Phil Leigh Wrote: > I've two observations to contribute: > > 1) I remember a demo by Linn in the mid 80's where they reversed the > polarity of the speaker cables to demonstrate the effect on perception > of surface noise from vinyl. I had to agree it made a noticeable > difference to how bad the pops and clicks sounded. It didn't change the > rest of the music for me. The offered explanation was that the most > annoying "clicks" were caused by wall damage that was physically > predominantly in one direction with regard to the movement of the > stylus.So, the initial transient (which is pretty much all you hear) is > the stylus going in one particular vector and and thus the speaker cone > moving either out or in depending on absolute phase of the post-stylus > electrical chain (the transient is asymmetrical with regard to 0V and > so the "recoil" movement of the cone coming back through zero to create > a whole-period waveform is NOT the same magnitude as the initial rising > wave. This is hard to describe in words - imagine a sine wave where the > bit above the line is bigger than the bit below it. If you've ever > edited clicks out of a vinyl transfer on a computer you'll know what I > mean.
Interesting. I've come across several claims on the web of audibility of absolute phase reversal in specific types of (non-musical) test signals. This for example is relevant: http://tinyurl.com/ok5wp The only statistically significant results in which subjects could hear the polarity inversion were obtained using headphones, and only for some specific test signal they call "impulse" - which presumably is some asymmetric square wave pulse or something similar. > > 2) If there is significant DC across the speaker coils, the speaker > cone will not be sitting in the 0v stationary position as its designer > intended. This could introduce a "constant" asymmetry in response which > would be absolute-phase sensitive - especially in closed box or port > loaded speakers. This would be audible with real music. > I'm not sure what significant would be in this context because as has > been stated its not clear what the limits of human perception are. > However, it might be worth checking for DC, as this would provide a > rational explanation for absolute phase differences. > > Could this be simulated with a manufactured WAV file? I think this could be simulated easily with a WAV file editor - wouldn't that just be adding a constant level to every sample? You would want to first rescale the levels with an overall multiplier to avoid clipping. However just because there's a DC offset, there isn't necessarily any significant asymmetry in the speaker response. To first approximation the speaker cone is still a harmonic oscillator, just with a displaced zero point. In fact if the DC offset did introduce significant non-linearities it would also mean significant distortion in music played at the corresponding levels _without_ the offset. Therefore a good speaker is probably rather insensitive to reasonable DC offsets. -- opaqueice ------------------------------------------------------------------------ opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=22118 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
