indra1,
Perhaps you are talking about the "Wood Effect", a book all about the importance of Absolute Phase.
If it is important, then prove that effect first (for yourself, and for everyone else too).
Although that may or may not be important, I am talking about something else.
The "Wood Effect" is an extremely long and complex problem, not just what is in the book.
Tat is a completely different opportunity for another Thread on diyAudio.
I am talking about a completely different effect than the "Wood Effect", and different than Absolute Phase effect.
I am talking about the partial cancellation of the 2nd harmonic, or the adding effect of two serial device's 2nd harmonic.
Most modern stereo systems and mono systems do not have an input signal phase inversion switch.
Lots of old integrated amplifiers and old preamps had that feature.
It is not simple to change the phase at the input of an amplifier; so that when you change the phase at the output connection of the amplifier, the "Absolute Phase" is preserved.
You would need a balanced input, and swap those leads.
Switching the input of an unbalanced system results in shorting the signal out . . . no sound out, nothing to compare.
"You should make things as simple as possible, but no simpler" Albert Einstein
Reduce the variability of experiments. Reduce the number of things that have to be compensated for.
When doing the test for 100 Hz and speaker reversal switch, use only 1 channel.
When doing the phase reversal music listening test, use only one channel (left only or right only).
Your ear, and your brain will process this simpler setup more quickly and accurately.
Just my opinions.
Have fun, and report back to us please.
Perhaps you are talking about the "Wood Effect", a book all about the importance of Absolute Phase.
If it is important, then prove that effect first (for yourself, and for everyone else too).
Although that may or may not be important, I am talking about something else.
The "Wood Effect" is an extremely long and complex problem, not just what is in the book.
Tat is a completely different opportunity for another Thread on diyAudio.
I am talking about a completely different effect than the "Wood Effect", and different than Absolute Phase effect.
I am talking about the partial cancellation of the 2nd harmonic, or the adding effect of two serial device's 2nd harmonic.
Most modern stereo systems and mono systems do not have an input signal phase inversion switch.
Lots of old integrated amplifiers and old preamps had that feature.
It is not simple to change the phase at the input of an amplifier; so that when you change the phase at the output connection of the amplifier, the "Absolute Phase" is preserved.
You would need a balanced input, and swap those leads.
Switching the input of an unbalanced system results in shorting the signal out . . . no sound out, nothing to compare.
"You should make things as simple as possible, but no simpler" Albert Einstein
Reduce the variability of experiments. Reduce the number of things that have to be compensated for.
When doing the test for 100 Hz and speaker reversal switch, use only 1 channel.
When doing the phase reversal music listening test, use only one channel (left only or right only).
Your ear, and your brain will process this simpler setup more quickly and accurately.
Just my opinions.
Have fun, and report back to us please.
Lazy is my middle name. I'd use foobar polarity plugin to reverse absolute phase. Some piece I can hear effect of absolute phase reversal, some other made no difference. It is just that switching polarity of speaker without switching source polarity introduces another and possibly unwanted new variable into the test. I check for my own needs and result agrees with what Nelson Pass shared on his H2 article. If you are curious you can check for yourself. Take your time, relax, listen for a few days. If phase of H2 makes no difference for you then terrific, otherwise more work ahead.
indra1,
1. You are talking about the "Wood Effect"
2. I am talking about the serial cancellation of the 2nd harmonic distortion, or the serial addition of the 2nd harmonic distortion.
That is according to the relative phase connection between the amplifier output and the loudspeaker input.
There is no way to do a listening test for # 1. and # 2. in the same test.
The testing has to be done in two separate test setups.
1. You are talking about the "Wood Effect"
2. I am talking about the serial cancellation of the 2nd harmonic distortion, or the serial addition of the 2nd harmonic distortion.
That is according to the relative phase connection between the amplifier output and the loudspeaker input.
There is no way to do a listening test for # 1. and # 2. in the same test.
The testing has to be done in two separate test setups.
About #2, when only the speaker cable polarity is reversed then polarity of both amplifier distortion and absolute signal phase are reversed. 2 variable changed simultaneously. Fine for a low distortion sine test but could mislead in case of listening to music material.
indra1,
For a test that is midway between these tests of a pure 100Hz test tone, versus testing using complex multi instrument music, try the following:
Absolute phase of a trombone.
If you often look at music waveforms on an oscilloscope, you will see many trombone recordings that have a particular wave shape.
Consider the trombone, and the player's lips opening and closing, the resultant compression and rarefaction of the air; and the length of the tubing as it resonates or does not resonate to some of the various frequencies of the fundamental and the first few harmonics.
You can look at the waveform on the oscilloscope, and easily see if the electrical waveform is in-phase or out-of-phase versus the actual compression and rarefaction phase of the air from the trombone.
Now that I laid out that 'groundwork' principle, try reversing the phase of the loudspeaker cable at only one end, but do not change any other phase setting.
Listen for any sound difference of absolute phase versus inverted phase settings.
Enjoy doing all kinds of listening tests. It may be worth the effort of setting them up.
For a test that is midway between these tests of a pure 100Hz test tone, versus testing using complex multi instrument music, try the following:
Absolute phase of a trombone.
If you often look at music waveforms on an oscilloscope, you will see many trombone recordings that have a particular wave shape.
Consider the trombone, and the player's lips opening and closing, the resultant compression and rarefaction of the air; and the length of the tubing as it resonates or does not resonate to some of the various frequencies of the fundamental and the first few harmonics.
You can look at the waveform on the oscilloscope, and easily see if the electrical waveform is in-phase or out-of-phase versus the actual compression and rarefaction phase of the air from the trombone.
Now that I laid out that 'groundwork' principle, try reversing the phase of the loudspeaker cable at only one end, but do not change any other phase setting.
Listen for any sound difference of absolute phase versus inverted phase settings.
Enjoy doing all kinds of listening tests. It may be worth the effort of setting them up.
Any amplifier that has so much distortion that it changes the essence of the wave shape of a typical trombone recording, needs to be . . .
Either fixed,
Or thrown into the garbage.
The characteristic wave shape of a trombone is very unmistakeable, and is very unique.
Please look at a typical trombone recording on an oscilloscope, and look for any visible difference when using:
Your LM1875
Any decent vacuum tube amplifier.
Just my opinions
"Perfection is the enemy of good" Frank Reagan
Either fixed,
Or thrown into the garbage.
The characteristic wave shape of a trombone is very unmistakeable, and is very unique.
Please look at a typical trombone recording on an oscilloscope, and look for any visible difference when using:
Your LM1875
Any decent vacuum tube amplifier.
Just my opinions
"Perfection is the enemy of good" Frank Reagan
Agreed for trombones. Use of low distortion amp is my attempt to have spatial cues least affected by the amp. Every pinna is a bit different, even the one on my left ear and my right. What my ears processed will be music with comb filtered specific to my own pinnae transform embedded in it, and will be slightly different than somebody else's.