Topic: what causes this waveform? one side "higher" on EACH channel

[jj69]

If you have clipped your microphones that will also cause asymmetrical waveforms.  That cannot be corrected by a phase rotator.

The recording does not seem to be clipped. 

[jj69]

Here is a two minute sample.  This is completely unedited, not even normalized.  Recorded at 48/24 with AT933 cardioids with a Church 9V battery box into a Sony PCM-M10. 

http://depositfiles.com/files/z4z2nxsxn

[jj69]

You mentioned something I should have pointed out.  The sound engineer was indeed a fill-in guy.  In the past, the sound has been excellent, and very, very loud, but comfortable if you're wearing earplugs. 

At this show, the sound was even louder than normal, and although I was wearing my foam earplugs, I kept subconsciously reaching up to be sure they were still in properly because it was so loud.  The sound in the room was not necessarly bad, but not as good as when the usual engineer is working the board. 

The vari-phase rotator in RX2 corrects the shape/appearance of the wave form, but I could not detect any audible change in the sound. 

Do you hear specifific frequencies that need attention? 

[jj69]

Thanks for the feedback and input. 

I'm not sure the recording is really worth investing a whole lot of time in.  Ironically, I was using no bass rolloff at all at this show. 

[Gutbucket]

I could not detect any audible change in the sound.

Phase rotators are designed that way; typically they are allpass filters which don't change frequency response.

They are also used in surround matrix encoding.  Surround channel info is phase rotated before being summed with the main L/R channels.  It's that phase difference which is used to 're-extract' the surround signals when decoded. You might notice some intersting effects if you play back your phase-rotated file through a home theater reciever and switch the Dolby/DTS/Logic7/Circle-Surround matrix decoder in/out (or you may not, since your rotated file isn't being summed with a non-rotated reference signal)

[jj69]

Unfortunatey, I just made another recording like this.  It's not as bad as the sample I posted, but the negative side of the wave is slightly larger than the positive side through the duration of the 75 minute recording. 

Now I'm starting to wonder if there's something wrong with my mics.  Can loud PA systems cause this?  These are all hard rock shows at high volume. 

Should I be using the "vari phase rotator" function to "correct" this, or is there a better tool to use on these recordings? 

This really has me concerned now.  I'm worried if a loud show damaged my AT933's (or the card capsules)? 

[willndmb]

I'd also add a clarification...Page was the first responder when the OP asked this a few months ago and he pointed out that this phenomenon is seen on waveforms with BRASS in the music, not bass...which it appears that the OP may have originally thought he meant.

bRass, yes
I just had a typo above

The waveform I posted in the op was a recording with a trumpet and trombone
It sounds great and after reading pages post I figured that was the answer FOR ME and THIS recording

[jj69]

Thanks for all the input on this.  I just stumbled onto this thread from a couple of weeks back, and it has all the answers:

http://taperssection.com/index.php?topic=162851.0

I was using the exact same mics (AT933) and my result is exactly the same.  The volume was too much for the mics, and it's soft clipping. 

I've gotta remember to switch to my AT943's with resistor mod for the louder shows. 

[Stagger]

While it is a different case from what turned out to have happened here, I can get that result sometimes with the c34. In this case it is because of the way that the S42 forms the patterns from the 4 diaphragms (2 for each channel). As you move between adding and subtracting different amounts of output from each cap to simulate directionality, you can wind up offsetting the track. It only happens in certain cases and it took me a long while to figure out how it was happening but it can.

[JimmieC]

The other night, I had this issue with the soundboard channels.  The microphones channels are fine.  Was using soundboard tape out (RCA) to DR-680 (XLR) with kind of an old RCA to XLR cable (over 10 years old), may be should get a new one made up.  Using Audacity to process the files and DC offset doesn't help.  Makes it hard to apply a little hard limiter and normalize.  No brass members in the band.