polarity inversion on the fly

koslowj

Hello,

I'd be interested in switching the polarity in both channels simultaneously during playback. Quite a number of CDs, and presumably other audio files have their polarity inverted. For some background on this issue, please check

http://www.absolutepolarity.com

That article may be a bit redundant, but makes the problem quite clear.

davidemania

Interesting issue, I would say, and something I never was aware of. It would be easy to encode two versions of a song, one straight and one reversed, and see what happens. It could be also done fragment by fragment, to make the test easier.

What leaves me a little puzzled is that the phase of sound waves (of any wave, indeed) change when you move from the source, and the change varies with frequency. So a wave that "pushes" in one point could "pull" in a different one, but the overall effect of a 180° phase change can not be reproduced just moving. At least not for a general waveform.

ACX

This could be accomplished using a lightweight DSP, for example BruteFIR. Anyone who could experiment with it and give us some feedback?

cmh714

I will try and check it out this week since there is an archlinux package and I dont have to deal with compiling

and I am interested in seeing if there is any sound change, since the OP article was interesting to say the least.

on that note I would say that its interesting when one person says somethings "better" but no one else seems to agree necessarily...or maybe they do, but I havent seen anything that will help me get better sound yet.

dwijtsma

Sorry to say, but the writer of this article doesn't know a lot about physics... Also he insults practically every electrical engineer of being incompetent. Check every single audio device you have. Your CD-player, power- and pre-amplifier etcetera. You'll find a lot of inverting and non inverting amplifiers, because phase shifts of 180° do not matter.
Also audio mixers have the possibility to invert the signal of a single channel/instrument. Recording studios use these buttons.

Now you know that single instruments on a CD might be inverted. Sorry for letting you know this.