Hi,
reading documents by Nelson Pass I've seen that most of the people like a negative phase for the 2nd harmonic, explaining it with the fact that it will counteract the inertia of the speaker, but... what about the phase of other harmonics? Need to be as close as possible to zero?
Anyone has direct experience on it or literature to link/attach?
Thank you in advance
Roberto
reading documents by Nelson Pass I've seen that most of the people like a negative phase for the 2nd harmonic, explaining it with the fact that it will counteract the inertia of the speaker, but... what about the phase of other harmonics? Need to be as close as possible to zero?
Anyone has direct experience on it or literature to link/attach?
Thank you in advance
Roberto
Hi Roberto,
member @Pinox67 has posted studies and data for 2nd and 3rd harmonics on another forum
https://www.audiosciencereview.com/...ion-of-low-order-nonlinear-distortions.34863/
Here are some other threads
https://www.audiosciencereview.com/...resent-the-actual-nonlinear-distortion.37561/
https://www.audiosciencereview.com/...tortion-on-the-perceived-sound-quality.24633/
member @Pinox67 has posted studies and data for 2nd and 3rd harmonics on another forum
https://www.audiosciencereview.com/...ion-of-low-order-nonlinear-distortions.34863/
Here are some other threads
https://www.audiosciencereview.com/...resent-the-actual-nonlinear-distortion.37561/
https://www.audiosciencereview.com/...tortion-on-the-perceived-sound-quality.24633/
I really envy the lucky ones who does not perceive a certain difference, less things demanding attention.
The man who wrote the notes on audiosciencereview proposed, time ago, an article to be published in Audioreview in Italy.
Some interesting point are discussed there
In every case another interesting article is here
https://worldradiohistory.com/Archi...iFI-Stereo/80s/HiFi-Stereo-Review-1987-01.pdf
I can only confirm what Papa said in H2 article. Effect is easier for me to hear on single wideband driver or multiway with no crossover point between 200 - 5000 Hz. Additionally, Eduardo de Lima in Whysingle-endedtubeamplifiers.pdf found that with dominant H2 amount of acoustic distortion depends on phase of signal.
But as nice as it is, the perceived effect is most probably an illusion.
But as nice as it is, the perceived effect is most probably an illusion.
A totally different phase effect:
1. Consider a push pull output stage, where the 2nd harmonic distortion of the 'push' tube is cancelled by the 2nd harmonic distortion of the 'pull' tube.
That is very well documented, and very well understood.
Right?
2. Now, consider a 2 stage single ended amplifier, where the 2nd harmonic distortion of the output tube is cancelled (at least partially cancelled) by the 2nd harmonic distortion of the input (driver) tube.
That is very well documented, and very well understood.
Right?
Theory and Experiment:
3. Then, consider a single ended output stage's 2nd harmonic distortion, versus a loudspeaker's 2nd harmonic distortion.
Depending on the polarity of the cable's connection between the output stage and the loudspeaker, the 2nd harmonic of the two can either partially cancel the 2nd harmonic distortion , or can add (increase) the 2nd harmonic distortion of the two.
A double blindfold listening test of a very low distortion 100Hz sine wave, using a double pole double throw switch (DPDT switch) to switch the phase, was heard to have a different sound, depending on the switch polarity setting.
For you to try:
4. Wire in a DPDT switch, and try it for yourself, if you have a single ended amplifier with a moderate to medium amount of dominant 2nd harmonic distortion at 100Hz, and a loudspeaker that has a moderate to medium amount of dominant 2nd harmonic distortion at 100Hz.
Listening to Music:
As to doing the same experiment with real music material, (versus the controlled test with a 100Hz sine wave), your listening test results may vary according to the music, amplifier distortion, loudspeaker distortion, and how loud you drive the amplifier and loudspeaker.
You probably will find it much harder to hear any difference between switch settings when it is music, than when it is a very low distortion 100Hz test tone.
1. Consider a push pull output stage, where the 2nd harmonic distortion of the 'push' tube is cancelled by the 2nd harmonic distortion of the 'pull' tube.
That is very well documented, and very well understood.
Right?
2. Now, consider a 2 stage single ended amplifier, where the 2nd harmonic distortion of the output tube is cancelled (at least partially cancelled) by the 2nd harmonic distortion of the input (driver) tube.
That is very well documented, and very well understood.
Right?
Theory and Experiment:
3. Then, consider a single ended output stage's 2nd harmonic distortion, versus a loudspeaker's 2nd harmonic distortion.
Depending on the polarity of the cable's connection between the output stage and the loudspeaker, the 2nd harmonic of the two can either partially cancel the 2nd harmonic distortion , or can add (increase) the 2nd harmonic distortion of the two.
A double blindfold listening test of a very low distortion 100Hz sine wave, using a double pole double throw switch (DPDT switch) to switch the phase, was heard to have a different sound, depending on the switch polarity setting.
For you to try:
4. Wire in a DPDT switch, and try it for yourself, if you have a single ended amplifier with a moderate to medium amount of dominant 2nd harmonic distortion at 100Hz, and a loudspeaker that has a moderate to medium amount of dominant 2nd harmonic distortion at 100Hz.
Listening to Music:
As to doing the same experiment with real music material, (versus the controlled test with a 100Hz sine wave), your listening test results may vary according to the music, amplifier distortion, loudspeaker distortion, and how loud you drive the amplifier and loudspeaker.
You probably will find it much harder to hear any difference between switch settings when it is music, than when it is a very low distortion 100Hz test tone.
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Tried and measure many things and combinations just to satisfy my curiosity. And as previously stated, I really envy the lucky ones who does not perceive a certain type of difference, less things demanding attention. Assuring phase of H2 and H2/H3 ratio I prefer is no walk in the park, totally wasted effort for you to make if no difference to you. 🙂
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So other effects like IMD become predominant over the phase of the harmonics, when more complex music is played through an amp, compared to a simple tone or maybe just a voice and an instrument?
So I guess you use SE amps only. Do you mind if I ask you what do you usually target on standard listening levels in terms of H2 and H3?
As for higher harmonics, is it considered enough to have them one order of magnitude below H2 and H3? Any consideration on their phase?
No, a very low distortion PP output stage such as employed by F4 or Amity are excellent with multiway and H2 from preceding stage. 0.1-0.3% H2 with 20dB or higher H2/H3 @1W 1kHz in general and attempt for monotonically decreasing harmonics. Different speakers works slightly different with different combination. What you prefer will also be slightly different than mine.
I was considering to perform some tests with a (heresy!) class D amp with low distortion and add a triode in front of it to generate harmonics.
Perform listening before and measurements after, trying to avoid as much as possible any bias on the perceived sound.
I will check with fullrange and multiway.
Perform listening before and measurements after, trying to avoid as much as possible any bias on the perceived sound.
I will check with fullrange and multiway.
Be Creative . . .
Listening:
Before the listening tests, be sure to adjust sound levels to be exactly the same. Sometimes a null subtraction method can be set, and allow a check for equal sound levels.
Figure out ways to work double blind listening tests.
Use Switches, Relays, etc.
AA, AB, BA, BB, . . . etc.
Use an assistant to click a computer Enter key for each connection change (assistant not to look at the computer screen).
Listeners only know when the switch settings are changed, but do not know from what connection to what connection.
Use software to randomize the switches and relays settings; nobody knows what combination is connected at any time: but keep record sheets of what is heard by each listener at each switch / relay setting/change (a change can also be BB, or AA (even though that is a 'no change', but perhaps the listener 'hears' a difference anyway).
Then compare the listeners sheets, versus the computer software connection settings.
Measurements:
No double blind measurements are needed. But if you mistrust the measurements, have them repeated 3 times.
Anything that does not match all 3 times, you need to research the cause, and fix it. Then repeat the measurements 3 more times.
Have fun, and good luck.
Listening:
Before the listening tests, be sure to adjust sound levels to be exactly the same. Sometimes a null subtraction method can be set, and allow a check for equal sound levels.
Figure out ways to work double blind listening tests.
Use Switches, Relays, etc.
AA, AB, BA, BB, . . . etc.
Use an assistant to click a computer Enter key for each connection change (assistant not to look at the computer screen).
Listeners only know when the switch settings are changed, but do not know from what connection to what connection.
Use software to randomize the switches and relays settings; nobody knows what combination is connected at any time: but keep record sheets of what is heard by each listener at each switch / relay setting/change (a change can also be BB, or AA (even though that is a 'no change', but perhaps the listener 'hears' a difference anyway).
Then compare the listeners sheets, versus the computer software connection settings.
Measurements:
No double blind measurements are needed. But if you mistrust the measurements, have them repeated 3 times.
Anything that does not match all 3 times, you need to research the cause, and fix it. Then repeat the measurements 3 more times.
Have fun, and good luck.
Whatever the relative phases of the harmonic distortions are, as they come out of the amplifier, there is another factor . . .
The loudspeaker's relative phases versus frequency of the driver(s), and crossover(s) if any, are not always the same either.
Complexity is not always as simple as you think it is.
The loudspeaker's relative phases versus frequency of the driver(s), and crossover(s) if any, are not always the same either.
Complexity is not always as simple as you think it is.
@6A3sUMMER Thanks. Indeed a fake switch was already considered in the equation. A fullrange and a multiway pair of speakers as well.
Just for curiosity, what has been your impressions when you did these tests?
Just for curiosity, what has been your impressions when you did these tests?
The test we did was the following:
Sine Wave:
100Hz very low distortion sine wave generator, distortion <70dBc.
2 stage 2A3 moderate distortion, dominant 2nd harmonic, single ended amplifier.
Spica TC- 50 loudspeaker
Double Throw, Double Pole 250V 15A switch, inline with the speaker cable. And most importantly, no markings on the switch.
The sound (Timber) of the 100Hz bass tone Was different from one phase switch setting, to the other phase switch setting.
99% Double Blind Test, but not exactly, you can see the 1% that is not true double blind.
That is because it was always A, B, A, B. It was never AA and never BB.
Music:
With no switch, and no instant A, B testing
I have also connected the speaker cable to the correct phase and listened, and then reconnected to the oppposite phase and listened.
But, that is not double blind, and certainly not a quick-switched A, B test.
As to what the sound difference was, I say Difference? I do not hear any difference.
For Newbies:
If you try this music test, be sure to only switch the speaker cable at one end; Speaker Or Amplifier, do not switch the cable connections at both ends.
And, for the protection of some amplifiers, first turn the volume down, turn the amp off, change the speaker cable setting, turn the amplifier on, and turn the volume to Exactly the same setting.
A completely different phase effect:
Set up for Stereo, and connect one speaker in-phase, and the other speaker out-of-phase.
Most have made this mistake at least once. Result:
No Bass
No music in the center
All of the music is outside of the spacing of the loudspeakers (as wide as, or wider than the speaker to speaker distance).
Fun with Audio!
Sine Wave:
100Hz very low distortion sine wave generator, distortion <70dBc.
2 stage 2A3 moderate distortion, dominant 2nd harmonic, single ended amplifier.
Spica TC- 50 loudspeaker
Double Throw, Double Pole 250V 15A switch, inline with the speaker cable. And most importantly, no markings on the switch.
The sound (Timber) of the 100Hz bass tone Was different from one phase switch setting, to the other phase switch setting.
99% Double Blind Test, but not exactly, you can see the 1% that is not true double blind.
That is because it was always A, B, A, B. It was never AA and never BB.
Music:
With no switch, and no instant A, B testing
I have also connected the speaker cable to the correct phase and listened, and then reconnected to the oppposite phase and listened.
But, that is not double blind, and certainly not a quick-switched A, B test.
As to what the sound difference was, I say Difference? I do not hear any difference.
For Newbies:
If you try this music test, be sure to only switch the speaker cable at one end; Speaker Or Amplifier, do not switch the cable connections at both ends.
And, for the protection of some amplifiers, first turn the volume down, turn the amp off, change the speaker cable setting, turn the amplifier on, and turn the volume to Exactly the same setting.
A completely different phase effect:
Set up for Stereo, and connect one speaker in-phase, and the other speaker out-of-phase.
Most have made this mistake at least once. Result:
No Bass
No music in the center
All of the music is outside of the spacing of the loudspeakers (as wide as, or wider than the speaker to speaker distance).
Fun with Audio!
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