Studies have shown that the hearing mechanism we are equipted with fires at positive and negative points at low frequencies without regard to absolute phase.
I've read this from various sources and am inclined to believe this. Phase relationships are far more important. I have reversed phase electronically via a DAC and also can not hear a difference. Absolute phase is only important in the recording and mixing process. For reproduction it does not matter in my view.
Djk,
I will agree that a designer must use test equipment and audition the results before a good sounding product is achieved. I have heard many examples from the listen only crowd and the measure only crowd. That is enough proof. There are some measurements that can be made that we are sure will sound good or bad depending. Just not everything yet.
-Chris (before cup of coffee
)
I've read this from various sources and am inclined to believe this. Phase relationships are far more important. I have reversed phase electronically via a DAC and also can not hear a difference. Absolute phase is only important in the recording and mixing process. For reproduction it does not matter in my view.
Djk,
I will agree that a designer must use test equipment and audition the results before a good sounding product is achieved. I have heard many examples from the listen only crowd and the measure only crowd. That is enough proof. There are some measurements that can be made that we are sure will sound good or bad depending. Just not everything yet.
-Chris (before cup of coffee
)I doubt that this is also the case for mid- and higher- frequencies.
Phase relationships are indeed important. The temporal relationship between fundamental and the various overtones (also between overtones) is an acoustical clue for the size of a sound source.
Regards
Charles
P.S. : According to the new "Colloms" (page 438): ".... Sensitivity to polarity increases with SPL, suggesting that a causal mechanism is an asymmetric non-linearity in the ear in respect of positive and negative pressures. This is of course not a fault, but an innate aural mechanism for which we are fully adapted. In consequency, signal polarity matters ...."
Hi Charles,
I pointed out that this was true for low frequencies. The phase relationship is important as I stated.
Therefore, if you globally reverse phase but maintain relationships, there should be no audible difference. I sure can't hear one. I haven't had anyone able to point out absolute phase correctly with a statistical certainly beyond guessing.
Not something someone who believes wants to hear. I am very open minded as I know humans can sense many things. This does not appear to be one of them.
-Chris
I pointed out that this was true for low frequencies. The phase relationship is important as I stated.
Therefore, if you globally reverse phase but maintain relationships, there should be no audible difference. I sure can't hear one. I haven't had anyone able to point out absolute phase correctly with a statistical certainly beyond guessing.
Not something someone who believes wants to hear. I am very open minded as I know humans can sense many things. This does not appear to be one of them.
-Chris
Chris, what phase_accurate said seems to be the conclusion of the experiment I have participated in as well, but it requires rather nasty high levels of SPL. The thing is, atthese levels, it gets progressivley difficult to avoid nonlinear mechanisms in the transdicer making them.
Driving a transducer that has even order phenomena (as most speakers do) indeed produces different time/amplitude relatinships of harmonics for very asymetrical signals (percussive). Simply, the respective halves of the signal do not get distorted equally for both + and - polarity (it strikes me again that 'phase' is really a msinomer here).
BTW we went to great pains trying to find headphones capable of really high SPL so that for normal levels we would not get into these kinds of problems. I have not been present for some of the experiments, but that friend of mine told me things get interesting with small compression drivers. They actually devised a rather clever experiment that used an isobaric pair of speakers in an enclosure and tried them in all the 4 possible orientations. The second order distortion canceling arrangements got the least detectability, but it was still there, which leads one to conclude that we are getting to hear the asymetry of adiabatic compression of the air in the enclosure
Driving a transducer that has even order phenomena (as most speakers do) indeed produces different time/amplitude relatinships of harmonics for very asymetrical signals (percussive). Simply, the respective halves of the signal do not get distorted equally for both + and - polarity (it strikes me again that 'phase' is really a msinomer here).
BTW we went to great pains trying to find headphones capable of really high SPL so that for normal levels we would not get into these kinds of problems. I have not been present for some of the experiments, but that friend of mine told me things get interesting with small compression drivers. They actually devised a rather clever experiment that used an isobaric pair of speakers in an enclosure and tried them in all the 4 possible orientations. The second order distortion canceling arrangements got the least detectability, but it was still there, which leads one to conclude that we are getting to hear the asymetry of adiabatic compression of the air in the enclosure
Phase_acurate
---Phase relationships are indeed important.---
As the phase of each frequency at ears is distance-dependant, it is not the phase per se which is important but group delays which express phase relationships. Basically, a change in group delay is a change of the apparent distance from the source and this may be audibly detectable (just as you said in thread "width of the crossover region" about the Linkwitz-Riley crossover).
---Phase relationships are indeed important.---
As the phase of each frequency at ears is distance-dependant, it is not the phase per se which is important but group delays which express phase relationships. Basically, a change in group delay is a change of the apparent distance from the source and this may be audibly detectable (just as you said in thread "width of the crossover region" about the Linkwitz-Riley crossover).
Hi ilimzn,
I'll believe that. Anything I've been a part of has been at normal listening levels to avoid any other artifacts. This would throw an uncontrolled variable into the experiment.
I'm keeping an open mind. I just have not experienced a difference yet.
Now the other wrinkle is this. The absolute phase may not be correctly transferred from cut to cut, recording to recording. Short of looking at the leading edge of percussive sounds for each and evey cut, how is the average listener to sort this out?
-Chris
I'll believe that. Anything I've been a part of has been at normal listening levels to avoid any other artifacts. This would throw an uncontrolled variable into the experiment.
I'm keeping an open mind. I just have not experienced a difference yet.
Now the other wrinkle is this. The absolute phase may not be correctly transferred from cut to cut, recording to recording. Short of looking at the leading edge of percussive sounds for each and evey cut, how is the average listener to sort this out?
-Chris
Absolute phase of a system to the speakers . . .
Let me give you one elementary school boy Q. The music signal is a wave (push and pull) of the sound along the time axis. The difference between non-inversed or inversed signal to the speakers is whether the wave begins from the push or pull, or opposite. Is this difference at the very beginning of the music signal giving us a real sound difference to our ears . . . ?
Let me give you one elementary school boy Q. The music signal is a wave (push and pull) of the sound along the time axis. The difference between non-inversed or inversed signal to the speakers is whether the wave begins from the push or pull, or opposite. Is this difference at the very beginning of the music signal giving us a real sound difference to our ears . . . ?
I've looked at music signals captured by an editor such as Goldwave. My observation is that they appear to be symetrical. Not only is the music symetrical but even impulse noise such as ticks and pops from LP transfers are symetrical as well. There may be some small non-symetricalites but they seem to be very rare and rather dificult to find even when you go looking.
It seems reasonable that one could deliberately create a non-symetrical signal, But in the normal course of events it happens so rare to me that it's not worth being concerned about. Setting aside the point that is often made regarding the indeterminate number of inversions in source material that may ocurr between microphone and disk, it your audio reproduction chain is determined to be net-inverting, the simple expediant swapping speaker wires between red and black bindind posts should be a zero-cost fix.
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