Topic: Phase inversion, or what?

[vwmule]

I've been meaning to pose this question for a month or so. A guy who downloaded my New Year's recording of Derek Trucks Band has raised questions about phase inversion.

I'd like to get some thoughts and have attached the waveform.

He writes: "As you can see the unaltered left and right waveforms look like mirror images of each other. This means: there is a strong center (good), and that the phase is inverted between them. I have a hunch the left channel has correct absolute phase, but there is no way to know that for sure."

From top to bottom, the waves are:

1. unaltered, Left

2. unaltered, Right

3. unaltered, Left

4. inverted, Right

[cleantone]

Yeah. Definitly have a polarity issue in the chain. I'm not sure of a foolproof way to tell which is right, unless you narrow down where it is being flipped (mic, cable, pre, recorder). The second one looks proper. If you want to take the new stereo file and open some plugin that allows you to flip polarity, try toggling abck and forth. The difference is very subtle. Hard to hear it, or to know if it is your brain making a subtle change when you toggle. I have found that while it is subtle there is surely a difference when you flip polarity on a track. A sound should start with a positive (upward) inflection as far as I know. It can be hard to figure out where it "starts" on a waveform though. It might be that the side (-/+) that extends the farthest in a series of cycles is + but I cannot claim that to be true. Either way you seem to have an issue and whne he flipped one of the channels he did the right thing to fix it. At a glance it "looks" like the proper channel was flipped. Now you need to find out where it is happening.