.

[bluesman]

3 hours ago, Ralf11 said:

Not sure what your point is re even ordered distortion.  However, that effect should not be confused with the Fletcher–Munson curves or their follow-on revisions.

Let's try again - you don't seem to understand what I'm telling you.  Your question, to which I'm responding, is why "...it is not clear to me that this... sounds better than no distortion at all". First of all, I don't think it does.  But most people apparently do.  It was you who called this "euphonic distortion".  So either you also think it improves SQ (the most common definition of euphonic is "pleasing to the ear") or you're saying that you understand that others think it improves SQ even though you do not.  You asked why it is considered euphonic.

 

Even order distortion means additional energy is being added to the recorded musical waveform at frequencies corresponding to the even harmonics of each and every fundamental tone in that waveform.  Because the even order harmonics reinforce the fundamental tones in the recorded spectrum, and because the energy in the lowest harmonics is greater than that in higher order harmonics, this harmonic addition actually does provide some reinforcement of the lows in the same way that equalizing to the F-M curves does. The lowest frequencies in the reproduced spectrum are perceived as being louder because they are. As far as the ear is concerned, this is a "correction" similar to the use of F-M equalization, and it's considered "better" by those who boost their low end with EQ / DSP. Why else would they do this?

 

So my suggested answer to your question of why some think that even order harmonic distortion is "euphonic" (your term) is that this adds weight to the fundamentals in a manner similar to F-M EQ. No, it's not the same response curve, and that's irrelevant. It has a similar sonic effect that supporters call "warm". Personally, I apply no EQ of any kind (other than the RIAA curve needed to play my vinyl). I'm simply offering a logical and well supported theory as to why many people think that even order harmonic distortion sounds better than none.  There's no question that it sounds better than an equal amount of odd order distortion unless that distortion is confined to 1st order energy (which does not happen).

[bluesman]

56 minutes ago, mansr said:

"what in our living room is lacking that a live concert has?"

Musicians.

Exactly!

 

 

[bluesman]

1 hour ago, NOMBEDES said:

Put 10 audiophiles in a room and you may get 7 opinions

I would have guessed 11.......

 

[bluesman]

6 hours ago, Kal Rubinson said:

Stereo is a compromise.

All reproduced music is a compromise - I've never heard a playback that was truly indistinguishable from a live performance.  I've always believed that this is because intermodulation among all notes from all instruments being played is captured in every recording as part of the source waveform.  During playback, the original "natural" IM is created again, so there's twice as much being played back as was generated in the original performance.  And it's now intermodulating anew with the source signal to generate yet more audible energy that wasn't present in the performance.  I strongly suspect that this is what throws a sonic "veil" over all reproduced music and what keeps it from sounding truly live.

 

If you record a simple C major triad played on a perfectly tuned piano with the pedals up to damp the other strings, a spectrum analysis of playback will show a lot of energy at frequencies other than 262, 330, and 392 Hz (middle C plus E and G above it). Add the sums and differences of each combination of those 3 (62, 68, 130, 592, 624, and 722) to their own natural harmonics, and you already have a rich sonic stew in which many of the "ingredients" are not in the recipe and were never added by the chef. Any IM distortion added by the devices through which the signal passes on its way from source to sound is miniscule by comparison and, at least to me, immaterial because it's truly inaudible.

 

Then throw in phasing.  All of the harmonics and intermodulation products from a single instrument are produced with phase relationships determined almost entirely by the instrument and its player.  But the same C major triad created by almost simultaneous striking of 3 sets of piano strings by 3 hammers then passes through devices that add frequency-dependent phase shifts before throwing it back out at you as separate notes from multiple drivers, none of which has the radiation pattern of a piano.  It's not the same triad any more, and we haven't even started to throw in the environmental factors.

 

So I certainly agree that stereo is a compromise - but the entire process of recording and playing back music is a compromise in which the basic limitations seem to have no current solution.  The fact that so many systems are so good is a minor miracle

[bluesman]

44 minutes ago, esldude said:

Yep that will work.  I've done this using 5 musicians close miked in a damped environment.  Then play back over 5 speakers.  It can have a sound that is very real.  It sounds real in your room, not so much real like where it was recorded. 

Isolating the instruments greatly reduces intermodulation between & among them, and a damped environment further reduces extraneous input from resonance etc. Playing each individual instrument, closely miked for recording to minimize bleeding, through its own speaker is the best way I know of to prevent intermodulation from contaminating the recording. It's closer to having the individual instruments in the playback setting.  That's why it sounds more like real instruments, but in the playback environment rather than the recording setting.

[bluesman]

3 hours ago, Kal Rubinson said:

Of course but some forms are more compromised than others.

Absolutely - and happiness is the ability to craft our compromises so that the pluses make us forget about the minuses!