Results 1 to 7 of 7

Thread: phase inversion

  1. #1
    dumi is offline Registered User
    Join Date
    Aug 2004
    Location
    bat country
    Posts
    116

    phase inversion

    Sign in to disable this ad
    i was reading on the ableton forum that someone makes beats by mixing the original break with a slightly distorted and phase inverted copy. so my (retarded) question is wtf is phase inversion? how is it achieved and more important what purpose does it serve? an audio example would be hugely appreciated.

    i have to ask you to excuse me for not taking more time googling on this, but as i am a lazy fcuk, i gave up after the first page of results like this

    ez, all

  2. #2
    DannyGantastic is offline Senior Member
    Join Date
    May 2003
    Posts
    317
    Phase inversion is simply "flipping" an audio stream about the zero crossing.

    Seen graphically, it would be turning this:

    /\/\_/\__

    into this:

    \/\/¯\/¯¯

    The sound produced has all the compressions of air replaced by rarefactions of the same magnitude, and vice versa.

    Phase-inverting an audio clip doesn't make it sound any different; Our ears don't differentiate between compression and rarefaction.

    However, let's say you have an audio sample. You take a copy of it, phase-invert the copy, and mix the two together. What do you get? Silence. Because one wave is just the negative of the other, their sum is zero.

    Now let's say you have an audio sample, and you copy it as before. You phase-invert the sample, then delay it by a few samples, and mix the two together again. What you get is somewhat odd -- Approaching silence, but not quite. It's still near silence because the magnitude of the audio at any one point is similar to the magnitude at any nearby point, but not the same.

    Frankly, the best way to find out is to go and try it yourself. A phase-inverter is an extremely simple effect, and if your sequencer doesn't have one, free plugins abound. Any waveform editor worth its salt can invert waveforms too.

    As for its particular applied uses: There are too many to name. There's mundane stuff: I use FL Studio, which lacks a direct way to mute one stereo channel and leave the other one untouched. It does have a phase inverter, though: I have it phase-invert the right channel, and I mix it to 50%. The net effect is that the left channel remains the same, while the right channel, at 50% volume, is mixed with an inverted copy of itself at 50% volume, and is thus silenced.

    Another common use is to take a stereo stream (Most commonly, a song you want to sample), invert one stereo channel, and mix the two together. The result is that all elements of the audio that were panned towards the center are eliminated or attenuated, while elements that were originally panned to the side are mostly intact.

  3. #3
    dumi is offline Registered User
    Join Date
    Aug 2004
    Location
    bat country
    Posts
    116
    much obliged kind sir very informative

  4. #4
    Manassés is offline Registered User
    Join Date
    Nov 2010
    Posts
    2

    Audio inverter

    Hi all, im from Brazil...
    a long time ago , i was looking for a audio phase inverter, and today i find this cirucit (showing in this topic).
    i have a question :
    This circuit can be used to avoid feedbacks?
    im musician in my church, and there all we have trobles with high sound lvls, and feedbacks, if this circuit can be used to cancel that feedbacks, maybe our problems can be solved....

    tnx for any hlp, and tnx for your time...

    []'s from Brazil

    Manassés

  5. #5
    hollandturbine is offline Registered User
    Join Date
    Sep 2008
    Posts
    2,719
    This is the page the picture comes from.

    http://sound.westhost.com/project107.htm

  6. #6
    bandcoach's Avatar
    bandcoach is offline Zukatoku - Mod Scientist
    Join Date
    Nov 2010
    Location
    Sydney Australia
    Posts
    15,694
    Quote Originally Posted by Manassés View Post
    Hi all, im from Brazil...
    a long time ago , i was looking for a audio phase inverter, and today i find this cirucit (showing in this topic).
    i have a question :
    This circuit can be used to avoid feedbacks?
    im musician in my church, and there all we have trobles with high sound lvls, and feedbacks, if this circuit can be used to cancel that feedbacks, maybe our problems can be solved....

    tnx for any hlp, and tnx for your time...

    []'s from Brazil

    Manassés
    This circuit won't avoid feedback. It looks like an active phase inverter module either found in an audio desk or as a box much like a di box.

    Your first step to solving the problem is to reduce the levels at the mixing desk, this may mean the musicians turning down slightly so that microphones can still be heard.

    Check that the gain on each microphone channel is at the minimum it needs to be, to be heard, rather than all the way over to compensate for loud musicians. When doing this, the channel slider should be at the 0 mark as should the master slider and any group buss sliders.

    Only the sound engineer and one person walking from microphone to microphone singing or speaking at the levels normally experienced at that microphone should be involved/in the room at this point..

    A side point here is that if the singers are expecting the pa system to do the work for them, i.e. amplifying the sound, then the system is being used poorly. It is better to have them sing full volume (projecting their voice) and amplify that rather than try to boost a (relatively) quiet performance.

    Once the microphones are set up on the desk, bring in the band/musicians and singers. Have them play a loud song. At this point it is the bands responsibility to match their volumes to the singers, not the other way around. Now have them play a quiet song.

    By properly setting up the gain structure on the pa system and getting the band to play within that gain structure, your feedback problems should disappear. Avoid the temptation to turn the desk up to compensate for musicians who do not cooperate. If you have problems, remind them that they are their to assist in the praise not to be praised.

    If the above is not possible or does not work because of other factors, then you need to invest in something like the Behringer or Alto range of equalisers with feedback squelch circuits

  7. #7
    Manassés is offline Registered User
    Join Date
    Nov 2010
    Posts
    2
    Hi Bandcoach !!!

    thank you for your reply, is very good tips you give to me...
    tnx so much...
    hugs from Brazil

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Special 93% Offer

Got beats? Samples? Mixing and mastering services? Get a head start with this 93% OFF special offer!