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absolute phase - Page 8

post #106 of 109
Originally Posted by gaboo
Look here for difference between longitudinal and transverse waves.

This is how a point source radiates in 2D.

And here for a loudspeaker model.
Very good links!
post #107 of 109
Originally Posted by rudi
Right and interesting but OT related to the basic question. Is phase rotation detectable as a change in sound?
I think where we're stuck, Rudi, is in the distinction between continuous and discontinuous sound sources. Your examples assume that we listen to a sustained note from an instrument, then turn off that sound, then play that sound with reversed phase and see if we can detect a difference. You say that we cannot detect a difference, and if you choose a symmetric waveform and start/stop it at arbitrary points on the waveform, then I would agree that there would be no discernable difference.

Music, though, does not consist of continuous, symmetric waveforms, even if the waveforms themselves can be MODELED as a series of sine functions. Musical information begins at a discrete point in time. It is discontinuous, and in many cases, asymmetric about the x-axis (when viewed on a scope).

Originally Posted by rudi
The answer is simple and related to our daily experience. When we move the head of few cm listening music detection of all sound frequncy shift or change phase , but music perception is not changing, therefore we verify that phase shift have no effect on sound in the way that human ear and brain detect sounds.
Simply incorrect. Yes, if we move our heads at a normal head moving speed then we can detect no frequency shift, but if we move our heads at a significant fraction of the speed of the incoming sound, then there is a doppler shift and we detect a change in pitch.
post #108 of 109
Using CDP (non phase inverting) to Cary SLP 98P (phase inverting) to AES superamp (non inverting) to Triangle spkers, I can definitely hear the difference in absolute phase particularly in the soundstage. I tested by simply reversing the polarity at both speaker terminals. In the out of phase position (in this case + to + at the speaker terminals because my preamp reverses phase) the soundstage is wider and more diffuse. It does not necessarily sound worse, just different (but there is a noticable difference). I prefer the tighter soundstage of the in-phase setup. I'm not sure if, hearing an unfamiliar system and an unfamiliar recoding cold without a reference to compare it to, I would be able to tell you if everything is in or out of phase, but listening to my own system and my own recordings it is easy for me to discern a (comparative) difference when reversing polarities at the speaker terminals.

I'm not sure if I would be able to hear the difference in headphones. My headphone setup is through my Cary 300SEI in my bedroom. I can't check the phase through the HP because I use HD600. The 300sei does not invert phase. I have not experimented with different speaker terminal hookups on the the 300sei. It has a completely different soundstage signature from my livingroom setup anyway.

I used to worry about this stuff, but I don't anymore. I just set it up how I like it (which is in phase).

From what I have read there are also instances where the speaker manufacturers install drivers with reversed phases, etc. This can be a problem when one driver (especially between R and L channels) is set up out of phase with another in the same set of speakers. This can cause actual out of phase-ness (if that's a word). Phase differences between channels is very easy to recognize, I think.
post #109 of 109
I have been exceedingly unable to get good ABX results out of the sonicyouth-stones samples, but I got 10/10 out of a section of Primus's "Hamburger Train" with foo_invert. Samples will be posted on HA.

EDIT: HA discussion.
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