Phase reverse?

  • Thread starter Thread starter brokenwindow
  • Start date Start date
Hey, BW-

Yes, you can use phase reversal on the VS880. I've done it to remove a bass guitar track that was already in a submix. By adding the original track in reverse phase and carefully adjusting the levels, I can drop it completely out of the mixed track.
 
What do you mean adding a track in reverse phase?
 
brokenwindow,

As you were reading about it, I'll presume you understood the notion of in-phase and out-of-phase. The term phase is used quite loosely.

Consider an "out-of-phase" or "reverse-phase" to mean the more intuitive "inverted" signal. ie a signal which has troughs in the places of the crests of an original signal.

If you add the inverted signal to the original signal (both signals of the same level) the two signals will cancel eachother. This is very similar to phase cancellation which all single-frequency waves can exhibit - hence the references to "phase".

I think Mooseboy is describing a shortcut or disaster recovery method where he took out the bass from a ready-mixed track by mixing that with an inverted copy of the bass track.

On the 1680, each source/track can be toggled between NORM and INV "phase".

Hope that was clear enough,
Jim
 
If you were referring to my post about phase reversing a distant or room mic what this does is to switch the hot lead on the XLR from pin 2 to pin 3 or vice versa.This polarity reversal can fatten up the sound if it is thin . This is similar to wiring your stereo with one speaker out of phase( one wire reversed) the bass goes away if the speakers are the same distance from your ear. If you put one speaker 9 feet closer to you then reversing the phase will increase the bass response.Yes you can do it on the Roland if you really want to plug a mic into those pres, but I sure don't recommend it.Most good mic pres have a phase reverse switch to make this easy.
 
That's exactly it, Jimi- I see that I didn't really elucidate on that very well.

I had a bass track laid down on a tune, and had a submix on the rhythm tracks. Then I had a chance for a really trick bass guitarist to come in and do the track for me, but I didn't really have time to unmix the rhythm track first.

So I just played the mixed rhythm track back to him, adding in the old bass part, but using the "INV" selection on the phase selector. I then carefully brought up the fader on the old part, finding the "sweet spot" where the two parts cancelled out perfectly.

The thing that was funny is that I thought it might work in theory, but wasn't really sure how sample accurate this whole thing was. When it worked, I was laughing like crazy- but I couldn't really explain it to the bass player, who was still learning some of the tricks of the recording trade.

So the motto is- "whatever works". Isn't it?
 
That's cool. Is that the way voice cancel works or is that just EQ? I read about a bridge somewhere that had microphones to pick up the noise of the bridge . They then amped the vibration from the bridge and sent it back at the source through huge speakers. The effect was that it phase cancelled out the noise and vibration from the bridge so it shook less.Really.
 
Dorian,

A little birdy told me that a voice canceller only attempts phase cancellation in the voice frequencies - it's quite normal to sit the lowest frequency stuff panned dead centre as well as the lead (eg the voice). This is because:

a) it will be maximum volume,
b) the low freq stuff doesn't really affect stereo image,
c) it's mono friendly (where mono=L+R),

As for the famous bridge, well it's actually the bridge on my Washburn. I have to hold it steady when playing though. ;)
 
Normally they just cancel my voice by turning off my mic but I'll take your word for it.It sounds like the same principle but frequency selective I.e cancelling the mids instead of the sub harmonics as on the bridge ( of your Washburn, you nut :D). The stuff with wavelenght VS phase cancellation is pretty interesting.I got interested in it after reading the manual for the fishman blender with my Taylor. It has instructions for adjusting the phase in relation to your distance from the speaker.They tell you to flip the switch to find the fullest sound. If it is in phase at 3 feet for instance , if you move 9 feet away the key guitar frequencies are out of phase so you have to throw the switch. if you move to 12 to 14 feet away it will shift back out of phase due to the frequencies wavelength and you will need to flip the switch back.As you might know all Fishman blenders have a phase reverse switch for this purpose. I took this theory and applied it to amp micing technique and solved my problem of the thin sounding room mic by phase reversing it. I actually have a link to a phase/frequency length calculator on my site @ www.blues2001.com/rolaids I'm a lot dumber looking than I am.... I think....????




[This message has been edited by Dorian (edited 06-07-2000).]
 
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