Ian MacGregor
Well-known member
Yo,
I've been doing more and more engineering these days and have been running into weird phase issues more often that have me thinking. For example, this has nothing to do with "polarity"; I fully know how to work with a multiple mic setup (like a drum kit) and get everything working with proper polarity.
What I'm experiencing is more subtle phase shifts that still cause issues with low end in multiple mic situations. For example, a studio I did a mix at had a Calrec stereo comp (sort of Neve-ish) that I used for parallel drum compression (mixing analog). When bringing the compressed channels up on faders, the low end would start to get phasy. Not "out of polarity" though. I could flip the polarity and it wouldn't get better, just different.
I've experienced this same phenomenon occasionally with similar arrangements. Kick in & kick out mics, bass DI & bass amp mic...
My EE instinct thinks that somehow there is a less than 180 degree phase shift going on and it's due to the inevitable low roll off frequency through the processing path. For example, if a transformer has a bit too high LF rolloff point (say 40Hz), there will be 45 degrees shift @ 40. Right?
Am I headed in the right direction? Am I hearing bad caps and their respective low freq rollof's moving higher? I just acquired a AP system one with all the bells and whistles and I'm going to start putting some gear under the microscope to see what's going on.
ian
I've been doing more and more engineering these days and have been running into weird phase issues more often that have me thinking. For example, this has nothing to do with "polarity"; I fully know how to work with a multiple mic setup (like a drum kit) and get everything working with proper polarity.
What I'm experiencing is more subtle phase shifts that still cause issues with low end in multiple mic situations. For example, a studio I did a mix at had a Calrec stereo comp (sort of Neve-ish) that I used for parallel drum compression (mixing analog). When bringing the compressed channels up on faders, the low end would start to get phasy. Not "out of polarity" though. I could flip the polarity and it wouldn't get better, just different.
I've experienced this same phenomenon occasionally with similar arrangements. Kick in & kick out mics, bass DI & bass amp mic...
My EE instinct thinks that somehow there is a less than 180 degree phase shift going on and it's due to the inevitable low roll off frequency through the processing path. For example, if a transformer has a bit too high LF rolloff point (say 40Hz), there will be 45 degrees shift @ 40. Right?
Am I headed in the right direction? Am I hearing bad caps and their respective low freq rollof's moving higher? I just acquired a AP system one with all the bells and whistles and I'm going to start putting some gear under the microscope to see what's going on.
ian