twotoedsloth wrote:I have an Audient Mico, and it has a variphase controller on one of the mic pres.
I've never used it, but I remember reading it wasn't true phase alignment. Is there a quick summary of what it does available?
It's them words again....
You could try my review in which I gave a description of what this control does and doesn't offer:
http://www.soundonsound.com/reviews/audient-mico
The Mico's Variphase control provides a continuous phase-adjustment facility, derived from the use of adjustable all-pass filters, and I think that could be said to offer 'true phase alignment' since it allows the phase of one signal to be aligned in phase with another at any given frequency (and its harmonics)...
What it can't do, though is provide true 'time alignment' -- and ironically that's the problem for which this approach is typically advocated!
As I said in the review, it is not uncommon to record some sources with more than one microphone (acoustic guitars, snare drums, and so on), or with a microphone and a DI combination (acoustic and electric guitars, for example).
The fundamental problem in these situations is that the two signals may not be time aligned because the different microphone distances from the source (or mic distance relative to the instant DI) capture the sound at different times The resulting time offsets between the two signal can cause phase cancellations (at specific frequencies related to the timing difference) that colour the sound, often in unflattering ways.
This problem can be fixed in the studio given time and care in placing the mics, or if the material is recorded into a DAW simply by sliding one microphone's track along the time‑line relative to the other.
What Audient offer with the Variphase control is not the ability to time‑align the two channels — there is no built‑in variable time delay facility here — but to adjust the phase-shift of one channel relative to the other. The control affords a 180 degree shift, and by switching in the polarity inversion you can access the 180 to 360 degree range too.
It's an interesting tool which sounds a lot like a manually-controlled phaser or phase shifter pedal — so by adjusting the Variphase control you can effectively decide which frequency components are aligned and emphasised, and which are sacrificed through partial cancellation.
This solution enables the user to compensate to some extent for the dominant phase cancellations caused by incorrect time-alignment that would otherwise colour the sound in an objectionable way, and enhance those musically constructive phase additions instead.
The key difference, though, is that whereas correct time‑alignment would bring
all frequencies into phase alignment, the Variphase control only brings
some frequencies into phase alignment (you choose which by adjusting the control). So while this phase-shifting tool doesn't replace true time‑alignment, it often renders a sufficiently pleasing result that genuine accurate time‑alignment becomes unnecessary.
In practice, at least with a DI'd and miked guitar, I found it was possible to get some very pleasing results, with nice musically-enhancing colourations rather than nasty ones.
Hope that helps.
H
. Is that to get left and right equal, or to get several stereo arrays equal?
