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Is it possible to hear absolute phase?

post #1 of 5
Thread Starter 
Can we hear absolute phase? If my speakers are in phase with each other, and I flip BOTH speaker leads so they are still in phase with each other, but now phase inverted from the original signal, is it humanly possible to hear that?

My CJ preamp phase inverts and the owners manual says that some people can hear this. They suggested trying to flip the speaker leads to decide which way sounds better. I believe I heard a difference and kept the speaker leads flipped (which put the resulting signal back to correct phase of the original).

I bought a pair of Stax headphones and headphone amp, liked the sound, but wanted the tube sound of my preamp. I figured I should phase invert again, but didn't know how. A fellow head-fier suggested reversing the phase of some interconnects and using those to connect the headphone amp to the preamp. I had technical problems and couldn't get it to make any sounds at all this way, plus heard some noisy switches and pots due to the sensitivity of the Stax, so brought the preamp in to get cleaned and checked out.

I told my audio repair guy the problem with hearing the phase inversion, and he says scientifically impossible, even though some audiophiles say they hear it, don't worry about it. He says you can hear it if one channel is out of phase with the other, but if left is in phase w/ right, it doesn't matter if the sound wave starts with a push or a pull. And with headphones especially, he says no way. He said he's worked in many recording studios, and no one cares about it, and they plug all kinds of stuff with whatever is lying around, and there is no thought given to phase, so the end result is that during recording, phase is all out of whack anyway.

I think I hear a difference in the initial attack of the instruments, and my owners manual suggests some people can hear it. What does the science say?
post #2 of 5
I heard a while back that some people can apparently tell, but who knows if that's true. The question here is can you tell, and there's an easy way to find out. Go here and download Java ABC/HR. It is the best ABX program I've come across - very well designed.
Then grab a lossless file and make a copy of it. Invert the phase in one of them using an audio program (this is free). Load them up in an ABX session and if you can tell them apart with p < 0.05, there you have it. Good luck.
post #3 of 5
there is solid physiologic evidence for absolute phase descrimination

but it is also correct that many studios/engineers ignore it during recording/production

diyAudio Forums - Audibility of Absolute Phase - Page 1
post #4 of 5
Thread Starter 
Thanks jcx, that link is very helpful.

I a-b'd a pair of speakers against itself for quite a while, by flipping wires, and I really felt I heard a difference. I just wondered if there was a physiological basis to justify what I heard. After the repair guy said it's not scientifically possible, I wondered if maybe it was one of those audiophile 'only true in my own head' kind of things.

Thanks for the info.
post #5 of 5
I know for sure that you can hear phase changes (simultaneous L+R, not just L or R) in speakers because changing the phase changes at what point in it's cycle the audio waveform will collide with the surrounding walls/ceiling/floor. Since so much of a speakers sound is coupled to room geometry, flipping the phase of a stereo signal can definitely make an impact on the perceived audio quality. (This is most audible in the low frequencies). If I am unsatisfied with a speaker setup, I would first try to correct any imbalance through re-positioning, but if that didn't work will sometimes try flipping the phase. This procedure is almost the rule used when setting up a dedicated subwoofer. In fact many professional subwoofers come with a phase adjustment built in so you can dial up your desired angle of phase: Genelec Inc. - Genelec 7071A

As for detecting absolute phase in headphone listening I'll have to actually try it before I can say anything of my own experience.

Fun reference for the actual wavelengths of sounds:

20,000 Hz = 0.678 inches
20 Hz = 678 inches (56.5 feet)

that is a 1000:1 range!
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