Absolute Polarity—A Recording Frame of Reference (2/5)
I have rarely seen a recording where the process resulted in a recording which actually had absolute phase—whether it matters is another thing. Take a single mic recording, about as simple as a recording system gets. A one-man-band sings and plays into the microphone, that mic-level signal is then sent via a mic cable to a mic amplifier (mic preamp) that boost the signal to line-level, the mic preamp sends the signal through an interconnecting patch cable to the line-level mixing box, which does no mixing in this case but does afford signal level control before it is sent through another interconnecting patch cable to the recording device: direct-to-disc, magnetic wire or tape. Add digital capture and you add an additional layer of analog to digital conversion and then to the storage medium. This simple system is how some recordings are made today, and when I say some I mean way less then one percent, the vast majority are complex and multi-mic with layers of manipulation and production.
So what does it mean to have an absolute polarity recording, within the above system outline, of Eagle-Woman playing the Navajo log drum? It would mean that the recording in your hand will cause positive voltage correlative to the original acoustic events compression of air particles (and negative voltage in response to the rarefaction of air particles). It means that the recording engineer knows that it is, and that the recording reproduction company also knows that it is, and that the recording player, the DJ, knows that it is. Sounds easy enough, but it is not easy, and it might not really matter—the majority of recording and sound engineers that I know or have read don’t really care about absolute polarity, and not because they haven’t considered it.
As hi-fi playback freaks we might look at the recording process and their boxes and see a phase switch and surmise that this is for making sure absolute phase is preserved, it is not. Those phase switches are there to assist the engineers in getting the sound that they and those in the process want, they have virtually nothing to do with absolute phase. Here are some things we in hi-fi do not consider in our recordings and the process:
There are mics that output negative voltage when a compression signal is presented—inverting or flipping phase.
There are microphone preamps and line-level boxes that output negative voltage when positive voltage is present at the input—again inverting phase. Patch cables sometimes intentionally flip phase.
There are as many ways to mic a drum as there are recording engineers.
Take a snare drum for example, keeping it simple, one way to get a good blend of top and bottom textures from the snare is to mic both sides, and when messing around with the mix of that drum the desired summed sound might happens when one or two (or more) mics have phase flipped.